[Talk-us] Recent Aerial Photo Imagery Changes

Mark Wagner mark+osm at carnildo.com
Tue Sep 26 17:50:31 UTC 2017


On Tue, 26 Sep 2017 11:07:55 +0300
Rihards <richlv at nakts.net> wrote:

> On 2017.09.26. 03:09, David Wisbey wrote:
> > Fellow mappers,
> > 
> > So what's up with the recent changes in our aerial photo imagery?
> > 
> > It used to be so simple and I followed the rule(?) of making sure
> > features line up with Bing imagery.  I'm wondering about that now -
> > big time. I have been mapping in a variety of locations lately and
> > the situation is different in each location.  In Minnesota, for
> > instance, I really don't want to use Bing imagery unless at some
> > zoom level it shows me the most current images (especially in high
> > growth areas like northwest Rochester). And when recently updating
> > an intersection in southwest Minnesota to a new roundabout, I was
> > aghast at what Bing was giving me and so only used it where the
> > quality/resolution "wasn't TOO bad". Sad. Mapbox, ESRI and other
> > imagery were all much better choices, especially between Blomkest
> > and Hutchinson, MN.
> > 
> > So the main question now is: Does the "line up with Bing" rule
> > still stand? In recent work around the city of Virginia, Minnesota
> > (re-routing of US 53) I felt I had to use Mapbox imagery and so
> > lined up what I could with it rather
> > than Bing. In most cases, they matched or were off by only 2 meters
> > or so.  
> 
> there has never been a rule to "line up with Bing", quite the
> opposite - you should not unconditionally line up with any imagery
> layer, unless you know for sure it's extremely precise.
> regarding imagery layers like sat/ortophoto, it has always been
> suggested to check and align them to gps traces from the area (while
> keeping in mind that one or few traces might be all wrong, the centre
> line of many traces being the best).

When possible, I line up imagery to Strava cycle heatmaps -- Strava's
already done the work of averaging dozens/hundreds of traces for you.
When doing this, keep in mind that, especially in hilly areas, cyclists
sometimes prefer one direction of travel over another, biasing the peak
to one side or the other.  Alignment to Strava works best when you've
got two distinct peaks from the shoulders of a road, or a single narrow
peak from a dedicated bicycle route.

With the old Bing imagery, I usually didn't bother, since the
disagreement between Bing and Strava was usually less than the
resolution of the imagery.  With the new imagery, I prefer not to use
the imagery unless I can align a nearby feature to something I know is
reasonably accurate (and when mapping locally, I don't use Bing at all
-- ESRI is newer, better-aligned, and has resolution that would let
me map the shingles on a roof.)

-- 
Mark



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