NYS Countywide Floodplain Mapping Surveys
Elevation Reference Marks
The New York State Department of Environmental Conservation (DEC) is a Cooperating Technical Partner with the Federal Emergency Management Agency (FEMA), and is an active participant in FEMA's Map Modernization Program. DEC's responsibilities include the collection of survey data used for countywide floodplain mapping projects.
In addition to published survey benchmarks contained in the National Geodetic Survey Database, the DEC has established permanent 3-D survey monuments. These Reference Marks (RM's) can be of great use to local surveyors, engineers, contractors, and government agencies. This data can be used for many purposes in addition to those related to National Flood Insurance Program. Many of the RM's were set in pairs, which will provide an azimuth when using a total station.
A geodetic control network was established in each project area in accordance with procedures presented in the National Oceanic and Atmospheric Administrations Technical Memorandum NGS-58, Guidelines for Establishing GPS-Derived Ellipsoid Heights (Standards: 2 cm and 5 cm), 1997, and FEMA's Guidelines and Specifications for Flood Hazard Mapping Partners, 2003. All RM's were established from this geodetic control network.
