I am trying to calculate the mean raster values (mean RedTPI) for each of the 9 squares of my fishnet. Here is my workflow and what is going wrong:

enter image description here ^I calculated the layer I am working with by extracting the part of a DEM that overlaps with a shapefile and calculating a new raster layer (RedTPI) by subtracting the mean elevation from the original DEM.

enter image description here ^(THIS IS WHERE IT WENT WRONG) I placed a fishnet over RedTPI and tried to calculate the mean raster value from RedTPI within each vector square of the fishnet.

enter image description here ^I wanted each ObjectID to show the mean RedTPI value for each square, but none of the means make sense when I look at the range of the TPI values in the Contents pane, which are much higher than the means in the Zonal Stats table. I also don't know why Count is equal to Area.

I tried to include all the information I can but I'm new to GIS and I'm not sure if this is informative enough.

1 Answer 1


These values could be accurate. The range and the mean are not directly related statistically. The mean is based on the distribution of values between the min and max values. You may want to use the median instead, but there is no reason to think that the average values are not accurate. Each mean is larger than the min and smaller than the max which is to be expected.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.