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Archive for the 'GPX' Category Page 3 of 5

Splitting A GPX Track Into Smaller Files

Some GPS models, such as most Garmin handheld units, allow you to record up to 10,000 points as the active track. But if you save an active track with more than 500 points, the unit will automatically simplify the track to a maximum of 500 points, dropping what it considers to be redundant or unnecessary points; you have no control over which points get dropped by the unit. One option is to simplify the track yourself with GPS Trackmaker’s Tracklog Reducer, which also drops points but gives you some control over the degree of simplification. But if you absolutely have to preserve all the points, there’s another option; GPX Track Splitter lets you chop a track with more than 500 points into a set of smaller tracks that come in under this limit, but which preserve all the points.

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AZ Garmin Topo Maps And More From The GPS File Depot

Dan Bloomberg wrote to tell me of his new website, the GPS File Depot. Some useful stuff for GPS users, especially Garmin owners:

Prune Updated: Now With Automated Photo Geotagging For Windows, Mac, And Linux

Prune is a Java-based GPS-track viewing and editing program that runs in Windows, Mac and Linux. When I last posted about it, the photo geotagging capability was a bit awkward – it required you to manually link a photo to a trackpoint, not automatically correlating trackpoints with photos based on time like most photo geotagging software. Version 4.1 is now out, and it now can automatically correlate and tag photos with data from a GPX track file. You need to have EXIFTool installed on your system; for Windows, put it the same folder as Prune, or into a system folder. Open a GPX track with File => Open Command, select either individual photos or an entire folder with File => Add Photos (or Photo => Add Photos). Select the photos you want to geotag in the file list at left, then select Photo => Correlate All Photos:

geotag photos with Java Prune

Prune lets you adjust for the time difference between the camera time and the GPS time (the former is usually the local time, the latter UTC). You can also set the correlation limits, i.e. how close the time or distance a trackpoint needs to be in order to be correlated with a picture. After correlating photos with track, you still have to select Photo => Save to EXIF to have the position data written into the picture’s data:

Save to EXIF

If you leave “Overwrite file” unchecked, the original will be saved with “_original” appended to the file extension; it would probably make more sense to append it to the filename instead, but that’s apparently a limitation of EXIFTool.

Another useful new feature in Prune is the ability to create a GPX file from an imported set of geotagged photos. Add the photos to the file list with the Photo => Add Photo command, select File => Export GPX, and Prune will create a GPX track file, connecting all the points where a photo was taken in the correct order.

Other new features in Prune:

  • Automatic correlation of photos with points based on timestamps
  • Manual disconnection of photos from points
  • Reading of photo thumbnails from EXIF data (speeds up photo loading)
  • KML and KMZ export now includes altitude option for airborne tracks
  • Track points in map can be connected by lines
  • On loading a text file, fields are now guessed according to data or column headings
  • Polish language

Prune is released under GPL, and there’s a copy of the source code available for download. Not sure I would use Prune instead of GeoSetter for photo geotagging in Windows, but it looks like a great free alternative for Mac and Linux users, who have fewer free geotagging options.

Creating GPS Routes And Tracks In Google Earth

EarthNC has a new Google Earth tool for taking points, paths, and polygons created in Google Earth, and either converting them to GPX or uploading them directly to a Garmin GPS (Windows only for the latter). Points are converted to points, paths to routes, and polygons to tracks. The downloadable KML file, full text instructions, and a demonstration video, are available at the website. They also have a simple online tool for converting KML files directly to GPX format by copying the KML file into the online text box and clicking a conversion button.

Via Ogle Earth.

Beta Version Of DNRGarmin

One of the first posts on this blog was about the 5.1.1 stable version of DNRGarmin. Long story short, if you work with GIS and you use Garmin units for your data acquisition, this program is a must-have. It can upload/download data in text, DBF and shapefile formats to/from Garmin GPS units, and also comes with an extension for direct interfacing with ArcGIS software. Version 5.1.1 had some utility for non-Garmin GPS units and applications, but version 5.2, currently in beta, has some new features that make it a worthwhile installation for anyone with a GPS.

