https://community.esri.com/t5/arcgis-pro-questions/average-slope-of-line-using-add-surface/m-p/1309796#M71232 <P>I work a lot with slope lines, specifically of trails and roadways. I just used Add Surface Information to calculate the slope of a line, using a raster.&nbsp;</P><P>The lines low point is&nbsp;5409 FT. The high point is&nbsp;5294 FT. The line is&nbsp;3190 LF. Basic rise/run math would tell me this is a slope of 3.6. Add surface information is telling me the average slope is 6.5. This is happening in a variety of instances. Why would Add Surface Information not be yielding the same value?&nbsp;</P><P>All data is projected to the same coordinate system, which is&nbsp;NAD 1983 StatePlane Utah Central FIPS 4302 (US Feet)</P> Wed, 19 Jul 2023 21:15:24 GMT AvidTrails 2023-07-19T21:15:24Z https://community.esri.com/t5/arcgis-pro-questions/average-slope-of-line-using-add-surface/m-p/1309796#M71232 <P>I work a lot with slope lines, specifically of trails and roadways. I just used Add Surface Information to calculate the slope of a line, using a raster.&nbsp;</P><P>The lines low point is&nbsp;5409 FT. The high point is&nbsp;5294 FT. The line is&nbsp;3190 LF. Basic rise/run math would tell me this is a slope of 3.6. Add surface information is telling me the average slope is 6.5. This is happening in a variety of instances. Why would Add Surface Information not be yielding the same value?&nbsp;</P><P>All data is projected to the same coordinate system, which is&nbsp;NAD 1983 StatePlane Utah Central FIPS 4302 (US Feet)</P> Wed, 19 Jul 2023 21:15:24 GMT https://community.esri.com/t5/arcgis-pro-questions/average-slope-of-line-using-add-surface/m-p/1309796#M71232 AvidTrails 2023-07-19T21:15:24Z https://community.esri.com/t5/arcgis-pro-questions/average-slope-of-line-using-add-surface/m-p/1309845#M71239 <P>apparently the low point and high point aren't at the start and end of the line, therefore you line length needs to be determined between those two points</P><P>Addendum</P><P>It would also be better to determine the sequential differences to obtain an overall average</P><P><A href="https://support.esri.com/en-us/knowledge-base/how-to-calculate-the-slope-of-a-line-feature-across-a-s-000025428" target="_blank">How To: Calculate the Slope of a Line Feature across a Surface in ArcGIS Pro (esri.com)</A></P> Wed, 19 Jul 2023 23:09:10 GMT https://community.esri.com/t5/arcgis-pro-questions/average-slope-of-line-using-add-surface/m-p/1309845#M71239 DanPatterson 2023-07-19T23:09:10Z