Map Datum

venado

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I have a Mexican topo map that indicates the datum as Norteamericano de 1927. I have a Garmin 12 Map and wonder if I should use the datum referred to there as NAD27MEXICO or the NAD27CONUS since I am only 10 miles across the border. Anyone have any brilliant ideas?
 

Tinhorn

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I'd make a guess it would be Nad27 Mexico but one thing you might try is to go to  Topozone.com and enter a Coordinate off the map you have and see if what Topozone site gives matches your map

I believe Topozone topo's are all Nad27 (famous last words huh!)
 

venado

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Tried that after your suggestion and nothing came up...do you suppose that Topozone recognizes that it is not in the US and rejects the numbers?
 

Kevin

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I tried it for Sault, Ontario and it doesn`t work but it does work for Sault, Michigan.
 

spectr17

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Hey Venado,

I was going to say NAD1927Mexico and then I thought I'd better ask for sure. From Matt in the sci.geo.satellite-nav newsgroup.

It isn't going to make a lot of difference.
CONUS   delta x=-8   delta y=160  delta z=176
Mexico    delta x=-12 delta y=130  delta z=190

The values are all mean anyway, which means the difference represent the difference between the mean values in the Continental USA and Mexico. All up the error is about 35 meters between the two.  

However if the map is in Spanish, and was published in Mexico, it is probably Mexican Datum..
 

venado

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Thanks folks, and hello Jesse. Good site that you have here and I appreciate the opportunity to post on it. The maps in question are in Spanish and just for kicks think that I'll use the 27MEXICO...35 yards won't make a difference for my purposes anyway but I always like to think I'm working with the best technical qualities possible.
 

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