Measurement Processing
Measurement Types
The MeasTypes property specifies the list of specific measurement models that may be used for the estimation process. If specific measurement types are included in this list, any measurements of types not included will be discarded during the estimation process. An empty MeasTypes list is equivalent to including ALL measurement types.
The default behavior is to create an empty list, which now has the same behavior as including all measurement types. If you want to turn off all measurement types for a facility, satellite, GNSS satellite, or surface vehicle object, set the AllowMeasProcessing flag to false. In the text below, please interpret the term “satellite” to refer to satellites and GNSS satellites.
The MeasTypes list on a facility, satellite, or surface vehicle, if not empty, must contain the types of measurements to be processed from a GNSS Receiver attached to that facility or satellite or surface vehicle. Measurements of types not included in this list will not be processed during estimation even if the associated measurement statistics are defined in the GNSS Receiver.
The contents of the MeasTypes list are not related to the contents of the MeasurementStatistics list, which specifies the types of measurements that may be made of other objects from this facility or satellite or surface vehicle.
Click to the right of the MeasTypes attribute to display a List dialog that enables you to add and remove any or all of the measurement types that are listed. To add measurement types, click to display an Add List dialog box in which you can select the items you want to add. To delete an item, select it in the List dialog box and click . Use for deletion of all measurement types.
When selecting items in the Add List dialog, you can use multi-select techniques with the CTRL and SHIFT keys.
Selection of pseudo-range and phase count measurement types has certain implications to the simulator and filter processes. The following table shows the results of selecting various measurement types for the case where the measurement type list in the facility, satellite, or surface vehicle is the same as that in the filter
| Results of Selecting Various Pseudo-Range Measurement Types | ||
|---|---|---|
| MeasType | Simulator | Filter |
| CA | Generated | Processed if SD CA not selected |
| SD CA | ... | Processed |
| P1 | Generated | Processed if DF and SD DF not selected |
| P2 | Generated | Processed if DF and SD DF not selected |
| DF | ... | Processed if SD DF not selected |
| SD DF | ... | Processed |
| Results of Selecting Various Phase Count Measurement Types | ||
|---|---|---|
| MeasType | Simulator | Filter |
| LA | Generated | Processed if LA SD not selected |
| SD LA | ... | Processed |
| L1 | Generated | Processed if DF , SD DF , SD L1 and SD L2 Phase not selected |
| L2 | Generated | Processed if DF and SD DF, SD L1 and SD L2 Phase not selected |
| DF Phase | ... | Processed if SD DF and SD L1 and SD L2 Phase not selected |
| SD DF Phase | ... | Processed if SD L1 and SD L2 Phase not selected |
| SD L1 and SD L2 | ... | Processed |
As you can see from the above tables, the processing of derived measurements takes precedence over the processing of raw measurements. This enables you to perform, for example, analyses in which you simulate CA pseudo-range measurements and process SD CA pseudo-range measurements without having to change the selected measurement types.
To process any measurement type, including the singly differenced measurement types, the associated measurement statistics must be defined in the GNSS receiver.
You can determine the measurement types that a filter run will process by looking at the measurement types that you selected both in the object (facility, satellite, etc.) list and in the filter list. If you select a derived measurement type in the object but not in the filter, then the filter will not process the associated raw measurement type(s). For example:
- Selecting CA and SD CA in the object and only CA in the filter will result in the processing of CA measurements. Similarly, selecting LA and SD LA in the object and only LA in the filter will result in the processing of LA phase measurements.
- Selecting P1, P2, and DF in the object and only P1 and P2 in the filter will result in the processing of P1 and P2 measurements. Similarly, selecting L1, L2, and DF Phase in the object and only L1 and L2 in the filter will result in the processing of L1 and L2 measurements.
- Selecting P1, P2, DF and SD DF in the object and P1, P2, and DF in the filter will result in the processing of DF measurements. Similarly, selecting L1, L2, DF Phase, and SD DF Phase in the object and L1, L2, and DF Phase in the filter will result in the processing of DF Phase measurements.
- Selecting CA in the object and SD CA in the filter will result in no measurements being processed. Similarly, selecting LA in the object and SD LA in the filter will result in no measurements being processed.
- TDOA, FDOA, SD TDOA, and SD FDOA follow the same rules.
- Direction cosine measurements will be constructed from azimuth and elevation if the direction cosine measurement types are included in the measurement statistics of the facility and direction cosine measurements are included in the MeasTypes list of the object and the filter.
