On 4/1/2012 10:53 AM, Arun Ganesh wrote:
It recently struck me while identifying mountain peaks in the himalayas
that something may not be right. All of us have noticed that the top of
skyscrapers is off from the base of the building owing to parallax error
of the satellite capturing the image at an angle. The average seems to
be around a 0.2m displacement for every 1m increase in height (based on
calculations made in a couple of cities in India). For an imagery tile
which has 1000m variation in elevation, various objects could be
displaced by as much as 200m from its real position.

It's not as bad as it seems. Imagery is adjusted using an elevation dataset. Since this data doesn't (and shouldn't) include buildings and bridges, these appear distorted. You'll also see problems where recent heavy construction has caused changes in topography.

_______________________________________________
talk mailing list
talk@openstreetmap.org
http://lists.openstreetmap.org/listinfo/talk

Reply via email to