photography & architectural photogrammetry

Detail of Building Corner

Measuring and drawing existing structures for preservation work can be accomplished with the aid of a variety of technologies – laser scanning and photogrammetry chief among them – that increase both  project accuracy and the speed of data collection in the field. Increasingly, both of these leading technologies are sought after at the same time in order to capitalize on each technology’s individual strengths. Rich laser-scan-data in dense clouds of 3D points provides a great point of departure for the creation of a “BIM” model. Meanwhile, mosaics of scale-able, rectified photographic images – created through photogrammetry – offer the users of the project documentation direct information about the physical conditions of the structure. “Hybrid drawings” consisting of building-information-modeling (BIM), rectified photography and record measured drawings provide an efficient and definitive means to quantitatively describe the structure.

So in cases when a project requires a combination of lidar sourced point cloud data and photogrammetry, how do the two systems talk to each other?  The current answer is through the identification of registration points/conjunction points. These are “smart points” that correspond to a specific location on the structure being measured and drawn. Sometimes these locations or points are somewhat “theoretical”, existing as an idea as much as a point in space – for example “the northwest corner of the building”.

Four different locations for the Building Corner

There are some important distinctions between point clouds created automatically by machine and those created through a process of selection based on the experienced judgement of a human.

Theoretical Intersections

Interesting article coming out of a 3-D laser scanning conference (SPAR) going on in Houston, TX right now…

http://www.sparpointgroup.com/News/Vol10No18-Will-photogrammetry-make-laser-scanning-obsolete-/

Fountain, sculpture, mosaic paving at Kykuit

A variety of photos were taken in order to capture the architectural- and sculptural features that compose this fountain located on the grounds of the Rockefeller estate on the lower Hudson, just north of New York City, known as Kykuit.

Below are some screen shots of the point cloud in plan and elevation. Click on the images to see them in higher resolution.

Point Cloud Elevation

Point Cloud Plan

While archiving some files today I had a brief look at the work that I was part of in 2009 in Vladivostok.  It just struck me as stunning when I realized just how much we documented in such a short period of time. We covered miles of streetscapes, and everywhere we covered, we can zoom in and see more of what was happening all over town that week. See below…

Partial View od Street Scene (Autocad screen shot)

Zooming in a little further

Measuring the approximate height of the lady in red's high heels...

…Confirmed: four inch heels!

If you click on these images, you’ll see them in even higher resolution! More can be learned about the project here.

Just wanted to share a technique that I find pretty useful when you need to remove a color cast from a photo. Its a little labor intensive since its tailored to the specific image, but I find it works wonders – or alternately it sometimes can confirm that there is little or no color cast to remove…

Anyway, here’s the link:

http://www.petapixel.com/2012/03/06/how-to-quickly-find-and-select-black-and-white-points-in-photoshop/

Removing Color Cast manually using thresholds and curves

Detail

Here’s a link to the ::new page::