July 2008 Archives

This page describes the procedures used to record and process a series of Garmin GPX files for display online as a Google Map, or as a detailed report that displays a GPX file in the form of graphs and useful statistics.

In March 2008, I joined a Dragoman truck to embark on an Overland journey from the UK to St Petersburg, via Central Asia, China, Mongolia, and Kazakhstan. (See the full route here.) Starting in Istanbul, and continuing every driving day since then, I have been recording the route that the Dragoman truck has taken, using my Garmin GPSmap60Cx GPS receiver. This model of GPS receiver has a removable microSD card that can be used to store tracks. The GPS receiver comes with a 64MB card, but I exchanged this for a 1GB card, in order to have plenty of room to store the daily files. Is that big enough? Yes - the files take up very little space on the card - typically 120 bytes per trackpoint. That's approximately 8.3 million trackpoints on a 1GB card. In other words, if you are recording at the rate of 1 per second, 24 hours a day, it would take 96 days to fill up! I estimate to have generated about 20MB of data for the whole 6 month journey.

To get the GPSmap 60cx receiver to store a daily file of constantly updated positions, find the 'Tracks' page, and notice that there is a dot next to 'Off'. Use the Rocker Key to highlight the word 'On', then press 'Enter' to move the dot to there. You are now recording all your moves, and will continue to do so until you change the setting back to 'Off'. As well as storing positions in a file called the 'Active Tracklog', which we will ignore for the moment, the GPS also stores positions in a daily file, which will be named something like '20080327.gpx' i.e. YYYYMMDD. This is created and named automatically, and can be downloaded to your computer for processing. Whilst you can remove the microSD card from the GPS and put it in a card-reader to see the files, it is a lot easier just to access the data via a USB link. Plug your GPS receiver into your computer's USB port, turn the GPS on, and click Main Menu > Setup > Interface. Select the bottom button marked 'USB Mass Storage'. The computer will then alert you that a new Drive has been detected - use 'My Computer' or 'Windows Explorer' to locate the drive, which will contain the .gpx files that you have generated so far. Copy these to a new folder on your computer's hard drive, then eject the GPS using the 'Safely Remove Hardware' button in the System Tray, and turn off the GPS.

There are a number of ways to produce an online map of your stored GPX files. The following Web sites allow you to plot your GPX data on a Web map:

However, if you want to display a map on your own website, already formatted with all the details of your track, you will need some software that can create it. First of all, you must sign up for a Google Map API. This authorises you to embed Google Maps in your own web pages with JavaScript, and provides a unique API password that you will need for each map. Note that the API applies to just ONE FOLDER on your website. You have to specify the address of the folder when you sign up for the API - for instance: http://www.mysite.com/webmaps/ All the maps that you authorise with the API code MUST be in that folder.

Next, the software. There are various programs that can be used to create the map code. I use RoboGEO, a program primarily designed to geo-reference photographs (more about doing that here). One of its other many abilities is to produce a Google map page showing the location of each photo. You can also add a track on the map, which is what we are interested in here. I simply omit to upload any photos, but make sure the Tracklog is displayed when creating the webpage. To do this, follow these steps:

1. Start the 'RoboGeo' program
2. Click File > Get Locations > Tracklog > Import Tracklog file
3. Select the required file - when it is imported, the total number of points will be displayed
4. Click File > Export > Google Maps
5. Paste your API code to the 'Google Key' box
6. Set the Webpage Title to '20081231' or similar
7. Set the View to 'Map'
8. Check the box 'Include the GPS Tracklog on the Map'
9. Set the 'Approx max number of polylines to create' to a value greater than the total points in your file
10. Click 'Create Google Map', and save it in a folder with the same name as the Title
11. Upload the map.htm and map.xml files to your server, and view the map online in a web-browser

To view the maps I've already generated, click on the links below. The map will initially load as a standard roadmap, but you can also select a Satellite view, or a hybrid view of the two, using the buttons in the top right of the screen. The amount of detail that the Satellite view will provide depends on Google's current satellite photos for that area. In the countryside this might just show a general view that identifies built-up and rural areas, whilst in bigger cities you can often zoom in to see individual buildings, and decide which exit we took from a carpark, or even where we parked in that carpark! The detail can be astonishing. You can click-and-drag to move the map around, and zoom in and out using the +/- slider on the left of the screen. Note that Google provides no maps for Georgia or Azerbiajan (why not?), and the western parts of China are similarly blank, so you will have to use the satellite photos instead.

To create the detailed Route-Reports, I use the online uTrack report generator at http://utrack.crempa.net This page will upload a GPX file from your computer and produce a detailed Route-Report that shows a number of graphs and statistics, such as:

• Elevation profile graph - elevation plotted against distance.
• Elevation profile graph - elevation plotted against time.
• Elevation statistics: Minimum elevation, Maximum elevation, Average elevation, Maximum difference, Total climbing, Total descent, Start elevation, End elevation, and Final balance.
• Speed profile graph - speed plotted against distance.
• Speed profile graph - speed plotted against time.
• Speed statistics: Minimum speed, Maximum speed, Average climbing speed, Average descent speed, Average flat speed, and Average speed.
• Time statistics: Date of track, Start time, End time, Total track time, Climbing time, Descent time, and Flat time.
• Distance profile graph - distance plotted against time.
• Distance statistics: Total flat distance, Total real distance, Climbing distance, Descent distance, and Flat distance.

Once the report has been generated, an option is presented to save it as a PDF file, which can later be uploaded to your server. To view the Reports I have generated so far, click on the links below. You will need a PDF reader installed on your computer to read PDF files - suitable software is available free from Adobe. Some errors still exist - for instance, when the satellite signal is lost when we drive through a tunnel, the altitude can have unexpected results. When I have more time, I will try and edit these files to remove such glitches, but for now, whilst I am 'on the road', these reports will at least give you an idea of what we have been doing.

The table below contains links and details of all the maps and reports generated so far:

Then, after a break in Beijing...

Then, after a few days in Almaty...

And so to the end of a truly memorable journey. Since we started at Calais on the 17th of March, the truck has driven exactly 38,138 Kms, or in other words, 23,836 Miles. Many thanks are due to drivers Toni, for UK to Beijing; Blair, for Beijing to Mongolia; Vernon, for Kazakstan to Calais; and a very big thanks to Jay, who drove the whole way with me, Calais to Calais.

Note: All route and stored position data are copyright 2008 Tim Makins and MapAbility.Com