Question

A Digital Elevation Model of a large region (like South Texas) has a spatial resolution of 30 m and is too slow to load into ArcGIS Pro. So, you decide to generalize this dataset by resampling so that the spatial resolution is now 90 m. Describe the decrease in file size associated with this generalization process. Assume that the original 30 m resolution file was 3 GB in size. Hint: when you change the spatial resolution by a factor of two the file size increases by a factor of four.

Answer 1

When the spatial resolution is decreased from 30 m to 90 m, the file size associated with the digital elevation model (DEM) will decrease significantly. The decrease in file size is due to the reduction in the amount of data needed to represent the terrain at a coarser resolution.

Assuming that changing the spatial resolution by a factor of two results in a file size increase by a factor of four, we can apply the inverse relationship to estimate the decrease in file size. In this case, the spatial resolution is increased by a factor of three (from 30 m to 90 m), so we can estimate the decrease in file size by a factor of 1/3^2 = 1/9.

Given that the original 30 m resolution file was 3 GB in size, we can calculate the decreased file size as follows:

Decreased file size = Original file size / (Factor of decrease)^2

= 3 GB / 9

= 0.33 GB

Therefore, after generalizing the dataset to a 90 m spatial resolution, the file size is estimated to be approximately 0.33 GB, which is significantly smaller than the original 3 GB file size.