Forum : Advice & Critiques

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Topic: X, Y, Z values

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Sinaya77 (Over 1 year ago)
I am trying to create a DEM using  the point cloud data extracted from Photosynth. I need to gain a little more understanding of the X, Y, Z values; what do they represent? 
I also noticed that the software flips the Z and Y and, therefore, the orientation is skewed. I was able to reverse the values but wold like to know if there is a way to control the values before exporting the point cloud data. 
Any suggestions, comments, useful tips, would be extremely appreciated!
Thanks, 
Sinaya
Nathanael (Over 1 year ago)
Greetings, Sinaya,

This topic may very well answer some of your questions: Photosynth coordinate system
http://photosynth.net/discussion.aspx?cat=6b63cb81-8b57-4d5d-a978-41d5509bf59a&dis=a26a7660-1d0f-4f12-a39c-e6e952b7da99

Mark Willis (sir_ivar) did some of the first Photosynth to DEM work that I remember seeing: 
http://photosynth.net/discussion.aspx?cat=6b63cb81-8b57-4d5d-a978-41d5509bf59a&dis=38f61e67-d4c5-4d30-9b42-f627d91b608b

There are some useful comments from Mark and Nathan Craig in this discussion: 
http://photosynth.net/discussion.aspx?cat=6b63cb81-8b57-4d5d-a978-41d5509bf59a&dis=7b771e05-8a31-4109-8258-e97e4a9f41ae

When the majority of photos' tops do not point upward, a correct 'up' vector cannot be calculated: http://photosynth.net/discussion.aspx?cat=a6bad539-de7d-4a16-8c4d-b143f7d5f984&dis=3af6ae0c-3fcf-412b-bb22-ac51d370b159
Nathanael (Over 1 year ago)
Early commentary on more full reconstruction: 
http://photosynth.net/discussion.aspx?cat=01b6f15f-42eb-49cb-a221-ed56615e1c47&dis=7bacd111-e922-4201-93e2-3bc7ae8e398f

You will likely be interested in improving the density of the reconstruction if you want to use it for a DEM.

See these videos to hear how the camera positions that Photosynth's sparse reconstructions provides can be used with other techniques such as multi-view stereo to generate dense reconstructions: http://video-jsoe.ucsd.edu/asx/AguerayArcas.asx http://www.youtube.com/watch?v=6cnP8FqRoPI

A community effort to connect Photosynth output to a multi-view stereo solution: http://synthexport.codeplex.com/Thread/View.aspx?ThreadId=204015

Henri Astre's PhotosynthToolkit connects Photosynth to Yasutaka Furukawa's PMVS2: Introduction: http://bit.ly/photosynthtoolkit Latest update: http://bit.ly/photosynthtoolkit4
Sinaya77 (Over 1 year ago)
Thank you much, will be sure to look into all of your suggestions.
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