Sportrak Map

tictac80

I have an old Magellan Sportrak Map that I used reliably for years and then was put away for about 4 years. recently, I inserted new batteries and reset the unit and now it is very inaccurate. After marking a waypoint, walking around the block, back to that waypoint, it is sometimes off by 100 feet. I have tried this numerous times and, when returning to the waypoint the bearing is fairly close but the distance is always way off. There are always lots of satellites connected. Does anyone have any idea why this could be and what i could do about it? Thanks in advance.

Boyd

My first thought was that this could be Y2k related, like some of the problems with old Garmin devices. But it appears the Sportrak was released after Y2k. :)

For starters, I would find a place with a clear view of the sky and just let the unit sit stationary for about an hour. That should give it time to download all the almanac data from the satellites and might improve accuracy (should also improve the time needed to get a fix in the future).

I would also try your same test in another location that doesn't have any obstacles, like a field or parking lot, and see if the accuracy is any better.

Beyond that, Magellan claimed 7 meter accuracy for this device. So if you record a waypoint, walk around for awhile, then return to the same spot and record another waypoint, they could be separated by 14 meters (46 feet) and the unit would still be performing up to specs. For example, the first waypoint might be 7 meters South of the actual location and the second waypoint could be 7 meters North.

tictac80

Thank you for the quick reply, Boyd. I used to do geocaching with it and the accuracy seemed somewhat better than 7 meters. I'll be going to a field next week, away from city influences. Then I'll follow your advice to see if it improves and I will report back.

Boyd

According to the specs, it can acheive 3 meter accuracy with a good WAAS lock. I used to have a Magellan Meridian Gold but don't recall a lot about it. I know on Garmin devices, enabling WAAS can be sort of a mixed bag and you're often better served with it off.

When you tested the Sportrak recently, did you have WAAS turned on? There should be a setting for this somewhere in the menus.

Also, what accuracy was it reporting on the satellite screen during your test?

tictac80

My manual states that WAAS is "included in this GPS". I believe it is always on as I can't find any ON/OFF option for it. I took the unit into the back yard for a while and it found 7 or 8 strong satellite signals, including the 2 WAAS ones.For accuracy it just shows either solid bars (strong) or open bars (weak) and there is a "W" for each WAAS satellite. It also displays "2D" which later changes to "3D" when more satellites join in. In a few days I can take it into a more open area and try again.

t923347

When you do try again you should insure you have enough time to insure you get all of the almanac data downloaded to the device. As Boyd mentioned before this can take a good hour.

tictac80

OK. I will be in an open field next week for a few hours and I'll just leave it ON. I didn't realize it re-used the positioning data from previous usage. I also noticed there are numbers under those satellite bars, probably the strength indicators. I'll try to take a photo of that when it has gathered the almanac. Thanks for the help.

Boyd

Found this old review. Interesting that they felt the Sportrak was the most accuate GPS on the market back in 2004: http://gpsinformation.net/mgoldreview/sportrak-pro-rev.html

Note the comment about waiting 10 minutes to get a WAAS lock however, and that you could get significant errors in places where WAAS isn't strong. It's weird that Magellan didn't offer a menu choice to disable WAAS, but that review tells you a "secret salute" to do it (but heed the advice that it could lock the unit up).

tictac80

I think I should keep the WAAS enabled. I took the GPS to an open field and left it on for about an hour. I got the satellite strengths shown in the attached photo...

http://i1360.photobucket.com/albums/r641/schakelf/Misc Photos/GPS_zps03xl0edx.jpg

I went around the block again to test my return point. It was only off by 2 meters!
It looks like you fixed my GPS. Thank you very much and now I'll know to turn it on early and let it find itself.

Boyd

Cool B-)

You shouldn't need to let it sit for an hour unless it's been a long time since the last use. But, as per that review, you should probably give it 10 minutes to acquire a good WAAS fix before using if possible. At minimum, you want it to have a 3d fix.

tictac80

ok.
Thanks again.