Remote Sensing with Multispectral Scanners

Classification: Classification: a closer looka closer look

Classification: Classification: a closer looka closer look

Phoenix classified image

Land Cover map of the Phoenix Area, 1998

Classification by W. Stefanov, ASU School of Geological Sciences

An image with pixels classified into 6 categories – based on RS data with 2.5-m pixel size

Ground truth

a process in which a pixel on a satellite image is compared to what is there in reality -- in order to verify the contents of the pixel on the image

Goal is to collect information that can be used to improve the accuracy of the classification, or at least to assess the amount & type of error

How could we “ground truth” this image?

Ground truth exercise

Use either GPS, visual alignment with buildings, or distance measuring to find a sampling location

On data sheet, list the 4 pixels’ land covers, as identified by classification

For each pixel, give your best estimate of what is actually on the ground

When done, come back to class – we’ll look at results as a whole