Tag Archives: aerial

Aerial Photography > Dense Point Clouds

Since 2009 I’ve done a fair amount of work with aerial photography, all the while continuing to explore architectural photography and photogrammetry while on the ground. I’ve tried in the past with some success to merge the two things but have found the results to be lacking something. That something, I think, is the hyper dense point cloud – and now I have it pretty much figured out.

Below are tow animated GIF images showing first the point cloud describing our local hospital (which I was contracted to cover with aerial photographs a few years back) and the second is a textured 3-D model of the scan.

Its so amazing to think that the flight over this structure can be reconstructed virtually a few years later with even more options to “fly around”…

Dense Point Cloud

Dense Point Cloud

Textured 3-D model

Textured 3-D model

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Point Cloud from Aerial Photos using photogrammetry

Here is a shot of the quarry in Staunton from the air, shot back in May:

Quarry

This is only one of a series of photos that I processed into a large 3-D point cloud that captures the real world shape and size of this big hole in the ground. The point cloud can be imported into AutoCad as tens or hundreds of thousands of discreet point measurements (along with true color values in RGB). This approach is very cumbersome in AutoCad but can be useful to then creat a 3-D mesh and eventually a “solid” in order to make difficult volume calculations.

Or it can be exported to a text file/table and brought into AutoCad (11 or later) as an indexed point file (*.pcg) which is much more easily managed in AutoCad.

Here is an animated GIF file showing the three dimensional nature of the point cloud.

Quarry point cloud viewed in AutoCad

a few recent aerial photos

Last friday Virginia Aerial Photography was contracted to shoot a variety of waste water treatment facilities between Staunton and Winchester. On the way home I shot these three pictures for myself.

Apple Shack

Quarry

Orkney Springs Hotel 1873 (listed on the National Register of Historic Places)

Telescoping Tripod

Using my telescoping tripod in Renssalaerville, NY

Using my telescoping tripod in Renssalaerville, NY

Over the summer I started a business venture with a friend doing aerial photography with his 1946 Cessna. I do the photos, he does the flying… Anyway, this experience got me hooked on the possibilities of enhanced points of view.

For a long time I’d thought of the cherry picker (aerial lift/bucket truck, etc.) as my only option and had often worked around the lack of great points of view with creative alternatives when budgets and such would not allow the use of a cherry picker.  But, being hooked as I was, I did more research and realized that a relatively low cost solution was available which could yield surprisingly good results – if you have the guts to put your calibrated camera up in the air on a telescoping tripod.

Even if you purchase a well made tripod with adjustable legs that allow the whole rig to be leveled, and even if you attach guy wires to stabilize everything ( if you have the need plus the manpower), even so, it takes some nerve to put your specially calibrated SLR way up into the air!

Of course its range is nothing compared to a big boom lift, but it can let you see over cars and trucks, and bushes and fences and all sorts of things.  Its just one more trick up your sleeve that can help your work become just a little better.

Franklin & Marshall Exterior Survey

Old Main at Franklin and Marshall

Old Main at Franklin and Marshall

Last spring I did some work at Franklin and Marshall College in Lancaster, PA.  I prepared a combination of measured drawings in CAD linked  to rectified photographs of the three oldest structures on the campus. These were then used as base documentation for an assessment of the existing conditions of the masonry surfaces across the extent of these buildings’ exterior facades.

The sequence of this work went roughly as follows:  I first shot photos of all of the buildings from points of view available on the ground (using a specially calibrated digital SLR).  Back in my offices in Virginia I used photogrammetric software to “back calculate” the camera stations and to make precise 3-D measurements of points on the three structures.  I used this dimensionally accurate point cloud as a reference to create rectified photographs of the surfaces visible from grade.

F and M Old Main Rear Elevation

F and M Old Main Rear Elevation

Using the point cloud and the rectified photographs I then created measured line drawings of the structures and laid them out onto tabloid size sheets for use in the field.  These were taken by hand up into an aerial lift so that conditions could be noted with a fair degree of accuracy once assessment were made both visually and manually.

tabloid size field sheet with notes

tabloid size field sheet with notes

Once the assessment was completed the data recorded on the field sheets was entered in the CAD drawings.  At this point the line drawings in CAD were enriched by a mosaic of rectified photographs visible inside of AutoCAD.  This allows for an accurate transfer of notes from the field to eventual construction documents.  A sketch of an area or region can be transferred to CAD and become dimensionally reliable.  This is a very important step because it provides for an accurate tally of areas to be treated in one way or another.

aerial lift

aerial lift

Since the main structure was rather tall, I also returned to the site to go up in the aerial lift to collect more photographs to further enrich my drawings with better rectified images of areas that were either blocked by vegetation, neighboring buildings, or were too foreshortened to provide good rectified images.

F and M Old Main Rear Elevation with photos

F and M Old Main Rear Elevation with photos

Aerial Photogrammetry

Massing Study from Aerial Photos

Massing Study from Aerial Photos

While I was working in France for Innova, we did some photogrammetry using shots taken from a helicopter. Some of this was mapping related for transportation studies, and some was more three dimensional in nature.  It is not a market that I have pursued here in the US – it was very difficult to do in those days and required a fair amount of support from ground based control data derived from theodolites and such.  Recently I did an experiment using an aerial photo that I shot of the Blackfriar’s theater in Staunton and integrated it into a photogrammetric model and found the whole thing considerable more accurate and easy to do than I rememeber it was 18 years ago. Shown here is a cut sheet from a project completed with Innova back in the early days.