Memory Map And Accuracy

[+Alboy]

I recently bought a BT-338 to go with my PDA and Memory Map for caching. But it doesn't seem "quite right".

 

Have a look at the picture attached of yesterday's caching. Where possible I followed paths, but the track seems a little off?

 

http://uk.pg.photos.yahoo.com/ph/aliaird/d...scd.jpg&.src=ph

 

Sorry, can't get thumbnails to work!

 

Whenever I got to a cache the Memory Map said I was about 20ft off. Even when sitting on a waypoint with a clear view of much of the sky it wasn't getting an accurate reading.

 

Also when using it with TomTom I get the feeling that it is struggling to keep up. It's annoying when going round roundabouts for example as I can't be sure from TomTom which is the correct exit, as it is too far behind to give me advanced warning.

 

I don't recall this problem with my old Sirf II based bluetooth receiver (I've given that to my dad in Canada so can't get it back for comparison!).

 

Any ideas? There doesn't seem to be any way to calibrate it or add in some sort of correction figure.

 

Any thoughts much apprciated.

[Master Mariner]

This forum topic may help explain the problem. Hope the link works.

[+Learned Gerbil]

Have you got custom POIs displayed in the 3D view on TT?

[+Alboy]

I'll see if I can check the firmware version on my GPSr. I was under the impression that they were no longer being sold with the Static Navigation on.

 

Happy Humphrey says that SN is not on for the BT 338?

 

Any idea how I can check?

 

Re TT, yes I have the pocketgps speed camera pois enabled (oh, and caches!!)

 

I think I need to keep those enabled if poss (points on licence and all!)

[+Learned Gerbil]

TT5 has a bug which TT seem detirmined not to fix. TT4 which had the same graphics worked fine. The bug is that if you have custom POIs enabled in the 3D view you will have your position shown some two seconds or so behind your actual position. The solution is to not have in view all the POIs that you have added to your system. Don't worry about your license. You can have warnings on without the problem appearing, and the POI you are being worned of will appear in view when the warning goes off.

 

So go into Enable/Disable POI and disable them all. Then go into Warn When Near POI and set the relevant warnings. Of course this means you can't spot POIs as you drive past them, but that is why TT5 is broken.

TT's view is that custom POIs are not supported! Their support of the PPC version of TT5 is terrible!

[Nediam]

Thanks Learned Gerbil about the TT5 info. I used to run TT3 with no problems (except that the maps were too old ). TT5 seemed rubbish and I was going to re-install version 3. Now I'll use your fix, cheers .

 

Re the accuracy for memory map. I've found that roads and tracks etc are plotted very accurately, however the public footpaths are quite often several metres out. This may be due to the speed issue as linked in the other thread by Master Marinor.

 

I tend to walk in a dead straight line towards the cache at a fair pace, when the display reads 20 feet to go, I stop and wait to see what the GPSr does. This usually get me to within 5 feet of the cache.....usually

 

Good luck with your set up and happy caching

[Nediam]

...Then go into Warn When Near POI and set the relevant warnings....

 

Oh what great noises!!!

[+Alboy]

I've read somewhere that you can customise the noises so that you get a voice warning you that you are in a 30mph zone etc. I think it's on pocketgpsworld.co.uk. I'll have a look.

 

Do other BT338 users have this problem re caching accuracy?

[+Moote]

Tree cover, do this with a standard GPS chipset and it would look worse. But mapping and BT338 are fine

[+Alboy]

Thanks for that.

 

Moote, as far as you are concerned, is there Static Navigation enabled on the BT338? Do you know how you can tell which firmware is running?

 

The changed POI warnings are at http://www.pocketgpsworld.com/tomtom-poi-alerts.php

[+Learned Gerbil]

Yes, you can replace the noises by replacing one of the ststem files for TT with a version with customised sounds. Personally I like the noises TT produces. A gentle Ding Dong reminder for Gatso, a Ping for a traffic light camera, and the full Start Trek red alert sound for a SPECS zone!

Edited April 23, 2006 by Learned Gerbil

[davester]

I've walked 1000s of miles with Memory Map and GPS combo and after looking at your picture I would say that is nothing out of the ordinary. There is no systematic shift to suggest a positioning error. It is therefore more likely that it is a combination of tree cover, inaccuracy of the 1:50,000 scale maps and the footpath being in a different place on the ground to that shown on the map (not an infrequent occurance).

[+John Stead]

Yes, you can replace the noises by replacing one of the ststem files for TT with a version with customised sounds. Personally I like the noises TT produces. A gentle Ding Dong reminder for Gatso, a Ping for a traffic light camera, and the full Start Trek red alert sound for a SPECS zone!

I have set a mooing cow as the SPECS warning - thinking of all the drivers who slam on their brakes when they see the camera and then speed up again until the next one!