Nokia N810 accuracy

[+ravenx99]

I recently started geocaching when I got a Nokia N810 internet tablet with integrated GPS as part of my job. (I have to support them for sales people.)

 

Lots of people are complaining about the time to fix, but I can live with that... what I'm having trouble with is accuracy.

 

I can set the unit down on my counter with tracking turned on and eleven satellite signals seen, and my track will wander as much as 75 feet off of my actual position. (Based on a Google Maps overlay.) Always southerly... the track ends up describing an approximate oval 75 feet from north to south and about 35 feet east to west, with my actual position at the northern end of the oval. The GPS will never move, but it thinks it's moving at about 0.2 mph on the average.

 

Now, the N810 has a cheap GPS chip meant for the cell phone industry, so I'm not terribly surprised. (The primary features of this chip is small size, low cost, and low power... oh, and it sometimes receives GPS signals, apparently.

 

Is anybody else using an N810 and having better luck? Any tips on how to work within these limitations? (And how in the world am I going to hide a cache with such inaccuracy?)

 

Is this unusual behavior and should I look at exchanging the unit?

 

Thanks!

[+qlenfg]

I haven't played with the 810 -- only the 770 and 800 and a bluetooth GPSr. I assume you are using an included mapping program? Might be some kind of settings to tweak to improve the accuracy or to tell it don't assume the position has changed if the speed is below a certain point or if you don't move a certain distance. Might also look at Maemo Mapper if its available for the 810.

 

If you have a friend with a bluetooth GPSr, you might see how it compares.

[+ravenx99]

Thanks for your reply.

 

I'm using Maemo-Mapper.

 

The "some kind of settings" is the thing I'm hoping someone will provide. I'm a Linux developer/administrator by trade, but I'm a GPS novice. There are a lot of people poking around at the lower-level stuff, but they're looking to fix the 15-minute cold fix problem and nobody's reporting a problem with inaccuracy. So I was hoping there was some experience with this model in the geocaching community.

 

And I've never owned a GPS or used one before... I have no idea if this is typical for a cheap GPS or if it's wildly busted and in need of replacement.

 

Hopefully I'll meet someone at the local geocacher's breakfast on Saturday that has a Bluetooth-capable GPS and I can give that a try... it'll at least tell me what level the inaccuracy is occurring at.

 

Thanks!

[+qlenfg]

Depending on where the GPS antenna is located within the 810, how you hold it may make a big difference in what it receives. Most GPSr units have a small external antenna, which works best when pointed up. An internal antenna is used on the 810 to keep the package small and rectangular.

 

Might set the 810 out on a non-metallic surface elevated above the ground in an area without trees and see how far the track jumps around. You can play with the position of the unit to see if it has any affect.

 

Even a fancy GPSr will 'wander' when you have it zoomed in really close and it doesn't have a strong signal. Just because the satellite screen shows a large number of satellites in view, it doesn't mean your position is more accurate. I don't recall if Maemo Mapper has an accuracy figure it can display, but if it does, this will tell the tale as far as your real position goes.

 

In any case, the 810 is a neat package. I love my 770, although its slower, has a mish-mash of hardware, and uses an oddball memory card. I'm seriously looking at an 800 as they are down pretty cheap and I have a whole bunch of movies and TV shows formatted for the Nokia units. Not to mention I can enable the speech on Kismet

[+ravenx99]

Okay, I've spent some time with the N810 and a basic eTrex (borrowed), and it looks like the N810 is at least as accurate if not more.

 

The real "problem" is that the high resolution of zoom level 0 creates an illusion of mapping accuracy that the GPSr doesn't provide. With the eTrex, you don't get this because the resolution only goes down to 200' to a centimeter on the screen, while Maemo-Mapper will zoom much further in.

 

So realizing that an accuracy of 15 meters is the best that's expected from the eTrex, I'd say that the N810 is doing pretty well.

 

I still don't like traipsing about in the woods with a device that isn't built for rough handling. I'm buying an "outdoor" GPSr and using the N810 for higher-level navigation and cache database management. GPXView and Maemo-Mapper combine to make a pretty nice paperless system.

[+qlenfg]

RAM makes a good mount if you want to put the N810 in the car. Here is my N770 mounted in the van:

 

[+ravenx99]

RAM makes a good mount if you want to put the N810 in the car.

 

Cool. The N810 comes with a car mount, but it's designed to be screwed to the dash! It's a two-piece assembly, and Nokia sells a suction-cup base for it... for over $50.

 

It has an AMPs mount interface, and I see that Ram has a suction-cup base that will fit it for $13. Excellent. Thanks for the tip... I'd spent time searching for a compatible suction-cup base and came up empty-handed.

[+qlenfg]

There are four parts to the RAM mount I have. The suction cup and one of their compact bases (2), a long arm (1), and their RAM PDA (3rd style) mount. Here is the link to the RAM PDA (3rd style) mount.

 

You can also get one of their standard 2 1/2 round bases which I believe is drilled for AMPS mounting as well. I know it fit on several cell phone cradles and satellite receivers, which I thing accepted AMPS mounting plates. It looks like they now have a square AMPS plate too, so just snag the kit with the suction cup, compact base, arm and AMPS plate.

 

The neat thing is the PDA mount holds the Nokia on all four sides and its easy to remove the unit. I added a cable clamp to hold my power cable so it can't be jerked out of the Nokia accidentally.

 

You can buy the individual parts or the whole thing. My preferred vendor is cyclegadgets.com.

 

(I was looking for the photo of the N770 with Kismet running, but I guess I deleted it. I sent it to RAM for their photo gallery to get a chuckle out of a few folks who know what it is.)

Edited May 22, 2008 by qlenfg