Saturday, 23 July 2011

On GPS Part III: Update on the Garmin Foretrex 401, Garmin Basecamp and Anquet Maps

I have had some time to fool around with the Foretrex 401, Basecamp and Anquet and been quietly pleased with the results. As I have said, it is important to set the elevation before you start walking. If this is done, the information displayed in the Foretrex will be accurate. That said, I wanted to know whether it was possible to export the 'track' saved in the Foretrex to Garmin Basecamp and then onto Anquet where the mapping is more detailed. It is.

Basecamp is a useful basic tool from which to garner a wealth of information. It also retrieves easily, from the Foretrex, the stored track information. Once this is done, it is possible, within Anquet, to import that track. Within Basecamp, the track can be exported as a .gpx file - go to the File Menu, and select Export (the track name will be contained in "quotation marks") and where to export it to. In Anquet, under the File menu, Open Database and select the .gpx file containing the track. It automatically appears, in exactly the right place with all the waypoints and route information intact. It seems to be automatically saved as an .adf file - an Anquet Database File.

Below is a screen shot of my Anquet with the data. One thing to note is that the map provides the actual trip data, it would appear, rather then the GPS (as with Basecamp). Elevation, route, distance and so on come from the interpretation of the placement of the track on the map conducted by Anquet. Consequently, the time estimate is somewhat inaccurate as it is an estimate given Naismith's Rule, not what actually occurred on the ground. That is stored within the Foretrex (and Basecamp). In one sense, if your calibration of the Foretrex has been inaccurate at any stage, this process will then provide a more accurate result in terms of distance and ascent/descent.

Below is a screen shot of Garmin Basecamp's information screen. Note the ascent and descent is different. This, I am guessing, is down to the fact I did not set the elevation correctly at the beginning of the track and re-set it after about fifteen minutes and 1km. I am not quite sure how that disparity of 400m has occurred, as there was only a 150m disparity to be re-set, but I will investigate as I use the Foretrex. If I re-plot the route on Anquet from scratch it matches more closely to the information seen above rather than that on the Basecamp track information. I like the Leg Length/Time and Speed information. You can tell the flat parts and the climbing parts easily!

One thing that worked really well was the selection of Geographic Co-ordinate System (for an explanation of all this, see my post On GPS Part I: General Principles). I was able to select the OSGB36 option and navigate via the OS Grid System rather than longitude and latitude. I did this deliberately as I wanted to see how easy it was to use that rather than WGS84. It was easily interpreted and fully functional.

I am really pleased with the Foretrex. Attached to my sternum strap, it's easy to access and I looked at it frequently. As we moved, I was able to discern quickly if we were still on course and, if not, by how much we were off course and what heading we would need to take in order to correct this. The route to be taken is shown as a thick black line and it's easy to read after a short period of use. It was rugged enough to withstand some rocky scrambling and the rain. Battery life, with the compass turned ON, is not bad. 7-8hrs or so of continuous use (I include a couple of 30 minute runs in that time frame too) drain around 35-40% of the battery. Without the compass turned on - and I am not sure I need it, so this will be turned off - that will be improved. I'll continue to use it, get to know it and report back again.

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