NEXT MEETING: Wednesday, April 19, 2023: the GCAS meets at 2045 Memory Lane in Silver City, New Mexico. Light refreshments provided; OK to bring your own light snacks or handy meal (burrito, etc.) & beverage if desired. Doors open at 5 PM for socializing. Meeting starts at 5:30 PM sharp with a short business meeting followed at 5:45 PM by featured speaker and GCAS member Carolyn O’Bagy Davis, who will discuss Bert and Hattie Cosgrove, avocational archaeologists who were instrumental in documenting and preserving a number of local sites including Arenas Valley's Treasure Hill. Meeting to adjourn about 7:00 PM. In order to offer our members a safe and comfortable experience the GCAS follows CDC and New Mexico Department of Health guidelines for indoor gatherings including masking, distancing, and vaccinations. We recommend all attendees follow the same.

NEXT FIELD TRIP: Sunday, April 2, 2023, beginning 9:00 AM: Regular GCAS field trip to City of Rocks State Park - view remnants of Apache shelters along the Cienega Trail, plus features in other easy-access locations like a rock shelter, Apache petroglyph, kiva, and multiple mortar holes. City of Rocks is about a 1-hour drive one-way from Silver City. At 9:00 AM meet at the Cienega Trail trailhead parking (a few hundred yards from the Highway 61 turnoff to the City of Rocks - look on the left side of the road for a parking area with a Port-o-Let). Walk the 1-mile easy Cienega Trail loop to inspect some off-trail features. About 11:00 AM, non-hikers can join the rest of the group to learn about the kiva site a few yards from the Visitor Center. About 11:15 AM, drive round the park’s perimeter road to the north side to view the rock shelter, Apache petroglyph, and mortar holes (short but moderately steep walk uphill from area near campsite #35). Picnic lunch follows at any convenient unoccupied campsite.

Navajo Culture On Mars!
MAREC Progress Report - Phase III

Meet D-Stretch: the Archaeologist's Friend

Picto 3 - natural Picto 3 - StretchSome avocational archaeologists have already learned of the fascinating technology of D-Stretch, aka decorrelation stretch, a digital imaging tool that was originally developed to enhance (i.e., "stretch") the color differences in aerial photographs. Today, this technology has become more widely used and user-friendly to boot. It is now an essential tool to analyze rock art images, especially ones too faint for the naked eye to see.

Picto 4- Stretch Picto 4- naturalThe two pairs of images you see on this page were taken by the GCAS's own Marglyph, alias Margaret Berrier. She has kindly given us permission to post them here so that we can all see how significant the D-Stretch enhancement can be. The left-most photos are her examples of natural, "naked eye" photos of rock art; and the brightly colored photos next to them reveal the same image in D-Stretch.

For many more images of rock art in D-Stretch as well as technical data, start at the D-Stretch home page itself.

In its most professional format, D-Stretch is a plugin to the Javascript program, ImageJ, that must be installed before D-Stretch can be used. Some of our more tech-savvy readers may be inclined to select this alternative. However, for the more casual of us avocational archaeologists who do not necessarily need high functionality, there's an app for that. Our GCAS President, the straightforward Kyle Meredith, opted for the straightforward app and reports: "...I looked up the app on Google Play for my android phone and ordered it. I think the price was $19.99. SO EASY!" Kyle adds that use of the D-Stretch app has a bit of a learning curve but it promises to be big fun for anyone interested in photographing and enhancing rock art in the field. Like all of us GCAS members who've spent a year itching for resumption of field trips.

If Joe Bob Briggs were into rock art, he'd say check it out.

/s/ webmaster


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