[talk-ph] Be careful with unaligned Bing imagery!
Eugene Alvin Villar
seav80 at gmail.com
Wed Feb 8 15:44:05 GMT 2012
With all of the new Bing imagery that's available, I'd like to remind
everyone to be careful with unaligned Bing imagery.
Here's an example showing how two different satellite images are not
aligned with each other (look at the LBC roof sign):
Obviously, one (and likely both) of the images is not positioned
correctly. This shows that Bing's imagery (and even Google's) is not
always aligned or positioned very accurately. There may be an offset
of up to 10 meters.
If there are multiple GPS traces in the area, you should use them to
align the satellite imagery first before tracing buildings, roads, and
other features. You can average multiple GPS traces to get a good
enough positional accuracy and Potlatch, Merkaartor, and JOSM all
support manually moving the background imagery to the correct
If there are no available GPS traces, then it's acceptable to trace
the Bing imagery directly. Someone can realign the map later on when
GPS traces would become available.
For more information, please check out this e-mail that I sent last year:
Happy tracing!!! :)
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