Transfer GPS-data, gpx -Format (e.g. from Garmin Dakota/Oregon devices), to a GIS Application (here: gvsig, Open Source GIS)

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1 Transfer GPS-data, gpx -Format (e.g. from Garmin Dakota/Oregon devices), to a GIS Application (here: gvsig, Open Source GIS) 2012, by Klaus Schäfer, GIZ-Advisor RS Kilimanjaro, Moshi Version , last update: Step 01: In this optional step we compile several individual gpx files into a single gpx file with the help of the GPSBabel utility. Since GPS-devices deliver daily work files, which has it's own benefits, one may want to merge all this files for simple, single processing. GPSBabel (current version 1.4.4, released ) is a free software that allows converting files of different GPS/GIS-formats into another format and/or, as we do here, to compile multiple files into a single one of the same format. The picture below shows the settings in GPSBabel for this purpose. Picture 1: GPSBabel - compiling several gpx files into a single one The actual version of the software can be downloaded here:

2 Step 02: Unfortunately, gvsig does not allow for direct import of gpx files. Hence another step is needed to convert the gpx -file into a format that GIS (gvsig) can read. Here a tool named DNRGarmin (current version , released ) comes into play. In fact, there is a newer version of the software, called DNRGPS (current version , released ). Both versions are free software, developed by the Minnesota Department of Natural Resources, that can be downloaded here: and Since DNRGPS creates 3D spacial objects, which still may create problems in gvsig, this description refers to the DNRGarmin version, which works with 2D spacial objects only. Nevertheless, DNRGPS may be used and in most cases works more comfortable, e.g. allows for direct data storing into PostgreSQL/PostGIS spacial database tables. First, the gpx -file shall be loaded into DNRGarmin. When opening the file, the application asks for the type of objects to be loaded. Waypoints should be selected in this dialogue. Picture 2: DNRGarmin select waypoints to be loaded Next we should look into some configurations of DNRGarmin. Per default many waypoint attributes are defined which do not receive data from the file. This attributes should be made invisible. The Waypoint Properties dialogue allows to select the relevant fields. Picture 3: DNRGarmin select relevant waypoint attributes

3 The gpx -file contains raw (unprojected) data, regarding projection and date/time information. This means, the projection is given as WGS84, POSC code 4326 (lat/long, decimal format). If we choose not to project the coordinates different, we can use it as is. Both pairs of lat/long and y_proj/x_proj show the same values. Picture 4: DNRGarmin unprojected coordinates If we need another projection, we can configure it in the Projection Properties dialogue, e.g. to UTM zone 37S (POSC code 32737). The y_proj/x_proj attributes then reflect the projected coordinate values, while the lat/long fields still contain the unprojected coordinate values. Picture 5: DNRGarmin projected coordinates (UTM zone 37S)

4 The date/time values coming from the GPS are assumed to be UTC time (Coordinated Universal Time). In the Units Properties dialogue you can configure that this value (which can be found in the time waypoint attribute) will be converted into a selected timezone date/time value, e.g. you can use the settings of your local computer time. Picture 6: DNRGarmin date/time configuration Now we are ready to save the data as unprojected or projected shape file (depending on the projection we have specified respectively that we are using in our GIS) or any other format DNRGarmin offers. Shape files usually can be directly used as layers in a GIS. Picture 7: DNRGarmin save data as shape file Remember that with DNRGPS you can also save the data directly into PostgreSQL/PostGIS spacial database tables, ArcGIS version 10 and above or as Google Earth kml -file. Storing the data directly into a spacial database allows you for full SQL manipulation and operation of your GIS data with high speed database performance, reliability and security.

5 Step 03: Adding the shape file or database table as a layer in the GIS (gvsig). Remember this was the data we originally received from the GPS device as gpx files. How to add such a layer depends, of course, from the functionality and handling of your GIS software. In gvsig you use the add layer function, which allows you to add a new layer from different sources like shape files or from a spacial database directly (which is shown here). Picture 7: GIS (gvsig) adding a layer from PostGIS spacial database The final view in gvsig shows the customers surveyed and added to the GIS as a new point layer in red. Other objects/layers, except the network scheme, are marked invisible for demonstration purpose only. Picture 8: GIS (gvsig) final data presentation originating from a GPS survey