SAN LUIS VALLEY— The Colorado Department of Transportation (CDOT) advises travelers that they may encounter or see survey activity taking place along US Highway (US) 160 over the next few months.
The National Geodetic Survey (NGS) is conducting a very large field research project along much of the US 160 corridor in southern Colorado, between Walsenburg and Durango. The project, known as the 2017 Geoid Slope Validation Survey, started in May and is expected to be completed later this fall in September.  
Colorado was chosen for the survey testing because of its high, rugged terrain. The survey uses prepared concrete piers positioned approximately every mile. Survey teams will gather information from each of these points at different times throughout the summer.
The goal of the survey is to “ground truth” or confirm data results collected from of a larger project, GRAV-D (Gravity for the Redefinition of the American Vertical Datum). The purpose of GRAV-D is to use accurate knowledge of the Earth’s gravity field as a basis for precise elevation measurements.
NGS is an agency within the National Oceanic and Atmospheric Administration (NOAA). NGS provides the framework for all positioning activities in the United States, including elements of latitude, longitude, elevation, and shoreline information which is used by engineering, surveying and mapping activities in the United States across federal, state and local governments.
For more information about the survey project contact Derek Van Westrum, NGS Project Manager, [email protected] or 240-988-6341. Information is also available on the web at www.ngs.noaa.gov.