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Measure building height in the bird's eye (Silverlight)

    Question

  • is there way to measure height of a building when looking at it in the Birds eye?

    Will that require 3d reconstruction, or knowledge of projection angle / photography position.

    Is there enough data provided to do the job, if we use birds eye mode of the Silverlight bing maps control?

    Thursday, September 23, 2010 9:29 PM

Answers

All replies

  • There's a lot of math involved. Currently there is an issue with pushpins being added when in Birdseye mode. They tend to be out of place when you switch into road or aerial mode. I'm looking into this and hope to come up with a work around.
    Windows Live Developer MVP - http://rbrundritt.spaces.live.com | http://inknowledge.co.uk
    Friday, September 24, 2010 8:47 AM
  • As I am a math major, math will not be a problem :). However the question remains, do we (end users of maps API) have enough data to do these calculations.

    By looking at the math it seems like the distance from Camera to the Object which height is being measured is unkown, subsequently hight cannot be measured. Unless we measuring from the ground up. Am i missing something?

    BTW Heigh measuring problem already been solved by Pictometry (see one of their demos at http://pictometry.com/commercial/products.shtml). But they have enought images/data to reconstruct 3d landscape...

    Monday, September 27, 2010 5:44 PM
  • I've been playing around with the Birdseye imagery in the Silverlight control recently and found it to be a bit more work to deal with. For the AJAX control and web services I've used the following to be able to do calculations against the imagery:
    http://rbrundritt.spaces.live.com/blog/cns!E7DBA9A4BFD458C5!585.entry
    http://rbrundritt.spaces.live.com/blog/cns!E7DBA9A4BFD458C5!582.entry
    http://rbrundritt.spaces.live.com/blog/cns!E7DBA9A4BFD458C5!559.entry

    Windows Live Developer MVP - http://rbrundritt.spaces.live.com | http://inknowledge.co.uk
    Monday, September 27, 2010 11:51 PM
  • I've read all three articles before. They are great. And It's makes sense to be able to determine lat/longs of the pixels on a images with assumption that photographed surface is flat and close to the sea level. (Or flat within view range that is significantly smaller compare to the surface of the Earth.)

    However, when photographed surface has some elevation profile these "simple" calculations will not work.

    The ground elevation profile needs to be taking into consideration.

    For example, the point on a mountain, shot from the plane will have different lat long, compare to the point that is "behind" that mountain, located on intersection of sea level and the ray originated from the camera through the point on a mountain. The point on a mountain is closer to the "viewer"; however flat photograph does not has enough information to say how much closer. In order to get that information we either need another image, taken within known distance from the first one (like two eyes estimating the distance), or presence of the reference object on a screen, that has known dimensions, like a credit card. Theoretically there is another way to take care that by using public elevation profile web-services and some complex-ray-tracing-kind-like calculations.

    Are these the only options?

    BTW, i think the PushPin problem you described is caused by not taking elevation/building profile in considiration.

    Tuesday, September 28, 2010 6:54 PM
  • I've used data from the USGS for the elevation information along with the calculations above. In the end the estimates are just estimates and have a decent amount of error to them (+/- 50 meters). You might find it best to use the 3D control. You can use the 3D control in Silverlight: http://rbrundritt.spaces.live.com/blog/cns!E7DBA9A4BFD458C5!1163.entry

    You can then write a plugin to get the height of objects:http://rbrundritt.spaces.live.com/blog/cns!E7DBA9A4BFD458C5!1017.entry

    This has proven to be fairly accurate.


    Windows Live Developer MVP - http://rbrundritt.spaces.live.com | http://inknowledge.co.uk
    Tuesday, September 28, 2010 8:00 PM
  • That is sounds very promising.

    Will it limit ability to measure only objects that rendered in 3D control?

    What's about any others, like street Poles, which you can see on birds eye, or buildings that do not have representing 3d objects?

     

    Btw, I am using data from USGS and ngs.noaa to properly align objects in birds eye, works like a charm.

    Thursday, September 30, 2010 3:27 PM
  • Where I can find math formulas for these calculations? I have very similar task. Did you find solution for ur task?
    Wednesday, December 08, 2010 4:19 PM
  • Hi - Were you able to find the solution? 3D maps are going away in Dec and I am trying to measure the height of oblique images but got stuck at the camera angel part so not sure what to do next. Once I know the camera angle I will zip this tool. 
    Thursday, August 25, 2011 4:49 PM