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Height Modernization

Height Modernization. Presentation by: Krag Caverly Senior Student, FSU. Overview. What is Height Modernization, and why is it needed? Current HM Areas Goals Benefits NGS/NOAA Report HM Programs. What Is It?.

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Height Modernization

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  1. Height Modernization Presentation by: Krag Caverly Senior Student, FSU

  2. Overview • What is Height Modernization, and why is it needed? • Current HM Areas • Goals • Benefits • NGS/NOAA Report • HM Programs

  3. What Is It? • Height Modernization (HM) is the establishment of accurate, reliable heights using GPS technology in conjunction with traditional leveling, gravity, and remote sensing information.

  4. What Is It? NAVD 88 GEODETIC CONTROL NSRS Reliable Accurate Cost-effective Standardized Legally Established

  5. Key Terms • Geoid – the equipotential surface of the Earth’s gravity field that best fits mean sea level. • Ellipsoid – a mathematically-defined surface that defines a reference frame (coordinate system). • Geoid Height – difference between the geoid and ellipsoid. • Orthometric Height – height on the surface above the ellipsoid obtained from methods such as leveling. • Vertical Datum – a datum specifying where vertical points are located. (NGVD 29, NAVD 88)

  6. Why Is HM Needed? • There is a separation between the geoid and NAVD 88. • This separation has been estimated for most areas, but it is not always accurate. • The error in NAVD 88 comes from several factors, including sparsely gathered data, subsidence, and rebound. • Height Modernization seeks to minimize the error in the separation by updating NAVD 88 information, which also allows for better geoid modeling.

  7. Why Is HM Needed? Geoid 03 GRS 80 Ellipsoid

  8. Why Is HM Needed? Ho = Orthometric Height(leveling) Ho = he - N he = Ellipsoidal Height (GPS) N = Geoid Height (model) TOPOGRAPHIC SURFACE he (NAD83) (NAVD88) Ho N Geoid Height (GEOID03) Geoid Ellipsoid

  9. Regions of Changing Height

  10. How HM Began • Began in California in 1994 • It was needed because some areas had elevation errors of more than 3 feet. • The National Geodetic Survey received 1.0M in 1998 for a HM study. • In 2000, NGS was budgeted 500k for HM planning. • Starting in 2001, some states and specific areas of high subsidence have begun to receive funds for HM programs.

  11. HM States

  12. NGS HM Stations

  13. Goals of HM • Improve transportation systems by reducing design and construction costs • Accurate determination of floodplains • Study runoff amounts and effects • Improve agricultural yields • Manage coastal resources

  14. Benefits • Flood Management – More accurate Flood Insurance Rate Maps (FIRMs) to help better decide which areas need flood insurance. • Elevations are critical to determining possible flood levels. • Construction – GPS guided machines • Water Management – Monitor ground water and surface water. • Transportation – Monitoring of rails, roads, and airways, and guided inland shipping navigation.

  15. Benefits • Survey Control - Accurate survey control becomes widely available, which reduces future costs. • Farming – Combining geographic information systems (GIS) with accurate information helps decide amount of fertilizer and pesticide to use. • Another benefit is minimized runoff waste. • Earth Movement – Monitoring of the crust to track movements.

  16. Areas of Impact • The following tables portray elevation requirements for five applications as found in the 1998 National Height Modernization Report by NGA. • It is obvious that most applications can benefit from Height Modernization efforts. Public Safety

  17. Areas of Impact Transportation Management Infrastructure Management

  18. Areas of Impact Construction And Mining Agriculture and Natural Resource

  19. Case Study - 1998 Report • Long Beach Subsidence Survey Results • “..sub-centimeter vertical motion and one centimeter orthometric heights could be determined from a high-precision GPS network covering a limited area… when the geoid model is accurate.”

  20. HM In Michigan • Goal: to provide a 3D statewide network of reliable NSRS (National Spatial Reference System) utilizing the existing MDOT CORS GPS stations. • Michigan already has a highly accurate 2D component in place (MSRN), and Height Modernization seeks to add the height component, creating a 3D geodetic control network.

  21. Gravimetric Geoid Geoid model Used as a base for creating Geoid03

  22. Error Prediction for the LP Areas with no points will be of poor accuracy

  23. Gravity Points HM In Michigan

  24. HM In Michigan Current HM Points In Michigan

  25. Summary • There are inconsistencies in the current vertical datum due to gaps in the modeling data. • In order to improve NAVD 88 and fill in the gaps, Height Modernization must be implemented. • The benefits of having a centimeter-accurate vertical datum positively affect the public’s welfare, along with many public and private industries.

  26. Questions?

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