3 ms·

Somewhat unrelated to the original article, but: I got great results with GPS on my droid in north Florida, but I recently moved to Seattle and the performance

by buss 16y ago

Somewhat unrelated to the original article, but: I got great results with GPS on my droid in north Florida, but I recently moved to Seattle and the performance decreased. It takes me 2-3 times longer to get a GPS fix, and it's often off by as much as a block. Could it be the latitude?

sprout 16y ago
There's definitely some variability based on location. I've used my phone in various places around the Midwest. Usually, it's pretty good. Last time I was on I-65 between Chicago and Indianapolis, it went haywire. Regularly claimed I was out in west Illinois near Decatur. (A friend of mine reported similar behavior.) Other than that, it's pretty solid. I haven't really paid too much attention to how off it is, usually it seems to manage at least 30 meters without a problem.
- buss 16y ago
  Last time I was in Chicago with the Droid it was snowing pretty heavily, and I figured bad GPS readings were normal with that kind of weather. Didn't get to test it out in clear weather, unfortunately.
celoyd 16y ago
In theory, GPS fix quality is roughly the same in all mid-latitudes[0]; any difference between Florida and Washington should be lost in other factors. Probably, either your sky is more covered in Seattle (by trees and hills, for example), or there’s more reflection and interference in the radio signal. 0. http://blogs.agi.com/navigationAccuracy/?cat=4 http://blogs.agi.com/navigationAccuracy/?cat=4 has some nice illustrations. “DOP” is a sort of ideal fix quality, with smaller numbers meaning more accurate fixes (under various assumptions); Wikipedia will explain the math. Edit: https://gps.afspc.af.mil/gpsoc/PerformanceReports.aspx https://gps.afspc.af.mil/gpsoc/PerformanceReports.aspx is a live-ish map. When I check it, FL and WA are both in the lowest (best) category. However, it’s worst-case DOP for only the 4 best satellites; under a clear sky, a good receiver will usually see several more. I often get DOPs of 1.5 in residential neighborhoods.
- buss 16y ago
  Thanks for that interesting info. I guess it's all of the buildings that are interfering.

by buss 16y ago

sprout 16y ago

There's definitely some variability based on location. I've used my phone in various places around the Midwest. Usually, it's pretty good. Last time I was on I-65 between Chicago and Indianapolis, it went haywire. Regularly claimed I was out in west Illinois near Decatur. (A friend of mine reported similar behavior.) Other than that, it's pretty solid. I haven't really paid too much attention to how off it is, usually it seems to manage at least 30 meters without a problem.

buss 16y ago
Last time I was in Chicago with the Droid it was snowing pretty heavily, and I figured bad GPS readings were normal with that kind of weather. Didn't get to test it out in clear weather, unfortunately.

celoyd 16y ago

In theory, GPS fix quality is roughly the same in all mid-latitudes[0]; any difference between Florida and Washington should be lost in other factors. Probably, either your sky is more covered in Seattle (by trees and hills, for example), or there’s more reflection and interference in the radio signal. 0. http://blogs.agi.com/navigationAccuracy/?cat=4 http://blogs.agi.com/navigationAccuracy/?cat=4 has some nice illustrations. “DOP” is a sort of ideal fix quality, with smaller numbers meaning more accurate fixes (under various assumptions); Wikipedia will explain the math. Edit: https://gps.afspc.af.mil/gpsoc/PerformanceReports.aspx https://gps.afspc.af.mil/gpsoc/PerformanceReports.aspx is a live-ish map. When I check it, FL and WA are both in the lowest (best) category. However, it’s worst-case DOP for only the 4 best satellites; under a clear sky, a good receiver will usually see several more. I often get DOPs of 1.5 in residential neighborhoods.

buss 16y ago
Thanks for that interesting info. I guess it's all of the buildings that are interfering.