TAG: David B. Zilkoski

Discussing the new North American-Pacific Geopotential Datum of 2022 — Part 1

June 7, 2017By

On April 24-25, 2017, the National Geodetic Survey (NGS) hosted the 2017 Geospatial Summit in Silver Spring, Maryland, to discuss its plans for replacing the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88) in 2022. The Summit was a day and a half long and provided an opportunity for NGS to... read more

A look at NGS’ GPS on benchmarks program in Alaska

April 5, 2017By

The last column, February 2017, focused on addressing the following questions: (1) Is the large GPS on benchmarks residual due to an issue with the NAVD 88 orthometric height or the NAD 83 (2011) ellipsoid height? and (2) Should stations with large GPS on benchmarks residuals be included in the development of NGS’ hybrid geoid models? The column provided suggestions... read more

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Establishing orthometric heights using GNSS — Part 11

February 1, 2017By

Strategically Occupying Stations to Support NGS’ GPS on Bench Marks Program This is the 11th segment in my series on “Establishing Orthometric Height Using GNSS.” Each column has focused on a specific topic and provided procedures and tools for analyzing that topic. The columns are meant to build on each other. When addressing a topic that has been discussed in... read more

This article is tagged with , , , and posted in Opinions, Survey

Establishing orthometric heights using GNSS — Part 8

August 3, 2016By

Upcoming Survey Scene newsletters will carry additional columns in this series. Basic procedures and tools for determining valid published NAVD 88 GNSS-derived orthometric heights for constraints These columns have provided the reader with basic concepts, routines and procedures for understanding, analyzing, evaluating and estimating GNSS-derived ellipsoid and orthometric heights. In my last column, Part 7 (June 2016), we analyzed the changes in adjusted heights... read more

Establishing orthometric heights using GNSS — Part 7

June 2, 2016By

Basic procedures and tools for determining valid NAVD 88 heights for constraints To date, the six parts of “Establishing Orthometric Heights Using GNSS” have provided the reader with basic concepts, routines and procedures for understanding, analyzing, evaluating and estimating GNSS-derived ellipsoid and orthometric heights. In Part 5 of this series, we discussed National Geodetic Survey’s NGS 59 guidelines and methods for evaluating the results... read more

Establishing orthometric heights using GNSS — Part 6

April 6, 2016By

Basic procedures and tools for ensuring GNSS-derived orthometric heights meet the project’s desired accuracy To date, this series of columns has addressed the following topics: basic concepts of GNSS-derived heights, National Geodetic Survey’s (NGS) guidelines for establishing GNSS-derived ellipsoid heights (NGS 58), differences between hybrid and scientific geoid models, procedures and tools for detecting GNSS-derived ellipsoid height data outliers, and basic... read more

Establishing orthometric heights using GNSS — Part 4

December 2, 2015By

Part 1 of this series appeared in the June Survey Scene newsletter, Part 2 appeared in the August newsletter, and Part 3 appeared in the October newsletter. Upcoming Survey Scene newsletters will carry additional columns in this series. Basic Procedures and Tools for Ensuring GNNS-Derived Ellipsoid Heights Meet the Project’s Desired Accuracy In Part 1 of this series, I discussed the basic concepts of GNSS-derived... read more

Establishing Orthometric Heights Using GNSS — Part 3

October 7, 2015By

Part 3 describes the differences between a scientific gravimetric geoid model and a hybrid geoid model, and why it is important to use both geoid models in your analysis. read more