Accurate GPS receivers for boundary mapping

nomadros · Occasional Visitor Joined: Feb 22, 2007 Posts: 11

Hi..Apolgies for what may be a dumb newbie question but... I've bought some properties in the middle of nowhere in Northern Spain and I need to map out the boundaries accurately. All the properties are large but the boundaries are hidden in dense bush, forests or your typical snake infested wilderness. I therefore need something that'll position me accurately, but I'm toiling with keywords for searches. Most stuff, I've looked at seems happy telling me where I'm going rather than where I am (exactly). Can anyone give me keywords or point me at some lists of products or reviews? My wish list is.... I stand still and the thing tells me that I'm at X by Y within a metre or so. Hope this is possible and any help would be appreciated.

barryd · Posted: Sat Feb 24, 2007 9:19 am Post subject:

Hi there

You won't get a definitive position to "within 1 metre" from consumer units, particularly not in "dense bush, forests" where many will struggle to give you a steady fix at all.

There are plenty of things that will tell you with good probability where you are to about 5 metres, if you keep still for a bit and they have a good fix, which is perfectly adequate for most leisure uses. For your conditions I'd expect anything using the Sirf III chipset to tend to get and hold a fix better than other older ones.

Look at handheld GPS units e.g. from Garmin or Magellan, or at the wide variety of free to expensive GPS utilities or topographic software products available for your PC, PDAs Pocket PC etc. (which will need to be connected to a GPS receiver, of course, to give your position).

You will be swamped with options, so one search term that might help you narrow it down to your needs is "GPS averaging" or "waypoint averaging" which is based on the principle that lots of approximate position readings can be averaged out to give a better one. This will lead you to products that have it built in, or to free utilities such as those from VisualGPS.

Good luck with the snakes!
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Barry Davies

nomadros · Occasional Visitor Joined: Feb 22, 2007 Posts: 11

Cheers Barry...I was really toiling with this as the newest receivers seem to gain better accuracy from a mix of more channels and cell masts (and guess what, no cell masts anywhere near where I am). I'll see if I can find something at around 5 meters accuracy as that'll give me a chance of finding any boundary walls in the undergrowth. This 15 meter accuracy business is just no use to me.

Anyway, have been looking at the magellan stuff which comes with barometric altimeters which I need as I have to pump water up a few hundred meters from my well head, so height is important too.

And I appreciate the keywords to help drown out the noise.

BTW, the snakes are the least of my problems. I was up at one site the other day as saw cat prints the size of my palm. I got hold of a hefty branch at that point and have decided to get BIG DOGS and join the gun club! They tell me in the local village that someone let a panther loose. Could be rubbish, but the prints were too big for a lynx!

Hey ho!

Thanks again
Neil

Skippy · Posted: Sat Feb 24, 2007 2:32 pm Post subject:

You want something like this:

http://www.garmin.com/products/gpsmap60cx/

It has the new SiRF III receiver which gives very good reception in difficult areas (under very dense trees etc). It doesn't come with street maps and they may be an expensive add on too.

The Garmin Quest is also a good all round GPS unit (not quite as good reception as the SiRF III GPS units) and you can use it off road as well as for street navigation.

You can download the tracks from the Garmin unit and view them in other applications, including Google Earth.

Good luck!
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Gone fishing!

Skippy · Posted: Sat Feb 24, 2007 2:35 pm Post subject:

As for accuracy, most GPS units support WAAS (Also known as EGNOS in Europe) and you should be able to get accuracy down to a few meters with a reasonably clear view of the sky.

You can get very accurate fixes (better than 1 meter) using survey grade GPS units but they are well expensive....
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Gone fishing!

nomadros · Occasional Visitor Joined: Feb 22, 2007 Posts: 11

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