Most accurate GPS mouse

spook · Occasional Visitor Joined: Nov 13, 2003 Posts: 11

Has anyone else found that handhelds e.g. Garmin and especially Magellan make the best GPS mouse Question

I don’t mean the mice made by these companies, I mean the handhelds like the GPSMAP 76C and Sportrack when connected via cable to a PDA or Laptop running whatever map software you choose. In my opinion they work with the minimum of hassle and their position accuracy is far better than BT GPS mice which might be an overstatement, but I have a Fortuna Clip On and my position wanders all over the place. A friend has a Rikaline X7 and another has a SysOnChip and both report the same position wander. My neighbour with his Magellan delights in showing me the track of him walking from room to room INSIDE my house. He proved its accuracy by walking from my house back to his with a sheet over him and the GPS. 8O Don’t get me wrong I find the Fortuna works ok for road navigation and I suppose herein is the lesson. There are GPS's and there are GPS's, for people who need to know which road and for people who need to know which side of the road.
The puzzling bit to me is, I thought that my position was derived from the signal arriving at the GPS therefore the same satellites giving the same signal to two different GPS's at the same place would display the same position within reason. The computations of these signals must be very complex. Do some GPS's compute to like less decimal places than others thereby saving on processor power Question

How else can one make of GPS consistently wander 40ft another 20ft and another 3ft when they use the same chip and the same satellites Question

Has anyone in the UK actually taken their GPS to a OS Surveyed site and noted exactly how accurate there GPS is Question

This would make a good forum subject "My GPS is good to: ft. How good is yours" . I know they are dearer but you get a full working GPS with data logger and not just a PDA add on. Anyone out there with a Garmin/Megallan and a BT mouse Question

What do you find Question

Would You buy a BT enabled Garmin/Megallan Question

Spook

lbendlin · Posted: Wed Sep 22, 2004 3:25 am Post subject:

There are different forms of antennae (helix versus planar) and different signal evaluation algorithms. Some of the BT receivers nowadays have XTrac algorithms etc. I think it really is a question of the target audience. Why would a street routing receiver need to be accurate enough not to bump into a door inside your house? It becimes a different story when the visual confirmation is lacking - as your friend demonstrated, and as the Darpa Grand Challenge has shown too.

Now what was your problem again ? ;-)
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spook · Occasional Visitor Joined: Nov 13, 2003 Posts: 11

Hi lbendlin
No prob at all Wink

I was just making a comment from my very limited observation and wondering if others found the same.
So I am not too far off the mark then. Forget about the x-trac cause this is designed to overcome a specific environment and forget jump to road map software. I am just looking at the wee dot that says your here that sometimes becomes a big circle that says your somewhere near here. All GPS has the same potential accuracy, it’s just down to the manufactures how much accuracy they want to build in. It does seem that one or two manufactures are willing to build in that little bit more and from what I have seen, this increased accuracy does not adversely affect their road map software and its every bit as sensitive as my Fortuna in x-trac. I suppose I must be a belt and braces type. Imagine the following scenario. I navigate 50 miles to a beach, I build a few sandcastles there, I return home, I discover I have lost my wallet, I return to the beach. I would rather dig a 1m hole than a 20m hole. The reassurance is knowing there is more there if it’s needed. Me, I feel like I am red lining my Fortuna all the time.
In answer to your Q: Why would a street routing receiver need to be accurate enough not to bump into a door inside your house- A: Because many of these so called "street routing receivers" pretend to be "Topo routing receivers"
So has anyone out there made any comparisons Question

Would the best all round BT GPS mouse be a BT Garmin/Megallan Question

If there was one, would you put it on your wish list Question

Spook

lbendlin · Posted: Thu Sep 23, 2004 12:00 am Post subject:

I am making a wild guess here but the best all around GPS receiver will be the one that is integrated in my mobile phone/PDA. And it could even have a helix antenna...
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Taxman · Posted: Fri Sep 24, 2004 12:05 pm Post subject: Accuracy

Some very valid points. OK so for driving long distance then getting arouns a town accuracy does not have to be within a couple of feet. But if used when hiking accuracy can become something of an issue. I'd rather know that I'm still on track when walking across open areas (think of the highlands or western isles) rather than find that I've wandered off by 20 - 30 metres and am now on the wrong side of a yawning gap! Yes I could still use maps and a compass - but I really thought that using GPS could rid me of these.

Question

Hows about bringing that comparisons tables pu to date by including an accuracy field?

lbendlin · Posted: Fri Sep 24, 2004 1:54 pm Post subject:

Not sure 20 metres make such a difference in the wild - your maps aren't that exact either.

You will need to understand that there are also other limiting factors - atmospheric disturbances, satellite constellations, satellite clock shifts, whatever that make a focus on accuracy highly speculative. It takes a good hour for a surveying GPS to filter out all the errors for a fixed position, not even speaking of a moving position.
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icsys · Posted: Fri Sep 24, 2004 3:11 pm Post subject:

Quite an interesting thread.

My experience of accuracy is using OS maps on a PDA with a BT receiver. I have seen accuracy down to less than 2 metres on more than one occasion.
Yes I know that atmospheric disturbances, satellite constellations, satellite clock shifts etc... and the calibration of the maps can affect accuracy but whenever I have followed a marked footpath my position on the PPC has followed it with remarkable prescision.

So I am more than happy with the receiver that I have Thumbs Up

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