AnswerID: 6434 Submitted: Friday, Sep 06, 2002 at 00:00
Alex
replied:
G'day Kim, the only dumb questions are the ones you don't ask for fear of looking dumb. First off, the map needs lattitude/longitude gridlines or eastings and northings on it, and the
GPS needs to be reading in the same units as the map. After that its a matter of following the gridlines for the
GPS position to their intersection on the map to establish your position (although this takes a bit of practice and will still only be approximate). There probably will only be gridlines every so often on the map, so you need to estimate the intermediate point where your
GPS tells you you are. There are 60 seconds of lat/long to a minute of lat/long, and 60 minutes to a degree. A minute of lattitide is one nautical mile, or approximately 2km.
Another potential problem is that the map and the
GPS are using different datum points. There have been several used in
Australia over the years, and on my last
Canning Stock Route trip I found that the map was using a different datum to the
GPS, and I was up to several km off on survey marker posts I had definite locations for.
Once you get these issues sorted, there should be no problems. Alternatively, a 4wd training commpany or
accessories store such a s ARB should be able to point you in the right direction on how to learn this sort of thing. Hope this helps, cheers, Alex.
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FollowupID: 2896 Submitted:
Monday, Sep 09, 2002 at 00:00
Kim posted:
Thanks for that Alex.
I guess what I was leading up to, is that I find it difficult (even with a finely graduated ruler) to measure out the minutes,degree and seconds on both the Latitude and longitude sectors,to arrive at an accurate intersecting point.
For example, when I was in the Simpson last year I was parked at a well know feature and decided to test the accuracy of my calculation on a map. I was not able to come close to an accurate fix on the map. Meaning that if I was out in the scrub and wanted to know where I was, I could be kilometres away from where I thught I was.
Hope that makes some sense.
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