DOCSLIB.ORG

History of the Development of Geodetic Datums in the United States

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
History of the Development of Geodetic Datums in the United States History of the Development of Geodetic Datums in the United States Professional Land Surveyors of Oregon Salem January 24, 2014 Dave Doyle NGS, Chief Geodetic Surveyor (Retired) [email protected] 301-704-9578 1807 PRESIDENT THOMAS JEFFERSON SIGNS LEGISLATION ESTABLISHING THE SURVEY OF THE COAST FERDINAND HASSLER (1770-1843) What’s In a Name? 1807 - Survey of the Coast 1836 - Coast Survey 1878 - US Coast and Geodetic Survey 1970 - National Ocean Service National Geodetic Survey JASPER BILBY BILBY TOWER CONSTRUCTION Cutting Edge Surveying Technology circa 1890 Salina, KS Baseline Measurement – 1896 6.5 km/4.1 mi required about 5 weeks Precision ~ 8 mm/0.03 ft (1:721,600) Advances in distance measurement technology Early 1900s Electronic technology 1950s - 1970 A Game Changer 1984 AN END OF AN ERA GLOBAL SATELLITE TRIANGULATION NETWORK (BC-4) 1964-1973 ECHO/PAGEOS BALLOON SATELLITE TYPE PHOTOGRAPHED BY BC-4 BC-4 CAMERA PHOTOGRAPH PAGEOS SATELLITE AGAINST THE STAR BACKGROUND U.S. NAVY NAVSAT TRANSIT SATELLITE “Doppler” Prototype Launched (Failed) 1959 First Successful Test 1960 Operational 1964 (Military) Civilian Access 1967 Transit Geoceiver and VLBI Relative Positional accuracy ~ 0.002 m Relative Positional accuracy ~ 1 m International VBLI Network Global Positioning System GPS Block I GPS Block II GPS Block III . February 22, 1978 - 1st NAVSTAR Satellite launched . July 17, 1995 - System Fully Operational . May 1, 2000 - Selective Availability turned off . September 26, 2005 - L2C band added . May 28, 2010 - First L5 Satellite added . Mid 2014 – First Block III scheduled for launch . 2020? - 10-50 cm real-time accuracy! Macrometer V-1000 GPS Receiver 1982 ~ appox. $250,000 each Where are we now?? Global Navigation Satellite System US - GPS Russia - GLONASS EU - Galileo China – BeiDou Four positioning and navigation systems . NAVSTAR/GPS – US (Currently 31) . GLONASS – Russia (Currently 24) . GALILEO – EU (Currently 4, 30 by 2019) . BEIDOU – China (30+ by 2020?) GEODETIC DATUMS HORIZONTAL 2-D (Latitude and Longitude) U.S. Standard Datum, NAD 27, NAD 83 (1986) Fixed and Stable - Coordinates seldom change GEOMETRIC 3-D (Latitude, Longitude and Ellipsoid Height) Fixed and Stable - Coordinates seldom change NAD 83 (“HARN”), NAD 83 (CORS96), NAD 83 (2007), NAD 83 (2011) 4-D (Latitude, Longitude, Ellipsoid Height, Velocities) Coordinates change with time (e.g. ITRF00, IGS08) VERTICAL 1-D (Orthometric Height) (Leveling constrained to 1 or more long-term tide stations) (e.g. NGVD 29, NAVD 88, PRVD 02) GEOPOTENTIAL 1-D (Orthometric Height) (Realized by GNSS + High Accuracy Gravimetric Geoid Model – e.g. GRAV-D) National Spatial Reference System (NSRS) Consistent National Coordinate System • Latitude • Longitude • Height • Scale • Gravity • Orientation and how these values change with time NSRS COMPONENTS • National Shoreline - Consistent, accurate, and up-to-date • Networks of geodetic control points - Permanently marked passive survey monuments • National CORS Network - A network of GPS Continuously Operating Reference Stations • Tools -Models of geophysical effects on spatial measurements -e.g., NADCON, INVERSE, SPCS83, UTMS, FORWARD U.S.HORIZONTAL DATUMS NORTH AMERICAN DATUM 1983 (1986 – PRESENT) NORTH AMERICAN DATUM 1927 (1927 – 1986) NORTH AMERICAN DATUM (1913 – 1927) U.S. STANDARD DATUM (1901 – 1913) NEW ENGLAND DATUM (1879 – 1900) ALASKA DATUMS (17 Different 1890 - 1954) BESSEL ELLIPSOID (1848 – 1879) PUERTO RICO DATUM (1901 – 1986) OLD HAWAIIAN DATUM (1928 – 1986) AMERICAN SAMOA DATUM 1962 (1962 – 1993) GUAM DATUM 1963 (1963 – 1993) U.S.VERTICAL DATUMS NORTH AMERICAN VERTICAL DATUM 1988 (1991 – PRESENT) NATIONAL GEODETIC VERTICAL DATUM 1929 (1973-1991) SEA LEVEL DATUM 1929 (1929 – 1973) FOURTH GENERAL ADJUSTMENT (1912) THIRD GENERAL ADJUSTMENT (1907) SECOND GENERAL ADJUSTMENT (1903) FIRST GENERAL ADJUSTMENT (1899) (a.k.a. Sandy Hook Datum) AMERICAN SAMOA VERTICAL DATUM 2002 PUERTO RICO VERTICAL DATUM 2002 NORTHERN MARIANAS VERTICAL DATUM 2003 GUAM VERTICAL DATUM 2004 VIRGIN ISLAND VERTICAL DATUM 2009 HORIZONTAL POSITIONAL CHANGES IN OREGON ASTOR POINT 1851 (SC2012) 46-11-27.99214 123-50-25.73269 NAD 83 (2011) (0.063 m / 0.21 ft) – GEOCON11 46-11-27.99066 123-50-25.73474 NAD 83 (2007) (0.098 m / 0.32 ft) - GEOCON 27.98848 25.73805 NAD 83 (1991) (0.511 m / 1.68 ft) 28.00036 25.72144 NAD 83 (1986) (98.669 m / 323.72 ft) 28.62426 21.20853 NAD 27 (46.863 m / 153.75 ft) 29.759 22.660 USSD/NAD (1093.889 m / 3588.87 ft) 27.62 49-31.74 BESSEL National Spatial Reference System North American Datum of 1983 (NAD 83) – Released 1986 National Geodetic Vertical Datum of 1988 (NAVD 88) – Released 1991 NAD 83 - First civilian datum designed to be consistent with space-based observations (GPS) NAD 83 - First civilian datum to be best-fitting globally not locally NAD 83 - First geodetic datum to be fully automated First geodetic reference system to be available free from WWW Only reference system to freely integrate data from outside sources EARLY NAD 83 NETWORK PROBLEMS NOT “GPSABLE” POOR STATION ACCESSIBILITY IRREGULARLY SPACED POSITIONAL ACCURACY HIGH PRECISION GPS NETWORK (HPGN) HIGH ACCURACY REFERENCE NETWORK (HARN) 1989 - 1997 “GPSABLE” Clear Horizons for Satellite Signal Acquisition EASY ACCESSIBILITY Few Special Vehicle or Property Entrance Requirements REGULARLY SPACED Always within 20-100 Km HIGH ACCURACY A-Order (5 mm + 1:10,000,000) (3 5.5 hr sessions) B-Order (8mm + 1:1,000,000) (2 5.5 hr sessions) OREGON OBSERVED 1991 AVERAGE NAD 83 (1986) POSITIONAL CHANGE 0.25 – 0.65 m / 0.8 – 2.1 Ft ALL NAD 83 (1986) TRIANGULATION READJUSTED TO FIT NEW COORDINATES FEDERAL & COOPERATIVE BASE NETWORKS (FBN/CBN) 1997 -2004 MORE STATE PARTNERSHIPS REMOVE DISTORTIONS IN EARLY HARNS (3-10 CM) ENSURE CONNETIONS TO CORS IMPROVE ELLIPSOID HEIGHT ACCURACY (Not more than 2 cm) AVERAGE NAD 83 (HARN) POSITIONAL CHANGE 0.01 – 0.07 m / 0.03 – 0.2 Ft OREGON OBSERVED 1998 NAD 83 (HARN) TRIANGULATION NOT READJUSTED TO FIT NEW COORDINATES HISTORY OF VERTICAL DATUM IN THE U.S. Pre-National Geodetic Vertical Datum of 1929 (NGVD 29) The first geodetic leveling project in the United States was performed by the Coast Survey from 1856 to 1857 in the vicinity of New York City. General Adjustments of leveling data yielded datums in 1899, 1903, 1907, and 1912. (Sometimes referenced as the Sandy Hook Datum) 1st General Adjustment, Report of the Superintendent of the Coast and Geodetic Survey, 1900, Appendix 8, pgs 347 – 886 2nd General