Support for GPS Devices

With version 2.3, TransDEM supports external GPS devices, as a geo data source or as a geo data target.

As a source, a GPS device can be used to record GPS position data in TransDEM. As a target to export georeferenced raster maps in a format compatible with certain Garmin® models.

Recording GPS Track Logs

GPS devices which support the NMEA1083 protocol, can be connected to the computer TransDEM runs on. TransDEM will then receive and record the GPS coordinates, draw the trace on top of a map or a DEM and optionally save to file in one of the TransDEM supported vector formats. For GPS devices with a USB interface, a third-party converter software is needed, like GpsGate.

Mobile PCs, from Lapbook to Netbook, running Windows (full version), are suitable devices for TransDEM to record GPS data en route. For this, TransDEM shall have loaded arbitrary georeferenced maps and DEMs, covering the current position. The larger screen allows more complex geo data visualisation than on the GPS device itself.

Navigating the Leeds & Liverpool Canal in Yorkshire, UK. GPS track-log by Netbook on top of a 1:50;000 historic topographic map and 50m DEM data.

Export of Raster Maps as a KMZ Package

TransDEM can export one or more raster maps, including different scale, as a package in .kmz format which can be used by recent Garmin® models that support mapping. Creation and export of a .kmz package is largely automated and optimised for the requirements of Garmin devices.

The export region can be defined by a rectangular mask and/or by a vector path.

During export, TransDEM transforms the coordinates and splits the export region into suitably sized tiles, determined by scale, by employing a quad tree. Image tiles and description data are then compressed into a single KMZ package.

Three KMZ export examples as screenshots taken on a Garmin Montana™:

Some Garmin devices also allow to combine different scale raster images. TransDEM tales a layered approach to support this feature.

In this example ortho images are added to an historic UK topo map 1:50,000 (Foxton Locks as above) In TransDEM it looks like this:

On the Garmin Montana™, the larger scale ortho images are only shown when zoomed in:

TransDEM created raster map KMZ packages can also be used with Google Earth. This may be helpful to check the results before uploading them to the GPS device.

Exported tiles in a .kmz package, visualized in Google Earth. The export was defined by a path, the Durango & Silverton Railroad in Colorado in this example.

© 2012 Roland Ziegler