GPS setups/Datums??
Submitted: Monday, Jun 30, 2008 at 09:01
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Member -Signman
With GPS devices now becoming 'de rigueur' for outback touring- it might be a good idea to know how to set up and use the devices..
I was 'logging in' a VKS737 member a few weeks ago & he was giving his location with GPS readings. Anyhow, with HF conditions not all that good- it was difficult to resolve the degrees /minutes /seconds, so I asked him to give it in decimal degrees. "how do I do that" was the response...
At this stage I did have confirmed full degrees (S28 E122) and had him somewhere in the
Laverton area...
I then asked for the closest known location or town..
Response "
well 6 on the Canning"...Anyhow-
Well 6 is about S25.2476 E121.0956. Hmmmmm, something wrong here !! So I asked what datum he had the GPS set- Response "Whats a datum?"
Anyhow- long story/short- he had just got the GPS before the trip- put it in the vehicle and that was it !!
Question- If it had have been purchased for the Northern hemisphere would it make a difference???? Do different Datums vary that much??
Moral to the story- if you've got the hi-tech gear, at least learn the basics to use it. It would have been interesting if we had to get a RFDS response to this fellow using supplied GPS fixes !!
Reply By: David and Justine Olsen's 4WD Tag-Alongs - Monday, Jun 30, 2008 at 09:26
Monday, Jun 30, 2008 at 09:26
wgs84 is the normal datum used these days. Most are withing 300 metres or so. I'd suggest he misread or you misheard.
Hearing Lat and Lon over HF is a a big ask, as you would know. You would need a good copy.
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Follow Up By: Member -Signman - Monday, Jun 30, 2008 at 09:33
Monday, Jun 30, 2008 at 09:33
Hi David...
All good now after your trip?? Good to speak with you on HF..
Yup- I do realize WGS84 (or 94) are the norm. in our part of the paddock..
I did get full confirmation on the 'whole' degrees- so I was wondering if it was a Northern Hemisphere purchase, or the Datum was set to some strange "Outer Monrovia" standard ???
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Follow Up By: David and Justine Olsen's 4WD Tag-Alongs - Monday, Jun 30, 2008 at 09:38
Monday, Jun 30, 2008 at 09:38
Hi David
All
well here. Off to the Cape tomorrow.
I am not the full bottle on odd datum settings.
David
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Reply By: Tony MD - Monday, Jun 30, 2008 at 09:58
Monday, Jun 30, 2008 at 09:58
Hi David.
A Datum is simply a reference point in which to secure a
grid to the planet.
The
grid accuracy becomes less the further one is from that reference point. Thus, we have numerous local reference points (local datums) in order to provide a greater accuracy.
The map datum and the GPS datum needs to be the same.
There are also many different ways of showing position. With the full degrees, minutes, seconds; degrees & decimal minutes etc & this sounds a bit more like what the error could have been (apart from mis reading the information)
Although not finitely accurate, the Maiden Head
Grid to 6 characters as used in Amateur Radio (mostly 6 metres & up) is much easier to use via radio.
You were a good signal into
Melbourne last night on 8022
Anne Beadell Hwy trip starts next Monday. Heading out of
Melbourne on Thursday
Cheers Tony - QF22MC
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Follow Up By: Member -Signman - Monday, Jun 30, 2008 at 10:11
Monday, Jun 30, 2008 at 10:11
Thanks Tony,
Yup- I had them stacked up last night !!
A few EO members out and about (including Vince NSW)- probably on their way to Innaminka.
Catch ya on air on the A/B Hwy- (don't forget a cookie & a pat for Bill the black dog at Ilkurlka...
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