On Saturday, October 18, 2003, at 10:15 PM, geoff carver wrote:
> apologies for cross-posting -
> i was just wondering how many excavations out there are using some
> form of digital photogrammetry for documentation? i've seen the
> arctron ads for years
> (http://www.arctron.com/3D_Surveying/Photogrammetry/Examples.php), but
> i've never seen anyone outside of arctron actually using the stuff -
> has anybody else tried other systems, or seen something similar in
> action...?
The Virginia Department of Transportation pioneered the use of
low-level terrrestrial photogrammetry in the 1980's. A Zeiss lens
costing $49k in a box costing $1k and using glass plate negatives was
the first. Photos were processed using a Kelsh plotter costing an arm
and a few legs. It was used at Monticello for Bill Kelso at the Nailery
and for a VDOT project in Fluvanna County, VA documenting a canal lock.
The accuracy was 1/100 of a foot which was basically the accuracy which
was measurable, not the true accuracy. Recording of a wooden bridge was
so good that wood grain, graffiti and nails could be observed.
That has now been replaced by a digital system run through Intergraph,
if memory serves. When I saw it about 5 years ago, two monitors were
used for stereo effect and glasses were used to combine the images for
direct tracing.
At present, I'm using a Nikon Coolpix 5000 as my normal dig camera. The
images are superb and translate well onto my computer screen for
blow-up details. I've found that my picture count per site has
increased from dozens/hundreds to hundreds/thousands as the cost of
digital storage and manipulation is miniscule compared with the
$45/roll for B&W that my architectural colleagues typically have. Plus
the ease of integration and use for report production helps more than
slightly.
Taking this one step farther, I'm using DigiCad 3D as my
photogrammetric software. I'm still very much in the learning curve
with this one but thus far, it appears to be as accurate as any
measured and drawn work. The benefit is of course that if there's a
question, the photos are there for re-interpretation.
DigiCad is at www.interstudio.net. They have just recently produced a
Windows beta-test version of their software. Google searches showed a
few other firms with similar software (www.ilexsoft.com). They
basically use a photo of a building and by having known distances, can
rectify the structure to vertical and then the drawings are also
accurately sized. It translates to archaeological site work for either
vertical or horizontal surfaces as long as there are points in the
photo for which the distances are known.
By this time next year I intend to have a radio controlled helicopter
outfitted with a digital camera for site work. The heli will be flown
over the site, hovered over selected points, photos taken, photos
uploaded and images rectified and features traced. Again, Google
searches through the R/C world shows companies with the same technology
doing archaeological and architectural work. This isn't cutting edge
experimental technology, but rather proven technology moving over into
our end of the world. Realtime video looking down at terrain with a GPS
for finding the site on the ground used for locating sites out in the
middle of rocky rapids in downtown Richmond is one of the places I'm
going to be using it. So rather than spending hours slogging around in
the midst of goose poop covered rocks, I can sit in my office and
cherrypick the spots, drag out the canoe and get there and out quickly
and efficiently.
If we could just get some of the SHPO's to come into the 20th century,
perhaps glimpse the 21st and see the capabilities of digital work
rather than dogmatically demanding emulsion film prints and negatives,
life would be improved.
Lyle Browning
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