Adjustment, Report of the Superintendent of the Coast and Geodetic Survey, 1903, Appendix 3, pgs 189 – 809 3rd General Adjustment, USC&GS publication “Precise Leveling In the United States 1903- 1907” 4th General Adjustment, USC&GS Special Publication 18 NGS does not offer a utility which transforms from these older datums into newer ones (though some users still work in them!) NATIONAL WATER LEVEL OBSERVATION NETWORK HTTP://WWW.TIDESANDCURRENTS.NOAA.GOV/ Earliest USC&GS Tide Station in Oregon – 1905 at Ft. Stevens Stations Provide Water Level Wind Speed/Direction Barometric Pressure Air/Water Temp. Conductivity/Temp Tsunami/Storm Surge Data Transmission Many but not all are tied to NAVD 88 1st General Adjustment – 1899 http://docs.lib.noaa.gov/rescue/cgs/003_pdf/CSC-0102.PDF 2nd General Adjustment – 1903 http://docs.lib.noaa.gov/rescue/cgs/004_pdf/CSC-0107.PDF 3rd General Adjustment – 1907 http://docs.lib.noaa.gov/rescue/cgs_suppl/QB296U88H391903-1907.pdf 4th General Adjustment – 1912 http://docs.lib.noaa.gov/rescue/cgs_specpubs/QB275U35no181914.pdf HISTORY OF VERTICAL DATUM IN THE U.S. National Geodetic Vertical Datum 1929 (NGVD 29) Original name: “Sea Level Datum of 1929” “Zero height” held fixed at 26 tide gauges Not all on the same tidal datum epoch (~ 19 yrs) Did not account for Local Mean Sea Level variations from the geoid Thus, not truly a “geoid based” datum The National Geodetic Vertical Datum of 1929 is referenced to 26 tide gauges in the US and Canada HISTORY OF VERTICAL DATUM IN THE U.S. NORTH AMERICAN VERTICAL DATUM OF 1988 Use of one fixed height removed local sea level variation problem of NGVD 29 Use of one fixed height did open the possibility of unconstrained cross-continent error build up The H=0 surface of NAVD 88 was supposed to be parallel to the geoid…(close again) The North American Vertical Datum of 1988 is referenced to a single tide gauge in Canada HEIGHT DIFFERENCES IN OREGON N 1904 (QB0688) 2151.19 Ft NAVD 88 (- 0.56 ft) 2147.99 Ft NGVD 29/SLD 29 (- 0.59 ft) 2148.58 FOURTH GENERAL ADJUSTMENT OF 1912 (+ 1.02 ft) 2147.56 THIRD GENERAL ADJUSTMENT OF 1906 (- 0.20 ft) 2147.76 SECOND GENERAL ADJUSTMENT OF 1903 Problems with NAD 83 and NAVD 88 NAD 83 is not as geocentric as it could be (approx. 1.5 m for CONUS). Surveyors don’t see this – Yet NAD 83 is not well defined with positional velocities NAVD 88 is realized by passive control (bench marks) most of which have Not been releveled in 30-40 years NAVD 88 does not easily account for local vertical velocities (subsidence / uplift) Post glacial isostatic readjustment Subsurface fluid/hydrocarbon extraction Sediment loading - Compaction Sea level rise – Astoria = – 0.3 mm/yr (0.1 ft/100 yr) Charleston = + 1.3 mm/yr (0.4 ft/100 yr) NAVD 88 Leveled heights do not truly represent changes in gravity potential When was the passive mark last leveled? Why isn’t NAVD 88 good enough anymore? ELLIPSOID – GEOID RELATIONSHIP H = Orthometric Height - NAVD 88 h = Ellipsoid Height - NAD 83 (2011) N = Geoid Height - GEOID12A H = h – N H h N Geoid Geoid Model Ellipsoid GRS80 Types and Uses of Geoid Height Models Gravimetric (or Gravity) Geoid Height Models (e.g. USGG2012, USGG2009) Defined by gravity data crossing the geoid Refined by terrain models (DEM’s) Scientific and engineering applications Composite (or Hybrid) Geoid Height Models (e.g.
