User:Kjerag Troll
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Jeg heter Kjerag Troll
I am a physicist and currently living in Bavaria, Germany. Primarily I map the regions around Pocking and Regensburg.
You may contact me by email about concerns related to OpenStreetMap. Please encrypt emails using my PGP public key and sign it with your own key. My email address is included in the User ID of my PGP public key. Unencrypted and unsigned emails are likely to be disposed without being read...
| This user uses or has experience with a Garmin eTrex Vista HCx and is willing to answer questions on it from OSM users |
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My equipment
- light
- Garmin eTrex Vista HCx
- Transcend microSDHC card, 8 GBytes
- heavy
- Navilock NL-402U (GPS mouse)
- Dell Vostro 1320 (Laptop) with Ubuntu Jaunty Jackalope
- Micro-USB-stick, 8 GBytes
- Headset (Skype-certified, bought at Norma)
My projects
Hardend laptop with Linux on USB stick and without harddisk
Currently I am preparing and hardening a laptop (DELL Vostro 1320) for outdoor usage. Probably the laptop harddisk (which is not a solid-state disk) does not like the bumpiness of foot and bicycle trails. Thus I plan to remove the harddisk and boot the laptop from a bootable USB stick instead. I acquired a micro-USB stick with a capacity of approx. 8 GB; it sticks out only 4 mm or so from the laptop housing. It is very unlikely that it breaks off.
On the USB stick I installed a very small Linux distribution: Puppy Linux. The only things / programs I need on the laptop is gpsd and an audio recorder. I found that gpsd is not really necessary as it is possible to simply cat the corresponding device (/dev/ttyAMC0 in my case).
I am still experimenting with the audio recorder. It must support the microphone jack.
To reduce the write-cycles on the USB stick it is reasonable to use a ramdisk. When the mapping session is finished, the content of the ramdisk is copied to harddisk / USB stick.
The laptop project is still in progress / development. As soon as I have more time I will finish it and present a working solution here.
Ubuntu
Besides the USB variant I have a harddisk version running with Ubuntu Jaunty Jackalope. With gpsd and a Python command-line tool showing current coordinates and precision. I will publish the code in near future...
Command line tools
I write command line tools that "clean up" GPS tracks. For example, they remove points at the beginning or end of a track. They remove consecutive points with the same coordinates (e.g., when waiting at traffic lights). They disguise the timestamp -- preserving or destroying information of velocity. The NMEA data is cleaned up; I keep only GPGGA which has lon/lat and precision data.
The tools work quite well, but are not ready to be published yet.
Average multiple GPS tracks
Currently only a vage concept exists: I'd like to think of an algorithm that takes two or more GPS tracks of the same path and calculates the average track. This is supposed to result in a better track, i.e., fluctuations due to reception conditions, satellite constellations, etc. should be... well... averaged.
I thought about two-dimensional correlation functions. Horizontal delution of precision should be taken into account by the algorithm. The plane has to be discretized reasonably: small enough to have appropriate precision, but not too small, otherwise computing power is too expensive........
Well, we'll see...
Kjerag Troll 00:53, 25 May 2010 (UTC)
