For a variety of reasons, you may want to modify a GPX track log before uploading it to OSM.
Warning: You should only upload raw data you collected yourself. Also, OSM is interested in the raw data, so you shouldn't edit your tracks to match what you would like to see mapped. In particular, don't edit the locations of points, just exclude bad ones and split the tracks as required.
To protect your privacy:
- Your GPS tracks can reveal your exact address and show when you were where. This can give people a lot of information you don't want them to have. You may want to exclude the area around your house (Using filters with GPSBabel shows how to do that with gpsbabel) and possibly modify the timestamps.
To improve the remove or correct bad data:
- You may want to remove points where your GPS receiver had poor reception (say you were inside a building).
- Also, if you spent a while at some place, the resulting cloud of points is not that useful for mapping.
- If the receiver produced implausible results:
- distance between trackpoints more than 500m,
- speeds higher than 300km/h lower than 1km/h (values can be computed by gpsbabel)
- You may want to split your logs into parts depending on some criteria. For instance, separate the flight log and the bus trip from the airport. This allows more accurate tagging of the uploaded logs.
To reduce the data volume, you may want to :
- compress a track to reduce the number of points and speed up uploading.
- to delete sections of data which have already been uploaded or are not relevant.
- Gpx Splitter is a simple utility that aids in separating large GPX files in multiple files each of which has a predetermined number of instructions.
- CourseCompacter is an online application that reads CRS and GPX Files and compacts the files by eliminating excess trackpoints.
- GPSBabel provides filters (see using filters with GPSBabel). Some of these only work on waypoints, so you may have to convert a track to waypoints and back (gpsbabel allows this).
- JOSM permits reading and writing GPX files. By converting the GPX layer to a data layer, it can be edited, then saved again as a GPX file, or directly uploaded to OSM using a plugin. In older versions of the program (certainly earlier than Sept. 2010), the GPX file may not be properly saved.
- Viking   allows visualizing, editing and uploading tracks to OSM.
- RouteConverter is a platform independent java application that can edit GPX files.
- Check Perl_Scripts#osmtrackfilter and http://svn.openstreetmap.org/applications/utils/filter/ for some command line tools.
- gpsman is very useful if you can see past the unusual tcl/tk user interface.
- GpsPrune allows visualisation (2D, 3D, osm, Google Earth) and editing of GPX files.
- GPX Editor allows splitting, joining and pruning of tracks, visualises tracks in Google Maps, simplifies tracks using various methods etc. English support forum.
- gpxsplitter splits multi-track GPX files, containing waypoints, into individual one-track GPX files with their respective waypoints. It's useful for GPS units (such as those based on MTK chipsets) that munge tracks and waypoints together.
- gpx_reduce is a small python script that yields high-quality gpx-track reduction/compression.
- Merge Tool and Anonymize Tool are two small console applications (for Windows) to merge gpx files or randomly shift their timestamps.
- Trakclean is a simple Windows console application to eliminate spurious trackpoints (typically recorded when stationary) using a minimum speed or distance criterion.
- TrackProfiler is an online GPS track editor. It allows you to split/merge/move tracks, edit routes, detect and remove GPS errors and add coordinates to images.
- GPS Track Editor is a Windows application to analyze and edit GPS tracks (split/merge/filter).
- TrekView (Czech language) is a fast web application able to show and edit GPX routes on Czech commercial tourist maps layer.
- GPS TrackMaker (Windows) allows GUI editing of gpx tracks (e.g. deleting parts)
- How to edit GPX files in a text editor - a rough description.