Load more

Recommended publications
  • State Plane Coordinate System
    Wisconsin Coordinate Reference Systems Second Edition Published 2009 by the State Cartographer’s Office Wisconsin Coordinate Reference Systems Second Edition Wisconsin State Cartographer’s Offi ce — Madison, WI Copyright © 2015 Board of Regents of the University of Wisconsin System About the State Cartographer’s Offi ce Operating from the University of Wisconsin-Madison campus since 1974, the State Cartographer’s Offi ce (SCO) provides direct assistance to the state’s professional mapping, surveying, and GIS/ LIS communities through print and Web publications, presentations, and educational workshops. Our staff work closely with regional and national professional organizations on a wide range of initia- tives that promote and support geospatial information technologies and standards. Additionally, we serve as liaisons between the many private and public organizations that produce geospatial data in Wisconsin. State Cartographer’s Offi ce 384 Science Hall 550 North Park St. Madison, WI 53706 E-mail: [email protected] Phone: (608) 262-3065 Web: www.sco.wisc.edu Disclaimer The contents of the Wisconsin Coordinate Reference Systems (2nd edition) handbook are made available by the Wisconsin State Cartographer’s offi ce at the University of Wisconsin-Madison (Uni- versity) for the convenience of the reader. This handbook is provided on an “as is” basis without any warranties of any kind. While every possible effort has been made to ensure the accuracy of information contained in this handbook, the University assumes no responsibilities for any damages or other liability whatsoever (including any consequential damages) resulting from your selection or use of the contents provided in this handbook. Revisions Wisconsin Coordinate Reference Systems (2nd edition) is a digital publication, and as such, we occasionally make minor revisions to this document.
    [Show full text]
  • Part V: the Global Positioning System ______
    PART V: THE GLOBAL POSITIONING SYSTEM ______________________________________________________________________________ 5.1 Background The Global Positioning System (GPS) is a satellite based, passive, three dimensional navigational system operated and maintained by the Department of Defense (DOD) having the primary purpose of supporting tactical and strategic military operations. Like many systems initially designed for military purposes, GPS has been found to be an indispensable tool for many civilian applications, not the least of which are surveying and mapping uses. There are currently three general modes that GPS users have adopted: absolute, differential and relative. Absolute GPS can best be described by a single user occupying a single point with a single receiver. Typically a lower grade receiver using only the coarse acquisition code generated by the satellites is used and errors can approach the 100m range. While absolute GPS will not support typical MDOT survey requirements it may be very useful in reconnaissance work. Differential GPS or DGPS employs a base receiver transmitting differential corrections to a roving receiver. It, too, only makes use of the coarse acquisition code. Accuracies are typically in the sub- meter range. DGPS may be of use in certain mapping applications such as topographic or hydrographic surveys. DGPS should not be confused with Real Time Kinematic or RTK GPS surveying. Relative GPS surveying employs multiple receivers simultaneously observing multiple points and makes use of carrier phase measurements. Relative positioning is less concerned with the absolute positions of the occupied points than with the relative vector (dX, dY, dZ) between them. 5.2 GPS Segments The Global Positioning System is made of three segments: the Space Segment, the Control Segment and the User Segment.
