Friday, April 30, 2010

[android-developers] Drawing of location accuracy in Google Maps app

Hi folks,

I'm working on a mapping application which uses the
Projection.metersToEquatorPixels method to convert distances in meters
to distances in screen pixels. Here is what the documentation says
about this method:

"Converts a distance in meters (along the equator) to one in
(horizontal) pixels at the current zoomlevel. In the default Mercator
projection, the actual number of pixels for a given distance will get
higher as you move away from the equator."

Therefore I adjust the resulting distance based on the current
latitude, and this seems to work just fine.

But I am puzzled when I compare my results to those in the official
Google Maps app. The circle of accuracy drawn around the same location
and at the same zoom level is significantly smaller in the Google Maps
app than in my app. If I revert to using the metersToEquatorPixels
without adjustment in my app, I get the same result as in the Google
Maps app.

Now to my question: have I overlooked something fundamental, or is
there a bug in the drawing of location accuracy in the Google Maps

Any clarification on this matter would be much appreciated.

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