Measurement Types and Statistics

The MeasurementStatistics property comprises a list of measurement models with associated defining parameters supported by the object. You can choose to generate measurements of the types contained in this list during simulations and have them processed during estimation.

Measurement types

Depending on the object, the following measurement types may be available:

Measurement Types
Type	Description
1W Bistatic Doppler	This is a doppler measurement represented in terms of average range rate over the Doppler integration interval, using links to two separate facilities: Uplink from Ground Station to Satellite; uses relay transponder on satellite if the receive station is configured for transponder tracking Downlink to Bistatic (Receive) Ground Station You should add the statistics for this measurement to the bistatic receiving ground station. If you configure the receive ground station for transponder tracking (using the Ranging/Method attribute), then ODTK uses a relay transponder on the satellite, if it exists. In this case, ODTK uses the locations of the associated antennas in the modeling of the measurement.
1W Bistatic Range	This is ranging using links to two separate facilities: Uplink from Ground Station to Satellite; uses relay transponder on satellite if the receive station is configured for transponder tracking) Downlink to Bistatic (Receive) Ground Station You should add the statistics for this measurement to the bistatic receiving ground station. If you configure the receive ground station for transponder tracking (using the Ranging/Method attribute), then ODTK uses a relay transponder on the satellite, if it exists. In this case, ODTK uses both the transponder delay and the locations of the associated antennas in the modeling of the measurement.
1W Doppler	This is a one-way Doppler measurement, a noncoherent, one-way downlink measurement. It is a phase count measuring the change in frequency of a signal caused by the relative motion of the ground station and the satellite. An option is available for you to model this measurement as instantaneous range rate.
1W Range	This is a one-way range measurement where the range signal is transmitted from a satellite and received at a ground station. The measured value of range is dependent on the phase offset of the satellite's clock in addition to environmental conditions and geometry.
2L CA Pseudo-range	This is a two-legged coarse acquisition pseudo-range. For a ground-based GNSS receiver, the range from a GNSS SV through a transponder (relay type) on the user spacecraft to a ground-based receiver is the modeled measurement. Visibility from the GNSS SV to the user spacecraft is subject to the MinGrazingAlt setting on the user spacecraft. ODTK models and estimates the receiver clock phase error and clock frequency error (group receiver clock) along with the transponder delay at the user spacecraft. It also models tropospheric effects at the ground receiver location.
3L Doppler	This is a measurement type used by the TDRS satellite system. It is also called "Return-Link Doppler", and there are three legs to this measurement. One leg is a pilot tone, transmitted from the ground to the TDRS satellite and used by the TDRS satellite in handling the Doppler signal. The Doppler signal is generated by the user satellite (Hubble, TOPEX, etc), and transmitted through the TDRS satellite to the ground station. The measurement is in units of Hz, and is the frequency difference between the received signal and a reference generated on the ground. Visibility from the TDRS satellite to the user spacecraft is subject to the MinGrazingAlt setting on the TDRS satellite.
4L Range	This is a TDRSS Range model, a four-legged range measurement of the total time for a signal to travel the following four links: Uplink - from a Ground Station to a Relay Satellite Forward - from the Relay Satellite to a User Satellite Return - from the User Satellite back to the Relay Satellite Downlink - from the Relay Satellite back to the Ground Station Visibility from the TDRS satellite to the user spacecraft is subject to the MinGrazingAlt setting on the TDRS satellite.
5L Doppler	This is a TDRSS Doppler model, a phase count measuring the Doppler shift caused by the relative motion of the Relay and User satellite to each other and to the ground station. This is a five-legged model where four legs are as defined in the 4L Range model (above) and the fifth leg is an uplink pilot tone leg from the ground station to the Relay satellite arriving at the Relay satellite at the downlink time. Visibility from the TDRS satellite to the User spacecraft is subject to the MinGrazingAlt setting on the TDRS satellite.
Accel	This is a linear acceleration measurement reported by a single accelerometer sensor. The measurement is indicative of sensed acceleration in the direction specified by the referenced accelerometer sensor. Sensed accelerations include all nonconservative accelerations such as atmospheric drag, solar radiation pressure, and thrusting. The sensor picks up additional accelerations (gravity gradient and centripetal) it is displaced relative to the center of mass of the satellite. You should add the statistics for this measurement to the MeasurementStatistics set for the associated AccelerometerSensor object.
Azimuth Elevation	This is a pair of ground station angle measurements that ODTK can use together to determine a line-of-sight pointing vector from the ground station to the satellite. Azimuth is a horizontal angle measured in the local tangent plane clockwise (eastward) from the north. Elevation is a vertical angle measured from the local horizon, positive up to the satellite. You can model Azimuth and Elevation with or without light time delay. If you include light time delay, then the modeling assumes one-way measurements with the measurement time tag as the ground reception time. ODTK applies aberration corrections based on the facility AberrationCorrection setting when you set LightTimeDelay setting to true.
BRTS Doppler	This is the same as 5L Doppler (above) except that a ground (BRTS) transponder replaces the user satellite.
BRTS Range	This is the same as 4L Range (above) except that a ground (BRTS) transponder replaces the user satellite.
Bistatic Ground TDOA	The Bistatic Ground Time Difference of Arrival measurement type is applicable to the tracking of satellites using radio signals. A signal travels from a ground-based emitter along two paths to a common ground-based receiver. Path 1 is a direct link between the emitter and the receiver. Path 2 goes to a satellite, which either uses a transponder or reflects the signal, and the signal path ends at the receiver. Path 2 uses the transponder option if the satellite is configured with a relay transponder. The measurement is time-tagged at the time of receipt on path 2 and is computed as follows: time of receipt on path 2 minus time of receipt on path 1.
Bistatic Ground FDOA	The Bistatic Ground Frequency Difference of Arrival measurement type is applicable to the tracking of satellites using radio signals. A signal travels from a ground-based emitter along two paths to a common ground-based receiver. Path 1 is a direct link between the emitter and the receiver. Path 2 goes to a satellite, where it is reflected and ends at the receiver. The measurement is time-tagged at the time of receipt on path 2 and is computed as follows: frequency of receipt on path 2 minus frequency of receipt on path 1.
CA DD Pseudo-range	For coarse acquisition double-differenced pseudo-range, the modeled measurement is the difference of two distinct single-differenced C/A code range measurements. These measurements are free from the effects of receiver and GPS satellite clock errors. However, ionosphere effects remain. Unlike single-differenced measurements, you must construct double-differenced measurements outside of ODTK.
CA Nav Sol	These are navigation solutions generated from coarse acquisition pseudo-range. X, Y, and Z components share the same statistical parameters. You can specify solution-specific (X, Y, Z get the same or independent values) white noise sigmas via the navsol format and enable them by setting the scenario-level attribute EmbeddedWNSigmas.Use to true. Alternatively, the input white noise sigma can be automatically scaled based on Dilution Of Precision (DOP) if the associated GPS satellite IDs are specified in the navsol formatted data. The use of DOP based deweighting is controlled by the WhiteNoiseDeweighting setting in the measurement statistics. If you use DOP-based deweighting AND custom sigma values are read in from a navsol formatted data file, ODTK scales the custom sigma values by the DOP.
