Jump to content
Taylor

Photogrammetry and DStretch to Document Donner Pass Petroglyphs

Recommended Posts

A panel of Style 7 Martis Complex petroglyphs at Donner Pass in the Sierra Nevada range in California was recently documented using a combination of photogrammetry and DStretch, a plug-in for ImageJ that uses Principal Components Analysis (PCA) to enhance color contrasts.

 

Although DStretch has been used effectively to enhance rock art, wall paintings, and other art works, it has been assumed that it would not be effective for petroglyphs because they're created by carving or pecking, rather than using pigments.  However, the Style 7 petroglyphs at Donner Pass were pecked into pink granite (Lake Mary tonalite, dated to approximately 95-120 million years before present).  There is enough contrast between the pecked glyphs and weathered pink granite to allow DStretch to work. 

 

Photogrammetry was used to create a textured 3D model of the panel of petroglyphs using RGB images.  The images were enhanced using the LRD setting in DStretch, and the model was re-textured using the DStretched images.  Orthophotos from both versions of the model were then produced.  A comparison of orthophotos without DStretch and with DStretch to enhance the contrast of the petroglyphs is here.  A higher resolution orthophoto of the petroglyphs with DStretch can be found here (7 Mb).

  • Like 2

Share this post


Link to post
Share on other sites

Taylor!

 

hey this is really great work. I've been to this petroglyph site on Donner Pass many times, (usually with the family), I've always wanted to document this, but it was always more important to try and keep the kids off of it!

 

The subject has always been very difficult to view in day light conditions. What you did here is great work. You should share this data with the Tahoe Donner / Truckee city. I'm fairly confident that they would be interested to see this new imaging. I know of, and know that there are additional petroglyphs in the area.

 

again, great work!

Marlin.

  • Like 1

Share this post


Link to post
Share on other sites

Thanks, Marlin and Carla!

 

The last time I visited the site, it was about 4:00 - 4:30 pm in August and the angle of the sun was raking over the surface, making many of the glyphs more visible. They are really fascinating petroglyphs!  DStretch is no substitute for RTI but it can help with visualization, to see what's there, and for monitoring.  I'll contact the agencies you mentioned and see if they're interested.  I know a couple of the archaeologists in the area and have shared the images with them.

 

Every time I've visited this site, I've watched hikers, rock climbers, mountain bikers and other visitors walk and ride all over the petroglyphs without realizing that they're there.  When they're told what's there, most are very considerate and interested in the petroglyphs and promise to avoid walking on them in the future.  Apparently, there's a poorly marked trail nearby the site where everyone gets lost and they go cross-country to find their way back.  In 2013, CalTrans had staged heavy road construction equipment (metal-tracked dozers, etc.) adjacent to the petroglyphs and they scarred the rock extensively--far too close for comfort.  The site is extremely vulnerable because of the ease of access and high visitor traffic, and it needs better protection and monitoring, in my opinion.

 

Best,

Taylor

  • Like 1

Share this post


Link to post
Share on other sites

Taylor,

 

I could not agree more with you. This area is a very high traffic zone. The kids, the bikes, hikers --- most of them do not know what they are walking on! I'm not saying that it should be fenced off, but at least somehow --- there should be a call out to make it more obvious.

 

Its also vulnerable bc its in an area that natural snow fall, ice and elements will gather there ... somewhat sitting at the bottom of a natural V ... this godzilla El nino winter coming as well.

 

Again, great work! bravo.

 

marlin.

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×