1. Ohio Height Modernization Related Activities Great Lakes Regional Forum Sept 24-25, 2008 Madison, Wisconsin David Conner Geodetic Advisor to the State of Ohio National Geodetic Survey, NOAA

2. TOPICS Overview

3. Ohio Height Modernization The Early Years (or…What is Modern anyway?) 1983-2008 … Dozens of Bluebooked GPS projects throughout the State, all tied to NAVD88 benchmarks which now contribute to the Geoid model 1993 - L25429… a first order level line run the length of the State by NGS in cooperation with ODOT... over 300 BM's including hundreds of new ones suitable for use by GPS. Many of these new NAVD88 BM's were subsequently included in GPS surveys and now contribute to the Geoid model.

4. Ohio Height Modernization High Accuracy GPS 1995 - OH HARN established GPS BM’s at 50 km spacing recommended by NGS to support geoid modeling 1996 ODOT sponsors a study by NGS “An Accuracy Assessment of the Geoid96 Geoid Ht Model” to guide future planning 2003 - FBN/CBN re-obs included many BM’s using A-order specs to provide local vertical network ties to the CORS network

5. Ohio Height Modernization GPS CORS 2001 – ODOT CORS Network a seventeen station network with 70 km average spacing selected in accordance with NOS NGS-58, a spacing that would allow these CORS to serve as Control for "Height Mod" surveys. 2003 - ODOT CORS Network expanded to ~53 stations with real-time positioning capability. Avg 40-45 km spacing would serve as "Primary Base" control in accordance with NOS NGS-58 … all are National CORS

6. Ohio’s GPS CORS Network 2003 Brought to you courtesy of ODOT Bureau of Aerial Engineering VRS/ CORS information Telephone: 614-275-1372, or 614-351-2839. cors@dot.state.oh.us

7. Ohio Height Modernization 2005 – Great Lakes GPS Project – partnership between US and Canada… NOAA/NGS and eight Great Lakes States, including many people in the audience today 2006-2008 – ODOT Sponsored studies and pilot project, intended to build a case for HT Mod funding 2008 – Leveling to CORS ARP

8. Ohio Height Modernization

9. 2008 ODOT begins leveling to establish precise ortho ht on CORS ARP

10. Vertical standard error achievable when a user submits 15 minutes of GPS data to OPUS-RS

11. OPUS-DB Sample Datasheet