topic Re: Calculating uphill/downhill areas on a raster map in ArcGIS Spatial Analyst Questions

Calculating uphill/downhill areas on a raster map

MikeTotti — Tue, 17 Jan 2012 15:53:46 GMT

Hi folks,
I need to determine uphill or downhill areas along a road section on a raster map. I know MapCal program can do this but it only accepts maps in 100x100 pixels but my study area is too big to run this program (1500 x 1500). I was wondering if there is a way to do this in ArcGIS.

Thanks in advance.

-Mike

Re: Calculating uphill/downhill areas on a raster map

JoeBorgione — Tue, 17 Jan 2012 20:34:09 GMT

Hi folks,
I need to determine uphill or downhill areas along a road section on a raster map. I know MapCal program can do this but it only accepts maps in 100x100 pixels but my study area is too big to run this program (1500 x 1500). I was wondering if there is a way to do this in ArcGIS.

Thanks in advance.

-Mike

Hmmm. You and I are in two cars traveling towards each other on the same road and we are in an area that is hilly. Which one of us is going down hill and which one of us is going uphill? My point is for every uphill lane typically there is a corresponding down hill lane, unless we are talking about a very well divided highway, or extra climbing lanes right?

What is your objective here?

Re: Calculating uphill/downhill areas on a raster map

DarrenWiens2 — Tue, 17 Jan 2012 21:01:49 GMT

Can you define "uphill area"? Are you talking about sloped sections of highway (use the Slope tool)? Or are you talking about land adjacent to roads being uphill or downhill from the road (seems like you should be able to apply a flow direction type analysis)?

Re: Calculating uphill/downhill areas on a raster map

MikeTotti — Wed, 18 Jan 2012 20:51:57 GMT

Hmmm. You and I are in two cars traveling towards each other on the same road and we are in an area that is hilly. Which one of us is going down hill and which one of us is going uphill? My point is for every uphill lane typically there is a corresponding down hill lane, unless we are talking about a very well divided highway, or extra climbing lanes right?

What is your objective here?

Hi there,
Here is my objective: I am working on forest fire prevention. I have DEM and forest road network for the study area. Lets say that (hypothetically) a fire truck can extend its hose up to 100m for uphill areas while extending its hose up to 200m for downhill areas to fight against forest fires. Based on this assumption, I would like to find out whether current road network covers the whole area or not. As you pointed out the uphill and downhill are direction dependent. From point A to point B left side of the road is uphill and right side of the road is downhill but from point B to point A left side of the road is downhill while right side of the road becomes uphill. I was just wondering how I could do this in ArcGIS.

Re: Calculating uphill/downhill areas on a raster map

DarrenWiens2 — Wed, 18 Jan 2012 23:07:11 GMT

Here's one way (I spend 99% in the vector world, so there's probably a raster way that I don't know about):

1.) Make a raster that filters out everything > 200m from any road (Euclidean Distance, max. distance = 200)
2.) Convert that raster to points (Raster to Point). There will be a point for every cell < 200m from a road.
3.) Convert your roads to a raster (Polyline to Raster)
4.) Convert the roads raster to points (Raster to Point). There will be a string of points running down the roads.
5.) Assign elevation from your DEM to each distance point (Extract Values to Points)
6.) Assign elevation from your DEM to each road point (Extract Values to Points)
7.) Associate each distance point, with elevation, to the nearest road point, with elevation (Spatial Join)
8.) Calculate the elevation difference between each point and the nearest point on the road (Calculate Field)
9.) Delete any points < 100m from the road and a negative elevation.
10.) Convert those points back to a raster (Point to Raster)

Re: Calculating uphill/downhill areas on a raster map

MikeTotti — Fri, 20 Jan 2012 11:27:45 GMT

Here's one way (I spend 99% in the vector world, so there's probably a raster way that I don't know about):

1.) Make a raster that filters out everything > 200m from any road (Euclidean Distance, max. distance = 200)
2.) Convert that raster to points (Raster to Point). There will be a point for every cell < 200m from a road.
3.) Convert your roads to a raster (Polyline to Raster)
4.) Convert the roads raster to points (Raster to Point). There will be a string of points running down the roads.
5.) Assign elevation from your DEM to each distance point (Extract Values to Points)
6.) Assign elevation from your DEM to each road point (Extract Values to Points)
7.) Associate each distance point, with elevation, to the nearest road point, with elevation (Spatial Join)
8.) Calculate the elevation difference between each point and the nearest point on the road (Calculate Field)
9.) Delete any points < 100m from the road and a negative elevation.
10.) Convert those points back to a raster (Point to Raster)

Thank you, dkwiens, for your reply,
I'll let you know the results after I give it a try 🙂

Re: Calculating uphill/downhill areas on a raster map

MikeTotti — Thu, 22 Mar 2012 08:02:24 GMT

Thanks Darren, it worked fine. I know it's been a while but just got time to give it a try. I do appreciate your help.

Re: Calculating uphill/downhill areas on a raster map

AndreaLeoni — Tue, 18 Mar 2014 19:18:07 GMT

Here's one way (I spend 99% in the vector world, so there's probably a raster way that I don't know about):

1.) Make a raster that filters out everything > 200m from any road (Euclidean Distance, max. distance = 200)
2.) Convert that raster to points (Raster to Point). There will be a point for every cell < 200m from a road.
3.) Convert your roads to a raster (Polyline to Raster)
4.) Convert the roads raster to points (Raster to Point). There will be a string of points running down the roads.
5.) Assign elevation from your DEM to each distance point (Extract Values to Points)
6.) Assign elevation from your DEM to each road point (Extract Values to Points)
7.) Associate each distance point, with elevation, to the nearest road point, with elevation (Spatial Join)
8.) Calculate the elevation difference between each point and the nearest point on the road (Calculate Field)
9.) Delete any points < 100m from the road and a negative elevation.
10.) Convert those points back to a raster (Point to Raster)

I'm using this post to make my question.
I have a raster of mountain region.
I need to calculate the uphill side as txcowboy35 but I need to extend the calculation for the whole uphill side, from the lowest part of the road untill to the pick of mountains (the highest points). So, there isn't a fixed distance but it will change from the position of the roads and from the altitude of mountains.
Is it possible to make it?

Thank you in advance for your help

Re: Calculating uphill/downhill areas on a raster map

MarkBoucher — Wed, 19 Mar 2014 22:50:40 GMT

Seems like you are looking for the watershed boundary uphill of the road. Could you use hydrology tools to do define the watershed boundary (ridege line) and then use the road to slice the watershed and define only the uphill side of the road.

Re: Calculating uphill/downhill areas on a raster map

AndreaLeoni — Fri, 21 Mar 2014 15:47:27 GMT

The principle is similar (to calculate untill the ridge line), but probably the boundary will be a triangle and I don't want it.
I need to define the uphill side because I have a rockfall hazard map and I need to filter the real areas makes damages to the roads. Further the rocks fall not as the same rule as a water flow and for this reason I don't want a triangular boundary.

Re: Calculating uphill/downhill areas on a raster map

MarkBoucher — Fri, 21 Mar 2014 17:00:20 GMT

I don't quite understand the "triangle" you are talking about.

If you define the watershed for a piont, not on the road, but far downstream so that it includes all of the drainage points that cross the road, then you will have a polygon that covers the entire road. Then slice this polygon with the road and choose the side/sides that is/are uphill of the road.