Tools and tips for GPS navigation and mapping
How to get GPS waypoints and tracks into Google Earth?
The latest version of Google Earth (v 5.0) lets you interface directly with Garmin or Magellan GPS receivers and download your waypoints and tracks. An alternative method good for any GPS receiver is to reformat your GPS data to the GPX format. Google Earth (v 5.0) also opens .gpx files (GPX files can be drag-and-dropped into any version of Google Earth).
Why use GPX files?
GPX (GPS eXchange format) is essentially xml for GPS data. It’s the standard format for interchanging GPS data between GPS receivers, mapping software and Web-based services. You can get free GPX files of waypoints and tracks from several websites catering to outdoor activities (e.g. hiking and cycling). These files can be uploaded to your GPS receiver or viewed in Google Earth.
Where to get POI’s (Points Of Interest) for your GPS?
Maps in GPS receivers and car navigation systems usually contain a good selection of points of interest but they may be incomplete or out-of-date. At http://poifriend.com/ you can download official, up-to-date files of popular points of interest (e.g. coffee shops, banks, restaurants, service stations, arenas) in GPX format for easy uploading to any GPS receiver.
How to create your own POI files using Google Maps?
Go to Google Maps http://maps.google.ca/maps and use the “Search the map” feature to create placemarks. If you sign-in to Google (free registration required) you will be able to save your placemarks to your personal “My Maps”. The advantage of using Google’s My Maps is that your map data is accessible from any (online) computer. Each map you create has its own link. Click “Link” to display the map URL.
Copy and paste the map URL into the input field of http://www.takitwithme.com/ and load the map. You can then download a GPX file (or upload directly to a Garmin GPS).
How to create POI files using Google Earth?
Use Google Earth’s “Search” utility to create placemarks. Regroup them into a directory and save as a KML file.
Transform a KML file to GPX.
- Several free programs can do this (e.g. EasyGPS, GPSTrackMaker, GPSUtility, GPSBabel)
- You can also submit your files online to GPSVisualizer (using the basic input page)
How to transform an Excel spreadsheet of georeferenced data to .GPX?
In the first row of the Excel table add the headers “name, latitude, longitude, height (optional) and description (optional)”. Make sure coordinates are in decimal degrees and longitude west is indicated by a negative number. Columns can be in any order.
Submit your Excel file to GPSVisualizer (basic input page) and transform to GPX. The GPX file can be opened in Google Earth or uploaded to a GPS receiver.
How to collect GPS data and verify its quality?
Most GPS receivers can be set to output a real-time stream of position information in the format known as NMEA (National Marine Electronics Association). NMEA is the recognized ASCII standard format for GPS position real-time output. The $GPGGA string is of particular importance as it contains many useful fields (GPS position type, # of satellites and HDOP) that are indicators of the quality of the positions.
GPSVisualizer can read the NMEA format ($GPGGA string). If you use the Detailed Google Earth input form, you can generate a 3D track color-coded according to any field (# of satellites is very useful).
You can now see the data and where it was collected allowing you to investigate gaps or poor data. Keep in mind that the geocoding of the satellite imagery in Google Earth is not perfect, it can easily be off by 5 m or more.
How to log an NMEA file?
Most mapping-grade receivers come with software capable of logging NMEA data, consult your user manual.
Most GPS receivers have an interface control allowing you to output NMEA (usually out a Serial or Bluetooth port, GPS receivers equipped with only USB ports may not be able to output NMEA). The NMEA can then be logged:
- on a remote device such as a PC (using free program VisualGPS or GPS Diagnostics)
- on a Pocket PC (using free program VisualGPSce)
- on a hardware Serial logger (no need of a PC or Pocket PC).
