5.1.6 Track with GPS
Level of expertise required for this Chapter: Intermediate for Garmin / Advanced for PDA; general GIS training
General process: Setup of GPS (see Annex 12) --> Installation of driver on computer (see Annex 1.3) --> Track (explained in this Chapter) --> Download from GPS to computer (see Chapter 5.1.7) --> Edit, particularly with snapping (see Chapter 2.11) and tidy line junctions (see Chapter 2.2).
A) With handheld GPS (Garmin):
The easiest and most user-friendly way of tracking works with a handheld GPS, such as the Garmin GPSMAP 76Csx.
After having been configured for the first time use (see Annex 12), you just turn it on, when you are in the field, for example at the start of the road to be tracked. When you are in a car, place it under the windshield. The GPS should always 'see' as much of the sky as possible.
The location error is displayed on the satellite page, next to the coordinates (see below). It should always be less than 10 m.
Be aware, that it takes time for the GPS to acquire (‘find’) the current satellites on the sky and to communicate with them. Thus, wait some time after you turned the GPS on.
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The internal memory can hold upto 10,000 points (= 100 km , at the recommended 10 m interval settings, see step 4.5 of Annex 12.1). But when saving the track to the memory card, this will be reduced to 500 points, i.e. there is a huge loss of accuracy.
Thus, the best is to download the track to a computer after not more than 100 km (see Chapter 5.1.7 for the procedure to download data to LUPMIS).
If this is not possible, you have to save the track after less than 5 km: PAGE till ‘Main Menu’ > Tracks > Save > OK > Clear
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You can always read the coordinates of the current location at the top right corner of the satellite page (1st page when you turn on the GPS). Be sure that you have always the ‘30 N UTM’ displayed (except when you are in Volta: UTM 31). The displayed error (below ‘Location’) at the right side should read less than 10 m for standard TCPD surveys.
Also, be aware, that the accuracy of the coordinates displayed at the GPS is not as accurate as the coordinates, which are stored internally and later transferred to Map Maker.
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B) With PDA:
More powerful, but also more sensitive and prone to user errors, it the method of tracking with a PDA.
1. Turn on the PDA.
2. Load GPS Tuner (If not available, contact TCPD-HQ / LUPMIS, email. For installation see Annex 7
3. You might have to wait a while, till all files are loaded.
4. Press receiver (dish) icon till GPS Panel window is displayed and be sure, that the icon says 'Stop GIS' (if it says 'Start GPS', click on it).
5. Press receiver (dish) icon till Settings window is displayed > Track, and select the interval distance of tracking (in town 5 m, outside towns 25 m).
6. Wait some 5 minutes, till audio message says 'GPS tracking is ok'.
7. After tracking, load your file: Press flag icon till Waypoint Manager window is displayed and press floppy disk icon (bottom right) > Track > SD-MM card > Select KML for export (KML), leave filename as suggested (date and time stamp) > Save
See Chapter 5.1.8 for the procedure to download these data to LUPMIS.