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I am in the process of editing gpx files and need to write the files back to .gpx in order to put them in a GPS unit. Basically, I am cleaning up some data and removing some track points. However, when I write the .gpx file, it clears out the timestamp, which makes it very difficult to work with the data later.

I am using the writeOGR function from the rgdal package to export the file. An example that can be reproduced with any .gpx file is as follows:

writeOGR(track, dsn='myfile.gpx', layer="track_points", driver="GPX", dataset_options="GPX_USE_EXTENSIONS=yes", "FORCE_GPX_TRACK=true", overwrite_layer = T)

When you read this back into R using readOGR("myfile.gpx", layer="track_points), the 'time' column is all NA.

I am looking for a way to write the original time information to the new .gpx file.

Here is an example workthrough:

library(rgdal)

track<-readOGR(system.file("vectors/test_trk2.gpx", package="rgdal"), layer="track_points")

track<-track[is.na(track$time)==F,] #eliminate NAs from track's time column

writeOGR(track, dsn='myfile.gpx', layer="track_points", driver="GPX", dataset_options="GPX_USE_EXTENSIONS=yes", "FORCE_GPX_TRACK=true", overwrite_layer = T)

track<-readOGR("myfile.gpx", layer="track_points") #read track back in

track@data

  • You can't really deal with time in GIS-like vector data. I'd avoid going through writeOGR for this if you can, you get equivalent of a location-with-other-columns from readOGR so I'd stick with the tabular form until absolutely needed. In a pinch you might keep the "third coordinate" using sf but must assume types all the same, putting coordinates in a matrix, so it's a non-starter as well. One way or another you'll have to keep a separate data frame indexed by row to each "spatial location" to use these GIS-y tools. There's probably a more GPX-focussed package that could help, though. – mdsumner Jul 22 '17 at 0:45
  • Can you supply a sample data and illustrate what you are trying to do, or maybe use a supplied GPX file like the one in the rgdal package: system.file("vectors/test_trk2.gpx",package="rgdal") – Spacedman Jul 23 '17 at 11:00
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The answer is quite strange but simple. readOGR() still reads the timestamps as you can see with track$time but it dosn't write it since it's expecting time to be written in capitals. therefore track$TIME <- track$time solves the problem.

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