[OSM-talk] Strange location reading

Nicolás Alvarez nicolas.alvarez at gmail.com
Wed Sep 28 14:25:21 UTC 2016


> El 28 sept 2016, a las 04:59, Warin <61sundowner at gmail.com> escribió:
> 
>> On 28-Sep-16 04:44 PM, Oleksiy Muzalyev wrote:
>>> On 27.09.16 21:51, John Eldredge wrote:
>>> This past weekend, I made a long road trip. At one point, while in a highway rest stop, I checked Google Maps to see how far I had come. To my surprise, it showed me at a different rest stop, about 200 miles from my actual location. I suspect that my phone couldn't get a good GPS reading, and was relying on the WiFi ID from the rest area office. The other rest area was probably using the same SSID.
>>> 
>>> I didn't think to launch OSMand for comparison, but I suspect it would have given me the same bogus results, as the choice of whether to use WiFi, cell tower, GPS, or a combination, to determine your location is set in the system settings, not inside the mapping applications.
>> GPS signal is not influenced by clouds, rain, and snow. The GPS signal frequency of about 1575mhz was chosen expressly because it is a "window" in the weather as far as signal propagation is concerned [1]. However a coating of water, snow, or ice on a smartphone or on a car may block GPS signal. A coating of water, even a fairly thin one is NOT the same as raindrops.
>> 
>> 
>> So if one is outside and a device is dry, the GPS reading should be correct no matter what is the actual weather. Otherwise it makes sense to restart the device, or change it if an incorrect GPS location reading persists.
> 
> John .. could you have the GPS function on the phone turned off? I usually have mine turned off to save battery power .. for use as a phone. There is a GPS Status app that I use to check various sensors .. including what the GPS is doing, suggest you use it .. that is an android app ... apple should have something similar.

There is nothing similar for Apple. As far as iOS APIs are concerned, there is no such thing as "GPS". Apps can only request the device's location at different levels of accuracy, and the OS decides how to achieve that (eg. at coarse levels of accuracy it won't even turn on the GPS hardware). But an app can't even know if the location it got came from the GPS, let alone which satellites it's locked to or anything like that.


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