How to estimate landscape orientation of irregular features?

[FrankHanssen]

Hi

I am developing a model where I aim to estimate the bimodal landscape orientation (azimuth angles) of ridges, valleys and fjords. The purpose of this work is to develop an index on how landscape orientation relate to bird migration from a certain direction.

Calculating horisontal landscape orientation is straight forward but gives in my opinion only meaning for regular shaped features with a distinct directional shape (lets say from east to west). The challenge is how to estimate the direction of irregular shaped features (having a very curly perimeter of outliers and inward bends). I would like to use a moving window to calculate mean angles of sub-polygonal elements of each irregular polygons in order  too measure how these mean azimuth angels  deviate from the master polygon mean azimuth angle (along its long axis). I also want to figure out how to use morphological shape metrics to estimate the angular shape dispersion of each irregular polygon (in order to remove those polygons that disperse equally in all directions).

Any ideas out there?

Kind regards,

Frank Hanssen

[DanPatterson_Retired]

Minimum Area Bounding Rectangles (MABR) should give you the option. The tool is Minimum Bounding Geometry in ArcMap

[FrankHanssen]

Thanks Dan. Yea I already use this tool, but as said it does not seem reasonable for irregular polygons (of course correct with respect to the minimum bounding genmetry). Have also calculated the angular mean of line segments for each polygon (but I am still not satisfied). Currently looking at the angular dispersion (the average euclidian distance from the polygon centroid to all perimeter points).

[DanPatterson_Retired]

The implementation should determine the convex hull, then the MABR which is more than adequate.

As for determining the means of directional data you can't use simple math. Read my blog post and its associated one on this topic.

[FrankHanssen]

Thanks a lot for the tip! I will check that option when using MABR.

And yes- I am not using simple math for calculating means of directional data☺

[DanPatterson_Retired]

Now that the links are back up to the scripts site, give Bounding Containers a try.  Shapefiles as inputs and outputs are required.