|USING ADOBE PhotoShop TO
MEASURE EarthKAM IMAGES
By James H. Nicholson and Ellen Vaughan
Charleston County School District CAN DO Project for the EarthKAM Teacher Training Institute
EarthKAM teachers have often expressed a desire to be able to use a single software program to perform image processing, image annotation and quantitative measurements. Most often they have indicated a preference for Adobe PhotoShop. PhotoShop, however, did not support scaled measurements. NIH image, which could be used for measuring, had proven difficult for many to use. This article will give instructions for using PhotoShop v5.0 for quantitative linear and area measurements.
|While PhotoShop does not provide a way to directly scale an image in kilometers, it does have the ability to accurately measure image structure in photographic and imaging units. Therefore we need to establish a constant relationship between kilometers and image pixels (individual image units). Fortunately, because most images for measurement do not to be very high resolution, the simplest one to one (1 pixel = 1 kilometer) ratio will often be quite suitable. For high resolution measurements, or measurements of a smaller cropped image, a 10 to one (1 pixel = .1 kilometer) scale will be more accurate and almost as simple to use.|
To set the PhotoShop system to use pixels as the default unit:
In the new smaller image you have now created, every pixel represents 1 km in linear measurements and1 sq. km in area measurements. Save the image under a new file name indicating that this is a special scaled image for measurements. (STS08901102125_scale.jpg)