    [Show full text]
  • HORIZONTAL DATUM CONVERSIONS Helping Vermonters Visualize Choice
    PART 3: SECTION K HORIZONTAL DATUM CONVERSIONS Helping Vermonters Visualize Choice A Discussion, Examples, and Recommended Conversion Methodology for the Transformation of ARC/INFO Coverages from the North American Datum of 1927 to the North American Datum of 1983 in Vermont. This paper would not have been made available without the thoughtful writing of Milo Robinson, NGS Geodetic Advisor to the State of Vermont, and Gary Smith of Green Mountain Geographics. These recognized leaders in the VGIS community have all of our thanks. EXECUTIVE SUMMARY This paper outlines the steps required to convert ARC/INFO coverages from the North American Datum of 1927 (NAD27) to the more accurate North American Datum of 1983 (NAD83). Until recently, most contemporary maps of Vermont used the NAD27 as the reference datum. This made it the logical option for direct digital conversion and subsequent inclusion in the Vermont GIS database. With the arrival of the new Vermont Digital Orthophotography, expanded GPS activity and new maps from the U.S. Geological Survey being prepared using NAD83, it is increasingly necessary to convert existing NAD27 data to NAD83 to properly incorporate new information. The need of particular data developers or users to convert data depends on the location in the State, and particular mapping requirements. As this paper is released the Vermont counties for which NAD83 digital orthophotos are available are Rutland, Windsor, Franklin, Grand Isle and Addison, plus portions of Washington County. The remainder of Washington and Orange Counties will be available soon, with the remainder of Vermont to be processed in coming years. The remainder of this paper provides more detail on the datum change, suggests new data entry guidelines, details the coordinate and naming convention for Vermont's orthophotos, and provides the procedures for converting Vermont's NAD27 data to NAD83 using software by ESRI (Environmental Systems Research Institute, Redlands, CA).
    [Show full text]
  • Datums in Texas NGS: Welcome to Geodesy
    Datums in Texas NGS: Welcome to Geodesy Geodesy is the science of measuring and monitoring the size and shape of the Earth and the location of points on its surface. NOAA's National Geodetic Survey (NGS) is responsible for the development and maintenance of a national geodetic data system that is used for navigation, communication systems, and mapping and charting. ln this subject, you will find three sections devoted to learning about geodesy: an online tutorial, an educational roadmap to resources, and formal lesson plans. The Geodesy Tutorial is an overview of the history, essential elements, and modern methods of geodesy. The tutorial is content rich and easy to understand. lt is made up of 10 chapters or pages (plus a reference page) that can be read in sequence by clicking on the arrows at the top or bottom of each chapter page. The tutorial includes many illustrations and interactive graphics to visually enhance the text. The Roadmap to Resources complements the information in the tutorial. The roadmap directs you to specific geodetic data offered by NOS and NOAA. The Lesson Plans integrate information presented in the tutorial with data offerings from the roadmap. These lesson plans have been developed for students in grades 9-12 and focus on the importance of geodesy and its practical application, including what a datum is, how a datum of reference points may be used to describe a location, and how geodesy is used to measure movement in the Earth's crust from seismic activity. Members of a 1922 geodetic suruey expedition. Until recent advances in satellite technology, namely the creation of the Global Positioning Sysfem (GPS), geodetic surveying was an arduous fask besf suited to individuals with strong constitutions, and a sense of adventure.
