Issued: 06/09/2014
INTRODUCTION TO SAINT LOUIS COUNTY BENCH MARK SYSTEM The Purpose of the Saint Louis County Benchmark System is to compile established information listing the known Bench Marks within Saint Louis County. The Survey Section of the Saint Louis County Department of Highways and Traffic assumed sole responsibility for the Saint Louis County Benchmark System in 2000. Maintenance of the system prior to 2000 was a coordinated effort between the Department and the Metropolitan Saint Louis Sewer District. Previous published editions (all as paper books) under the coordinated effort are as follows: 1st printing - February 1981 3rd revision - November 1993 1st revision - July 1986 4th revision - July 1997 nd 2 revision - March 1992 Previous editions under the Saint Louis County Department of Highways and Traffic are as follows: February 2001 - Published paper book dated January 1, 2001. September 2002 - First digital publication as ".pdf" files to Saint Louis County web site. June 2014 – First publication with NAVD88 elevations resulting from a multiyear project to improve and modernize the Saint Louis County Benchmark System. Individual chapter files will be periodically updated on the Saint Louis County web site.
Supported Datum(s): All publications of the Saint Louis County Benchmark System prior to 2014, were based upon benchmarks indexed to the National Geodetic Vertical Datum 1929 (commonly NGVD29) as established by the United States Geological Survey (USGS) or its successor, the National Geodetic Survey (NGS). This datum was historically, but imprecisely, known as USGS Datum. The Saint Louis County Benchmark System was the subject of a comprehensive review and modernization project between 2009 and 2014. Between November 2009 and January 2010, the Survey Section of the Saint Louis County Department of Highways and Traffic performed static GPS observations on a network of 43 monuments for a height modernization project in collaboration with the Missouri Land Survey Program and with the National Geodetic Survey. The Survey Section was relying upon the National Geodetic Survey to publish North American Vertical Datum 1988 (NAVD88) elevations on those 43 monuments. As of May 2014, neither agency has completed the Saint Louis County NAVD88 height modernization. The Survey Section lacks the statutory authority to independently establish NAVD88 elevations on new primary control monuments. Between 2009 and now, the Survey Section has run a network of differential level observations covering much of Saint Louis County. Saint Louis County has adopted 14 monuments where the published NGS datasheets include NAVD88 orthometric heights in order to propagate NAVD88 elevations throughout the Saint Louis County Benchmark System. This implementation of NAVD88 by Saint Louis County has been designated NAVD88(SLC2011a). Refer to "Addendum 1" for summary of NAVD88 implementation by Saint Louis County as NAVD88(SLC2011a).
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