Paul H. Rydlund Jr. PLS U.S. Geological Survey Missouri Water Science Center

1. ESTABLISHMENT OF THE USGS GPS COMMITTEE, CHARGE AND CURRENT PROGRESSNAVD 88 DATUM CONVERSION UPDATE Paul H. Rydlund Jr. PLS U.S. Geological Survey Missouri Water Science Center

2. First order (ft) Second order Class I & II (ft) Third order (ft) Current Guidance – Vertical Datum Techniques of Water-Resources Investigations of the United States Geological Survey Chapter A19 LEVELS AT STREAMFLOW GAGING STATIONS Suggested criteria for tying to NGVD 29 control. Suggested distance under 8 miles, greater than 8 miles should wait or defer to other agencies to establish benchmarks. “Ordinary Levels” – describes Third Order levels run with ordinary equipment and procedures (as opposed to special equipment and meticulous procedures designed to minimize systematic errors). Fourth order levels are run for the purpose of referencing gaging-station datums to NGVD 29.

3. Third order (ft) Rough/Hilly exception (ft) Current Guidance – Vertical Datum Techniques of Water-Resources Investigations of the United States Geological Survey Chapter A19 LEVELS AT STREAMFLOW GAGING STATIONS • Suggested criteria for tying to NGVD 29 control. • Double run lines • Sight lengths limited to 300 feet • Rods read to 0.01 ft • Closure errors kept under Third Order, exceptions due to rough or hilly terrain.

4. Establishment of the USGS GPS Committee, charge and current progress Why???? Stuff Stuff GPS OSW sponsored, Liaison Robert R. Holmes, Jr.,PhD,PE Committee Members Paul H. Rydlund Jr., PLS, Chair (MOWSC) Brian Fiehler (MCGSC) Doug Nagle (SCWSC) Chad Ostheimer, PE (OHWSC) Kenneth Skinner (IDWSC) Brenda Woodward (NEWSC)

5. Establishment of the USGS GPS Committee, charge and current progress Charge Action Plan: Addressing needs of technically strong GPS activities in the USGS and a set of actions that will address such needs and set a firm foundation for sound and robust use of GPS to achieve accurate and defensible survey data Completion of 2 or 3 highest priority actions from the Action Plan Accomplishment of the remainder of priority action items

6. USGS GPS Survey Web Portal • Introduction • Mission & Members • USGS State Contacts • National Equipment Inventory • Training And Workshops • On-line References • Status Of GNSS

7. USGS GPS Survey Web Portal - Linked Pages • Coastal Storm Surge Sensors • Coastal State Control Evaluation • GPS Campaign Guidence • Pre-deployment preparedness • Methods • Data dissemination • USGS publications • Real-Time Networks • State Network Overview & Contacts • Method

8. USGS GPS Survey Web Portal - Linked Pages • USGS Projects Involving GPS • Well Field Surveys • Flood Studies • Land Science Aerial and Ground-based LiDAR Verification • Hydrographic Surveys

9. Techniques and Methods Anticipated Publication Methodology in establishing datum by GPS methods Variable methods of practice and guidelines in ensuring minimum solution standards • Survey grade RTK • Single base • Network RTN • Survey grade Post Processed • Static • Kinematic • Fast Static • Data Dissemination CASE STUDIES CASE STUDIES

10. Techniques and Methods Anticipated Publication Guidelines and Procedures for Different Real-Time Accuracy Classes CLASS RT1 CLASS RT2 CLASS RT3

11. 2nd Order Techniques and Methods Anticipated Publication “RTK as a level” Autonomous field base at midpoint 5 miles Autonomous field base at midpoint Derivation of Class RT1 or Class RT2 Procedures, Bridge & Gage 12 miles 4 miles 2nd Order 3rd Order • Occupy approximate midpoint 5 mile baseline • Redundant rover observations (180 epochs each) tied to bridge • Occupy approximate midpoint 4 mile baseline • Redundant rover observations 180 epochs tied to bridge and 3rd Order check • Occupy different base location near midpoint 5 mile baseline (best 2nd Order control source) • Redundant rover observations (180 epochs) tied to bridge 13 miles 2nd Order

12. Techniques and Methods Anticipated Publication “GPS over large areas” Benchmark Benchmark Datum brought in using Static Autonomous Autonomous • Consider beginning with outer network first. • Consider minimally and fully constraining inner network.

13. NGS-NWS-USGS Streamgage Datum Conversion Committee NGS: Renee Shields, Christine Gallagher NWS: Victor Hom, Laurie Hogan (NY), John Sikora (WV), Jonathon Brazzell (LA)USGS: Jim Kolva, Paul Rydlund (MO), Brenda Woodward (NE) NCGS: Gary Thompson, Scott Lokken Objective: To develop a coordinated effort to convert existing NVGD 1929 datum to NAVD 1988 while ensuring a datum quality sufficient for public and cooperative interest NAVD88 NGVD29

14. NGS-NWS-USGS Streamgage Datum Conversion Committee VERTCON 2 cm at 1 sigma 68% confidence 4 cm at 2 sigma 95% confidence Cooperative GPS Campaigns Methods sufficient to meet accuracy needs

15. NGS-NWS-USGS Streamgage Datum Conversion Committee • USGS database updated to include NWS location IDs • NCGS setting control to aid USGS gaging stations • Additional parameter dissemination from USGS database to local partners • Missouri conducting local pilot study • Local spreadsheet (database) nearly complete (needed to scope) • 3-4 cm accuracies at NWS forecast sites (other criteria?) • Anticipated cooperation with NGS state advisor, NWS, and USACE