topic Re: how can measure general slope, aspect and height of polygons? in ArcGIS Spatial Analyst Questions

how can measure general slope, aspect and height of polygons?

mortazapirouz — Thu, 12 Jan 2012 14:23:15 GMT

Hi everybody
I have a polygon shp file from 300 landslides and I need to have some information for this landslides
1- general slope of landslide`s polygon (not cell by cell)
2- general aspect of polygons
3- average height and max and min height of polygons
I need all this data for each polygon one by one.
I know which I have to do this in several steps but I dont know how? please tell me how can I do this. I searched a lot but ,no solution.
Thanks

Re: how can measure general slope, aspect and height of polygons?

DanPatterson_Retired — Thu, 12 Jan 2012 14:34:15 GMT

Did you rule out some of the information that can be obtained from ZonalStatisticsAsTable?
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z000000w8000000.htm

Re: how can measure general slope, aspect and height of polygons?

JeffreyEvans — Thu, 12 Jan 2012 15:33:37 GMT

I am not sure exactly what you mean by "general slope and aspect" but a Zonal function will return a specified statistic (min, max, mean, median, stdv, etc...). I should point out that if you are after the mean aspect, this is quite erroneous because aspect is a circular variable. If you want mean aspect for an area you should transform aspect into a linear measure.

Re: how can measure general slope, aspect and height of polygons?

DanPatterson_Retired — Thu, 12 Jan 2012 17:28:03 GMT

Good point ... a quick Google search using "circular statistics" will provide numerous links on how to derive 'circular' or 'directional' statistical parameters from input data.

Re: how can measure general slope, aspect and height of polygons?

Luke_Pinner — Thu, 12 Jan 2012 20:21:22 GMT

For "general slope and aspect" I'd generate an elevation trend surface from your DEM (masked to your polygon):

Clip and mask your DEM to the polygon then convert the masked DEM to points, or...

Create Random Points constrained by your landslide polygon which you can use to sample the elevation values.

Then

Generate the elevation trend surface from those points and then calculate slope and aspect from that.

Repeat 300 times (batch or script)

Re: how can measure general slope, aspect and height of polygons?

mortazapirouz — Fri, 13 Jan 2012 08:48:01 GMT

Thanks Luke Pinner
I will try.