CA Pseudo-range	This is coarse acquisition pseudo-range, where CA L1 pseudo-range is the input measurement. The range between the GNSS space vehicle (SV) and the user's receiver is the modeled measurement.
CA SD Pseudo-range	This is coarse acquisition single-differenced pseudo-range, where the modeled measurement is the difference of two distinct SV C/A code range measurements. In this case, the receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. If you request CA SD measurements (by adding CA SD Pseudo-range to the GPS receiver MeasurementStatistics and to the MeasTypes on the satellite), then ODTK converts the CA measurements to CA SD measurements and does not process any pure CA measurements.
ClockNoiseScaling	This is a scale factor for deweighting of GNSS phase measurements to account for the unknown variation of GNSS satellite and GNSS receiver clocks over the count interval for the phase measurement. Set the value to 1.0 to deweight measurements based on the total process noise for all relevant clocks. Set the value to 0.0 to ignore variations in clock behavior over the count interval. This setting only has an effect when ODTK is estimating the GNSS receiver and/or the GNSS satellite clocks, and it is usually only used for simulations where the distinction between clock behavior and white noise is known. For SD phase measurements, ODTK only computes deweighting based on the GNSS satellite clocks, since the effects of the GNSS receiver clocks are differenced out. ODTK does not perform additional deweighting for DD phase measurements. When simulating L1 Phase, L2 Phase, and deviating clocks, the ClockNoiseScaling should be = 1.
Delta Declination	This is a single-differenced declination measurement. If you request Delta Declination measurements, by adding Delta Declination to the Facility MeasurementStatistics, then ODTK will convert observation sets containing more than one declination measurement into a new observation set containing one declination measurement from the original set with other declination measurements replaced by corresponding delta declination measurements that are referenced to the remaining original. ODTK cannot directly simulate Delta Declination measurements. This measurement type is useful in estimating the orbits of closely spaced objects.
Delta Range	This type actually has ODTK processing two-way range data from a ground station in a Doppler-equivalent manner. The absolute value of the range values is differenced out, and the change in range from measurement to measurement is used to estimate the satellite's orbit. This measurement type is useful when the absolute bias of the range data in a tracking pass is unknown and rather high, but the measurement-to-measurement relative bias is low.
Delta Right Ascension	This is a single-differenced right ascension measurement. If you request Delta Right Ascension measurements, by adding Delta Right Ascension to the Facility MeasurementStatistics, then ODTK will convert observation sets containing more than one right ascension measurement into a new observation set containing one right ascension measurement from the original set with other right ascension measurements replaced by corresponding delta right ascension measurements that are referenced to the remaining original. ODTK cannot directly simulate Delta Right Ascension measurements. This measurement type is useful in estimating the orbits of closely spaced objects.
Delta SB Dec	This is a single-differenced space-based declination measurement. If you request Delta SB Dec measurements, by adding Delta SB Dec to the Facility MeasurementStatistics, then ODTK converts observation sets containing more than one space-based declination measurement into a new observation set containing one space-based declination measurement from the original set with other space-based declination measurements replaced by corresponding space-based delta declination measurements that are referenced to the remaining original. ODTK cannot directly simulate Delta SB Dec measurements. This measurement type is useful in estimating the orbits of closely spaced objects.
Delta SB RA	This is a single-differenced space-based right ascension measurement. If you request Delta SB RA measurements, by adding Delta SB RA to the Facility MeasurementStatistics, then ODTK will convert observation sets containing more than one space-based right ascension measurement into a new observation set containing one space-based right ascension measurement from the original set with other space-based right ascension measurements replaced by corresponding delta right ascension measurements that are referenced to the remaining original. ODTK cannot directly simulate Delta SB RA measurements. This measurement type is useful in estimating the orbits of closely spaced objects.
Differenced One Way Doppler (DOWD)	ODTK constructs these measurements by differencing two simultaneous one-way TDRS Doppler measurements (3L Doppler). They are typically used in early orbit operations, prior to availability of the primary tracking system, for user satellites that do not have TDRS transponders or ultra-stable oscillators. The differencing operation removes the effects of the user satellite clock.
DirCos East and North	This is a pair of ground station direction cosine measurements. The east direction cosine is measured as the projection of the relative position unit vector onto the local antenna East direction. The north direction cosine is measured as the projection of the relative position unit vector onto the local antenna north direction. The local antenna reference frame directions differ from the standard topocentric east and north direction by a rotation about the zenith direction given by the DirectionCosineAzimuthOffset, which specifies the azimuth of the antenna local north direction. You can specify the DirectionCosineAzimuthOffset when you set the AntennaMountType to DirCos_EW. You can choose to model direction cosine measurements with or without light time delay. If you include light time delay, then the modeling assumes one-way measurements with the measurement time tag as the ground reception time. ODTK applies aberration corrections based on the facility AberrationCorrection setting when you set LightTimeDelay setting to true. ODTK can read in direction cosine measurements directly from the tracking data or it can construct them from input azimuth and elevation measurements. The construction from azimuth and elevation will occur if ODTK sees (1) the direction cosine measurement types in the measurement statistics and (2) direction cosine measurements in the MeasTypes list of the estimation process.
DF DD Phase	This is a double-differenced (dual-frequency) phase count, where the modeled measurement is the difference of two single-differenced dual frequency phase-count measurements. These measurements are free from the effects of the ionosphere and receiver and GPS satellite clock errors. Unlike single-differenced measurements, you must construct double-differenced measurements outside of ODTK.
DF DD Pseudo-range	This is a double-differenced dual frequency pseudo-range. The modeled measurement is the difference of two distinct single-differenced DF code range measurements. These measurements are free from the effects of the ionosphere and receiver and GPS satellite clock errors. Unlike single-differenced measurements, you must construct double-differenced measurements outside of ODTK.
DF Nav Sol	These are navigation solutions generated from dual frequency pseudo-range. X, Y, and Z components share the same statistical parameters. You can specify solution-specific (X, Y, Z get the same or independent values) white noise sigmas via the navsol format and enable them by setting the scenario-level attribute EmbeddedWNSigmas.Use to true. Alternatively, ODTK can automatically scale the input white noise sigma based on Dilution Of Precision (DOP) if the associated GPS satellite IDs are specified in the navsol-formatted data. The use of DOP-based deweighting is controlled by the WhiteNoiseDeweighting setting in the measurement statistics. If DOP-based deweighting is used AND custom sigma values are read in from a navsol formatted data file, the custom sigma values will be scaled by the DOP.
DF Phase	ODTK computes these measurements by mathematically combining the L1 and L2 Phase measurements to produce a measurement that is independent of the first-order effects of the ionosphere. If you select DF Phase measurements, ODTK converts L1 and L2 Phase measurements to DF Phase measurements and does not process L1 or L2 Phase measurements.
