William Henning Prof LS

William Henning, Prof.LS., is a Registered Professional Land Surveyor with over 46 years of active experience in all phases of the land surveying profession. He has been actively involved with education and outreach to the geospatial community for 20 years, presenting over 120 talks and workshops on surveying and GNSS technology. Mr. Henning has authored articles for professional journals and trade magazines on GNSS positioning as well as authoring an extensive guideline document on single base real-time GNSS positioning and editing a real-time network guideline document while working at NOAA’s National Geodetic Survey (NGS). He has trained various federal and local personnel in using GNSS equipment and correct positioning techniques. Bill has been the project lead for new height modernization geodetic networks in county-wide projects in the U.S., where he planned, helped construct, processed, adjusted and managed new geodetic control systems. He has over 19 years experience working with various GNSS manufacturers’ real- time positioning systems. Mr. Henning is Past President of the American Association for Geodetic Surveying (AAGS) and is an ACSM/AAGS Fellow. He has been presented with the NOAA Administrator’s Award for outstanding accomplishment in producing real time GNSS guidelines. He is currently retired from the NGS, where as a Geodesist he helped develop guidelines and support methodology for real time GNSS positioning with state, national and international organizations. Bill is currently working part time in private industry as the geospatial manager for George William Stephens, Jr. & Associates, Inc. and as a faculty member for GeoLearn where he is recording videos for the use of surveyors, engineers and other geospatial professionals. Mr. Henning was awarded the Maryland Society of Surveyors “Surveyor of the Year” for 2013-14.

William's Courses

Real Time GNSS Positioning (Part I) – How Does Real Time GNSS Positioning Work?

Geospatial professionals must be aware of how their tools and programs work to evaluate their results and diagnose potential problems. This part of the four part series on real-time GNSS positioning will attempt to present and explain in simple terms how real time positioning works. After a short look at the current and near future state of the GNSS constellations, the concept of ambiguity resolution will be discussed noting some techniques used to resolve the unknown integer number of cycles using differencing and other methodology. Highlighted sections of the NGS guidelines for single base positioning will be will be shown and static positioning options will be briefly contrasted to the precisions obtainable with real-time methods. Additionally, a short look will be taken at the augmented autonomous GNSS positioning developments that are approaching usable survey-grade precisions with shortening initialization times.

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Real Time GNSS Positioning (Part II) – What Affects the GNSS Signal?

To fully appreciate their GNSS tools, geospatial professionals need to understand the amazing and complicated machinations their GNSS software and hardware perform to produce centimeter level positions. The native condition of the GNSS signals alone require clocks accurate to several nanoseconds. Complicating the picture are many things that affect the signal, such as the ionosphere, troposphere, orbital information, space weather, satellite geometry, electrical interference and multipath. This course will visit these affects on the signal, referencing NGS guidelines that can aid in achieving precise and accurate GNSS positions.

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Real Time GNSS Positioning (Part III) – Single Base vs. Real Time Network Positioning

Real time GNSS networks (RTN) are the current high precision tool for many geospatial professionals for their cost savings and ease of use. This course will present information on using RTN, their advantages to traditional single base real time methods, and NGS goals to support their alignment to the National Spatial Reference System (NSRS). NGS guidelines for RTN will be summarized, in particular how the RTN should obtain coordinates for their reference stations, and concerns for the RTN administrator and RTN user. A brief discussion will be presented on the emerging precise point positioning (ppp) high precision methodology that will perhaps displace the role of the RTN in a decade or so.

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Real Time GNSS Positioning (Part IV) – Best Methods for Accurate Field Data Capture

Unlike static GNSS positioning methods, real time procedures require the geospatial practitioner in the field to perform the data collection correctly with a knowledge of conditions and methods that will affect their results. This course will point to NGS guidelines for best methods in both a single base scenario as well as with using real time networks (RTN) to achieve precise and accurate data collection. Techniques that can give increased confidence with the field work will be presented and a summary table with specific criteria for achieving four different precisions at the 95% confidence level will be highlighted. Ultimately, the control is at the pole.

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GNSS Derived Heights (Part I) – What You Need to Know About Heights and Gravity

Geopspatial practitioners are familiar with using active stations to remotely provide control data to produce high precision horizontal positions. However, when our new national vertical (geopotential) datum is rolled out around 2022, we will also be able to remotely access active stations for high precision orthometric heights. This session will explain the new national geometric and geopotential datums in comparison to NAD 83 and NAVD 88 and underline the transition from passive monuments in the ground to active antennas in the air as the basis for our vertical “truth”. Additionally, the different heights, such as ellipsoidal, orthometric, dynamic and geoid, found on a typical NGS data sheet , will be explained with the role (or non-role) that gravity plays for each.

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GNSS Derived Heights (Part II) – Using the NGS Hybrid Geoid Model & Height Modernization Procedures

Geospatial practitioners understand that geodetic leveling procedures are the most accurate means to propagate NAVD 88 orthometric heights. However, the time, effort, resources and specifications to produce publishable 1st or 2nd order vertical heights on bench marks are too onerous a task for most to take on in an economical fashion. Fortunately, NGS Height Modernization techniques allow for users to obtain orthometric heights at usable accuracies for most project work. This session will describe the NGS height modernization program and the important elements of which it is comprised – such as the hybrid geoid model used with GPS derived NAD 83 ellipsoid heights, establishing site control for flood certificate work, and the relationship of local mean sea level to our vertical datums. Additionally, the new vertical geopotential datum, to be released around 2022, will be explained.

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GNSS Derived Heights (Part III) – Using the NGS 58 & 59 Guidelines and Real-Time Precisions

Geospatial practitioners have several methods to produce precise and accurate data from GNSS. However, there are many facets of GNSS positioning that might lead them to selecting one method over another depending on their needs. This session will compare static GNSS methods with real time methods and the precisions available from each one. A real world static GPS project for a county-wide height modernization network will be presented as it followed the NGS 58 & 59 guidelines for GPS derived ellipsoid heights and GPS derived orthometric heights, respectively. A summary of real time guidelines will be shown along with a discussion on site localization that is recommended for vertical data from a real time GNSS network (RTN). (For a thorough discussion of real time methods and important considerations the practitioner is referred to the four part GeoLearn series on real time GNSS positioning). Finally, static data from the NGS OPUS-S and OPUS-RS programs will be evaluated with a tip on editing Rinex data to submit to both of the programs.

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