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Expedition Medical Services

NAVIGATION II – GPS


Handheld Global Positioning Systems are probably the single greatest development in desert (and other wilderness) navigation in the last 50 years. Prices have fallen so that a basic handheld unit is now well under £100 and will tell you where you are to within 15 meters. Calculations and measurements with a sextant that would have taken an hour now happen in fractions of a second to a hitherto unimaginable accuracy. However they depend on chips and batteries – but you could bring 3 just in case for less than the cost of a secondhand sextant. Maps and compasses are still needed and the prudent keep a written log to fall back on.


GPS110tataJOHNHARPER
Garmin GPS III plus with remote aerial & World Map Morocco data ©Dick Morgan

Basic GPS unit give your location and can display “waypoints” that you have previously visited or entered onto the unit as coordinates, but crucially they do not have a background map giving details of roads, rivers and places. Having basic mapping embedded enables waypoints to be put in context. More expensive GPS units enable a link to a PC to enable up and downloading of data including compatible digital mapping data. Garmin and Magellan are 2 of the major players. Whilst in Europe there is little to choose between them in Morocco I have found the map datum uploaded from Garmin’s MapSource CD: World Map (£50.07 from www.globalpositioningsystems.co.uk ) to be pretty good if not always foolproof. It has often had barely visible desert tracks on its base map when I have been out in the desert. A detachable aerial on a long lead enables the navigator to sit with the unit out of the dashboard sunshine comfortably held on his – or her – lap. Sensitive electrical equipment doesn’t like 120ºF temperatures. Although this unit is now discontinued, newer Garmin units are capable of uploading Moroccan Maps from this CD. The cheapest is the e-Trex Legend (£194.85 from supplier as above). This unit runs on AA batteries but doesn’t have a detachable aerial. More expensive Garmin units capable of utilizing the Moroccan map datum include the Quest v7 (which offers European voice guided route finding at £297.99) to the large screen dash-mountable GPS 276C at £489.95 + £149.95 for the dash mount & European voice guided route finding software. As they say you pays your money and takes your choice. Suction dash mounts are available for the eTrex Legend as is a voice guided route finding mount & european ble pensive Garmin units capable of utilizing the Moroccan map datum include the Questd gives spo upgrade. The advantage of the smaller handheld units is that they slip in your pocket when you leave the vehicle so they are less likely to attract unwanted attention.

We will be issuing a detailed waypoint list to everyone so the time onboard ship to Tangiers can be usefully employed entering the waypoints! For those with Garmin units with PC connecting cords we can do it as a simple waypoint upload.

Since we will be travelling as a group GPS is not vital for each vehicle. Garmin’s basic GPS 12 costs £113.39 and a serial data cable to enable waypoint uploads is £26.21 and if your laptop doesn’t have a serial port you can get a serial to USB converting lead for £12.95. This is a basic but robust unit: Matthew has 3 which have withstood 5 years in the field. I don’t pretend this is an exhaustive guide – but it is based on field experience. All these units are water resistant and can be used in the rain. I’m happy to learn more from any of you with better knowledge.

 


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