DF Phase Range	These are dual-frequency phase measurements modeled as range measurements with unknown initial bias. Processing of this type of measurement requires the addition of states for each receiver/GPS satellite combination. These measurements are free from the effects of the ionosphere.
DF Pseudo-range	ODTK computes this by mathematically combining the P1 and P2 measurements to produce a measurement that is independent of the first-order effects of the ionosphere. If you select DF measurements, ODTK converts P1 and P2 measurements to DF measurements and does not process P1 or P2 measurements.
DF SD Phase	This is a single-differenced dual-frequency phase-count. This means that the DF Phase is computed for two satellites that are being simultaneously tracked and that these two DF measurements are then differenced. These types of measurements are free from the effects of the ionosphere and the receiver clock bias.
DF SD Pseudo-range	This is a single-differenced dual-frequency pseudo-range. This means that the DF pseudo-range is computed for two satellites that are being simultaneously tracked and that these two DF measurements are then differenced. These types of measurements are free from the effects of the ionosphere and the receiver clock bias.
Doppler	This is a phase count measuring the change in frequency of a signal (Doppler shift) caused by the relative motion of the ground station and the satellite. You can choose to have ODTK model this measurement as instantaneous range rate.
DSN DOR	This is a Deep Space Network (Spacecraft) differential one-way range difference measurement requiring two DSN ground antennas and only using downlink from the spacecraft. The two antennas are located in DSN complexes on separate sides of the Earth. The imaginary line connecting the two antennas are like an interferometer where radio waves from the target spacecraft arrive at the interferometer in approximately parallel rays. The differential one-way range measurement is then the path length difference of the signal arriving to each of the antennas.
DSN QDOR	This is a Deep Space Network (Quasar) differential one-way range similar to DSN DOR except that the measurement refers to light emitted from a quasar instead of a signal from a spacecraft.
DSN Delta DOR	This is a Deep Space Network delta differential one-way range that requires a single quasar and spacecraft to be tracked essentially simultaneously. Reference the description of the DSN DOR and DSN QDOR measurements. A Delta DOR measurement is formed by combining and processing three measurements: QDOR at time t1, DOR at time t2, and QDOR at time t3. ODTK uses the QDOR measurements to estimate a QDOR measurement at time t2; then, it forms the Delta DOR measurement at time t2 by differencing DOR (t2) - QDODR(t2).
DSN Seq Rng	Deep Space Network Sequential Range is an ambiguous two-way range measurement where the length of the ranging code is provided with the observation. DSN Sequential Range measurements are always modeled in the solar system barycentric reference frame.
DSN 3W Seq Rng	Deep Space Network Three-way Sequential Range is an ambiguous two-way range measurement where the length of the ranging code is provided with the observation. DSN Sequential Range measurements are always modeled in the solar system barycentric reference frame. It is similiar to DSN Seq Range except that the uplink and downlink ground stations are different. The clocks at the two ground stations are assumed to be synchronized.
DSN PN Rng	Deep Space Network Pseudo Noise Range is an ambiguous two-way range measurement where the length of the ranging code is provided with the observation.
DSN 3W PN Range	Deep Space Network Three-Way Pseudo-Noise Range is an ambiguous two-way range measurement where the modeling provides the length of the ranging code with the observation. DSN pseudo-noise range measurements are always modeled in the solar system barycentric reference frame. This is similar to DSN PN Range except that the uplink and downlink ground stations are different. ODTK assumes that the clocks at the two ground stations are synchronized.
DNS INS	Deep Space Network Interferometric Narrowband Spacecraft measurements are derived measurements generated through the differencing of DSN 1W Doppler or DSN 1W TCP measurements collected at two DSN ground stations at common epochs. This measurement type may be useful in early orbit operations before two-way tracking is available.You can select to generate DSN INS measurements from raw DSN 1W Doppler or DSN 1W TCP measurements in ODTK using the GenerateDOWDFromFiles or GenerateDOWD functional attributes on the application. The measurement strand has the following form: Satellite - Facility1, Facility2. ODTK forms the INS measurement as Meas2 - Meas1, where Meas2 is the 1W measurement taken from Facility2. Facility 2 also hosts the measurement statistics. ODTK assumes that the clocks at the two ground stations are synchronized.
DSN Doppler	Deep Space Network Doppler is a coherent two-way measurement of the number of carrier cycles received at the DSN downlink station over a count interval specified with the observation. The transmitted frequency from the uplink station can either be constant or ramped. The frequency (ramp) schedule for transmitting ground stations is provided in the tracking data file. The time tag of this measurement is in the center of the count interval. The uplink and downlink stations are the same.
DSN 3W Doppler	Deep Space Network Three-way Doppler is similar to the DSN Doppler measurement except that the uplink and downlink stations are different.
DSN 1W Doppler	Deep Space Network One-way Doppler is similar to the DSN Doppler measurement except that the signal is one-way from the satellite to the downlink station. The one-way signal is also not ramped in frequency. Processing of one-way Doppler usually requires estimation of the frequency of the spacecraft clock, unless the one-way measurements are differenced as is done in the processing of DSN INS measurements.
DSN TCP	Deep Space Network Total Count Phase is a coherent two-way measurement of the number of carrier cycles received at the DSN downlink station since an epoch specified with the observation. The transmitted frequency from the uplink station can either be constant or ramped. The frequency (ramp) schedule for transmitting ground stations is provided in the tracking data file. The time tag of this measurement is at the end of the count interval. The uplink and downlink stations are the same.
DSN 3W TCP	Deep Space Network Three-way Total Count Phase is similar to the DSN Total Count Phase measurement except that the uplink and downlink stations are different.
DSN 1W TCP	Deep Space Network One-way Total Count Phase is similar to the DSN Total Count Phase measurement except that the signal is one-way from the satellite to the downlink station. The one-way signal is also not ramped in frequency. Processing of one-way TCP usually requires estimation of the frequency of the spacecraft clock, unless the one-way measurements are differenced as is done in the processing of DSN INS measurements.
E1 Phase E5a Phase E5b Phase E6 Phase E5ab Phase E2 Phase	These are Galileo Carrier Phase Measurements broadcast on the E1, E5a, E5b, and E6 frequencies respectively.
E1 SD Phase E5a SD Phase E5b SD Phase E6 SD Phase E5ab SD Phase E2 SD Phase	Galileo single-differenced (single-frequency) phase count is the difference of two SV phase-count measurements (two E1, two E5a, two E5b, or two E6 measurements). In this case, the receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. However, ionosphere effects remain. If you request SD Phase measurements, then ODTK converts the "raw" phase-count measurements to SD Phase measurements and does not process the "raw" phase-count measurements.
E1_E5a DF Phase E1_E5b DF Phase	These are Galileo dual-frequency (DF) phase measurements computed by mathematically combining the two single-frequency “raw” phase measurements to produce a measurement that is independent of the first order effects of the ionosphere. If you select DF measurements, then ODTK converts the corresponding “raw” single-frequency measurements to DF measurements and does not process the single-frequency measurements.
