Height Modernization guidelines NOS NGS 58 GPSderived ellipsoid

Height Modernization guidelines NOS NGS 58 GPS-derived ellipsoid heights (November 1997) 10/9/2014 NOS NGS 59 GPS-derived orthometric heights (March 2008) NGS 58/59 update projects 1

A new & improved NGS 58/59 • Factors to evaluate include: – – – – – Distance to passive & active control Number of simultaneous GPS occupations Occupation duration and data logging rate Number of multiple occupations and time between them Strategies and software used for processing and adjustment Effects of multipath, signal propagation, antenna calibrations Viability of real-time data (both single-base and network) Effect of GLONASS observables on results Impact of network design on results (including “trivial” vectors) Evaluation of new equipment & data, and of existing data 10/9/2014 NGS 58/59 update projects 2

Two NGS-58/59 update projects • 2013 project – – – Gustin, Cothern & Tucker, Inc. (GCT) – data collection, coordination South Carolina Geodetic Survey (SCGS) – recon & real time support The Ohio State University (OSU) – data analysis All data collected, organized, and submitted for analysis Report prepared on data content and format (under review) Two phases • Phase 1: Vertical Precision (Florida) • Phase 2: GPS Bench Marks (South Carolina) • 2014 project – Data collection and analysis by Oregon State University – Fieldwork underway in Oregon 10/9/2014 NGS 58/59 update projects 3

2013 project: Phase 1 (vert precision) • Repeatability of heights with different antennas – Four antenna types used at test site in Florida panhandle • Choke ring, large and small diameter groundplane, integrated unit • Rotate through stable semi-permanent setups – Not under ideal conditions (some mild obstructions and multipath) • Data collection – Eight 72 -hour sessions, both post-processed and real-time data – Raw data logged at 1 sec rate (includes GLONASS) – Real time position durations range from 5 seconds to 10 minutes 10/9/2014 NGS 58/59 update projects 4

2013 project: Phase 2 (GPSBMs) • Perform “Height Mod” survey in South Carolina – – 20 leveled bench marks occupied (6 times for 5 hours each occupation) Real-time position durations from 5 seconds to 10 minutes 12 marks are geoid model GPS BMs (8 are not) Distances range from < 1 km to > 100 km (to CORS used as real-time base) • Data collection – Log raw data at 1 -sec rate (with GLONASS) – Collect real-time data, network and single-base, with and w/o GLONASS – Reconnaissance and real-time support provided by SCGS 10/9/2014 NGS 58/59 update projects 5