Tag Archives: analog

Technical Elevation Drawings – exterior and interior

Exterior Elevations

Exterior Elevations

Here I am posting a few drawings from a project completed about 18 months ago.  These drawings depict the existing conditions of the Luzerne County Courthouse which is located in Wilkes-Barre, PA. More on the building can be found here.  I prepared these for a team of architects and engineers who were to conduct a survey of these surfaces in preparation for an extensive masonry and stone rehabilitation project.  It is a beautiful building with a grand atrium reaching up through the building.  I also did drawings of this interior space.

Interior Elevations

Interior Elevations

I am posting these to show that, for all the value of rectified imagery, point clouds, three dimensional models – sometimes the most apt documentation is the relatively “old school” approach of using 2-D drawings to depict 3-D conditions through plan elevation and section.  In the end, the documents that I have prepared for clients over the years have had to pass this test: Will these drawings help my team to communicate easily together when assessing and discussing the problems and solutions at hand with a given building?  Will these drawings help me to accuractly assess the scope of work involve – and, will I beable to use them to communicate with and direct the contractors in the field who are doing the actual work to the building?

Earlier this week I was giving a presentation to students at the University of Virginia.  I started off showing them work that I did 15 years ago when everything was more or less analog in nature, later showing how fantastic it is now to be able to merge raster and vector data together digitally. And then I thought of these drawings and how deftly drawings can handle such complex forms with precision and efficiency.  As an industry, we are doubtless moving towards wider use of three dimensional modeling and Building Information Modeling (BIM) – yet I admit to having a fondness for the “old school” approach that I cut my teeth on, so to speak.

View of building exterior

View of building exterior

View through atrium to dome

View through atrium to dome

Photogrammetric Analysis

Photo with reseau and digitizing puck

Photo with reseau and digitizing puck

Analyzing stereo-pairs of photographs is a matter of locating the same precise point as it is captured in two or more photographs. In the old days, this meant using a digitizing puck to magnify and locate the x,y location of a point (relative to a set of cross hairs that were essentially coplanar to the film).  Today, with digital photographs, it is a matter of specifying pixels.  In both cases, a handful of these comparison points is needed to construct a geometric model for each camera station: each point becomes the terminus of a theoretical “ray” that passes through the focal point of the lens.  When the precise nature of how light passes through the focal point of the lens onto the film plane (or digital sensor) is understood mathematically, then this geometrical model can be quite precise, allowing for an accurate “back calculation” of the relative relationship of the camera from on photo station to another.

Its uncommonly difficult to write about – when you see it “happen” it is a little easier to understand!

wire frame diagrams of point cloud and camera stations

wire frame diagrams of point cloud and camera stations

Today, this whole process is becoming more and more automated, allowing for the creation of very rich point clouds when needed – or quickly creating smaller “smart point clouds” when the goal is a vector line drawing of a building, for example.

Discovering Photogrammetry in France

I first encountered the concept of architectural photogrammetry while working as an architect in Paris in 1990 -and was immediately intrigued. So much so that I decided to swap my job with a 45 minute commute into the city for a new job just a short bicycle ride away (in the town of Egly)  in order to learn how to do this work.  Simultaneously I had to learn how to draw with a computer; up until then I had only drafted with pen and pencil (plastic leads for working drawings).  It was a lot to take in, but I think its fair to say that I loved it.

digitizing puck

digitizing puck

Back then, the process was nearly completely analog: We shot film and had it developed into 8″x10″ prints.  These were then taped onto a large format digitizer so that points on the photos could be communicated to software running on a PC.  Then after a photogrammetric analysis of this information was completed, we made drawings that were plotted to scale – and it was these prints that were the “deliverable” product desired by our clients.

I remember seeing a number of photos taped onto a digitizing table and watching my colleague Herve use the digitizing puck to point to the same location on a building as seen from various points of view and then push a button and seeing the point location appear in 3-D coordinates in an CAD drawing on a computer screen.  It seemed magical.

As more and more points were measured in this way, I could start to see the shape of the building.  This became even clearer as points were connected into lines and polylines; the “point cloud” was becoming a “wire frame”.

When I first got out of architecture school and was working for a firm in New York City, the first thing I had to do was to learn how to make measured drawings of existing conditions.  It was messy, confusing work on site and often yielded error-ridden results in the office that required repeated return visits to understand and clarify what was really happening architecturally.  When I saw a dimensionally accurate 3-D model representing an existing structure being created from a handful of photos, I was hooked.  Nobody I knew was doing anything like this in the United States.

 

Triumphal Arch Jardin de Tuileries

Triumphal Arch Jardin de Tuileries