Fujitsu-Siemens Loox accuracy

[Pajaholic]

I'm an absolute newbie who's yet to attempt his first find and who hopes to be able to use his current PDA for geocaching. The PDA is a Fujitsu-Siemens Pocket Loox N520, which has a built-in SiRFstar III GPS receiver. To this, I installed an evaluation copy of BeeLineGPS and ran some accuracy tests.

 

Test 1: Get the co-ordinates of a known landmark from Google Maps, create a LOC file with those co-ordinates and import to BeeLine. Take dog for walk to check whether the GPS would accurately direct me to the resulting waypoint.

Result: The least distance from the waypoint shown was just over 3ft when about 12ft away from the waypoint. When stood over the waypoint, the GPS claimed I was about 15ft away.

 

Test 2: Create several waypoints of the same point, moving away from and back to the location between each.

Result: According to Google Maps, the closest waypoint was about 4ft off and the farthest almost 40ft off.

 

Test 3: Create several waypoints with the back of the hand holding the PDA on the same point and without moving between each.

Result: Roughly the same as for test 2.

 

I'm disappointed with the results as I was expecting an accuracy of around ten feet. Are my expectations reasonable for this device? Is there something that I can do to improve accuracy?

 

TIA,

 

Geoff

[+Smurf]

Is there something that I can do to improve accuracy?

 

http://uk.ts.fujitsu.com/support/downloads.html

 

search for your model (n520) ..... there is a download for "GPS Instant Fix "

 

it doesn't improve it by much, but it does improve it

[+Indotguy]

In regards to Geocaches, don't sweat the accuracy thing too much. A GPS is good at getting you in the general area. Practice, experience and intuition are the main things when it comes to actually finding caches.

[Pajaholic]

Thanks guys. I installed the "GPS Instant Fix". It took half an hour or more to get the first fix out of the unit after doing the update and the reported HDOP seems to have increased, but now TTFF seems a lot quicker so I suspect that accuracy might improve also.

 

Since I made my OP I've spotted that some owners of dedicated handheld GPS units report similar accuracy to my PDA, so I guess that Indotguy is spot on. It just seemed to me that if my GPS was up to 40ft off and that was typical, once I'd got the minimum distance reading I'd potentially need to search a circle of diameter 160ft - which seemed huge considering the accuracy implied by the co-ordinates that geocaching.com provide.

 

After a little research, I conclude that lat/long co-ordinates to six decimal places imply an accuracy that just isn't possible with the sort of devices that geocachers use. AFAICT, six decimal places implies an accuracy of about 10cm, so surely five place (i.e. an implied accuracy of approx a metre) is more reasonable.

 

That said, I guess that attempting to find a few caches will be the acid test. My wife and I are off caravanning this weekend. I've loaded details of a few caches near the campsite into the PDA and hope to make my first finds.

 

Thanks again,

 

Geoff

[+Marky]

That said, I guess that attempting to find a few caches will be the acid test. My wife and I are off caravanning this weekend. I've loaded details of a few caches near the campsite into the PDA and hope to make my first finds.

Good luck with finding your first caches! I think you'll find that your PDA will get you close enough and from there, you would just use your powers of observation to find the cache. If GPSrs positioned you to within 10 CM of a cache, it probably wouldn't be as fun. I use my iPhone for spur of the moment caching, and I have no complaints. I bet it is not as good as the GPS in your PDA.

 

--Marky

[Pajaholic]

Thanks Marky.

 

Two finds made. However, the PDA was about as much use as a chocolate fireguard for the second. Both were in woodland, and for the second the PDA couldn't see the satellites for the trees and I couldn't get a fix for the last mile and a half to the cache. Thankfully, I'd plugged the co-ordinates into Google maps and printed off some aerial photos. Google maps was spot on. Even if that felt like cheating, I'd walked the five mile round trip so I didn't feel too bad about signing the log!

 

Geoff