Table 2. Global positioning system control points used in the river survey in the regions of the Union Gap and the Selah Gap near Yakima, Washington, August 2008.

[GPS control point designation: Designation used by: the National Geodetic Survey (NGS) on its datasheets, accessed online at http://www.ngs.noaa.gov/cgi-bin/datasheet.prl; the Washington State Department of Transportation (WSDOT) in its Survey Monument Database, accessed online at http://www.wsdot.wa.gov/monument/; or the U.S. Geological Survey in its river surveys in 2004. Abbreviations: GPS, global positioning system; cm, centimeter; m, meter; –, control points were established by 2004 river surveys by the U.S. Geological Survey and no accuracy values were published]

GPS control point designation	Base station or coordinate check	Northing	Easting	Orthometric height (m)	Published vertical accuracy or vertical order
State Plane South coordinates, in meters
SARG (NGS)	Check point	141,052.319	501,748.638	313.984	Class II
GP39082-10 (WSDOT)	Check point	145,339.366	498,617.515	333.937	1 cm
GP39082-23 (WSDOT)	Base station	144,531.286	498,545.501	369.416	5 cm
WW_Plant (USGS)	Base station	137,983.103	502,270.830	305.428	–
WAPCNTRL (USGS)	Check point	130,273.163	501,542.082	286.687	–
GP39012-9 (WSDOT)	Check point	143,681.039	498,450.197	344.526	1 cm