    [Show full text]
  • Vertical Datum Conversion Guidance
    Guidance for Flood Risk Analysis and Mapping Vertical Datum Conversion May 2014 This guidance document supports effective and efficient implementation of flood risk analysis and mapping standards codified in the Federal Insurance and Mitigation Administration Policy FP 204- 07801. For more information, please visit the Federal Emergency Management Agency (FEMA) Guidelines and Standards for Flood Risk Analysis and Mapping webpage (http://www.fema.gov/guidelines-and- standards-flood-risk-analysis-and-mapping), which explains the policy, related guidance, technical references, and other information about the guidelines and standards process. Nothing in this guidance document is mandatory other than standards codified separately in the aforementioned Policy. Alternate approaches that comply with FEMA standards that effectively and efficiently support program objectives are also acceptable. Vertical Datum Conversion May 2014 Guidance Document 24 Page i Document History Affected Section or Date Description Subsection Initial version of new transformed guidance. The content was derived from the Guidelines and Specifications for Flood First Publication May 2014 Hazard Mapping Partners, Procedure Memoranda, and/or Operating Guidance documents. It has been reorganized and is being published separately from the standards. Vertical Datum Conversion May 2014 Guidance Document 24 Page ii Table of Contents 1.0 Overview ..................................................................................................................................
    [Show full text]
  • Mind the Gap! a New Positioning Reference
    A new positioning reference Why is the United States adopting NATRF2022? What are we doing about this in Canada? We want to hear from you! • The Canadian Geodetic Survey and the United States • Improved compatibility with Global Navigation • The Canadian Geodetic Survey is working closely National Geodetic Survey have collaborated for Satellite Systems (GNSS), such as GPS, is driving this with the United States National Geodetic Survey in • Send us your comments, the challenges you over a century to provide the fundamental reference change. The geometric reference frames currently defining reference frames to ensure they will also foresee, and any concerns to help inform our path Mind the gap! systems for latitude, longitude and height for their used in Canada and the United States, although be suitable for Canada. forward to either of these organizations: respective countries. compatible with each other, are offset by 2.2 m from • Geodetic agencies from across Canada are A new positioning reference the Earth’s geocentre, whereas GNSS are geocentric. - Canadian Geodetic Survey: nrcan. • Together our reference systems have evolved collaborating on reference system improvements geodeticinformation-informationgeodesique. to meet today’s world of GPS and geographical • Real-time decimetre-level accuracies directly from through the Canadian Geodetic Reference System [email protected] NATRF2022 information systems, while supporting legacy datums GNSS satellites are expected to be available soon. Committee, a working committee of the Canadian
    [Show full text]
  • JHR Final Report Template
    TRANSFORMING NAD 27 AND NAD 83 POSITIONS: MAKING LEGACY MAPPING AND SURVEYS GPS COMPATIBLE June 2015 Thomas H. Meyer Robert Baron JHR 15-327 Project 12-01 This research was sponsored by the Joint Highway Research Advisory Council (JHRAC) of the University of Connecticut and the Connecticut Department of Transportation and was performed through the Connecticut Transportation Institute of the University of Connecticut. The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Connecticut or the Connecticut Department of Transportation. This report does not constitute a standard, specification, or regulation. i Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. JHR 15-327 N/A 4. Title and Subtitle 5. Report Date Transforming NAD 27 And NAD 83 Positions: Making June 2015 Legacy Mapping And Surveys GPS Compatible 6. Performing Organization Code CCTRP 12-01 7. Author(s) 8. Performing Organization Report No. Thomas H. Meyer, Robert Baron JHR 15-327 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) University of Connecticut N/A Connecticut Transportation Institute 11. Contract or Grant No. Storrs, CT 06269-5202 N/A 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Connecticut Department of Transportation Final 2800 Berlin Turnpike 14. Sponsoring Agency Code Newington, CT 06131-7546 CCTRP 12-01 15. Supplementary Notes This study was conducted under the Connecticut Cooperative Transportation Research Program (CCTRP, http://www.cti.uconn.edu/cctrp/).
