You can specify an external region list file (.rl) that contains user-defined points defining a specific grid region. Inside the RegionList are several keywords that identify the name of the regions as well as the list of boundary points for the region. Each region list file contains some common elements:
Keywords used in every region list file
| Keywords | Description |
|---|---|
| STK version number | The version of STK software for which the file is formatted to be used. |
| BEGIN RegionList END RegionList keywords |
Set off the beginning and end of the RegionList keyword group. |
The structure of a generic Region List file, then, looks something like:
Generic region list file structure
stk.v.6.0
Begin RegionList
.
.
.
End RegionList
The region list file can contain data to model one or several regions. To include a region, enclose the data in a BEGIN Region and END Region keyword phrase, which should include the following keywords and data points:
<RegionName> - Name of the region being modeled. It is not mandatory that you include the RegionName in your file.
<Latitude> <Longitude> pairs - Perimeter points that define an area. In degrees.
<ApplyWindingInclusionCheck> (Yes, No) - Indicates if a winding inclusion check will be applied to determine which side of the boundary is considered to be "inside". If Yes is specified, inclusion is defined to the right side of the boundary when along the boundary in the provided order of the points. For example, a circular boundary will be determined to include the inside of the circle if the points are specified in a clockwise order. This is useful if you want to represent an outer region with a hole inside. In the case of two circular regions, the outer region is specified with points in clockwise order, while the inner region is specified with points in a counter-clockwise order. This specification can also be used to define a region that spans more than half the globe. The ApplyWindingInclusionCheck is specified individually for each region in the file, and has a default of No when not specified. When No is specified or the keyword is omitted, the interior of the region is determined to encompass the smallest area.
A sample Region List file format is provided for your reference. Data contained in the region list file is geodetic latitude and longitude points.
Sample Region List file format
stk.v.4.2.1
Begin RegionList
Begin Region
RegionName CONUS
Begin BoundaryPoints
4.838850e+01 -1.247141e+02
4.892370e+01 -1.233761e+02
4.892370e+01 -1.207893e+02
4.883450e+01 -1.177564e+02
4.883450e+01 -1.158832e+02
4.883450e+01 -1.130287e+02
4.892370e+01 -1.105311e+02
4.892370e+01 -1.077658e+02
4.883450e+01 -1.051790e+02
4.883450e+01 -1.019677e+02
4.892370e+01 -9.929170e+01
4.883450e+01 -9.759680e+01
4.892370e+01 -9.599120e+01
.
.
.
3.813030e+01 -1.231085e+02
3.982520e+01 -1.240897e+02
4.178760e+01 -1.243573e+02
4.285800e+01 -1.241789e+02
4.517730e+01 -1.240005e+02
4.669370e+01 -1.238221e+02
4.838850e+01 -1.247141e+02
End BoundaryPoints
End Region
Begin Region
RegionName Alaska
Begin BoundaryPoints
6.957420e+01 -1.410545e+02
.
.
.
5.994430e+01 -1.416323e+02
5.989610e+01 -1.408619e+02
6.360370e+01 -1.410063e+02
6.716670e+01 -1.410063e+02
6.957420e+01 -1.410545e+02
End BoundaryPoints
End Region
End RegionList