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GT-120

Posted by mycae-gmx on 31 March 2014 in English (English)

I have an Igotu GT-120 GPS datalogger, for GPS-photo correlation. By combining gps-correlate, and any camera with a timer (or timestamps on files, see my previous diary entry for the code...) I can now do correlation. The device has no built-in display of any kind, so it won't be any use for anyone who needs on-the-fly GPS, with no external connections.

Summary

It works, but the connector is a bit worrying. As a simple mapping tool, it should be enough for those who are happy to do photo-correlation, but don't have/want or for some other reason can't use a mobile phone based GPS. It wont be super-high accuracy though!

Specs

The chipset in the device is apparently a "SiRF StarIII low-power" device. The usb A->proprietary connector is a bit dodgy (insertion/removal) at the proprietary end. Not sure why they didn't use USB mini...

There is a CHM file available on the manufacturer's website, which give the LED codes. I've reproduced them here for posterity

Warm-up times are claimed to be 35 seconds, but my first power on (albeit without a clear view of the sky) took several minutes after being outdoors before it woke up and started logging. I assume this has something to do with GPS almanac data, and that subsequent power-ons will be better.

LED codes

  • Turning on the device : press button for 1.5 seconds, until blue LED flashes once.
  • Turning off the device : press button for 1.5 seconds, red LED switches off.
  • If red LED blinks twice : memory low
  • If red LED blinks once: battery low
  • Charging : red LED on until charging complete (possibly 2 hrs?)
  • Logging individual waypoints : push button once -> log acknowledge.

The manufacturers claim 65,000 records, so at 1/second should give ~18 hrs. The battery only lasts for 10 hours, according to the specs.

Use

After using the device for a very short while (cycling), it seems to work, and I can load the tracks under linux (debian testing) using the igotu2gpx program. The capabilities include setting the logging time, and downloading tracks, as well as an on-screen display for maps. Most importantly, gpx export seems to work.

A deb file can be built by obtaining the .dsc and .tar.gz files from launchpad. This was quite easy, after

  • tar -zxf igotu*gz
  • dpkg-source -x igotu*dsc
  • ln -s igotu*gz igotu2gpx_0.4.0.orig.tar.gz
  • cd igotu2gpx-0.4.0; sed -i 's@native@quilt@' debian/source/format
  • dpkg-buildpackage -j2 -uc -us;

dpkg complained about missing dependencies. After installing them, everything went smoothly.

I haven't tried realtime logging with gspd; though gpsd seems to recognise the device, but I have no lock indoors. As a cheap entry-level USB device, so far, so good.

Hopefully some good mapping can be done with it!

Re-timing images without GPS data

Posted by mycae-gmx on 6 January 2014 in English (English)

I had the problem whereby images from my camera did not write the time in the EXIF data. This means I can't geo-correlate my tracks with my camera data.

Thanks to exiv2, and some crappy bash scripting, something like this works for setting the time from the timestamp (which is fine, as long as the camera time is OK). This is very budget, but it works well enough.

 #!/bin/bash

 #Set the exif timestamp using the file creation date
 for i in *jpg
 do
    THISDATE=`ls -l --time-style="+%Y:%m:%d %H:%M:%S" $i | awk '{print $6 " "$7}'`
    exiv2 -M"set Exif.Photo.DateTimeOriginal ${THISDATE}" $i
 done
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