Using technology to enhance faded Bow Valley rock art

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Pictographs in the Bow Valley, such as the ones at Grassi Lakes and Grotto Canyon, are beautiful and enigmatic. And while these images, painted on rocks and cliff faces in red ochre mixed with grease, are slowly fading away, they tell us that people have long had a complex and spiritual connection to the Bow Valley – just as many people do today.

But beyond that, what do they mean? The full meaning remains with the people who created the pictographs. Their descendents may know, but that knowledge is kept private as a treasured part of their spiritual practices and knowledge. However, what we do know about the pictographs tells us sites such as Grassi Lakes and Grotto Canyon were places where individuals went to seek guidance from the spirits through the vision quest. Short, straight lines painted on the rocks are believed to represent tally marks, telling us how many days an individual spent at a site. Other images, such as the one at Grassi Lakes that shows a hunter throwing a spear at a caribou could be thanks to the spirits for a successful hunt.

While, we may not know – or be entitled to know – the full story behind these approximately 1,000-year-old pictographs, a digital technique known as decorrelation stretch (D-Stretch) offers the opportunity to clearly see these  approximately 1,000-year-old images. D-Stretch works by increasing the differences in the hues in digital photographs, making it perfectly suited to bringing out the red pigment in the ochre. For this reason, D-Stretch is used by archaeologists, including those with Parks Canada, to better document pictographs throughout Western Canada and the world. NASA has also used D-Stretch to enhance images sent taken by the Mars Rover.

For more information about Parks Canada’s pictograph project – Forgotten Dreams: A New Look at Ancient Pictograph Sites in Western Canada – follow this link:


About Rob Alexander

I am a writer, photographer and historian and the author of The History of Canmore, published by Summerthought Publishing of Banff, AB.
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