The GPS Locator software is used to predict the GPS and Glonass satellite coverage from an observer’s location. It was written to assist in determining how many GPS satellites were in view from the westerly facing balcony of my apartment, for use with the Blitzortung lightning detection network. Once the observable satellite count gets below 3, then it would stop working, so was useful to estimate how many hours per day it would not work, and also assist in finding a better location.

 

This software has been dis-continued.

Most of the functionality has been included within the MySky2 software.

 


The GPS Locator software requires that the Microsoft Visual  C++ 2013 Redistributable (x86)  is installed on the PC before it will run. This can be downloaded from https://www.microsoft.com/en-sg/download/details.aspx?id=40784. Select the download for vcredist_x86.exe.

To install The GPS Locator software, extract the installer EXE file from the ZIP file and run it.

  1. When the software is started for the first time, it will request the user to download the current TLE data from the internet (TLE = Two Line Element), which will be stored in 3 files on disk. The directory for storing these files can be selected by the user during download, with the default location be set to the root directory on D: drive.
  2. An internet connection is required when downloading TLE data. To download the TLE data, click on File->Download/Update TLE files. If the TLE data is not downloaded in this first step, then you will not be able see any satellite predictions.
  3. The TLE data can be updated at any time from the File menu. After 30 days, the software will start suggesting you should update the TLE data, if not already done. If accurate results are required, the TLE data should be updated after several days.
  4. The data in the TLE files can be previewed by clicking Edit->View TLE. If for any reason, the TLE data becomes corrupted, simply delete these files and download them again.
  5. Update the Latitude and Longitude to your current location. The default location is set for Bangkok, Thailand. It will remember the last entered values upon restarting.
  6. Select the checkbox for the satellite types that you wish to show. GPS satellite will be shown in blue, and Glonass satellites are in red.
  7. Click “Plot/Update Satellite Locations” to show the position in the sky of the satellites.
  8. To see future or past satellite locations, click the right or left arrows. The time is advanced by the value shown in the dropdown box. Note that since the TLE’s change with time, using the current TLEs’ for historical satellite locations, or long term future predictions, is unlikely to be accurate. Click “Revert to Computer Time” to return to the current time.
  9. A click on”Satellite Trails and Visible Count” does two things.
    • Firstly, it shows a satellite trail for +/- 2 hours from the plotted time on the Satellite Location plot
    • Secondly, it displays a plot of the Visible Satellite Count. Graphs are plotted for looking in four directions, these being the N, E, S or W hemispheres. A total count curve is also plotted. The count is composed of all satellite types that have been allowed in the checkboxes (GPS and/or Glonass and/or Other). In the example shown below, we can see that the GPS satellite count in the Western hemisphere drops to 2 for a period of about 1 hour around 14:30 UTC on 18-Oct-2014, which is not enough to get GPS synchronization. However, GPS + Glonass give 7 satellites in view in the Western hemisphere at that time.
  10. A tabular list is also shown. The blue and red entries depict when a satellite is above the observer’s horizon while the black entries are below the observers horizon (the Elevation angle is negative when below the horizon). Azimuth and Elevation are in degrees. The Range column is the distance in kilometres from the observer to a satellite.
  11. You will notice the ISS is included in the “Other Satellites” list. Although this is not a navigation satellite, it may be of interest. Since the ISS is in a Low Earth Orbit, It will only be above the horizon for about 5 minutes, several times a day from any one location on the earth’s surface, so it is difficult to catch. It can only been seen either just before sunrise or just after sunset.

 

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Determining times for passes of the ISS

In its current form, this software is not optimized for following the ISS. However, if you want to find when it passes overhead, then follow this procedure:
  • Uncheck “GPS” and “Glonass”.
  • Check “Other”.
  • Bring up the Satellite Visible Count window
  • Use the Time Advance button to find when a satellite is above the horizon. Fine tune the Time Advance value, so as to centre the satellite pass at zero on the X-axis, as shown below.
  • Check that it is the ISS; it should be green in the List. The other option is it could be Tiangong.
  • Go to the Satellite window to see the ISS location and the observation time. Note the small dots showing the trail are spaced at 1 minute intervals.

GPS locator GPS locator

As mentioned earlier, most times when the ISS passes overhead, you will not be able to see anything. Only when it passes overhead within an hour or so of sunset/sunrise will you be able to see it.