GPS logging for long trips (with web map display): My solution

[blodulv]

I'm currently on a RTW and wanted a good, cheap way to make a log of my trip with good accuracy in both time and space.

I settled on the OHARARP SD GPS Data Logger ($150):




Despite the OtterBox case it's still not waterproof as there's a machined hole made for charging the unit. It logs to an SD card, I use a 2GB card. A day of riding with logs at 1 second intervals amounts to ~3mb or so in the NMEA format. This format is very easily converted to GPX with GpsBabel.

Since the unit isn't waterproof I usually just turn it on and put it in my tank bag, the accuracy doesn't seem to suffer at all. I did have one small problem with the first unit I received; the charging plug broke off the board after I inserted the charging cable. They got me a new one out immediately and the problem did not reoccur, I think it was a fluke due to a bad board.

Once I had some files in the NMEA format I needed a way to convert them all to a big GPX file. I used the aforementioned GpsBabel and fed all of the individual NMEA files to it on the command-line and it created a single GPX file. From there I used a Unix utility called gpx2shp to convert that GPX file into an ESRI Shapefile, which is a standard for storing geographic data. Once I had that I was able to start tinkering with some map display software. I settled on a mix of Mapnik, OpenLayers, and TileCache. The final result can be seen here:

http://www.bylandandsea.org/map/



You can pan/zoom and change background layers. I realize that many of the riders here many not be as geeky as I, so I'd be happy to answer any questions you all might have. I'm (slowly) working on making a version that might be easier for the average rider to use, though I thnk there already a number of services that let you upload a GPX file and get back a map image.

[tbirdsp]

I wonder how this would compare to Garmin units like my 60Cx which record the tracklog to the microSD data card in .gpx format?

This seems like a lot of money for what it is.

[JimC]

Originally Posted by tbirdsp

I wonder how this would compare to Garmin units like my 60Cx which record the tracklog to the microSD data card in .gpx format?

This seems like a lot of money for what it is.

I was thinking the same thing as I read the post. You can buy a Garmin Legend HCx on Amazon today for $190 which will log your fully detailed track in a GPX format to a micro SD card until the card is full. You get the all the features of the OHARARP SD GPS Data Logger plus a gps that you can actually use to navigate for about $40 more.

Jim in Sacramento

[blodulv]

What made this unit worth it for me was the 1hz update (it will log one point per second), the GIGANTIC rechargeable battery (40 hours+), the very fast acquisition time, and the fact that it was made to do only one thing and do it well. The 2GB card will come in handy if my laptop dies for some amount of time down the line and I'm not able to take tracks off the card.

You could switch the OHARARP out for any other GPS that will give you GPX files, though. It just happened to be the best fit for me.

[rwamf]

There are quite a few loggers out there, Here is a cool one as it is a Bluetooth GPS also. Earthmate Blue Logger $150 and comes with Delorme Street Atlas. The Garmin "x" series are great as you can save full res logs to the SD card, but can't import them back.
The Lowrance GPS's will log and save full resolution track files( no alt or speed data) to the SD card plus with the Lowrance you can import them from the card back into the GPS.
So many options so little time.

[JimC]

Originally Posted by blodulv

What made this unit worth it for me was the 1hz update (it will log one point per second), the GIGANTIC rechargeable battery (40 hours+), the very fast acquisition time, and the fact that it was made to do only one thing and do it well. The 2GB card will come in handy if my laptop dies for some amount of time down the line and I'm not able to take tracks off the card.

You could switch the OHARARP out for any other GPS that will give you GPX files, though. It just happened to be the best fit for me.

I'm curious about 2 things.

1) Why record a track point every second (which you can also do with the Garmin GPS's) this seems like severe overkill. At 60mph that is one point every 88ft. A 300 mile day on the slab will result in a track log of 18,000 track points. This is 28,800 track points for an 8 hour day. I just can't think of any reason why I would need such a large number of track points.

2) Do you carry a second GPS that you use for navigation?

Jim in Sacramento

[blodulv]

Originally Posted by JimC

1) Why record a track point every second (which you can also do with the Garmin GPS's) this seems like severe overkill. At 60mph that is one point every 88ft. A 300 mile day on the slab will result in a track log of 18,000 track points. This is 28,800 track points for an 8 hour day. I just can't think of any reason why I would need such a large number of track points.

2) Do you carry a second GPS that you use for navigation?

I record once a second because I can and because it makes prettier maps. I've got 2GB of space on the card, and if I need to upload a smaller file due to lack of a good wifi connection then I can always compress it (it's text) or use GpsBabel to get rid of points that are closer together than a certain distance (I originally tested this when displaying the data using Google Maps, which has a limit on the number of points it can show). I feel like I have the technology at my disposal to create a large amount of data without detrimental effects, and if I end up not needing it I can throw some of it away easily. I enjoy graphs and charts and data visualization, though, so it's inevitable that I will play with all of this data some day.

I do carry a second Bluetooth GPS that will interface with my laptop but I haven't had to use it yet. I've embraced getting lost on this trip, it makes for more interesting stories. ;)