GPS Sim

This app allows you to broadcast GPS baseband signal data streams.

Generator

You can use gps-sdr-sim to generate data for this app.

gps-sdr-sim -e RINEX_NAVIGATION_FILE -l LAT,LONG,HEIGHT -b 8 -o SOMENAME.C8

That will create SOMENAME.C8, but note that you also need to specify its sample rate and frequency in another file, as explained below.

RINEX navigation file for GPS ephemerides

Download the latest file for this parameter directly from Nasa: https://cddis.nasa.gov/archive/gnss/data/daily/

Sample rate and frequency specification

Create SOMENAME.TXT with:

sample_rate=SAMPLE_RATE
center_frequency=1575420000

Known working values for the SAMPLE_RATE:

• 2600000
• 2500000
• 1250000

This file should use the same filename as the .C8 file but with .TXT extension. It contains the sample rate and center frequency for the .C8 file. Copy the files to your PortaPack MicroSD and open the .C8 file in the GPS Sim app.

Example 1

Create a rather small polygon with a path in KML format (i.e. a path you might want to simulate to walk). You can use Google Earth or another solution like https://www.doogal.co.uk/polylines.php. Load that file in the free SatGen NMEA simulator. In the generator, change the frequency to 10 Hz and export the NMEA.

gps-sdr-sim.exe -e brdc1180.20n -g NMEA.txt -b 8 -o TESTGPS.C8

You also need to create TESTGPS.TXT as specified above.

Example 2

For a fixed position, use gps-sdr-sim -e brdc1500.20n -s 1250000 -b 8 -o gpssim.C8 -l 30.286502,120.032669,100 -d 100

Test with a gpssim.txt as follows:

sample_rate=1250000
center_frequency=1575420000

Example 3

NOTE: The website nmeagen may add timestamps to the output. That might be problematic for the simulation

We can create a realistic movement using a NMEA GGA stream generator like https://nmeagen.org/. In this website create several multi point lines with the positions you want. Download the NMEA file clicking "Generate NMEA file".

gps-sdr-sim.exe -e brdc3540.14n -g OUTPUT.nmea -b 8 -d DURATION -o MYGPSWALK.C8

You also need to create MYGPSWALK.TXT as specified above.

Compatibility

Depending on several factors, results may vary. A modern device will use several sources and methods to validate the current position, so spoofing positions may not be possible in all situations. To improve your chances to receive simulated GPS data, try:

• Turn off Wifi/BT/Cellular and positioning-enhancements (best airplane mode)
• Go inside, where the device loses GPS signal
• Reboot the device after doing the previous two steps

If the device runs Android, follow your attempts with GPS Test.

Known results

Type	Make	Model	Locks on spoofed GPS?	GPS acts "jammed"?	Comments
Tablet	Samsung	Note 7	No	Yes
Phone	Samsung	S8	Yes	No	WIFI must be off
Phone	Huawei	P30 lite	No	Yes
Phone	Huawei	Mate 10 Pro	No	NO	6 or 7 satelites: No fix
Smartwatch	Huawei	Amazfit Bip	Yes	No
Phone	Apple	iPhone 6	Yes	No	Works with WIFI on
Phone	ZTE	Axon 7	Yes	No	Works with WIFI on
Phone	Xiaomi	Mi5	Yes	No	Works with WIFI on
Phone	Samsung	S20+ 4G	Yes	No	WIFI must be off
Smartwatch	Samsung	Gear S3 WiFi	Yes	No	Location over GPS only
Phone	OnePlus	7 Pro	No	No	Doesn't seem to do anything
Phone	Samsung	S21 Ultra	Yes	No

References

https://blog.csdn.net/shukebeta008/article/details/103270214