Vertical Datum Conversion Process for the Inland and Coastal Gage Network Located in the New England, Mid-Atlantic, and South Atlantic-Gulf Hydrologic Regions Chapter 8 of Section B, U.S. Geological Survey Standards Book 11, Collection and Delineation of Spatial Data Techniques and Methods 11–B8 Version 1.1, July 2017 U.S. Department of the Interior U.S. Geological Survey Cover Photograph Credits Quinault Indian Reservation, Washington State, 2012 Blue Creek near Lewellen, Nebraska, July 8, 2014 The base station consists of Trimble R7 with a Zephyr Geodetic A USGS civil engineer surveys cross sections using survey-grade GNSS Model II antenna and RTK radio. The survey was performed for a regional paleoflood study near USGS streamgage 06687000 Blue on the Quinault Indian Reservation in 2012 in collaboration with Creek near Lewellen, Nebraska, on July 8, 2014. the Washington State Department of Ecology and Oregon State University. Surveying of the beach elevations was done with Photograph by Michael Stevens, USGS Hydrologist, Grand Junction, GNSS backpacks and nearshore bathymetry with GNSS and Colorado single-beam echosounders mounted on personal watercraft. This was one of the benchmarks that was established to provide geodetic control for the survey. Photograph by Andrew Stevens, USGS Oceanographer, Santa Cruz, California Vertical Datum Conversion Process for the Inland and Coastal Gage Network Located in the New England, Mid-Atlantic, and South Atlantic-Gulf Hydrologic Regions By Paul H. Rydlund, Jr., and Michael L. Noll Techniques and Methods 11– B8 Version 1.1, July 2017 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Jack Haugrud, Acting Secretary U.S. Geological Survey William H. Werkheiser, Acting Director U.S. Geological Survey, Reston, Virginia First release: 2017 Revised: July 2017 (ver. 1.1) For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://store.usgs.gov/. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Rydlund, P.H, Jr., and Noll, M.L., 2017, Vertical datum conversion process for the inland and coastal gage network located in the New England, Mid-Atlantic, and South Atlantic-Gulf hydrologic regions (ver. 1.1, July 2017): U.S. Geological Survey Techniques and Methods, book 11, chap. B8, 29 p., https://doi.org/10.3133/tm11B8. ISSN 2328-7055 (online) ISSN 2328-7047 (print) iii Preface This series of manuals on techniques and methods describes approved scientific and data- collection procedures and standard methods for planning and executing studies and laboratory analyses. The material is grouped under major subject headings called “books” and further subdivided into sections and chapters. Section B of book 11 is about U.S. Geological Survey standards for data-collection techniques. The unit of publication, the chapter, is limited to a narrow field of subject matter. These publications are subject to revision because of experience in use or advancement in knowledge, techniques, or equipment, and this format permits flexibility in revision and publication as the need arises. iv Acknowledgments The authors would like to thank Dru Smith, Daniel Martin, Scott Lokken, and Mark Schenewerk of the National Oceanic and Atmospheric Administration, National Geodetic Survey, for their technical reviews. Published manuals from the National Geodetic Survey, U.S. Army Corps of Engineers, National Weather Service, and the Federal Emergency Management Agency are referenced throughout the report. v Contents Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................2 Distinction and Purpose of Inland and Coastal Gages ............................................................................2 Surge, Wave, and Tide Hydrodynamics (SWaTH) Network Gages ..............................................5 Datum Transformation Models ....................................................................................................................5 Vertical Datum Transformation (VDATUM)—Coastal Land-Water Interface .............................5 North American Vertical Datum Conversion (VERTCON) ...............................................................6 Datum Uncertainty Evaluation and Determination ...................................................................................8 Differential Leveling Methods ............................................................................................................8 Trigonometric Leveling Methods ........................................................................................................8 Global Navigation Satellite System (GNSS) Methods ....................................................................9 Datum Conversion Process ..........................................................................................................................9 Evaluation ...............................................................................................................................................9 Process Selection and Execution ....................................................................................................12 Datum Uncertainty Requirements for U.S. Army Corps of Engineers (USACE), Federal Emergency Management Agency (FEMA), and the National Oceanic and Atmospheric Administration (NOAA)–National Weather Service (NWS) .......................................................................................................................18 Migration Planning and Publishing of Datum Changes .........................................................................20 Coordination and Processing ...........................................................................................................20 Dissemination ......................................................................................................................................20 Gravity for the Redefinition of the American Vertical Datum (GRAV-D) .............................................22 Expected Uncertainties .....................................................................................................................22 Implication of a NAVD 88 Conversion ..............................................................................................22 Future Datum Conversion Using GRAV-D ..............................................................................24 References Cited..........................................................................................................................................24 Glossary .........................................................................................................................................................27 vi Figures 1. Tri-hydrologic region overview map illustrating the U.S. Geological Survey inland, coastal, and Surge, Wave, and Tide Hydrodynamics gage networks ....................3 2. Diagram showing the relation of common tidal-based datum planes to the North American Vertical Datum of 1988 terrestrial-based datum plane at Battery Park, New York County, New York ...............................................................................4 3. Map showing the maximum cumulative error represented by tidal region for datum transformations using the coastal land-water interface vertical datum transformation tool VDatum ...........................................................................................7 4. Diagram showing the datum conversion decision tree and survey process ...................13 5. Map showing the vertical movement in the New England hydrologic region reflected by published continuously operating reference stations during the 2011 update of the National Spatial Reference System .......................................................14 6. Map showing the vertical movement in the Mid-Atlantic hydrologic region reflected by published continuously operating reference stations during the 2011 update of the National Spatial Reference System .......................................................15 7. Map showing the vertical movement in the South Atlantic-Gulf hydrologic region reflected by published continuously operating reference stations during the 2011 update of the National Spatial Reference System ....................................16 8. Map showing land elevation change rates from 1940 through 1971 in the Chesapeake Bay area ...............................................................................................................17 9. Diagram showing dissemination of both National Geodetic Vertical Datum of 1929 and North American Vertical Datum of 1988 at a gaging location as illustrated through the National Water Information System Web with Hypertext Markup Language coding