Bias files (inlcuding buffered Miniumumn Convex Polygon) - how to input multiple bias files

[Ashley Jensen]

Hello,

I'm using SDM toolbox to generate files for Eco Niche Modelling in MaxEnt. I want to use more than one bias files, but MaxEnt only allows the input of a single bias file. I have made two bias files I'd like to use.. one is Gaussian Kernel Density file to account for sampling bias. I definitely need this file, since my model only accurately predicts the species range in the far north when I use this file.

Second, I'd like to prevent the prediction of species distribution outside of the known range by a buffer distance. There are multiple ways to do this with SDM toolbox - for example the program uses occurrence data to create a user-specified buffer distance; outside this area, the model will not be allowed to predict species distribution. I have generated the buffered MCP bias file(AKA background point selection) with SDM toolbox, but don't know how to proceed now.
I'm at a loss on how to incorporate this information into the MaxEnt modelling. Is there a way to combine these two files???


The other option I came across is to proceed with MaxEnt modeling, and then take the SDM file and put it into GIS and use SDM toolbox to clip the prediction area by applying a buffered minimum convex polygon. I was able to do this, but now I don't know how to visualize my file. I don't know if there is a way to get the file back into MaxEnt, but if I view the file in GIS, it looks very different from how it looks as a MaxEnt output (the scale is totally different, and can't achieve the same colours for heat map).


Perhaps this is an easy fix, but I'm a newbie to all of these programs (including GIS!). Any advice would be much appreciated.



Thanks,

Ashley

[Lawrence, Kevin]

Would this work?

Convert the range buffer raster to 1 or 0 using raster calculator and then multiply this layer by the maxent model output

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[Ashley Jensen]

Perhaps, and I appreciate the suggestion. I am new to GIS, so I will give it a go. We'll see if I can get that to work.

I was also wondering if anyone could tell me how to get GIS to appropriately display a MaxEnt model. When I view them in GIS, they automatically load as black and white. I can go into symbology and change the colour ramp, but I can't figure out what values to input. MaxEnt displays the models on a logarithmic scale. When I go to change the colour ramp, it allows me to input Max, Min, Mean and Std Dev for the scale, but not sure how to input these values to make it display the colour values the same way they are displayed in MaxEnt.
Any suggestions are greatly appreciated!

Thanks,

Ashley

[Jamie M. Kass]

Are you using ArcGIS? If so, you may need to run Calculate Statistics on the output ASCII, which should allow you to view the range of values. Also try exporting the ASCII as a native GRID or TIFF file. ASCIIs sometimes give GIS software some trouble.

Jamie Kass
PhD Candidate
City College of NYC