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Does anybody have any suggestions for a projected coordinate system for the Northern part of South America? I have a data set that reaches from Venezuela to Southern Peru and I'd like to do some spatial autocorrelation on it. However, the current WGS84 is obviously a geographic coordinate system and not suitable for this type of analysis. I could just stick it in UTM 19 or 20 (north or south I guess given it spans the Equator) but I just wanted to know if anyone had any better suggestions.

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Thanks guys. I'm going to play around with a few of these suggestions and see what we get. Does anyone know where we can find a map of suitable Transformations? ESRI suggests WGS84 to SAD69 1 but there are other options in the transformation list. The first suggestion is not always the best in my experience. –  Oliver Burdekin Aug 26 at 12:24

2 Answers 2

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You first need to decide what distortion properties would you like to control for. That is to say, are you interested in preserving area, distance or shape? There is a decision support tool for selecting projections that is quite user friendly and available for free from Oregon State University (Map Projection Selection Tool). Note that you can select the distortion property and a specific area of interest. The tool yields a recommended projection, a central meridian and PROJ.4 code.

enter image description here

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You can use some projections that are provided by ESRI, depending on whether distance or area is important for you. They look very similar:

ESRI:102032 South_America_Equidistant_Conic

+proj=eqdc +lat_0=-32 +lon_0=-60 +lat_1=-5 +lat_2=-42 +x_0=0 +y_0=0 +ellps=aust_SA +units=m +no_defs

enter image description here

ESRI:102033 South_America_Albers_Equal_Area_Conic

+proj=aea +lat_1=-5 +lat_2=-42 +lat_0=-32 +lon_0=-60 +x_0=0 +y_0=0 +ellps=aust_SA +units=m +no_defs

enter image description here

Both projections are included in newer GDAL and QGIS versions as EPSG:102032 and EPSG:102033

A third choice can be EPSG:2317 PSAD56 / ICN Regional using Lambert Conformal Conical:

+proj=lcc +lat_1=9 +lat_2=3 +lat_0=6 +lon_0=-66 +x_0=1000000 +y_0=1000000 +ellps=intl +towgs84=-288,175,-376,0,0,0,0 +units=m +no_defs
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