Many scholars today expect to find data as datasets. When I took some courses in Geology at Binghamton University, specifically in Tectonics and Paleomagnetism, I learned that libraries serves, in many cases, as Geologists’ repositories of data. No, the libraries hadn’t any servers or big RAIDed disks, they had books and journals. Geologists published maps and charts with contour lines, and both synthetic and actual images. But they most often preferred greyscale for the images. At first I did not appreciate why.
I later learned, as a graduate student, this was because the way to get data out of a published paper was to take the graphics in the paper, and digitize them. This is done even today, such as when I took relative visit histograms from Google Maps to inform a study of plastic versus paper bag usage. I have used Engauge Digitizer as my main. I once estimated the volume of Fenway Park in Boston using a plan and profile of it, and using Engauge Digitizer. But I’ve also just used Inkscape, pulling in an image and measuring positions of features on a grid of pixels.
Often the data needs to be checked for smudges and corrections. This is an experiment-within-an-experiment. But it has little difference to when laboratory equipment is used, although there people tend to calibrate and recalibrate.
Accordingly it was refreshing to read Dr El-Ad David Amir’s piece on recovering heat map values from a figure, all the more because he took on the challenge of decoding a false color image, something the geologists eschewed.
Dr Amir also put together a YouTube video of his experience, linked below: