Electronics, Lighting, & Gadgets - Manipulating GPS Raw Data

I was given a raw data file from a Garmin GPS for a ride. What I would like to do is take the data and generate a cue sheet with the turn directions, street names, and mileage - as well as the time of day that each turn was made. Is this easily doable?

I suspect it's not easy to do. GPS data just contains sets of time, latitude, longitude and altititude. While Google Maps and other map mashup sites can turn GPS tracks into lines on a map, I don't know if any of them has the smarts to calculate back out the corresponding streets and work out the turns in order to give you cue sheet type directions. If anyone knows different, I'd certainly be interested in a solution too!

I was given a raw data file from a Garmin GPS for a ride. What I would like to do is take the data and generate a cue sheet with the turn directions, street names, and mileage - as well as the time of day that each turn was made. Is this easily doable?

If you were given a GPX file (sometimes the extension is XML), it can be imported into an online mapping program like Bikely or MapMyRide. These programs will draw the lines. You will have to manually add the cue points in by hand, though. If the ride is a century (or longer) this could take a very long time to complete.

Depends on the format of the data. Could load Garmin's Mapsource and read the file from there, especially if it's a track log.

If you don't have Mapsource you can download Garmin's training Center app and then use a mapsource patch to update it to the full Mapsource app.

Just thinking out loud, possibly some way to use Google cue sheet:
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If you can get your map into Google maps and then use this that'd do it. Possibly from Google Earth kml? (http://maps.google.com/support/bin/answer.py?hl=en&answer=41136)

Otherwise, you could just create the route in Google maps. As for reading the Garmin file, you can use Google Earth or something like this - http://gplotter.offwhite.net/

A program called GPSBabel is a great way to pull track logs out of dozens of different GPS devices, apply various functions and filters to them, and then write them out in something else that you can use, like KML for Google Earth
and its free,

Depends on the format of the data. Could load Garmin's Mapsource and read the file from there, especially if it's a track log.

If you don't have Mapsource you can download Garmin's training Center app and then use a mapsource patch to update it to the full Mapsource app.


You can get Garmin Basecamp for free from their site but it won't help much unless you've also got maps to go in it. Wander over to garmin.openstreetmap.nl and download maps for the appropriate area and you can see where you went.

Or you can load your GPX file into Google Earth, or any web site you can find that lets you upload track logs and overlay them. I use a couple but they are UK-based so unlikely to be much use to someone in CA.

You don't mean "GPS raw data", that means something else, you mean GPX (or less likely NMEA) logs.

I live in the US and I used to use GPSVisualizer to make GE KML files. Its basically a web site wrapper around GPSBabel. But now I just use GPSbabel for stuff like that. There are two versions, the command line version, and the GUIfied version. Whichever kind you feel most comfortable works. The GUI one is easier for casual use.

If you have the computer setup (have never seen this on a bike but of course people do it in cars and especially boats all the time) almost all GPS's (internally or externally) support NMEA i.e. the standard for serial ASCII output of your position (example below..)

Typical use scenario is a bicyclist who has a GPS logger that writes to a flash card.. then when they get home, they download the saved data.. which is basically a track file..every x number of seconds or x number of feet/yards/meters the logger will save the last valid fix data to a GPX (or whatever) file...

Use GPSBabel.. or the free josm openstreetmap editor may suport some of those formats as well..

OR, maybe you want to track yourself as you ride... (Please dont do this unless you are the rear rider on a tandem bike! :o )

Its easy to use serial data from a USB dongle, serial port or Bluetooth GPS to track yourself in real time, if you have either a live net connection for GE or all your local maps in your cache,

For that, there is a Unix daemon, gpsd, and a Python script, gegpsd.py you can use.

You can then track yourself in GE or in josm, the java open streetmap editor. I dont know how its done on Windows but its easy to do on either Linux or OS X. Just Google the above terms.. You can find decent quality NMEA capable USB GPS dongles for under $20 (really an amazing value considering the sophistication of what they do)

This is what a NMEA stream looks like.. The least common denominator among GPS modules is that they almost all (every one that I have seen) can be set to output NMEA ascii at 4800 baud, minimally you need either GPRMC or GPGGA (or both) but more frequently you get all of them as default. You may have to poke around a bit to find it, but somewhere, its in there.

However, if your GPS is a "personal navigation device" (PND) its often very hard to impossible to access the NMEA data stream. The reason is that a GPS-oriented PND is actually (at least!) two devices, a GPS module (sometimes its all done inside of one microminiature chip the size of your fingernail!) and a task-specific computer. (the rest of the thing) So, the basic computer can probably log to something like a flash chip or flash card.... as well as tell you where you are.. sort of. Or sometimes, you just have a GPS logger the size of a flash drive that you can download your info from later. (assuming the batteries didn't die on you while it was going)

A NMEA data stream will resemble this as it streams out of a serial port at (most often ) 4800 baud, but sometimes as fast as 115200 baud- useful if you want more precisely regular updates:

Also, you should be aware that some newer GPS modules can update up to 20 Hz - 20 times a second..

$GPGGA,092750.000,5321.6802,N,00630.3372,W,1,8,1.03,61.7,M,55.2,M,,*76
$GPGSA,A,3,10,07,05,02,29,04,08,13,,,,,1.72,1.03,1.38*0A
$GPGSV,3,1,11,10,63,137,17,07,61,098,15,05,59,290,20,08,54,157,30*70
$GPGSV,3,2,11,02,39,223,19,13,28,070,17,26,23,252,,04,14,186,14*79
$GPGSV,3,3,11,29,09,301,24,16,09,020,,36,,,*76
$GPRMC,092750.000,A,5321.6802,N,00630.3372,W,0.02,31.66,280511,,,A*43
$GPGGA,092751.000,5321.6802,N,00630.3371,W,1,8,1.03,61.7,M,55.3,M,,*75
$GPGSA,A,3,10,07,05,02,29,04,08,13,,,,,1.72,1.03,1.38*0A
$GPGSV,3,1,11,10,63,137,17,07,61,098,15,05,59,290,20,08,54,157,30*70
$GPGSV,3,2,11,02,39,223,16,13,28,070,17,26,23,252,,04,14,186,15*77
$GPGSV,3,3,11,29,09,301,24,16,09,020,,36,,,*76
$GPRMC,092751.000,A,5321.6802,N,00630.3371,W,0.06,31.66,280511,,,A*45


The higher the baud rate, the faster it goes by. Most GPSs can also be set to use proprietary binary command sets, which is faster than NMEA and may support some features that give the GPS more flexibility in a specific application.

Some GPSs can be sent special commands which tell them to only output raw "psudorange" or "carrier phase" satellite data.