Historical Surveying: Early Vertical Datums of the USGS

Interesting article about the early vertical datums used by the US Geological Survey field crews in the May 2014 issue of the American Surveyor journal.

Thanks to Steve Char for sharing this link with the GIS Colorado list-server. 

http://www.amerisurv.com/PDF/TheAmericanSurveyor_Penry-EarlyUSGSVerticalDatums_May2014.pdf

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Steve Char
Colorado Water Science Center
US Geological Survey
303-236-6880

(May 7, 2014)