E1_E5a DF SD Phase E1_E5b SD DF Phase	This is a single-differenced dual frequency measurement using Galileo signals’ DF phase. This means that the DF phase is computed for two satellites that are being simultaneously tracked and that these two DF measurements are then differenced. These types of measurements are free from the effects of the ionosphere and the receiver clock bias.
E1 Pseudo-range E5a Pseudo-range E5b Pseudo-range E6 Pseudo-range E5ab Pseudo-range E2 Pseudo-range	These are Galileo pseudo-range measurements using the E1, E5a, E5b, and E6 frequency bands.
E1 SD Pseudo-range E5a SD Pseudo-range E5b SD Pseudo-range E6 SD Pseudo-range E5ab SD Pseudo-range E2 SD Pseudo-range	Galileo single-difference (single-frequency) pseudo-range is the difference of two SV pseudo-range measurements (two E1,two E5a, two E5b, or two E6 measurements). The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. However, ionosphere effects remain. If you request SD pseudo-range measurements, then ODTK converts the "raw" pseudo-range measurements to SD pseudo-range measurements and does not process the "raw" pseudo-range measurements.
E1_E5a DF Pseudo-range E1_E5b DF Pseudo-range	These are Galileo dual-frequency (DF) range measurements computed by mathematically combining the two single-frequency “raw” pseudo-range measurements to produce a measurement that is independent of the first order effects of the ionosphere. If you select DF measurements, then ODTK converts the corresponding “raw” single-frequency measurements to DF measurements and does not process the single-frequency measurements.
E1_E5a DF SD Pseudo-range E1_E5b SD DF Pseudo-range	This is a single-differenced dual-frequency measurement using Galileo signals’ DF pseudo-range. This means that the DF Pseudo-range is computed for two satellites that are being simultaneously tracked and that these two DF measurements are then differenced. These types of measurements are free from the effects of the ionosphere and the receiver clock bias.
Eph Pos	Use this to process ephemeris position components as measurements. You should add the statistics for this measurement to the associated satellite object. Position X, Y, Z share the same statistical parameters. You must include this measurement as a choice in the measurement type list in the associated satellite object so that ODTK can process it.
Eph Vel	Use this to process ephemeris velocity components as measurements. You should add the statistics for this measurement to the associated satellite object. Velocity X, Y, Z share the same statistical parameters. You must include this measurement as a choice in the measurement type list in the associated satellite object so that ODTK can process it. You can choose to use "Eph Vel" measurements together with or separately from "Eph Pos" measurements.
Face Horizontal And Face Vertical	These are a pair of angle measurements pertaining to Phased Array radars. The Face Vertical angle measures the angle down from the radar "face" normal. The Face Horizontal angle is measured in the local radar "face" plane clockwise from the local X axis. The local frame has the Z axis aligned with face normal. The orientation of the local frame is derived from the two Facility input properties "BoresightAzimuth" and "BoresightElevation". The orientation is consistent with the STK Azimuth-Elevation Orientation Method, About Boresight Rotate option. Refer to the {BoresightAzimuth, BoresightElevation} properties for a further description of the local frame orientation. You can choose to model face angle measurements with or without light time delay. If you include light time delay, then the modeling assumes one-way measurements with the measurement time tag as the ground reception time. ODTK applies aberration corrections based on the facility AberrationCorrection setting when you set LightTimeDelay to true. ODTK can read face angle measurements directly from the tracking data or it can construct them from input azimuth and elevation measurements. It will construct them from azimuth and elevation if you include the face angle measurement types in the measurement statistics and the face angle measurements in the MeasTypes list of the estimation process.
FDOA	For Frequency Difference of Arrival measurements, a signal travels from an emitter through relay transponders on two satellites (path 1 and path 2) to a common receive station. The measurement is time-tagged at the time of receipt on path 1 and is computed as the received frequency on path 2 minus the received frequency on path 1.
FDOA 2 Receivers	For Frequency Difference of Arrival measurements, a signal travels from a ground-based emitter through relay transponders on two satellites (path 1 and path 2) to two receive stations. Signal path 1 is emitter-satellite 1-station 1. Signal path 2 is emitter-satellite 2-station 2. The measurement is time-tagged at the time of receipt at station 2 and is computed as the received frequency on path 2 minus the received frequency on path 1.
Ground FDOA	For Frequency Difference of Arrival measurements, a signal travels from a satellite-based emitter to two receiver stations. The measurement is time-tagged at the time of receipt at station 2 and is computed as the received frequency at station 2 minus the received frequency at station 1.
Ground FDOADot	For Frequency Difference of Arrival Dot measurements, a signal travels from a satellite-based emitter to two receiver stations. The measurement is time-tagged at the time of receipt at station 2 and is computed as the received frequency rate at station 2 minus the received frequency rate at station 1.
GroundTDOA	For Time Difference of Arrival measurements, a signal travels from a satellite-based emitter to two receiver stations. The measurement is time-tagged at the time of receipt at station 2 and is computed as the time of receipt at station 2 minus the time of receipt at station 1.
L1 Phase L2 Phase	ODTK computes carrier phase-count measurements on the basis of the P code on the L1 (P1) and L2 (P2) frequencies. It combines these two phase-counts to generate the DF phase-count (see below). A GPS receiver directly measures P1 and P2 carrier phase-counts. P1 and P2, however, are available only to military receivers and a new class of receivers that use patented algorithms to measure P1 and P2 without directly locking onto the P code.
L1 DD Phase L2 DD Phase LA DD Phase	This is a double-differenced (single-frequency) phase count. The modeled measurement is the difference of two single-differenced phase count measurements (two L1 SD Phase, two L2 SD Phase, or two LA SD Phase measurements). These measurements are free from the effects of receiver and GPS satellite clock errors. However, they still have ionosphere effects. Unlike single-differenced measurements, you must construct double-differenced measurements outside of ODTK.
L1 SD Phase L2 SD Phase LA SD Phase	This is single-difference (single-frequency) phase count. The modeled measurement is the difference of two SV phase-count measurements (two L1, two L2, or two LA measurements). The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. However, there are still ionosphere effects. If you request SD Phase measurements, then ODTK converts the "raw" phase count measurements to SD Phase measurements and does not process the "raw" phase-count measurements.
LA Phase	These are carrier phase-count measurements computed on the basis of the C/A code on the L1 frequency.
L1C Phase	This is GPS civilian carrier phase, broadcast on the L1 frequency. This measurement became available with the first Block III launch.
L1C SD Phase	L1C Single-differenced (single-frequency) phase count is the difference of two SV phase count measurements (two L1C measurements). The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. However, there are still ionosphere effects. If you request SD Phase measurements, then ODTK converts the "raw" phase count measurements to SD Phase measurements and does not process the "raw" phase-count measurements.
L1C Pseudo-range	GPS L1 civilian pseudo-range became available with the first Block III launch. The range between the GNSS space vehicle (SV) and the user's receiver is the modeled measurement.
