# Calculating slope between two points on DEM using ArcMap

I'm a forester, and I do lots of work with LiDAR derived DEM's. I'm looking for a quick-and-easy tool to calculate the slope between two points. The application for this would be drawing a proposed road, where the slope of each road segment must be below a certain value. After quite a bit of searching, I'm unable to find a tool to accomplish this in ArcMap. Can anyone suggest an existing tool to accomplish this?

I don't need the slope along the surface of a DEM; I simply need a FAST way to calculate the straight-line slope between two points. Currently, the only way I'm able to do this is as follows:

1. Load DEM into ArcMap.
2. Create a new shapefile.
3. Create a line feature with a single segment.
4. Get the elevation values for the lines two vertices from the underlying DEM.
5. Use math to calculate the slope of the straight line between the two vertices.

I'm looking for a workflow similar to the following:

1. Click on "slope" tool.
2. Click on point A, then click on point B.
3. Dialogue box displays the straight-line slope between point A and point B.

I've been looking for an existing solution to accomplish this, and have come up empty handed.

• As a new user be sure to take the Tour which introduces you to the site protocols. You say "After quite a bit of searching", but precisely where have you searched? Wherever possible questions should try to help potential answerers to know what you have tried so that their volunteer time is not used simply going over the same ground.
– PolyGeo
Commented Apr 15, 2016 at 23:25
• You wrote: "I'm looking for a quick-and-easy tool to calculate the slope between two lines", do you mean calculating the slope between two endpoints of a line? You will need to define how you would like to handle the slope along a meandering road for example. This is related and may be helpful: gis.stackexchange.com/q/15623/8104
– Aaron
Commented Apr 16, 2016 at 3:00

## 2 Answers

I understand you'd like to design a route between 2 points in the mountains with slope being a constraint.

The solution I use is neither quick or easy.

Place equidistant points over dem. Connect them by lines, using triangulation. Calculate length and slope for each and assign cost of travel through it using both values. Calculate least cost path between your points.

Setting higher cost for bigger slopes will help you to avoid steep climbs\descends

I use this model to produce an ideal hiking routes through forests. If you have the DEM and a feature classes of a start and end point, all you need to do is follow my model below. Calculate the slope of DEM, reclassify it, then use weighted overlay to further narrow down the slope criteria for the road, then use the cost distance tool where you input the weighted overlay raster along with the end Feature class of the road (make sure to create a backlink raster), then input the cost distance raster+backlink raster+the start feature class into the cost path tool. The output will be rasterized trail/road. Then convert it to a polyline with the Raster to polyline tool, then break it apart with feature vertices to points, then use the extract multi values to points tool where you would input your bare DEM and slope and each point of that line will be updated with the DEM elevation and slope