English

Problem: Incorrect results returned when applying the Slope function on a clipped raster in ArcMap

Description

The Slope function enables users to calculate the inclination of slope either in degrees, scaled, or percent rise. In some instances, incorrect output values are returned when applying the function on a raster clipped using the Clip button on the Image Analysis window.

Note:
When applying the Slope function, the raster is usually clipped to fit the study area.

Cause

When a raster is clipped using the Clip button on the Image Analysis window, the layer creates a temporary raster layer. Thus, when the Slope function is applied to this temporary raster layer, the returned values are from the input raster that was used instead.

The Slope function values are only calculated accurately once the clipped layer is exported to a geodatabase or a file-based raster.

Solution or Workaround

Export the clipped layer to a geodatabase or to a file-based raster to make it a permanent raster before applying the Slope function. To do this in ArcMap, select one of the following options:

Option A:

1) Zoom to the area of interest.
2) Navigate to Windows > Image Analysis, and click the Clip button to clip the image.
3) Click the Export button on the Image Analysis window to save it as a raster dataset.
[O-Image]

4) Use the exported layer to apply the Slope function.
5) Export the final slope layer to the geodatabase.

Option B:

1) Zoom to the area of interest.
2) Export the layer from the Table Of Contents by right-clicking the layer > Data > Export Data, and set the Extent to Data Frame (Current).
[O-Image]

3) Use the exported layer to apply the Slope function.
4) Export the final slope layer to the geodatabase.

Related Information