When I am hired to prepare a set of documents to describe the existing conditions of buildings I sometimes try to incorporate older drawings and the like. If I am working with original construction drawings it can be very interesting to see how and where the existing structure is different than the one designed. If I am working with measured drawings of unknown provenance it can be very frustrating to see how inaccurate the drawings are! So as a rule, I only deliver measured drawings that I create from my original site work since its the only way I know that I can really trust the work and stand behind it.
Realizing how valuable a good set of measured drawings truly is, it is wonderful to consider what a treasure our HABS HAER collections are! These are uniformly drawn to standards generally higher than the profession gets by on, even today. Sometimes I am looking at doing some work on a project and I am fortunate to learn that a HABS set of drawings already exist. This gives me an opportunity to overlay some of my work (with photogrammetrically derived images) onto this “layer” of information in seamless fashion.
I’ve long done this kind of work with rectified photography in a sort of manual approach. I’m discovering that its equally great to “Hybridize” the HABS line drawings with orthophotography as well (derived from 3-D models derived from a scanning process). The images posted here show a recent look at the Cape Hatteras lighthouse on North Carolina’s Outer Banks. The HABS collection of drawings is very nicely done and available to all to explore through the HABS web site (here). The images posted here show how the line drawings can be built upon with technology available today, They become the foundational layer of a living document that describes an important piece of architecture in great detail.