My area of interest is between UTM zone 22 and 23. I'm struggling in create a custom projection, so:

  • Can I create a custom UTM projection, would be this the minimum distortion?

  • I did not understand what is parallels 1 and 2 in South_America_Albers_Equal_Area_Conic for my customization, can anyone say which values it would be based on my area of interest below?

In the image are the UTM zones and the extremes coordinates of my area of interest. enter image description here

  • UTM only really works in 6-degree wide bands. Your data is 8-9 degrees wide, which puts you at, or just over, the effective limit of UTM. Standard parallels for conic projections are usually at 1/3 and 2/3 or 1/4 and 3/4 (or somewhere in between) of the latitude extent. It's rare that you need to use a custom projection with so many standardized ones already in use. – Vince Mar 17 at 1:40
  • Vince, so should I use the existent South_America_Albers_Equal_Area_Conic? – F. Almeida Mar 17 at 11:27
  • That's a value judgement on the part of the cartographer. You need to do your due diligence and evaluate the error as applies to your analysis. There should be a country grid zone between UTM and a standard continental scale to pick from as well. – Vince Mar 17 at 11:47
  • What GCS is the data using currently? Or is most of the data using? – mkennedy Mar 18 at 18:53

I wouldn't use the South America Albers definition because it's designed for the whole continent. There are other definitions for Brazil itself.

Look under National Grids, South America and there are some Brazil-wide definitions using Polyconic and Mercator. You can also go larger-scale and modify an existing UTM zone by changing the central meridian to -47 (change the name of the projected coordinate reference system too). Some UTM definitions using Brazil-specific GCS (SAD69 (96)) are in UTM, South America.

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