What is more reliable-GPS points or the USGS ortho imagery?
An ortho image is a photograph of a portion of the surface of the earth. While a photograph is flat (two dimensional), the earth is not. Thus, the photo has to be “warped” or “corrected” to fit the actual shape of the earth. GPS points represent precise coordinate locations. A point, having only one dimension, does not have to be “warped” to fit the shape of the earth. GPS points collected with differential GPS are more accurate than ortho imagery.
