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VCU Archaeology

Laser Light Show, Pink Floyd, and Rock…. Art

Dr. Means preparing to create a 3D digital image of a rock art panel.

By Project Director Bernard K. Means,

I left at 5 am (Spring forward!) to journey to The State Museum of Pennsylvania in Harrisburg, PA, to test our scanner’s ability to create 3D topological models of rock art.  The trip up was fairly uneventful, except that the rental car insisted that one of the tires—unspecified of course—was low on pressure.  I finally found a gas station, checked the pressure on all the tires, and they were all good.  The message went away—temporarily—and then came back, making the rest of the trip a bit uneasy.  I’d hate to have a real problem with the car!  When I arrived at The State Museum, the security guards could not find my name and this led to a delay as well, as Curator Janet Johnson had to come out and verify that I was not an international art thief or some such similar nefarious individual.

Rock art panel.

I chose The State Museum of Pennsylvania to see how well we could scan American Indian rock art, or petroglyphs, because they have several panels on display in their public gallery that were removed in the 1930s from sites along the Susquehanna River in Lancaster County, PA.  This is a much easier way to conduct our first attempt scanning rock art than trying to traipse down back, dusty roads and then climb to an inaccessible location, bringing along not only a laptop and 3D scanner, but a generator as well!  We did have power issues—the Museum is closed on Mondays and only the emergency lighting was active.  Janet was able to get us some power and then we were good to go!

Lasers from scanner on tripod recording rock art in 3D.

I set the 3D scanner on our new tripod, purchased thanks to funds from the VCU Center for Teaching Excellence.  I admit I was nervous putting a $2800 scanner onto a $100 tripod, but everything seems stable.  I wait poised and ready, just in case.  The first rock art panel (approximately 28 inches by 10 inches) I chose to scan contained a very distinctive image of a fish.  It took me seven scan sessions to capture the entire panel…. but, fortunately, each scan only took about 3 minutes, plus a couple of more minutes for computer processing and readjusting—carefully—of the tripod.  I probably could have scanned with one fewer “single panel” scans but decided to err on the side of caution. The digital model we will create from the scan requires some overlap between each scan session.  The angle of the scanner also affected what was captured in each 3D scan. I had to reposition the tripod and scanner during the scanning process several times.

The lasers passing across the scanner were impressive in the darkened room.  I decided to conduct the first part of the scanning session while listening to Pink Floyd’s Dark Side of the Moon. Rock art afficianado Paul Nevin came by as I was finishing scanning of this first panel, with his trusty copy of Donald Cadzow’s (2001) book on Susquehanna River petroglyphs.  He identified the first panel I scanned as being from the Walnut Island site, assigned number 44 by Cadzow in his book. I also scanned panels number 18 (also Walnut Island) and number 45 (Cresswell Rock) in Cadzow’s system.  Generally, the 3D imaging of the rock art went well—although in one case I had to image the rock art as two tiers of individual panel scans.  One large and ungainly rock art panel (Cadzow’s number 25) from the Walnut Island site was not successfully scanned and I’ll try to ascertain why this was the case.

Section of scanned rock art from the Walnut Island site.

For more information on Pennsylvania rock art, please click here.

Reference cited:

Cadzow, Donald (2001)  Petroglyphs in the Susquehanna River near Safe Harbor, Pennsylvania. Originally Published in 1934. Pennsylvania Historical and Museum Commission, Harrisburg.

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