[OSM-newbies] right angles and similar fine detail in Potlatch

[Andrew Errington]

On Sun, November 22, 2009 10:33, Ed Hillsman wrote:

>
> Can anyone suggest a way to get the building to stay squared up? I
> know that at low zoom levels, it doesn't make much difference, but we are
> developing an application for disabled students who will use it at high
> zoom levels, and fidelity to building shapes will help with our
> credibility. Thanks in advance for any suggestions you can offer.

1. Create the building outlines from the aerial photos in Potlatch[1] and
save your work.
2. Use JOSM to download the area you have been working on.
3. For each building select it and press 'Q' to square up the vertices of
the building.  JOSM does a reasonable job at this.
4. Upload your work.  Wait a while for it to be rendered, then check the
results.

If there's a better way someone will surely announce it here.

Best wishes,

Andrew

[1] I have found the aerials can be slightly offset in some areas.  To
improve accuracy, take a GPS reading for some obvious POIs (such as a
road, a statue, the centre of a park, and make sure these line up
correctly when you view the area in Potlatch.  If they don't then you can
hold down the spacebar and drag the aerials around *underneath* the
drawing layer.  Line up the photo features to the GPS surveyed points and
*then* start tracing.