Populate Elevation Data in GPX using FME

Question

New to FME, and I have now spent more time than I would like to admit on this and need some pointers.

I have a GPX file that was made from a Shapefile. It has no elevation data.

I have the Terrain50 DEM as a GeoTIFF. I am using PointsOnRasterValueExtractor in FME to allocate the elevation data to the points before resaving the GPX. I have many thousands of these to do so I want to be able to batch process this.

I have checked that the two datasets are in the same projection, when I view the raster dataset in FME it has the data I need but I can't seem to populate the GPX Elev field. What am I doing wrong?

Answer 1

How are you attempting to populate the Elev field? As per the documentation for the PointsOnRasterValueExtractor transformer,

The interpolated values are added to a new list attribute, named _band{}.value and _band{}.palette{}.value, respectively.

You will need to use an AttributeManager transformer to assign these values to the Elev field. Because, the PointsOnRasterValueExtractor transformer creates list attributes, you'll need to select the position of the list of your _band{}.value. Assuming your DEM is a single band, the list index should be 0. Then, with a writer, write them to the GPX files.

Answer 2

The doc for that writer says:

Feature Attribute   GPX XML Entity 
elevation           ele (The writer ignores this value, 
                    using the z-value of the geometry instead.)

So if you put a 3DForcer transformer in there, and set it to use the value of _band{0}.value then it should write that information out to the GPX file.