Esri Mapping Center - Ask a Cartographer

What's a good generic coordinate system for Search and Rescue operations across North America?

January 12 2010 | 4 comments
Categories: Page Layout

All,

I'm putting together some layer packages for the purpose of distributing to Search and Rescue, Emergency, and Wildfire Response folks across North America.

The coordinate system that should be used should:

a) maintain area throughout N. America
b) be fairly universal to everyone in N. America

I'm thinking Robinson, but not sure...

UTM would be nice, but I don't want to have different layer packages for every UTM zone in N. America...

Any thoughts?

Thanks!

Mapping Center Answer:

The Albers equal area conic projection should be used for the conterminous U.S. If you were also including Alaska and Hawaii, you could use the Lambert azimuthal equal area projection.

US National Grid posted by Chris Mathers on Jan 12 2010 1:42PM

The USNG is a Mercator varient developed for this specifically I believe. The developers wanted a standard national grid system that wasn't the MGRS though they wound being almost exactly the same.

Conformal projection posted by Aileen Buckley on Jan 12 2010 1:45PM

The underlying projection for this is Transverse Mercator (a conformal projection), so it is not equal area!

USNG posted by David VandenBos on Jan 13 2010 7:07AM

For what its worth, our Search and Rescue teams (who are also associated with both State and Fed USAR) use USNG for our search maps.

Grid cell location system posted by Aileen Buckley on Jan 13 2010 10:24AM

So how does that work? The USNG is a grid cell location system rather than a grid coordinate system. That is to say, it is used to identify an grid cell area rather than a specific location. If you get a location for someone using, for example, GPS coordiantes from a cell phone, and then you translate the position to the USNG grid coordinate system, you lose precision. Are there specific things that you use the USNG for and others that you use a grid coordinate system for?

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