Following are enhancements, limitations, and documentation notes for this version of the NI GNSS Simulation Toolkit.
Insufficient number of satellites selected
For a receiver to acquire a position fix, typically four or more satellites need to be available in the navigation view. With the toolkit simulator, based on the ephemeris file and the time of the week of the chosen, the number of optimal satellites selected may be fewer than four, for certain (rare) locations. When the toolkit is able to select only four satellites or fewer, a receiver position fix or the accuracy of the fix cannot be guaranteed. If such a situation occurs, changing the time or the ephemeris (and corresponding almanac) files may cause the simulator to select a greater number of satellites and hence, a more accurate position fix.
Poor Dilution of Precision
In addition to the number of satellites, the orientation of the satellites with respect to the receiver also plays an important role in determining the accuracy of the position fix, acquired by the receiver. The quality of the satellite orientation is measured by the dilution of precision (DOP) parameter. DOP provides an estimate of the quality of position fix that can be acquired by a receiver for the given satellite geometry and receiver location. In cases when the DOP value is very high (that is, poor), the receiver might not acquire a position fix or the acquired position fix might be inaccurate. The NI GPS Simulation Toolkit 2.0 and later attempts to detect such a situation and displays a warning if the estimated DOP is not sufficient for an accurate fix. If such a situation occurs, changing the time or the ephemeris (and corresponding almanac) files may cause the simulator to select a different set of satellites with better DOP and thus acquire a more accurate position fix.
Context Help Links
When linking to a topic in the NI GPS Simulation Toolkit Help from the context help or opening the help file from a VI within LabVIEW, the NI GPS Simulation Toolkit Help launches and the relevant topic displays, but the location of the topic might not be highlighted in the table of contents.
LabWindows/CVI does not support 64-bit file sizes in 32-bit applications.
Limit the file size to 2 GB or less when you create GNSS files using the Write Waveform to File example in LabWindows/CVI.
Contact NI regarding this document or issues in the document. If you contact NI in regards to a specific issue, reference the ID number given in the document. The ID number contains the current issue ID number as well as the legacy ID number (use the current ID number when contacting NI). You can contact us through any of the normal support channels including phone, email, or the discussion forums. Visit the NI Website to contact us. Also contact us if you find a workaround for an issue that is not listed in the document.