Mask using shapefile

[Prashant_mahajan]

I am attempting to use a shapefile as a mask, where the boundary around the detectors is defined with a hard boundary on either side, and a river/stream runs in between. However, I’m facing an issue where I can’t use the exact shapefile when applying a buffer of a certain width. Without the buffer, the mask only includes the detector locations as points and excludes other available habitats where detectors were not placed.

I am using the following code:

mask.2021 <- make.mask(traps(coy.cap2021), spacing = 100,
type = "trapbuffer", poly = area)

In this case, area refers to the shapefile, which contains the desired buffer and excludes the non-habitats.

Could you help me understand what I might be missing and how to use the exact shapefile for further analysis?

Thank you!

[murray.efford]

Hello
I suspect you have omitted to specify the 'buffer' argument. By default that is 100 m, which is probably much too small for leopards, tigers or whatever you are working on. The poly argument is used to clip the buffered region; it doesn't define the mask on its own.
Murray

[Prashant_mahajan]

Hi,

Thank you for your response. I tried specifying a buffer of 3000, but the resulting mask does not match the desired outcome. Instead of showing the shapefile with gaps and a hard boundary, it is producing a continuous mask that extends beyond the shapefile without any gaps.

How can I obtain a mask that exactly matches my shapefile? I have already included the desired buffer within the shapefile.

Thank you!

[murray.efford]

There's something screwy here. Perhaps the projections or scales of your trap file and shapefile do not match. Can you plot one over the other and show us a picture?

[Prashant_mahajan]

I had unmatched projections, but after correcting for projections also it's not showing the desired results.

Here are the images for the traps over the study area and traps over the buffer:

https://drive.google.com/file/d/1E_-XqL ... drive_link
https://drive.google.com/file/d/1YMqpRK ... drive_link

Thanks.

[murray.efford]

[For some unknown reason my reply yesterday was rejected by the microsoft or the phidot system - here it is again]

Is the shapefile a polygon shapefile? Lines aren't enough. Have you tried switching poly.habitat in case this is a negative habitat map? If you have exhausted all the possibilities then send the data to me offline and I'll sort it out.
Murray

[Prashant_mahajan]

It is a polygon. I have tested it with both habitat and non-habitat shapefiles. I have emailed you the shapefiles along with the trap and capture files.

Thank you!

[murray.efford]

Hi Prashant
In the code you sent me offline the 'poly' argument was spelled 'ploy'. I think it works if you fix that.
Murray

[Prashant_mahajan]

Yeah, it worked after correcting for it.

Thank you!