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Old 05-05-2008, 04:50 PM   #1 (permalink)
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I have a new 8130 with gps and have installed both bbtracker and GPSed to give them a try. Both seemed to work very well, until I went up to the Sierras to do a little hiking. Both programs are reporting my elevation several thousand feet in the negative. Interestingly, it seems to be almost exactly inverse. For example, when I know I'm at about 4,000 feet, it shows -4,000 feet. Since this happens in both apps consistently, I'm assuming it's something to do with the location api or the GPS itself. It's essentially just an annoyance, but it does cause problems with things like viewing the track in Google Earth, which attempts to fly at the elevation of the track and ends up crashing into its own terrain model.
Has anyone else noticed this?
Is it potentially a problem with the actual hardware?
Does anyone know of software that will strip elevation data from a .gpx or .kml file, or potentially reset it according to a terrain model?

Thanks all!
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Old 05-05-2008, 05:36 PM   #2 (permalink)
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Originally Posted by shrag View Post
I have a new 8130 with gps and have installed both bbtracker and GPSed to give them a try. Both seemed to work very well, until I went up to the Sierras to do a little hiking. Both programs are reporting my elevation several thousand feet in the negative. Interestingly, it seems to be almost exactly inverse. For example, when I know I'm at about 4,000 feet, it shows -4,000 feet. Since this happens in both apps consistently, I'm assuming it's something to do with the location api or the GPS itself. It's essentially just an annoyance, but it does cause problems with things like viewing the track in Google Earth, which attempts to fly at the elevation of the track and ends up crashing into its own terrain model.
Has anyone else noticed this?
Is it potentially a problem with the actual hardware?
Does anyone know of software that will strip elevation data from a .gpx or .kml file, or potentially reset it according to a terrain model?

Thanks all!
It's a known problem with the OS. Just ignore the minus sign and you should be ok.

Last edited by InstaMapper : 05-06-2008 at 01:14 AM.
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Old 05-05-2008, 06:47 PM   #3 (permalink)
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All of the BB GPS sytems have issues with the elevation. There is a great post in the bbtracker thread. Sorry can't sort through them right now but search the post for elevation.
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Old 05-05-2008, 10:05 PM   #4 (permalink)
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stinsonddog - I read the bbtracker discussion on elevation, and I think I understand the tidal vs. geodetic inaccuracy problem at a conceptual level. I don't think this is the same thing for a couple of reasons:
1. My understanding is that this inaccuracy should be rather limited in scale. In my example where I was at 4,000ft and it's showing -4,000ft, I'm off by 8,000 feet (2,500 meters). That's beyond inaccuracy to simply nowhere close.
2. When I went down the mountain, my elevation went up. E.g. back in the valley at sea level, I show within a few hundred feet of 0 elevation. No matter what your inaccuracy factor, you certainly shouldn't see your elevation go up by 4,000 feet as you go down by the same.

instamapper - If a problem with the OS, do you know if this has been reported? Seems like a fairly high impact / low complexity fix for RIM. I can ignore the minus but it makes external programs (read: Google) blow a circuit trying to interpret high-elevation paths (because they're recorded as somewhere nearer the Earth's core).
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