Raster Map Export as .kmz Ground Overlay for Garmin GPS

[geophil]

This new feature in the making is not directly related to Trainz. It's primary targeting outdoor GPS devices by Garmin. Their recent models allow custom raster maps. The overall approach to create such custom maps is similar to creating TransDEM UTM tiles. I reuse and extend some of those proven TransDEM methods for the new feature.

The format of such custom maps is a series of jpg images with an accompanying Google Earth kml file for the georeferencing information. For Google Earth and for Garmin, the coordinate system must be geographic lat/long, not UTM. That has been the major challenge: producing a seamless array of raster map clippings in correct lat/long pseudo-projection.

It took some time, but is seems to be working now. There is still need for a lot of fine tuning, though.

Raster map export in Google Earth for an area well known to most TransDEM users:




and on a Garmin Montana:



The examples have topo raster maps at 1:50,000 and 1:25,000 plus an aerial image in larger scale. TransDEM optimizes image resolution and image size for efficient use of the limited custom map capacity on the mobile device.