Here is how GPS system works:
The latitude and longitude of point of interest/street/polygon are stored in a GPS map file.
GPS owner then uses an application (send map) to send GPS map file to GPS device.
In order to make E680i become a GPS receiver such as Garmin device, I have to:
1. Study GPS map file format and understand how latitude and longitude of point of interest/street/polygon are stored.
2. Come out with algorithm to convert latitude and longitude to XYZ
3. Build a program to draw a map on E680i based on the infomation in GPS map file.
After the above steps are done, then we just copy any GPS map file to E680i and use it like a garmin device.
There are a lot of works need to be done, and I am just in initial stage.
I am going to make E680i/A780 become GPS receiver 
Linear Mode
