Tag Archives: existing conditions

Point Cloud Scan of L’Arc de Triomphe

L'Arc de Triomphe - Paris

I shot a series of photos around the Etoile at the center of which stands this grand monument.  It is incredible how busy the traffic is here at all hours, both vehicular and pedestrian! Anyway, from this series I was able to generate a point cloud to describe this massive arch at the head of the Champs Elysee. I then scaled the entire affair based on measurements taken from Google Earth.

Point Cloud Scan of Elevation

I also shot the ‘undercarriage’ of the monument to create a point cloud describing the vaulted surfaces there using photogrammetry. The point cloud itself is dense enough to create a sort of drawing. The location of any additional points – or edges etc. – can then be easily (an accurately) queried directly from the photographs.

Photos of the surfaces underneat

Point Cloud of surfaces underneath

Reflected Ceiling Plan of the Arch's central bay (point cloud)

Reclining Figure Arch Leg – Sculpture by Henry Moore 1973

Reclining Figure Arch Leg – by Henry Moore 1973

This summer (2010) marks the real debut of a reliable automatic generation of dense point clouds by using photogrammetry.  I travelled to Switzerland in July and gave this exciting new software module a try on something that would be a real challenge to document in anyway other way – a sculpture by Henry Moore.

The four panels below show different views of the point cloud generated from these photographs. For me the real lesson in this study is that objects to be documented in this way need to be photographed in conditions that produce as even lighting as possible. One can see that some of the reflectiveness from the metal (brass) surface of the sculpture resulted in less-dense-than-desired regions in the point cloud. Still, I was excited to see how well it performed under what I now understand to be relatively harsh conditions.

The density of these point clouds is considerably higher than what photogrammetry ordinarily would produce while not being the hard-to-manage overkill produced by laser scans. what’s more, these point clouds can be enriched with the same type of smart point clouds that provide a meaningful link to both rectified photography and architectural description.

Childs Restaurant -2

Sheet 1 with rectified images "thawed"

Sheet 2 with rectified images "frozen"

Childs Restaurant

Sheet 3 with some rectified images "thawed", others "frozen"

Traylor Hall – Mercersburg Academy

Cosmos Club Ballroom Rectified Photography

Title Sheet for a set of 14 sheets documenting this beautiful ornate ballroom

 

Reflected Ceiling Plan

Principal Wall Surface (sample)

Foreshortened surfaces

contact sheet of rectified images

Emmanuel Truss Layout

Emmanuel Truss Layout

A more co-planar Streetscape

Streetscape in San Miguel de Allende

click on image to see a 100% crop

Here is another streets-cape quickly composed from a half dozen photographs. These facades are more co-planar and thus more easily create a street-scape that is dimensionally faithful to real world conditions. Is it a drawing that looks like a photograph or a photograph that behaves like a drawing?  The tension between these two notions remains beguiling to me.

completed line drawings

Trinity Episcopal Church

Overview of Sheets prepared for Trinity Episcopal Church in Renssalaerville, NY

Drawing with a few rectified images "unfrozen" in the AutoCAD drawing.

Progress

progress 5Posted here are some snap shots of the Renssaelerville Trinity Church project in progress. You can see from the image to the left that I am drawing elevations of both the building’s  interior and exterior.  To make sure that all of my drawings “agree” with each other I start off by blocking everything out and drawing everything at the same time, in a way. I will go back later and address details and such.

progress 1Here is a view of five drawings together, laid out with construction lines to help align all the moving prices into a coherent whole: a plan drawing with north- south- east- and west elevations flipped out to the side.  While the source information is in fact 3-D I find that viewing it simultaneously from different vantage points useful for (relatively) quickly constructing a series of architectural drawings.

progress 3Here is a view of the church’s main elevation. This shows a partially complete drawings laid over a rectified image that was shot from a distance with a long lense, so it is optically the faced is already flattened out pretty well with regard to the drawing. In oreder to draw individual portions in detail I will use portions of closer up images that are rectified to a series of planes rather than a single rectification plane.

progress 2 Here is a side view of the building, the north elevation. This shows a mixture of drawing and rectified imagery. On this side of the building I was able to see the roof tops well enought to rectify them as well as the straight ahead portions of the facade.

progress 4 Finally, here is another interior view that is comprised of a series of rectified images that are assembled into a whole in a mosaic like fashion. In CAD, each individual rectified image can be turned on or off, or set o be screened at 50% or whatever.  I try to create the drawings files with a simple hierarchy that allows for maximum flexibility by the end user.

All of these are snap shots or “screen captures” from AutoCAD drawings software which integrates the line drawing and raster imagery into a virtual 3-D space.  From this point they can be transformed into wire frame models, solid models, or 2-D architectural drawings, or simple printed and/or exported to other digital formats such as photo shop, or PDF files.

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