imposing a depth threshold

[Rita Castilho]

Hi,

I am working with a marine species that has a shallow distribution, and I would like to delimit modelling to a 50m depth threshold along the coastline using a bathymetric dataset (e.g. Bio-Oracle, MARSPEC or GEBCO). I am working in R. I do not want bathymetry to be part of the model though. Does anyone know how to do this?

Cheers,

Rita

[Husam El Alqamy]

Hi Rita

In GIS You can achieve this by using the bathymetry layer to clip your study region so that modeling happens only within the clipped study region.

	Hossameldin ELALKAMY, MPhill., PhD. GIS Analyst  Conservation Data Center|  Victoria Ministry of Environment & Climate Change P. 250.614.7521 C. 778.896.3229|395 Waterfront Cres.  Victoria, BC., V8W 9M1
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[Rita Castilho]

Hi Hossameldin,

Thanks for the tip, but I actually need more detail instructions on how to do it, preferably in R, but if not, not a problem either.

Can you provide more detail?

R

On Thursday, 17 May 2018 17:27:43 UTC+1, alqamy wrote:

Hi Rita

In GIS You can achieve this by using the bathymetry layer to clip your study region so that modeling happens only within the clipped study region.

	Hossameldin ELALKAMY, MPhill., PhD. GIS Analyst  Conservation Data Center|  Victoria Ministry of Environment & Climate Change P. 250.614.7521 C. 778.896.3229|395 Waterfront Cres.  Victoria, BC., V8W 9M1
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On Thu, May 17, 2018 at 9:02 AM, Rita Castilho <rita....@gmail.com> wrote:

Hi,

I am working with a marine species that has a shallow distribution, and I would like to delimit modelling to a 50m depth threshold along the coastline using a bathymetric dataset (e.g. Bio-Oracle, MARSPEC or GEBCO). I am working in R. I do not want bathymetry to be part of the model though. Does anyone know how to do this?

Cheers,

Rita

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[Husam El Alqamy]

Sorry I am not that familiar with doing it in R, I use ArcMap GIS.

	Hossameldin ELALKAMY, MPhill., PhD. GIS Analyst  Conservation Data Center|  Victoria Ministry of Environment & Climate Change P. 250.614.7521 C. 778.896.3229|395 Waterfront Cres.  Victoria, BC., V8W 9M1
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[Rita Castilho]

I can access to ArcGIS. Can you give me some pointers?

R

[Rita Castilho]

That is no problem, I can access ArcMap GIS. It is too much trouble to outline the task?

Thanks,

R

On 17 May 2018, at 18:28, Husam El Alqamy <alq...@gmail.com> wrote:

Sorry I am not that familiar with doing it in R, I use ArcMap GIS.

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[Husam El Alqamy]

No not at all

1- in your bathymetry raster reclassify everything from 0 to 50 as to a new value of 1, and reclassify greater than 50 to 0.

2- convert  the new reclassified raster to polygon

3- apply dissolve to the new polygon layer where you have only 2 polygons of gridcodes 0 & 1 (do not use simplify option)

4- select all the polygons with gridcode=0 and delete them.

5- use the resulting polygon layer to clip your predictor raster layers. (use extract with mask not CLIP in Arcmap).

and you are done

hope that helps

	Hossameldin ELALKAMY, MPhill., PhD. GIS Analyst  Conservation Data Center|  Victoria Ministry of Environment & Climate Change P. 250.614.7521 C. 778.896.3229|395 Waterfront Cres.  Victoria, BC., V8W 9M1
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R

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[Rita Castilho]

Ok. Thanks.

I will give it a try. This is my first time as ArcGIS user...

R

R

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