Road designers or engineers need to analyse the slope of a road to determine speed limits or provide information on the condition of the road ahead to road users.
We can show this information as a long section (or profile graphs). Profiles show the change in elevation of a surface along a line.
profile graph is a tool from the ESRI 3D Analyst extension. So that means you'll need to activate the 3D Analyst license before using the toolset.
"The Profile Graph tools on the 3D Analyst interactive toolbar are used to derive a graphic representation of one or many profiles. Profiles can be generated from any 3D line feature(s) drawn over a surface. You can create profiles on either a raster, triangulated irregular network (TIN), or terrain dataset surface. Profile graphs can also be derived by drawing a 3D line over a set of points or multipoints."
Further information can be found on the ESRI ArcGIS Desktop website.
Preparing The Data
This is the profile graph tool. If it is grayed out it means you haven't selected a line for it to use as a reference or don't have a surface dataset it can work with.
Profile graphs need surface terrain data, so ideally from the source is best. LIDAR or TIN surfaces. If you only have contours, then you would need to create TINs but keep in mind that this is inferior to working directly from the captured data or source.
To create TIN surfaces you would use the
Create TIN tool.
TIP: If you don't want to spend eons geoprocessing, create a polygon feature class and use it as a cookie cutter to
clip the contours dataset to just the geographic extent of your investigation area. This should significantly reduce the amount of features being calculated.
This is the TIN surface created from a contours dataset, after being clipped. The line selected is the road investigation segment of about 1400 metres.
Make this new TIN surface as the target layer in the 3D Analyst extension.
Interpolating Heights From Selected Surface
This bit is weird, I thought it would interpolate the feature line I created but it didn't work. So I had to click on the
Interpolate Line and manually digitise the road following the feature line. I don't know if it is a bug in ArcGIS 10.6.
This tool requires you to start at the origin and click till you've reached the end. Double click at the end of the line.
Once this is done, and the target terrain layer has been selected, then the
Profile Graph button should light up. Clicking on this should create a line graph (by default) showing the elevation and distance. If the line is flat uniformingly something is PROBABLY WRONG. Check your graph's settings. Most likely one of the axis is referencing the wrong data.
Wrong! Elevation shouldn't be 0!
Note: If elevatin is '0', try running the
Interpolate Line step again.
And when it works...
Then you can adjust the properties like Graph Title and Subtitle. But the graph should be self explanatory. The X axis is elevation, the Y axis is line distance over the surface you've interpolated.
The profile graph line is boxy because it's interpolating a surface generated by a contour dataset with 0.5 metre intervals. A LIDAR dataset will probably be smoother. Although your road engineer or designer will probably just calculate the slope from the raw values anyway so it may not matter.