L1C SD Pseudo-range	L1C single difference pseudo-range is the difference of two distinct SV L1 C code range measurements. The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. If you request L1C SD measurements (by adding L1 SD Pseudo-range to the GPS receiver MeasurementStatistics and to the MeasTypes on the satellite), then ODTK converts L1C measurements to L1C SD measurements and does not process the pure L1C measurements.
L2C Phase	GPS civilian carrier phase broadcast on the L2 frequency became available with Block IIR-M.
L2C SD Phase	L2C Single-difference (single-frequency) phase count is the difference of two SV phase count measurements (two L2C measurements). The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. However, ionosphere effects are still present. If you request SD Phase measurements, then ODTK converts the "raw" phase count measurements to SD Phase measurements and does not process the "raw" phase-count measurements.
L2C Pseudo-range	GPS L2 civilian pseudo-range became available with the first Block IIR-M. The range between the GNSS space vehicle (SV) and the user's receiver is the modeled measurement.
L2C SD Pseudo-range	L2C single difference pseudo-range is the difference of two distinct SV L2 C code range measurements. The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. If you request L2C SD measurements (by adding L2 SD Pseudo-range to the GPS receiver MeasurementStatistics and to the MeasTypes on the satellite), then ODTK converts L2C measurements to L2C SD measurements and does not process the pure L2C measurements.
L5 Phase	GPS civilian carrier phase broadcast on the L5 frequency became available with Block IIF.
L5 SD Phase	L5C Single-difference (single-frequency) phase count is the difference of two SV phase count measurements (two L5 measurements). The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. However, ionosphere effects are still present. If you request SD Phase measurements, then ODTK converts the "raw" phase count measurements to SD Phase measurements and does not process the "raw" phase-count measurements.
L5 Pseudo-range	GPS L5 civilian pseudo-range became available with the first Block IIF. The range between the GNSS space vehicle (SV) and the user's receiver is the modeled measurement.
L5 SD Pseudo-range	L5 single difference pseudo-range is the difference of two distinct SV L5 C code range measurements. The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. If you request L5C SD measurements (by adding L5 SD Pseudo-range to the GPS receiver MeasurementStatistics and to the MeasTypes on the satellite), then ODTK converts L5C measurements to L5 SD measurements and does not process the pure L5 measurements.
L2C_L1C DF Phase L2C_L1CA DF Phase L5_L1CA DF Phase L5_L2C DF Phase L5_L1C DF SD Phase	These are GPS dual frequency (DF) phase measurements (using the modernization signals) computed by mathematically combining the two single-frequency “raw” carrier phase measurements to produce a measurement that is independent of the first-order effects of the ionosphere. If you select DF measurements, then ODTK converts the corresponding “raw” single-frequency measurements to DF measurements and does not process the single-frequency measurements.
L2C_L1C DF SD Phase L2C_L1CA DF SD Phase L5_L1CA DF SD Phase L5_L1C DF SD Phase L5_L2C DF SD Phase	This is a single-differenced dual frequency measurement using a GPS modernization signals’ DF phase. This means that the DF Phase is computed for two satellites that are being simultaneously tracked and that these two DF measurements are then differenced. These types of measurements are free from the effects of the ionosphere and the receiver clock bias.
L2C_L1C DF Pseudo-range L2C_L1CA DF Pseudo-range L5_L1CA DF Pseudo-range L5_L2C DF Pseudo-range L5_L1C DF SD Pseudo-range	These are GPS dual frequency (DF) range measurements (using the modernization signals) computed by mathematically combining the two single-frequency “raw” pseudo-range measurements to produce a measurement that is independent of the first-order effects of the ionosphere. If you select DF measurements, then ODTK converts the corresponding “raw” single-frequency measurements to DF measurements and does not process the single-frequency measurements.
L2C_L1C DF SD Pseudo-range L2C_L1CA DF SD Pseudo-range L5_L1CA DF SD Pseudo-range L5_L2C DF SD Pseudo-range L5_L1C DF SD Pseudo-range	This is a single-differenced dual frequency measurement using the GPS modernization signals’ DF pseudo-range. This means that the DF Pseudo-range is computed for two satellites that are being simultaneously tracked and that these two DF measurements are then differenced. These types of measurements are free from the effects of the ionosphere and the receiver clock bias.
LEX Phase	This is a QZSS experimental measurement, a carrier phase measurement broadcast on the LEX frequency (same as the Galileo E6 frequency). ODTK does not support this.
LEX SD Phase	This is a LEX Single-difference (single-frequency) phase count. ODTK does not support this.
LEX Pseudo-range	This is a QZSS experimental measurement, a range measurement using LEX frequency (same as Galileo E6 frequency). ODTK does not support this.
LEX SD Pseudo-range	This is a LEX single-differenced pseudo-range. ODTK does not support this.
NPRange	This is the model of range as a "Normal Point," as described by the International Laser Ranging Service. Normal Point Range has become the ILRS standard for reporting satellite laser range data. For details of the formation of Normal Point data, see the ILRS web site at https://ilrs.gsfc.nasa.gov/.
OpNav Landmark Declination	Landmark-based Optical Navigation Declination is the one-way derived declination measurement of a target body feature relative to a satellite’s tracking instrument in inertial space. The tracking instrument represents a pinhole camera that captures a picture of a resolved target body feature. The resolved feature bearing relative to the camera is derived from the image using image processing. ODTK computes measurement noise from the TrackingInstrument PixelSpaceDirectionalNoise setting. You can specify biases affecting measurement values by using settings in the TrackingInstrument OpNavCamera attribute. Specify landmark IDs and locations by providing a Landmark Database File associated with particular central bodies in the Scenario CentralBodiesList. ODTK does not directly simulate Landmark measurements. Instead, you can activate this simulation using a specialized functional attribute on the Simulator, SimulateLandmarkOpNav.
OpNav Landmark Right Ascension	Landmark-based Optical Navigation Right Ascension is the one-way derived right ascension measurement of a target body feature relative to a satellite’s tracking instrument in inertial space. The tracking instrument represents a pinhole camera that captures a picture of a resolved target body feature. The resolved feature bearing relative to the camera is derived from the image using image processing. ODTK computes measurement noise from the TrackingInstrument PixelSpaceDirectionalNoise setting. You can specify biases affecting measurement values by using settings in the TrackingInstrument OpNavCamera attribute. Specify landmark IDs and locations by providing a Landmark Database File associated with particular central bodies in the Scenario CentralBodiesList. ODTK does not directly simulate Landmark measurements. Instead, you can activate this simulation using a specialized functional attribute on the Simulator, SimulateLandmarkOpNav.
OpNav Point Declination	Point-based Optical Navigation Declination is the one-way derived declination measurement of a target body relative to a satellite’s tracking instrument in inertial space. The tracking instrument represents a pinhole camera that captures a picture of an unresolved target body against a space background. The unresolved target body bearing relative to the camera is derived from the image using image processing. ODTK can ascertain the center either against the star background astrometrically or using image processing methods and biases. ODTK computes measurement noise from the TrackingInstrument PixelSpaceDirectionalNoise setting if you set the TrackingInstrument PointObservationMethod to image processing; otherwise, ODTK takes the measurement noise from the associated measurement statistics.
