Habitat mapping of Southern Indian Ocean

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07-13-2021 08:33 AM
BertaR
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Dear all,

I need to project seafloor bathymetric data obtained in WGS84 format from GEBCO (https://www.gebco.net/) to use it as a explanatory variable for a habitat suitability model in the Southern Indian Ocean. Ideally, I would need an equal-area projection that would later help in evaluating the accuracy of the resulting models.

From reading ESRI and various other webpages it seems that Lambert Conformal Conic or Albers Conic Equal Area projection would be suitable options. In such case, I would be looking into centering the area of study at central meridian 70E and latitude of origin 30S. However, I can't figure out how to choose/calculate the two standard parallels (SP2) required to set either projection. 

I have tried as a test to reproject in the socalled "Asia_South_Lambert_Conformal_Conic" (Central meridian:125; Latitude of origin: -15; SP1: 7; SP2: -32) and it works. Nevertheless, I would like the least possible distorsion and therefore to center it properly in the middle of the Southern Indian Ocean.

Any suggestions on how to achieve it and/or select appropriate SPs?

Many thanks in advance and apologies if the question is too basic!

Kind regards,

Berta

 

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DavidPike
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I do remember a 1/6th rule i.e. placed at 1/6th and 5/6th of the N/S distance, but that might be too much of a rule of thumb.  If you search for Lambert Conformal Conic with 'rule of sixths' 'one sixth rule' '1/6' etc. where should be several sites to browse.

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DavidPike
MVP Frequent Contributor

I do remember a 1/6th rule i.e. placed at 1/6th and 5/6th of the N/S distance, but that might be too much of a rule of thumb.  If you search for Lambert Conformal Conic with 'rule of sixths' 'one sixth rule' '1/6' etc. where should be several sites to browse.

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BertaR
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Thank you for your response! I had seen something about the 1/6th rule in some of the websites I visited, but I kept thinking it was 1/6th from the latitude of origin (which didn't work with the examples I checked) rather then the N/S extent of the layer.

Cheers!

Berta

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