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Subject:
Re: A scale question.
From:
David Medeiros <[log in to unmask]>
Reply To:
Maps-L: Map Librarians, etc.
Date:
Fri, 18 May 2018 12:16:47 -0700
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What projection is the first map map in? Web Mercator is not an equal
distance projection so I'd expect some error especially if measuring
across latitude to some degree.  

David Medeiros

Stanford Geospatial Center 

On 2018-05-18 11:55, Rick Grapes wrote:

> Hi all, 
> 
> I have a calculating scale question.  This map I'm cataloging has a bar scale.  I measured the bar, did the math, and got the ratio.  
> 
> Just for the fun of it I also measured between 2 points on the map, as far apart as the map would allow, obviously much greater than the bar scale, then measured between the same 2 points on google maps, and again did the math.  The difference was about 10%.  Which calculation would you trust?  Granted, either entries in the 255 would be an approximation.  A potential issue could be divergent projections etc.  Any suggestions? 
> 
> Rick Grapes 
> 
> BYU Map Cataloger

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