OpNav Point Right Ascension	Point-based Optical Navigation Right Ascension is a one-way derived right ascension measurement of a target body relative to a satellite’s tracking instrument in inertial space. The tracking instrument represents a pinhole camera which captures a picture of an unresolved target body against a space background. The unresolved target body bearing relative to the camera is derived from the image using image processing. ODTK can ascertain the center either against the star background astrometrically or using image processing methods and biases. ODTK computes measurement noise from the TrackingInstrument PixelSpaceDirectionalNoise setting if you set the TrackingInstrument PointObservationMethod to image processing; otherwise, ODTK takes the measurement noise from the associated measurement statistics.
OpNav Limb Declination	Limb-based Optical Navigation Declination is the one-way derived declination measurement of a target body relative to a satellite’s tracking instrument in inertial space. The tracking instrument represents a pinhole camera which captures a picture of a resolved target body limb against a space background. The resolved target body bearing relative to the camera is derived from the image using image processing. ODTK computes measurement noise from the TrackingInstrument PixelSpaceDirectionalNoise setting. Biases affecting measurement values are defined in the TrackingInstrument OpNavCamera settings.
OpNav Limb Right Ascension	Limb-based Optical Navigation Right Ascension is the one-way derived right ascension measurement of a target body relative to a satellite’s tracking instrument in inertial space. The tracking instrument represents a pinhole camera which captures a picture of a resolved target body limb against a space background. The resolved target body bearing relative to the camera is derived from the image using image processing. ODTK computes measurement noise from the TrackingInstrument PixelSpaceDirectionalNoise setting. Biases affecting measurement values are defined in the TrackingInstrument OpNavCamera settings.
OpNav Limb Range	Limb-based Optical Navigation Range is the one-way derived range measurement of a target body relative to a satellite’s tracking instrument in inertial space. The tracking instrument represents a pinhole camera which captures a picture of a resolved target body limb against a space background. The resolved target body range relative to the camera is derived from the image using image processing. ODTK computes measurement noise from the TrackingInstrument LimbRoughness setting.
P1 Pseudo-range P2 Pseudo-range	These pseudo-ranges are computed on the basis of the P code on the L1 (P1) and L2 (P2) frequencies. It is these two pseudo-ranges that are combined to generate the DF pseudo-range (see below). A GPS receiver directly measures CA, P1, and P2 pseudo-ranges. P1 and P2, however, are available only to military receivers and a new class of receivers that use patented algorithms to measure P1 and P2 without directly locking onto the P code.
RCA Pseudo-range RCB Pseudo-range	This is GLONASS SA pseudo-range. RCA is associated with the G1 frequency; RCB is associated with the G2 frequency. The range between the GNSS space vehicle (SV) and the user's receiver is the modeled measurement.
RCA SD Pseudo-range RCB SD Pseudo-range	This is GLONASS SA single-differenced pseudo-range. The modeled measurement is the difference of two distinct SV SA pseudo-range measurements. The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. If you request RCA/RCB measurements (by adding RCA SD Pseudo-range or RCB SD Pseudo-range to the receiver MeasurementStatistics and to the MeasTypes on the satellite), then ODTK converts the “raw” measurements to SD measurements and does not process the pure “raw” measurements.
RDF Pseudo-range	These are GLONASS dual frequency (DF) range measurements computed by mathematically combining the two HA single-frequency RP1 and RP2 pseudo-range measurements to produce a measurement that is independent of the first-order effects of the ionosphere. If you select DF measurements, then ODTK converts the corresponding “raw” single-frequency measurements to DF measurements and does not process the single-frequency measurements.
RDF SD Pseudo-range	This is a single-differenced dual frequency measurement using GLONASS DF pseudo-range. The DF Pseudo-range is computed for two satellites that are being simultaneously tracked and that these two DF measurements are then differenced. These types of measurements are free from the effects of the ionosphere and the receiver clock bias.
RP1 Pseudo-range RP2 Pseudo-range	These are GLONASS HA pseudo-ranges. RP1 is associated with the G1 frequency; RP2 is associated with the G2 frequency. The range between the GNSS space vehicle (SV) and the user's receiver is the modeled measurement.
RLA Phase RLB Phase	These are GLONASS SA carrier phase measurements. RLA is associated with the G1 frequency; RLB is associated with the G2 frequency.
RLA SD Phase RLB SD Phase	GLONASS SA single-differenced phase is the difference of two distinct SV SA phase measurements. The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. If you request RLA/RLB measurements (by adding RLA SD Pseudo-range or RLB SD Pseudo-range to the receiver MeasurementStatistics and to the MeasTypes on the satellite), then ODTK converts the “raw” measurements to SD measurements and does not process the pure “raw” measurements.
RL1 Phase RL2 Phase	These are GLONASS HA carrier phase measurements. RL1 is associated with the G1 frequency; RL2 is associated with the G2 frequency.
RL1 SD Phase RL2 SD Phase	A GLONASS HA single-differenced phase measurement is the difference of two distinct SV SA phase measurements. The receiver clock errors are eliminated from the measurement model, obviating the need to estimate receiver clock phase and frequency. If you request RL1/RL2 measurements (by adding RL1 SD Pseudo-range or RL2 SD Pseudo-range to the receiver MeasurementStatistics and to the MeasTypes on the satellite), then ODTK converts the “raw” measurements to SD measurements and does not process the pure “raw” measurements.
RDF Phase	A GLONASS dual frequency (DF) phase measurement is computed by mathematically combining the two HA single-frequency RL1 and RL2 phase measurements to produce a measurement that is independent of the first-order effects of the ionosphere. If you select DF measurements, then ODTK converts the corresponding “raw” single-frequency measurements to DF measurements and does not process the single-frequency measurements.
RDF SD Phase	This is a single-differenced dual frequency measurement using GLONASS DF phase. This means that the DF Phase is computed for two satellites that are being simultaneously tracked and that these two DF measurements are then differenced. These types of measurements are free from the effects of the ionosphere and the receiver clock bias.
Range	This is the distance from a ground station to a satellite. More formally, it is the time delay of a radio signal from transmitter to receiver. Internally, ODTK models the two-way range, which is the round trip light time delay from the ground station transmitter through the satellite transponder and back to the ground station receiver. However, it can represent range-related inputs and outputs as either one way or two way depending on the setting for the Scenario.RoundTripRepresentation attribute.
Right Ascension Declination	This is a pair of ground station angle measurements that you can use together to determine a line-of-sight point vector from the ground station to the satellite. Given the definition of a reference frame with an "equator" and "north pole", right ascension is analogous to longitude and declination is analogous to latitude. The reference frame may be MEME J2000, MEME of Date, TEME of Date, or TETE of Date.
