BackgroundSurfaceGenerator error

[Stephen Chignell]

Hi all,

I am trying to use the BackgroundSurfaceGenerator module to create a binary mask for generating background points. However, when using Kernel Density (KDE) and adhoc option, I get the following error:

My field data (presence only, opportunistic sampling) were collected along riparian zones that are fairly linear, which makes me wonder if this is the source of the "Polygon is self-intersecting" message.

I did some testing, and the module does run when I instruct it to create a continuous surface or the minimum convex polygon.

Further context: my study area (and template layer) is an alpine plateau (approx. 1100 km2). I'm trying to limit bias in my sampling, but I'm wondering how necessary this is since the furthest I'm predicting from my field data is < 50 km and the area is all within the same life zone. I've run a number of models generating background points in the whole study area and the predictions and MESS are looking good so far.

Any thoughts on the error or the approach would be greatly appreciated!

Thanks,

-Steve

[Michelle Fink]

Steve,

This is just a guess, but try sorting your presence points by XY. It looks like the code does that automatically for KDE continuous surface, but not binary.

--Michelle

[Gericke Cook]

As a workaround, if you are able to create a continuous surface then you could apply your own threshold to create a binary mask. Then manually change the background layer in SAHM to the one you created.

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[Stephen Chignell]

Thanks to everyone for your responses! I had to prioritize some other work the last couple of weeks but am now revisiting this question. I will try these suggestions and let the forum know what ends up working.

All the best,
-Steve

On Thursday, October 27, 2016 at 3:44:11 PM UTC-6, Stephen Chignell wrote: