On 16/03/2017 21:46, Kate Chapman wrote:
1. We can't demand more of Facebook than others doing imports. When a
government releases data under an open license we don't demand to see
the imagery they used to make it. I purchase the same imagery Facebook
does for my job and our license also ensures that we have the rights
to release the derived vectors under the license we choose. I think
this is sufficient.
Indeed, but it's worth bearing in mind a couple of points:
1) One is that unless people can compare the source DG imagery with the
the derived roads, it's not possible to judge the process. The first
time that Facebook tried something like this in Egypt nad Thailand there
were a very large number of false positives - many straight edges with a
contrast change in the image (e.g. the edges of drainage channels in
Egypt) were detected as "roads", and even with real roads there were
many connectivity issues. It may well be that the method by which roads
are now detected is much improved (but it looks like image 3 may show
some of the same connectivity detection problems as before), but without
access to the DG imagery used, no-one can tell.
2) The discussion on the Thai forum has suggested that it'd be useful
for OSM mappers to access the DG imagery for mapping purposes other than
road derivation (see e.g.
https://forum.openstreetmap.org/viewtopic.php?pid=632472#p632472 and
https://forum.openstreetmap.org/viewtopic.php?pid=634119#p634119 ).
Obviously there may be commercial hurdles to climb in order to do either
of these, but it'd be difficult to comment on the accuracy of the the
import without at least (1). However in case people are unaware DG have
already responded in the forum thread
https://forum.openstreetmap.org/viewtopic.php?pid=634735#p634735 and
said "we are looking at options to publish", so this may be in hand.
Best Regards,
Andy
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