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What coordinate system should I use if I am mapping all of North America?

CarlyConticchio1

Forgive me if I am posting this to the wrong place, as I am new to this community and I am a GIS noob.

I am mapping species presence across North America (monarch butterflies). I am at a loss for what coordinate system I should use for this. Google gave me several conflicting answers. I was thinking web mercator but I don't want to do the whole analysis just for it to be wrong. Please advise!

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jcarlson

It probably depends on your analysis, but generally, web mercator is a bad idea for analysis, given how much distortion it introduces.

As a fun aside, checkout Mercator: EXTREME. It lets you place the north pole somewhere else, and see what a web mercator projection might look like based on that new pole.

You'd probably be okay going with something like an Albers projection. It's what the USGS uses, if that sways your opinion.

All comments

jcarlson

It probably depends on your analysis, but generally, web mercator is a bad idea for analysis, given how much distortion it introduces.

As a fun aside, checkout Mercator: EXTREME. It lets you place the north pole somewhere else, and see what a web mercator projection might look like based on that new pole.

You'd probably be okay going with something like an Albers projection. It's what the USGS uses, if that sways your opinion.

CarlyConticchio1

Thank you! That was the other option I was thinking. Now the points themselves on the map, they should also be in Albers? Or should just my map frame and North America polygon?

jcarlson

Any analysis output will probably default to the projection of the input data unless otherwise specified. I'd keep it all in the same projection, myself, but you don't have to.

CarlyConticchio1

Perfect. Thanks so much for the help!

HeatherSmith

Hi @CarlyConticchio1

I recommend North America Albers Equal Area Conic. If any of your analysis involves area or distance measurements, you'll want an equal area projection.

As @jcarlson said, your map frame is probably using the same coordinate system as your data. But you should probably check to make sure it is. If you are using ArcGIS Pro, you can check it here:

When you Geoprocessing tools, they will use the coordinate system of the input data to compute the analysis.

RobertBorchert

Not to detract to much from some responses, they are good information.

I will always suggest this projection for all GIS Projects until something more universally functional comes along.

WGS_1984_Web_Mercator_Auxiliary_Sphere
WKID: 3857 Authority: EPSG

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