As the navigation electronic maps in China are encrypted , the GPS signal is a true signal , there is a dislocation of about 600 meters: Traditional Chinese Shifting is up to 600 meters in azimuth 260 degrees. Almost inusable in non chinese gps
Every official China City navigators are shifted (governement choice).
You can read here in [Only registered and activated users can see links. ]
Usually after some days from publishing date ,our valuable member syzygy offers us the Venus version, that's is the NON shifted version.
Chineses call the shifted version Mars and the Non shifted version Venus.
If your Garmin device is bought in China or has the capability to add shifts to coordinates received from GPS chipset then use the Official map.
Basically, unless you bought your GPS in China, Venus is the map version you want to be using.
syzygy's advices to use correctly Venus maps:
If you really like to use Venus maps which have the shift corrected and to have no shift in recorded data, your GPS device must be re-configured as below:
1. Uncheck or remove all official City Navigator China and China DEM maps installed in internal memory and SD card.
2. Uncheck or remove all installed maps named gmapoem.img, China Country Map, and SCM Test Map
3. Optionally remove the file 006B082300.bin in internal mempry and SD card. Enable viewing hidden files to find it.
4. Optionally hard-reset the GPS device. Backup your important data first.
If you are using the Venus shift-corrected version, then there is no corresponding shift-corrected gmap3d.img.