Right Ascension Rate Declination Rate	This is a pair of ground station angle rate measurements that you can use together to determine the rate of change of a line-of-sight point vector from the ground station to the satellite. The Right Ascension and Declination rates are computed as the finite difference of the Right Ascension and Declination angles over the specified integration interval. The time tag of the rate measurements can be specified as corresponding with either the end or middle of the integration interval. Given the definition of a reference frame with an "equator" and "north pole", right ascension is analogous to longitude and declination is analogous to latitude. The reference frame may be MEME J2000, MEME of Date, TEME of Date, or TETE of Date.
SB 1W Doppler	This is a space-based, one-way Doppler measurement where the range signal is transmitted from one satellite and received at a tracking instrument attached to a second satellite. The measured value of Doppler depends on the frequency offset of the transmitting satellite clock in addition to the geometry and environment conditions.
SB 1W Range	This is a space-based, one-way range measurement where the range signal is transmitted from one satellite and received by a tracking instrument attached to another satellite. The measured value of range is dependent on the phase offset of the transmitting satellite's clock in addition to environmental conditions and geometry.
SB FDOA	A Frequency Difference of Arrival measurement is determined from a signal that travels from a ground-based emitter to two satellites (path 1 and path 2). The path 1 satellite must have a tracking instrument subobject defined. The measurement is time-tagged at the time of receipt on path 1 and is computed as the received frequency on path 2 minus the received frequency on path 1.
SB FDOA SBE	This is a Frequency Difference of Arrival measurement, where a signal travels from a space-based emitter to two satellites (path 1 and path 2). The path 1 satellite must have a tracking instrument subobject defined. The measurement is time-tagged at the time of receipt on path 1 and is computed as the received frequency on path 2 minus the received frequency on path 1.
SB Range SB Doppler SB Azimuth SB Elevation	Space-based Range is similar to Range except that the observer is a satellite-based tracking instrument instead of a ground station. Space-based Doppler is similar to Doppler except that the the observer is a satellite-based tracking instrument instead of a ground station. Space-based Azimuth and Elevation are similar to Azimuth and Elevation except that the observer is a satellite-based tracking instrument instead of a ground station and the azimuth plane is tangent to a sphere instead of the earth ellipsoid (as defined below). In other words, these are space-based angular measures from a tracking platform to a target. SB Elevation is the angle made with the local horizontal plane, which is normal to the satellite position vector. SB elevation is positive above the local horizontal and negative below. SB Azimuth is measured in the local horizontal plane, from the instantaneous ECEF north, positive to the east. This measurement includes the light time delay from the target to the tracker, and its time tag is at the receive time at the tracker. The space-based azimuth and elevation coordinate system is a true equator, true equinox, Earth-centered, and Earth-fixed system. The azimuth plane is perpendicular to the radius vector from the Earth's center to the sensor. Azimuth is a horizontal angle measured in the azimuth plane clockwise (eastward) from the North. Elevation is a vertical angle measured from the azimuth plane, positive up to the satellite.
SB Right Ascension SB Declination	Space-based Right Ascension and Declination is similar to Right Ascension and Declination except that the observer is a satellite-based tracking instrument instead of a ground station.
SB Right Ascension Rate SB Declination Rate	Space-based Right Ascension Rate and Declination Rate are similar to Right Ascension Rate and Declination Rate except that the observer is a satellite-based tracking instrument instead of a ground station.
SB TDOA	For these measurements, a signal travels from a ground-based emitter to two satellites (path 1 and path 2). The path 1 satellite must have a TrackingInstrument subobject defined. The measurement is time-tagged at the time of receipt on path 1 and is computed as the time of receipt on path 2 minus the time of receipt on path 1.
SB TDOA SBE	For these measurements, a signal travels from a space-based emitter to two satellites (path 1 and path 2). The path 1 satellite must have a tracking instrument subobject defined. The measurement is time-tagged at the time of receipt on path 1 and is computed as the time of receipt on path 2 minus the time of receipt on path 1.
SB TDOA Dot	This is the rate of change of SB TDOA, computed as an instantaneous derivative with respect to time.
SD DF Phase Range	This is a single-differenced dual frequency phase range. The modeled measurement is the difference of two dual-frequency phase range measurements. These measurements are free from the effects of the ionosphere and receiver clock errors.
SD FDOA	This is a single-differenced Frequency Difference of Arrival measurement, defined as the difference between two FDOA measurements at the same time with common relay satellites and a common receive station. Only the emitter is different. The measurement is computed as (FDOA 2 – FDOA 1). This type of measurement differences out errors in the downlink to the receive station, but also weakens the geometrical information.
SD TDOA	A Single-differenced Time Difference of Arrival measurement represents the difference between two TDOA measurements at the same time with common relay satellites and a common receive station. Only the emitter is different. The measurement is computed as (TDOA 2 – TDOA 1). This type of measurement differences out errors in the downlink to the receive station, but also weakens the geometrical information.
TDOA	For a Time Difference of Arrival measurement, a signal travels from an emitter through relay transponders on two satellites (path 1 and path 2) to a common receive station. The measurement is time-tagged at the time of receipt on path 1 and is computed as the time of receipt on path 2 minus the time of receipt on path 1.
TDOA 2 Emitters	For this Time Difference of Arrival measurement, signals travel from two emitters through a relay transponder on a satellite (path 1 and path 2) to a common receive station. The measurement is time-tagged at the time of receipt on path 1 and is computed as the time of receipt on path 2 minus the time of receipt on path 1.
TDOA 2 Receivers	This is a Time Difference of Arrival measurement where a signal travels from a ground-based emitter through relay transponders on two satellites (path 1 and path 2) to two receive stations. Signal path 1 is emitter-satellite 1-station 1. Signal path 2 is emitter-satellite 2-station 2. The measurement is time-tagged at the time of receipt at station 2 and is computed as the time of receipt on path 2 minus the time of receipt on path 1.
TDOA Dot	This is the rate of change of TDOA, computed as an instantaneous derivative with respect to time.
TDOA Dot 2 Emitters	This is the rate of change of TDOA 2 Emitters, computed as the change in TDOA over the supplied count interval.
X Y Angles	This is a pair of ground station angle measurements. The X angle is measured as the angle between the zenith direction and the projection of the relative position vector into a reference plane. The Y angle is measured as the angle between the relative position vector and the reference plane. The orientation of the reference plane depends on the Antenna MountType. You can have ODTK model X and Y angles with or without light time delay. If you include light time delay, then the modeling assumes one-way measurements with the measurement time tag as the ground reception time. ODTK applies aberration corrections based on the facility AberrationCorrection setting when you set LightTimeDelay to true.

For more complete descriptions of these measurement types, see ODTK Orbit Determination: Theorems & Equations. For a walkthrough of ODTK's TDRSS range and Doppler models, see Processing TDRSS Data with ODTK. For a walkthrough of ODTK's TDOA and FDOA models, see Processing TDOA and FDOA Data with ODTK.

