[talk-ph] Be careful in tracing from Bing Maps

Eugene Alvin Villar seav80 at gmail.com
Wed Jan 5 18:33:13 GMT 2011

Here's an example of aligning Bing Maps imagery.

This first image shows the default view of Bing Maps in Potlatch 2 and
with GPS traces loaded (the yellow arrows show the offset needed to
align the imagery):

This next image shows the Bing Maps layer moved to provide a best fit
alignment with the GPS traces:

This last image shows streets traced from Bing Maps now that it is aligned:

Tips: When trying to align the image, look over a larger area where
GPS traces are available and do a best fit over that area. In
addition, the best spots to inspect for alignments are intersections
and curves in the roads.

On Thu, Jan 6, 2011 at 2:03 AM, Eugene Alvin Villar <seav80 at gmail.com> wrote:
> Hi guys,
> Please be careful in tracing from Bing Maps aerial imagery. It is
> known that some of the imagery is not aligned to the correct position.
> To show an example, please see this Bing maps screenshot: [1]. The
> image shows the boundary between two satellite imagery. The imagery on
> the top covers Metro Manila is is for the most part correctly
> positioned. The imagery at the bottom covers parts of Cavite, Laguna,
> Batangas, and Rizal[3] and is *not* positioned correctly. Notice that
> the residential streets do not line up.
> In order to avoid the misaligned imagery problem that has been
> plaguing contributors in Google Map Maker, please try to align the
> imagery to GPS tracks or known good data before tracing.
> In Potlatch 2 and Merkaartor 0.17, the imagery can be moved by
> pressing down the spacebar then dragging. I don't know how to do this
> in JOSM but it also has a way to move the background image.
> [1] http://wiki.openstreetmap.org/wiki/File:Bing_misalignment_in_Daang_Hari_-_Bacoor.jpg
> [2] http://www.openstreetmap.org/?way=28738861
> [3] http://www.openstreetmap.org/?way=87284547


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