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The above image shows a petroglyph found by Dr. Eamonn Keogh in Red Rock Canyon National Conservation Area, only 10 miles from the Las Vegas strip. 

The petroglyph labeled "Red Rock 3" was used as a query in a database of several hundred petroglyphs from the Southwest of the US, the five best matches are shown clustered in a dendrogram. The best match is from some Kawaiisu petroglyphs at Sheep Springs. The second best match is from the same location in Red Rock (look under Eamonn's left hand), the next 3 matches come from Renegade Canyon

Note that while the images are presented in their original orientation, the indexing algorithm is "mirror image invariant". 

The image to the left is an example of how the petroglyphs are matched, using Dynamic Time Warping (DTW). Note that the feature extraction algorithm does not do a perfect job at extracting the shape, but DTW can account for this.