Measurement statistics

Depending on the measurement type, you can select one or more of the following measurement statistics:

Measurement Statistics
Property	Description
BiasDriftModel	This identifies the Stochastic Model that ODTK will use to model the Bias Drift parameter. This parameter only pertains to the accelerometer measurement. The options are: GaussMarkov: Bias will be modeled as a scalar exponential Gauss Markov sequence. RandomWalk: Bias will be modeled using a Wiener (Brownian motion) sequence. Vasicek: Bias will be modeled using a Vasicek stochastic sequence. This is a two-parameter model that solves for both a short-term and long-term bias. Reference the Stochastic Model topic for the description and inputs associated with each model.
BiasModel	This identifies the Stochastic Model that ODTK will use to model the measurement bias. The options are: GaussMarkov: Bias will be modeled as a scalar exponential Gauss Markov sequence. RandomWalk: Bias will be modeled using a Wiener (Brownian motion) sequence. Vasicek: Bias will be modeled using a Vasicek stochastic sequence. This is a two-parameter model that solves for both a short-term and long-term bias. Reference the Stochastic Model topic for the description and inputs associated with each model.
BoresightBiasModel	This is relevant for Phased Array range and face angle measurements. When set to true, the applied bias and white noise will vary as function of the angle between the tracking direction and the face normal direction. Bias and noise change will increase as this angle increases by 1/cos(angle).
CountInterval	This is applicable to Doppler only. It specifies the length of the interval over which ODTK generates the Doppler count.
EditOnDoppler	This is applicable to 4L Range and BRTS Range only (for the TDRSS system). ODTK will reject the range measurements if a valid doppler measurement is not available at the same time. You should set this flag to false when processing simulated data in the generic observation format, since knowledge of simultaneous measurements is not available.
EstimateBias	Set this to true if the Filter is to estimate a measurement bias component for this particular measurement type. If estimated, then the Filter will model the bias as a Gauss-Markov parameter using the given Gauss-Markov parameters. You must also set the estimate flag to true if you want to use this parameter as a Least Squares Consider State. When used as a consider state, it is modeled as a constant.
InstantaneousModel	This is applicable to Doppler only, and specifies that the Doppler measurement is to be modeled as “Instantaneous Range-rate.” This model optionally includes troposphere, ionosphere, measurement bias, and time bias corrections. Light time delay and phase center corrections are excluded.
LightTimeDelay	This is applicable to Range, Doppler, Azimuth, Elevation, Right Ascension, Declination, Delta Dec, SB Right Ascension, Delta SB RA, and Delta SB Dec. Select true to compute the light time delay correction during measurement modeling. If the reason for turning off light time delay effects is to model the measurement using only geometry, then to be consistent with that goal, set aberration effects to None in the Optical Properties of the tracker to prevent any aberration corrections from being applied.
ModelInSolarSystemBarycentricFrame	This is applicable to the Range model only. If true, the light time delay solution for the two-way range measurement is computed in the solar system barycentric frame. You should enable this option when processing range measurements to deep-space objects. Enabling this option is appropriate for the modeling of range measurements at any distance, but is more computationally intensive than the Geocentric model, which is used when the option is not enabled.
Randomize	This is applicable to single-differenced pseudo-range measurements only. Changes the order in which pseudo-ranges are combined for differencing from one observation time to the next.
RejectFirstNMeas	This is applicable to 4L Range and BRTS Range only (for the TDRSS system). If set to a number greater than 0, that many observations will be rejected at the beginning of each pass, in addition to the measurements edited out by the EditOnDoppler flag, if any.
Representation	This is applicable to Range and Doppler. It is a read-only value that reflects the setting for the scenario-level attribute, RoundTripRepresentation.
ScaleFactor	This identifies the Stochastic Model that ODTK will use to model an Accelerometer Scale Factor. The options are: GaussMarkov: Bias will be modeled as a scalar exponential Gauss Markov sequence. RandomWalk: Bias will be modeled using a Wiener (Brownian motion) sequence. Vasicek: Bias will be modeled using a Vasicek stochastic sequence. This is a two-parameter model that solves for both a short-term and long-term bias. Reference the Stochastic Model topic for the description and inputs associated with each model.
TimeTagLocation	Specifies the location of the measurement time tag for observations that are measured over a finite interval of time. Options for the time tag location are: at the end of the measurement interval at the middle of the measurement interval TimeTagLocation applies to Right Ascension Rate, SB Right Ascension Rate, Declination Rate, and SB Declination Rate.
TropoNoiseScaling	This is a scale factor for deweighting of phase measurements to account for the unknown variation of the zenith tropospheric delay estimate over the count interval for the phase measurement. Set the value to 1.0 to deweight measurements based on the total process noise added to the tropospheric delay estimate mapped to the current elevation angle. Set the value to 0.0 to ignore variations in the troposphere over the count interval. This setting only has an effect when a troposphere correction is being estimated for the facility hosting the GPS receiver and is usually only used for simulations where the distinction between tropospheric behavior and white noise is known. When simulating L1 Phase, L2 Phase, and deviating tropospheric refraction, then you should set TropoNoiseScaling = 1.
TropoSigma	This is not available on all measurement types. Specify the expected uncertainty in the tropospheric correction to the measurement as a fraction of the tropospheric correction. For example, a value of 0.05 corresponds to a 5% uncertainty in the tropospheric correction. All available troposphere models provide range corrections. Only the SCF model computes a correction to the elevation angle. The computed tropospheric uncertainty is included as part (added in an RSS sense) of the measurement noise contribution to the measurement error variance during the filter measurement update when a zenith tropospheric correction is not being estimated.
WhiteNoiseDeweighting	This is applicable to CA Nav Sol and DF Nav Sol only. This setting affects the processing of Nav Sol measurements during estimation. The effective use of this setting (if you do not select Constant) requires that a GPS constellation object be present and properly defined over the estimation time period and that the GPS satellites used in the generation of the navigation solution are identified in the tracking data. The GPS constellation is required to support the computation of the Dilution of Precision (DOP) associated with the navigation solution. Select between: Constant - The input value of WhiteNoise is used without any additional scaling. Scale by Component DOP - The white noise for each component of the navigation solution will be computed as the input value of WhiteNoise multiplied by the DOP in the direction of that component. You must set the scenario-level attribute EmbeddedWNSigmas.Use to true for this option to function properly. Scale by PDOP - The white noise for all components of the navigation solution will be computed as the input value of WhiteNoise multiplied by the Position Dilution Of Precision (PDOP), where PDOP is determined as the square root of the sum of squares of the component DOPs. You must set the scenario-level attribute EmbeddedWNSigmas.Use to true for this option to function properly. If you select the Constant option, you must provide a larger white noise value during estimation, since it must cover all geometries. Also, the scaling by DOP has a greater impact on the estimation process when the receiver is tracking a smaller number of satellites. The input value of WhiteNoise comes from the tracking data provider when you specify a white noise value in the tracking data; otherwise, it comes from the measurement statistics of the GPS receiver.
WhiteNoiseSigma	This is the square root of the variance representing the random uncertainty in the measurements.