Editing flags
The codes "A " and "U " must include a blank space after the initial letter (because the codes require two characters)
| Editing Flags | ||
|---|---|---|
| Code | Short Title | Description |
| "A " | Accepted | Means accepted. |
| "AD" | Accept High | Residuals are accepted via the Dynamic editing criterion. |
| "DN" | Down Angle | The angle between the direction to the satellite and radar face normal exceeds maximum angle down. |
| "DE" | Deployment Exclusion | The measurement was rejected due to being inside the measurement exclusion interval following a child satellite deployment event. |
| "ED" | Resid High | The Dynamic editor is enabled and residual is still rejected because sigma is above the upper limit of the dynamic editor. |
| "EX" | Earth Exclusion | The measurement was rejected due to an optical instrument pointing too close to the direction to the Earth. This is primarily for objects in orbit about the Moon. |
| "FR" | Forced Rej |
The measurement is one of the first N in a pass and is rejected by user specification to ignore the first N measurements in a track. This option is initially limited to TDRS 4L and BRTS data. Here are some typical cases in which this flag will appear:
|
| "GP" | GNSS Source Error | The GNSS satellite ephemeris is not defined at the current time. |
| "HE" | High El | This measurement is rejected for violation of facility or sensor constraints. |
| "II" | Integration Interval | The measurement was rejected due to it having an invalid integration interval. This applies to GNSS phase measurements. |
| "IO" | Invalid Object | The measurement was rejected because one or more objects in the measurement strand exclude the measurement type in the MeasTypes list. |
| "IT" | Invalid Tracker | The tracker is invalid in the sense that measurement statistics are not defined for the provided measurement type. For example, if a range measurement is being processed for a tracker which doesn't specify range measurements in its Measurement Statistics properties, then the measurement will be rejected with an "IT" flag. |
| "LE" | Low El | The measurement was rejected for violation of facility or sensor constraints. |
| "LG" | Low Graze | The measurement was rejected for satellite-to-satellite signal path passing below a minimum altitude. |
| "LX" | Lunar Exclusion | The measurement was rejected due to optical instrument pointing too close to the direction to the Moon. This is primarily for objects in orbit about the Earth. |
| "ME" | Measurement Exclusion | The measurement was rejected due to time falling within instant maneuver exclusion interval. |
| "ND" | No Doppler | The range is invalid if there is no Doppler measurement reported. This option is initially limited to TDRS 4L and BRTS range. |
| "NL" | Not Lit | The measurement was rejected due to violation of a required lighting condition. |
| "NV" | Not Visible | The measurement was rejected due to obstruction by a central body or not being within a camera field of view. |
| "OB" | Masked | Measurements are rejected if they are out-of-bounds with respect to the facility mask. The residuals are not computed. |
| "PA" | Phase Angle | The measurement was rejected due to bad phase angle geometry. The phase angle is the angle between the directions to the Sun and to the camera measured at the target location. |
| "PE" | Pole Excl | Edited angles data were collected too close to elevation of 90 deg or a Right Ascension of 90 degrees. |
| "RE" | Residual | The filter rejected the residual based on residual magnitude versus covariance. |
| "SB" | Space Background | The measurement was rejected because geometry does not indicate a space background when looking from the camera to the target. |
| "SE" | High Sun Elevation | The measurement was rejected due to the sun being at too high of an elevation angle. |
| "SN" | SNR | A GNSS receiver reported SNR below analyst-selected cutoff. |
| "SR" | Satellite Reference Ephemeris | Object ephemeris is not defined at current time. This is for the case where a satellite orbit or surface vehicle trajectory is not estimated. A reference ephemeris does not need to span the entire simulation interval for you to use it in simulating measurements, as long as you use a custom simulation schedule that restricts the simulation of measurements for the object using the reference ephemeris to be within the span of that ephemeris. When this situation occurs, the state history and generated ephemeris file from the simulator for the object of interest will indicate a constant position and velocity for the object during period outside the span of the reference. |
| "SX" | Sun Exclusion | The measurement was rejected due to an optical instrument pointing too close to the direction to the Sun. |
| "TR" | Tracker Reference Ephemeris | Tracker ephemeris is not defined at current time. |
| "U " | Unknown | This is a catch-all for a variety of extremely rare errors. |
| "WN" | Invalid WN | An invalid white noise can arise if the noise statistics are embedded in the tracking data and an invalid number is encountered (e.g. a negative number). |
If a residual type is rejected because of designation under the RejectMeasTypes attribute, it will nominally be designated as RE, but the residual is evaluated against other rejection conditions and can be labeled with most of the other codes.
Additional parameters
The measurement processing settings for an object include, in addition to the above, the following parameters:
| Measurement Processing Parameters | |
|---|---|
| Parameter | Description |
| TrackingID | Enter an integer representing the tracking ID. |
| TrackingIDAliases | See this description. |
| AllowMeasProcessing | Set this to false to turn off the use of all measurement types. |
| MeasTypes | Select each measurement type to be processed. An empty MeasTypes list is equivalent to including all measurement types. |
| MinPassDelta | Enter a time value to define the minimum interval between measurements to constitute a new pass. |