Cell Size

[Gilbert Alarcon-Cruz]

Hello. I am new to using Biodiverse. When I import basedata, on the "set column options" screen, what is the unit of measurement for cell size?

[Shawn Laffan]

Hello Gilbert,

The units of measurement are whatever your data use. 

If you have geographic data then they will be either latitude./longitude values or some projected coordinate system.  If the latter then it could be any number of units, but most commonly metres. 

Some other relevant information is in the FAQ: https://github.com/shawnlaffan/biodiverse/wiki/FAQ#i-imported-my-data-and-it-only-has-one-cell

Regards,
Shawn.

On 30/11/2022 09:25, 'Gilbert Alarcon-Cruz' via Biodiverse Users wrote:

Hello. I am new to using Biodiverse. When I import basedata, on the "set column options" screen, what is the unit of measurement for cell size? --

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[Gilbert Alarcon-Cruz]

I see. So if I import a csv file of occurrence data from GBIF that includes the decimal latitude and decimal longitude, the cell size will be in degrees?

[Shawn Laffan]

Hello Gilbert,

Yes, that is correct. 

If you are using a large area then it is worth projecting your data into an equal area coordinate system.  Which one to use depends on the area you are working with. 

This can be done most easily using a GIS, but also using tools such as the sf library in R. 

If you save the results to a shapefile then Biodiverse can read that also.  Details are in this post (it refers to polygons and polylines but the same procedure applies to points). 
https://biodiverse-analysis-software.blogspot.com/2018/12/import-polygon-and-polyline-data.html

Regards,
Shawn.

On 2/12/2022 04:13, 'Gilbert Alarcon-Cruz' via Biodiverse Users wrote:

I see. So if I import a csv file of occurrence data from GBIF that includes the decimal latitude and decimal longitude, the cell size will be in degrees?

On Tuesday, November 29, 2022 at 5:38:14 PM UTC-8 Shawn Laffan wrote:

Hello Gilbert,

The units of measurement are whatever your data use. 

If you have geographic data then they will be either latitude./longitude values or some projected coordinate system.  If the latter then it could be any number of units, but most commonly metres. 

Some other relevant information is in the FAQ: https://github.com/shawnlaffan/biodiverse/wiki/FAQ#i-imported-my-data-and-it-only-has-one-cell

Regards,
Shawn.

On 30/11/2022 09:25, 'Gilbert Alarcon-Cruz' via Biodiverse Users wrote:

Hello. I am new to using Biodiverse. When I import basedata, on the "set column options" screen, what is the unit of measurement for cell size? --

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[Gilbert Alarcon-Cruz]

So if I wanted to import the occurrence data but wanted the cell size to be in km I would have to do a conversion?

[Shawn Laffan]

Yes, that is correct. 

If you are comfortable using R then this seems to be a useful reference for the process of importing data, projecting it and exporting to shapefile: 
https://datacarpentry.org/r-raster-vector-geospatial/10-vector-csv-to-shapefile-in-r/

The process with a GIS depends on the software you are using. 


Regards,
Shawn.

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[Gilbert Alarcon-Cruz]

I see. So once I have converted my data into California Albers, I can assume that the cell size will be in meters when I import it into Biodiverse?

[Shawn Laffan]

Hello Gilbert,

There are several Califormia ALbers coordinate systems but they all seem to use metres. 
https://spatialreference.org/ref/?search=California+Albers

So when you import your data, a cell size parameter of 100,000 represents 100 km. 

Regards,
Shawn.

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[Gilbert Alarcon-Cruz]

I see. Thank you so much for your help!

[Shawn Laffan]

You're welcome.

Regards,
Shawn.

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