DNRGarmin has actually been in beta for a while, and I’d been waiting to see if it would come out of beta; the date on the last release is 5/18/07. The webpage indicates in big bold letters that in the beta, “THE ERROR RELATED TO USB CONNECTIVITY AND LOGIN RIGHTS HAS NOT YET BEEN RESOLVED“. But I’ve installed it successfully on 3 different computers without encountering this problem, so there’s a decent chance it should work on yours as well.

New features in version 5.2 include:

  • Load data in KML and GPX (in addition to the previous options of text, DBF and shapefile formats)
  • Load data directly from the “My Place” pane in Google Earth
  • Save data in KML and GPX (along with the previous options of projected/unprojected shapefiles, text and DBF)
  • Convert between the different formats
  • Collects waypoint time data from supported units

Note: The new version’s ArcGIS extension no longer works with ArcGIS 8.x, only 9.x. If that’s important to you, you should stick with version 8.1.1, still available on the web page. But the new version works fine in stand-alone mode.

Converting OpenStreetMap Data Into GPX Or Garmin .img Format

The OpenStreetMap project is “a free editable map of the whole world”, created by users with GPS data or by tracing over Yahoo Maps images (allowed by Yahoo) or public domain Landsat data. Data is viewable by anyone; registration assigns you a username and password that lets you contribute your own data to the project, using a multi-platform map editor like JOSM or Meerkartor. JOSM also lets you save downloaded data from OpenStreetMap, and this data can be converted to the .img format used by Garmin mapping GPS units, or converted to a GPX file for general import into GPS units.

The current OSM data in Garmin .img format is available for the UK, South Africa, and Africa at the Mkgmap wiki site, and for Germany/Netherlands and the entire world at this site. But if you want the most recent data, data subsets for different areas, or don’t want the entire dataset for the world, you can download data for a specific area from OpenStreetMap and convert it yourself to a Garmin .img file. Data coverage is still spotty, so you should check the OpenStreetMap site to see whether the area you’re interested in has data. If yes:

1. Click the “Download some data from the OSM server” link in JOSM, and specify the latitude/longitude bounds of the area you’re interested in (no more than 0.25 degrees square) (note: you’ll need to have entered your OSM username and password in the preferences section).

2. Save the downloaded data as an *.osm file if you want to convert it to Garmin format, else save it as a GPX file.

3. Use the command line Java program Mkgmap to convert the *.osm file to a Garmin img map file (always the same output filename, “63240001.img”, but you can rename it to a different 8-digit number after creation) . If your osm file is called test.osm and is in the same directory as mkgmap.jar, the command syntax is “java -jar mkgmap.jar test.osm”. Enter the appropriate data path if it’s located in a different directory, but the 63240001.img file will always be created in the directory where mkgmap.jar is located. If you’d prefer a GUI, I’ve created a simple one for Windows that you can download here; unzip it to the same directory as mkgmap.jar and run it. The *.osm file will have to be in the same directory as mkgmap.jar for this GUI to work; sorry about that.

4. Upload the .img file to your Garmin GPS using a program like sendMap, or MapUpload if you have a compatible Garmin unit. For GPX files, use the upload program of your choice (e.g. GPS TrackMaker or EasyGPS).

Thanks to David from the UK for the tip.

Prune – Java-Based GPS Track Visualization And Photo GeoTagging

Prune is another Java-based GPS tool with its own unique set of features, including:

– Load multiple text, GPX or KML tracks, appending them to each other

– Trim duplicate points, and compress the track (hence the name Prune)

– Save combined tracks in text or KML format (use GPS TrackMaker to convert the KML tracks to GPX format if desired)

– See a plot of position, and altitude if available

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Draw/Label On Google Maps, And Generate GPX/KML/Embeddable Maps

Not as useful as it was before Google Maps MyMaps came along, but has many of the features that MyMaps does, and a few it doesn’t:

– Draw lines on a map, either with line segments or arbitrary freehand (no polygons, unlike MyMaps)

– Add points to the map using a larger variety of full-color icons than MyMaps

– Add text labels directly to the map (not in MyMaps)

– Embed the map and your content in your website

– Export the map data directly into either KML format or GPX format for downloading into your GPS