    [Show full text]
  • Evolution of NAD 83 in the United States: Journey from 2D Toward 4D
    Evolution of NAD 83 in the United States: Journey from 2D toward 4D Richard A. Snay1 Abstract: In 1986, Canada, Greenland, and the United States adopted the North American Datum of 1983 (NAD 83) to replace the North American Datum of 1927 as their official spatial reference system for geometric positioning. The rigor of the original NAD 83 realization benefited from the extensive use of electronic distance measuring instrumentation and from the use of both TRANSIT Doppler observations and very long baseline interferometry observations. However, the original NAD 83 realization predated the widespread use of the global po- sitioning system and the use of continuously operating reference stations. Consequently, NAD 83 has evolved significantly in the United States since 1986 to embrace these technological advances, as well as to accommodate improvements in the understanding of crustal motion. This paper traces this evolution from what started as essentially a two-dimensional (2D) reference frame and has been progressing toward a four-dimensional (4D) frame. In anticipation of future geodetic advances, the U.S. National Geodetic Survey is planning to replace NAD 83 about a decade from now with a newer, more geocentric spatial reference system for geometric positioning. DOI: 10.1061/(ASCE)SU.1943- 5428.0000083. © 2012 American Society of Civil Engineers. CE Database subject headings: History; Datum; Transformations; Geodetic surveys; North America. Author keywords: History; Datum transformations; Dynamic datums; Crustal deformation; NAD 83. Introduction height, and how these three coordinates vary over time. NAD 27 provided a foundation for measuring only geodetic latitude and lon- In 1986 a group of institutions representing Canada, Greenland, and gitude; therefore, it is considered a horizontal datum.
    [Show full text]
  • Measuring the Water Level Datum Relative to the Ellipsoid During Hydrographic Survey
    Measuring the Water Level Datum Relative to the Ellipsoid During Hydrographic Survey Glen Rice LTJG / NOAA Corps, Coast Survey Development Laboratory 24 Colovos Road, Durham NH 03824 [email protected] ; 603‐862‐1397 Jack Riley Physical Scientist, NOAA Hydrographic Systems and Technology Program 1315 East West Hwy, SSMC3, Silver Spring MD 20910‐3282 [email protected] ; 301‐713‐2653 x154 Abstract Hydrographic surveys are referenced vertically to a local water level “chart” datum. Conducting a survey relative to the ellipsoid dictates a datum transformation take place before the survey is used for current navigational products. Models that combine estimates for the tide, sea surface topography, the geoid, and the ellipsoid are often used to transform an ellipsoid referenced survey to a local water level datum. Regions covered by these vertical datum transformation models are limited and so would appear to constrain the areas where ellipsoid referenced surveys can be conducted. Because areas not covered by a vertical datum transformation model still must have a tide model to conduct a hydrographic survey, survey‐ time measurements of the ellipsoid to water level datum can be conducted through the vessel reference point. This measured separation is largely a function of the vessel ellipsoid height and the standard survey tide model and thus introduces limited additional uncertainty than is typical in a water level referenced survey. This approach is useful for reducing ellipsoid reference surveys to the water level datum, examining a tide model, or for evaluating a vertical datum transformation model. Prototype tools and a comparison to typical vertical datum transformation models are discussed.
    [Show full text]
  • Map Projections and Coordinate Systems Datums Tell Us the Latitudes and Longi- Vertex, Node, Or Grid Cell in a Data Set, Con- Tudes of Features on an Ellipsoid
    116 GIS Fundamentals Map Projections and Coordinate Systems Datums tell us the latitudes and longi- vertex, node, or grid cell in a data set, con- tudes of features on an ellipsoid. We need to verting the vector or raster data feature by transfer these from the curved ellipsoid to a feature from geographic to Mercator coordi- flat map. A map projection is a systematic nates. rendering of locations from the curved Earth Notice that there are parameters we surface onto a flat map surface. must specify for this projection, here R, the Nearly all projections are applied via Earth’s radius, and o, the longitudinal ori- exact or iterated mathematical formulas that gin. Different values for these parameters convert between geographic latitude and give different values for the coordinates, so longitude and projected X an Y (Easting and even though we may have the same kind of Northing) coordinates. Figure 3-30 shows projection (transverse Mercator), we have one of the simpler projection equations, different versions each time we specify dif- between Mercator and geographic coordi- ferent parameters. nates, assuming a spherical Earth. These Projection equations must also be speci- equations would be applied for every point, fied in the “backward” direction, from pro- jected coordinates to geographic coordinates, if they are to be useful. The pro- jection coordinates in this backward, or “inverse,” direction are often much more complicated that the forward direction, but are specified for every commonly used pro- jection. Most projection equations are much more complicated than the transverse Mer- cator, in part because most adopt an ellipsoi- dal Earth, and because the projections are onto curved surfaces rather than a plane, but thankfully, projection equations have long been standardized, documented, and made widely available through proven programing libraries and projection calculators.
