Mark J Cox

mark :: blog :: geocaching

03 Mar 2008: Geotagging and route logging with Tom Tom

I'm out on holiday soon to Arizona, so we've been looking for ways to geocode the photos we'll be taking and get a record of our route. I use a Mio A701 phone which has built-in GPS, and this time we'll be using Tom Tom in the USA rather than Mapopolis. The problem with Tom Tom Navigator is that it doesn't keep a track log, and there doesn't seem to be any plugins to allow it to do so. So here is the solution I've been experimenting with over the weekend.

On the PocketPC:

Make sure the GPS Intermediate Driver is enabled, on the MIO there is a built-in "GPS Settings" utility where I have it set to COM4 and "Manage GPS automatically"
Use the GPS2Blue utility. Make sure it's set to GPS on COM4, 4800 baud, with logging only of GGA/GLL/RMC/VTG NMEA, and select 'Log processed raw data...'. You don't need to enable the "2blue" bit, we're just using it to write the tracklog.
Make sure your camera has a date and time that is close to the one being shown by GPS2Blue from the satellites
Start TomTom. Make sure it's also set to COM4, 4800 baud. This will work because the GPS Intermediate Driver is opened by GPS2Blue. You can't start TomTom first, but you can exit GPS2Blue and leave TomTom running.
After finishing you end up with a NMEA track log with an hour of logging taking up about 1.6Mb. Transfer it to your Fedora machine.

On my Fedora machine:

Use gpsbabel to convert the NMEA track log and clean it up a bit. I used:

gpsbabel -i nmea -f GPS_2008-03-03_122630.log -x discard,hdop=10,sat=5 -o gpx -F out.gpx

Use gps2photo.pl to add the geocoding to your images. This script looks at the time and date the photo was taken and tries to match it up to an entry in the tracklog, so you may need to play with the timeoffset to deal with timezone differences. Although we have snow, being in the UK in the Winter has it's advantages as we're UTC+0, so I just used:
```
gpsPhoto.pl --geoinfo=osm --dir ./ --gpsfile out.gpx --timeoffset 0 \
    --city=auto --sublocation=auto --state auto --country auto --kml out.kml
```

The exif metadata inside each jpeg now contains the approximate co-ordinates of where you were when you took the photo along with a guess of the location (city, country, etc). You can load out.kml into GoogleEarth to see the tracklog and photos on a map. If you've allowed Flickr to read the location data from exif then uploading a geotagged photo will automatically place it on a map. (Make sure you consider the consequences before enabling that option or you may end up unintentionally leaking information like the location of your friends houses or parties you've been to). Here's a quick pic taken in the snow today to test it out:

output from exiftool:
GPS Position : 55 deg 46' 58.21" N, 4 deg 0' 5.50" W City : Motherwell Province-State : Scotland Country-Primary Location Name : United Kingdom

06 Jun 2005: 100 Geocaches!

Completed our 100th cache last weekend after a day out to grab some caches just north of Edinburgh. Took us a year to get to 100, but rather than try to do as many caches as possible we're trying to do a selection of interesting ones in interesting places. Since most caches in Scotland seem to involve 2 mile hikes we don't tend to do many each weekend. A cache last weekend took us within a few hundred yards of a certain blue and yellow swedish furniture store, which proved amazingly expensive with more bookcases, a new bed, shelving, and a packet of mini-daim bars needed to make the construction process less stressful.

14 Oct 2004: Epoxy

What happens if you combine an old 32Mb USB key with a Geocaching travel bug dogtag and 50g of epoxy? A USBUG emerges. I thought that rather than the usual selection of TY toys or computer parts attached to travelbug tags I'd actually build a memory travel bug, fill it with mp3's, and see if it gets any interest. (Yes, legal mp3s)

Having spare potting compound is very dangerous however. When all you have is potting compound, everything looks like it needs to be covered in epoxy ;) Anyway let's see if Tesco can still read my clubcard.

02 Aug 2004: Looking in all the wrong places

I went Geocaching again this weekend. One of the things I love about Geocaching is that it takes us to places we never knew existed, but are well worth exploring. An amazing short walk up past some waterfalls near Ayr took us to a rock, behind which, stuffed into a crevice, was the usual black bag containing the plastic box of swaps. The place wasn't deserted, near the cache were several discarded beer cans, but yet this box has sat in the hole for over a year without being disturbed by any of the thousands of visitors. No one has found it because no one was looking for it. Knowing there is a hidden box within a 10 or 20 metre radius it's then quite easy to find. You have an idea what you're looking for, and you have the knowledge that something is there to find.

As I thought about this on the walk back to the car, I was reminded of a conversation I had with a security researcher on Friday. We were discussing an upcoming serious vulnerability that he found this week in a common library. This issue is under embargo, to give the vendors and upstream authors a few days to prepare updates. But not only is the actual flaw confidential, but the fact that there is a flaw in this library is also confidential. Just like the cache which is hidden under your nose, if you know that there is a security flaw in some named library, even if you don't really know what it is or where it is, you know that if you search hard enough it has to be there somewhere.

19 Jul 2004: FC2

The last couple of months have been quite busy and any spare time I've been using to go Geocaching. Only up to 8 finds so far, but I'm picking locations that sound interesting and worth visiting. Scottish Geocaches have some pretty amazing scenery and they've taken me to all sorts of places I'd never think of visting. So it took until today to finally getting around to configuring the T41 laptop the way I wanted to. It's running Fedora Core 2 and I figured it was time to use a dual-head so I'm not stuck at 1024x768 forever when theres a perfectly good 22" CRT next to me. "system-config-xfree86" had it working immediately; with just a manual tweak needed to XF86Config so the second screen was at 1280x1024. To complete the setup I plugged the USB IBM Trackpoint keypad into the laptop and it configured itself, set itself up, and now moving any of the trackerpoint mice moves the pointer, typing on any keyboard just works. What I've been putting off for the last two months took less time than typing this entry, I love it when that happens. Meanwhile, trying to get a bluetooth USB dongle working so I can just simply send and receive SMS via Fedora Core 2 is one of those more impossible missions that just sucks up time.

Hi! I'm Mark Cox. This blog gives my thoughts and opinions on my security work, open source, fedora, home automation, and other topics.

pics from my twitter: