GPS Navigation
October 8th 2006 20:18
Learning Coastal Navigation
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Recently I had the opportunity to help out some people who were a bit confused about GPS (Global Positioning System) accuracy.
They assumed that the accuracy problem was in the GPS unit. A common mistake as compasses have to be adjusted for deviation (magnetic fields caused by the vessel generaly) and other tools have other problems. However even the most basic of GPS will give an accuracy estimation when it turns on. Usually a few feet or metres. The accuracy is dependent on how well the satelites are picked up by the unit.
When you relate the information you have on your GPS to a paper chart, Latitude and longitude, then you must make up for an inherent error that exists on the chart. Usually a correction is stated on the top of the chart page. This can be a matter of some 50 to 100 meteres or points or % of a nautical mile. The reason is that when the chart was drawn the accuracy of the navigator was dependant on previous navigators (like James Cook) putting in the correct info. The system here in Austrlia and adjacent waters is very accurate considering the problems faced by early navigators (and some more recent)
So my suggestion to you if you plan to use GPS is to first do a navigation course that does not use GPS so you know exaclty how good your GPS is. There are many features and you will not know what they mean unless you have a good grounding in navigation to start with.
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Comment by Cibbuano
Hunt Famous
Orble Post of the Day
Fat Cult
Techbreak
Like you said, many of the original maps are inaccurate, which makes GPS look funky...
Comment by TomN
Boat Heaven