    [Show full text]
  • FDM 9-20 Spatial Reference Systems
    Facilities Development Manual Wisconsin Department of Transportation Chapter 9 Surveying and Mapping Section 20 Spatial Reference Systems FDM 9-20-1 General February 28, 2001 The discipline of surveying consists of determining or establishing relative positions of points above, on, or beneath the surface of the earth. In Wisconsin, there are two primary spatial reference systems for defining the location of a point: - The U.S. Public Land Survey System (PLSS). - The National Spatial Reference System (NSRS). The PLSS is based on a system of townships, ranges, and sections (see FDM 9-20-5). The PLSS provides the basis for almost all legal descriptions of land. The NSRS, which includes the former National Geodetic Reference System (NGRS), is a mathematical reference system (see FDM 9-20-10). The NSRS consists of precisely measured networks of geodetic control that support accurate mapping over large areas. To understand the roles of these reference systems, it is important to recognize that the PLSS was designed for land ownership purposes but not for accurate mapping, and the NSRS was designed for geodetic surveying and mapping but not for land ownership documentation. Since accurate property maps are becoming essential with digital-based ownership documents, it is important that there be a substantial link between the two reference systems. Methods are needed to utilize the spatial characteristics of the NSRS when addressing the location of landmarks. Fortunately, recent technological developments such as the Global Positioning System (GPS), electronic total station survey instruments, and computer aided drafting (CAD) now make the task of using the PLSS and NSRS together more efficient, economical, and practical.
    [Show full text]
  • Gravity and Geoid Modelling for Improved Heights
    Gravity and Geoid Modelling for Improved Heights Texas Height Modernization Workshop Houston, Texas August 28, 2015 Denis Riordan, PSM NOAA, National Geodetic Survey [email protected] Presentation Outline 1. - Introductions. 2. - Mission and Vision of the National Geodetic Survey. 3. - NAVD88 – Still good enough? 4. - GEOIDS – types and definitions. 5. - GRAV-D and what it’s about. 6. - NGS Gravity Survey Plan. 7. - New U.S. Datums for 2022. 8. - Questions. U.S. Department of Commerce National Oceanic & Atmospheric Administration National Geodetic Survey Mission: To define, maintain & provide access to the National Spatial Reference System (NSRS) to meet our Nation’s economic, social & environmental needs National Spatial Reference System * Latitude * Scale * Longitude * Gravity * Height * Orientation & their variations in time NGS MISSION - The NSRS Define - National Coordinate Sys. (NSRS) Maintain - the NSRS Provide Access The National Geodetic Survey 10 year plan Mission, Vision and Strategy 2013 – 2023 http://www.ngs.noaa.gov/INFO/NGS10yearplan.pdf • Official NGS policy as of Jan 9, 2008 (updated in 2013) – Modernized agency – Attention to accuracy – Attention to time-changes – Improved products and services – Integration with other fed missions • 2022 Targets: – Replace NAD 83 and NAVD 88 – Cm-accuracy access to all coordinates – Customer-focused agency – Global scientific leadership GEODETIC DATUMS VERTICAL 1 D (Orthometric Height) (e.g. NGVD 29, NAVD 88, Tidal) HORIZONTAL 2 D (Latitude and Longitude) (e.g. NAD 27, NAD 83 (1986)) GEOMETRIC 3 D (Latitude, Longitude and Ellipsoid Height) Fixed and Stable - Coordinates seldom change (e.g. NAD 83 (1994), NAD 83 (2007)) also 4 D (Latitude, Longitude, Ellipsoid Height, Velocities) Coordinates change with time (e.g.
    [Show full text]