[HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake
sbower at gmavt.net
Sat May 9 18:03:22 UTC 2015
When I talk about "moving the imagery" that is only to align it with Bing
imagery as I work in a very localized area, in order to confirm that the
features are (roughly) correctly located, relative to Bing. It does not
change the geo-referencing of the underlying data for other users - it is
only revising it for my display. I expect that how you understood it, but
in case that wasn't clear.
I haven't personally digitized anything from the DG imagery. I have only
used it to help with interpretation where the Bing imagery is poor (low res
or cloudy). But others may be locating features from the DG imagery -
hopefully only experienced mappers with careful reference to better
geo-rectified imagery ("hopefully" being the aspect that gives us all
concern, of course).
I fully agree this is not "best practice" for digital mapping - it's "best
available" within resource constraints for crisis response.
By the way, you may already be very familiar with this, but the elevation
aspect of ortho-rectification is described here (see image at top-right):
http://en.wikipedia.org/wiki/Orthophoto. Or see the first image in this
page: http://www.kevinroper.org/portfolio/ . These explain why the more
severe off-nadir angle causes greater location distortion, more difficult
to correct for.
On Sat, May 9, 2015 at 10:30 AM, Kevin Bullock <kbullock at digitalglobe.com>
> >>Does Digital Globe supply Bing images? Just curious, they are always
> referred to as different products.
> Yes, Microsoft licenses DigitalGlobe imagery for many parts of the world,
> you’ll notice the attribution in the Bing Maps platform. In various
> threads, I’ve seen Bing imagery “versus” DigitalGlobe imagery, and that is
> usually a contradiction. The proper way of characterizing it is:
> DigitalGlobe imagery through the Bing platform versus DigitalGlobe imagery
> being made available during this crisis.
> Cheers, Kevin
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