About David B. Zilkoski

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David B. Zilkoski has worked in the fields of geodesy and surveying for more than 40 years. He was employed by National Geodetic Survey (NGS) from 1974 to 2009. He served as NGS director from October 2005 to January 2009. During his career with NGS, he conducted applied GPS research to evaluate and develop guidelines for using new technology to generate geospatial products. Based on instrument testing, he developed and verified new specifications and procedures to estimate classically derived, as well as GPS-derived, orthometric heights.

Now retired from government service, as a consultant he provides technical guidance on GNSS surveys; computes crustal movement rates using GPS and leveling data; and leads training sessions on guidelines for estimating GPS-derived heights, procedures for performing leveling network adjustments, the use of ArcGIS for analyses of adjustment data and results, and the proper procedures to follow when estimating crustal movement rates using geodetic leveling data.

Posts by David B. Zilkoski

A look at NGS’ GPS on benchmarks program in Alaska Posted on 05 Apr 2017 in the Opinions & Survey categories.

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... Read more»

Establishing orthometric heights using GNSS — Part 11 Posted on 01 Feb 2017 in the Opinions & Survey categories.

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... Read more»

NGS to replace NAVD 88 in 2022: What GNSS users need to know Posted on 07 Dec 2016 in the Opinions & Survey categories.

Understand the differences between the North American Vertical Datum of 1988 and the new 2022 Vertical Reference Datum My Survey Scene columns have focused on procedures and routines for establishing... Read more»

Analyzing NGS’ GPS on benchmark dataset used to make GEOID12B Posted on 05 Oct 2016 in the Opinions & Survey categories.

These columns have focused on procedures and routines for establishing GNSS-derived orthometric heights. There are many ways to analyze and investigate GNSS data and adjustment results. I have provided some basic... Read more»

Establishing orthometric heights using GNSS — Part 8 Posted on 03 Aug 2016 in the Opinions & Survey categories.

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... Read more»

Establishing orthometric heights using GNSS — Part 7 Posted on 02 Jun 2016 in the Opinions & Survey categories.

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... Read more»

Establishing orthometric heights using GNSS — Part 6 Posted on 06 Apr 2016 in the Survey categories.

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... Read more»

Establishing orthometric heights using GNSS — Part 5 Posted on 03 Feb 2016 in the Opinions & Survey categories.

Basic procedures and tools for ensuring GNNS-derived orthometric heights meet the project’s desired accuracy
In the latest installment of our ongoing series, the focus switches from GNSS-derived ellipsoid heights to procedures and tools for ensuring GNNS-derived orthometric heights meet the project's desired accuracy. Read more»