Tag Archives: point

Test Project: Marquis Building

Angle View of Building

In between wrapping up summer projects and starting some new ones,  I wanted to work on my technique with Elcovision’s powerful new module that allows dense point clouds to be extracted from photographs.  I chose the “Marquis Building” on Beverley Street in Staunton for fairly obvious reasons. (In fact there it is at the top of this page on my mast head – from was a two dimensional rectification of the entire block)

Left Photo

(Note: I used considerably more photographs than just these three shown here)

Right Photo

Over the summer I did some training in Switzerland on how to use the new software module – but I did not have access to all of my regular equipment.  So this test project was the first time I had a chance to enhance my ‘overlap coverage’ by the use of a telescoping tripod.

The point cloud created from the analysis phase is dense enough to provide a quick sort of three dimensional model of the building even without any additional drawing.

In Elcovision – or AutoCAD for that matter – one can “hover” around the point cloud and take snapshots in either perspective or isometric views.

Plan View of Point Cloud

Understanding Photogrammetry thanks to Albrecht Durer

Understanding photogrammetry thanks to Albrecht Durer

For me this drawing goes a long way towards explaining the geometry of capturing 3D points on a 2D plane. With this drawing we can better understand how a photograph is, in its essence, a relationship between a 2D plane and a single 3D point of view.  In photogrammetry, it is the precise understanding of the relationship between the focal point of a lens and the plane defined by the sensor (used to be the negative) that provides the basis for “back calculating” camera stations. When I read back what I’ve written it sopunds like gibberish. Its just not easy to explain. Probably an animation sould do the trick. in the mean time, looking at this picture above and the diagram below might help.

Stereo pair diagram