In this course, we present what we really mean, as surveyors, when we use the term “fractional section.” We will learn about the federal law (not any state laws that may apply in your locality) that applies when dealing with fractional sections, and how and when to apply them. The discussion concludes with specific terms used in the USPLS and definitions that the surveyor must keep in mind. The danger of adopting one of the many common misunderstandings for terms such as fractional, controlling corner, returns and fixed are defined and discussed. Such understanding is essential to be able to move on to other topics such as that discussed in the next tutorial: computing a mean, weighted bearing and how to apply it to completion surveys.
The principal focus of this course is on the federal law on fractional sections and how to apply it mathematically, not ignoring the practical aspects of the fieldwork. The practical application of such computations and the results are discussed. Also discussed: the concept of “protect the plat.”
The concepts of completion and extension surveys are not usually encountered every day. Thus, a surveyor may not even recognize that such surveys are involved in the work being undertaken. The definition of these types of surveys is presented in this course. To be able to understand how to work with such surveys, we go all the way back to discussing the meaning of “fixed,” “monument” and “corner.” These are not the same thing and the distinctions must be well understood. As with measurements, many words that appear similar, such as accuracy and precision, are actually far from being identical. So it is with fixed, monument and corner.
This concluding tutorial on fractional sections covers matter relating to how fractional sections in completion surveys are to be subdivided. We begin by defining completion again and then discuss concepts that may not seem appropriate. Terms such as junior and senior rights can well apply when dealing with completion surveys. A well-educated professional surveyor must understand how such issues can exist even in the USPLS.
In this course, we discuss the term “ethics” and what it means in the context of any profession. Then we apply it to some of the important ways in which the word ethics applies to surveyors and the practice of professional surveying. We also compare and contrast ethical practice with adherence to rules and regulations of a licensing board. The course also addresses some ways in which you can assess your behavior to compare with what the public and the profession may expect for ethical practice. In practice, this course emphasizes how to interact with your clients and others in a “right” manner and to do the job in the “right” way.
There are seven NSPS professional canons. Whether we are members of NSPS or not, measuring ourselves against these canons is a great way to evaluate where we have room for improvement. Preeminent in the canons is the requirement to be mindful of the public’s interest and to do no harm, not just to clients, but all of the public in carrying out one’s professional services.
We discuss “proper” ethics and how it relates to the NSPS Creed. Topics include education, business practices, and obligations to the public (i.e. the public trust). Being able to be honest with clients, peers and yourself is an important part of this practice. How honest, for example, are you in ensuring that you are competent to carry out the task you’ve taken on even though nobody may know of shortcomings in your abilities? We also discuss how poor ethical practice by many of our colleagues casts a bad light on all of us endeavoring to honestly and ethically practice our profession.
In this course, we talk about some of the issues facing the profession that are most relevant to today’s practice of surveying. We also discuss how making a personal commitment to ethical behavior is much more important than trying to follow some rules. Some of the topics discussed include pincushion corners, moonlighting, recordation, and using insufficient or improper control to perform a survey.
Why errors should be of considerable attention in the life of a surveyor’s activities are first presented before moving to the topics to be covered in the series. We begin with a discussion on what errors are, where they come from (sources) and how they are classified into types. Mistakes or blunders, which are not errors, are also discussed. Precision and accuracy are covered, using the bull’s-eye analogy. The discussion then moves on to a discussion of residuals as a way of modeling errors. Concepts such as the mean, standard deviation and the histogram are presented. How uncertainty and probably are presented in surveying measurements are discussed, with concluding discussion on how standard deviation is calculated and how it can be used to analyze data, and when it can be used as an indicator accuracy, not just precision.
This first course in a series on this topic introduces the idea of state plane coordinates, and gives some of the background about why and how it was developed in the U.S. by the then Coast and Geodetic Survey. The concepts covered include the idea of developed surfaces (cylinder and cone), and how points on the earth are projected to these surfaces that are then laid out as two-dimensional grids. The variation in how the projections work when inside the lines of true scale, when the surface of the cylinder and cone are below the surface of the ellipsoid, and when outside, near the edges of the projections, above the surface of the ellipsoid. This is a good course for someone wishing to understand some basics about the system qualitatively, but who doesn’t intend to move on to the subsequent courses in this series.
This second course in the series on State Plane Coordinate Systems covers just a bit of material from the previous course, reviewing the idea of projections and how they work in the case of the Transverse Mercator and Lambert Conformal systems. The course then moves on to discuss how measurements on the topographic surface of the earth are first reduced to sea level (the geodetic distance), before projecting them onto the developable surface appropriate for each type of system. The distortions in east-west lines and north-south lines once they are projected to the grid are discussed. Then, the 1983 system’s overall points are covered, where necessary, contrasting them with those of the 1927 system. How the 1983 system deals with shapes of states that require use of more than one projection are briefly discussed. Also discussed is the importance of understanding which system of linear units (meters, feet or U.S. Survey feet) has been legislatively adopted, and making the appropriate conversions. When state plane coordinate system values are used, even the 2 PPM difference between the International foot and the U.S. Survey foot is considerable. The course again covers the matter of distortion for each type of projection.
This third course in the series on State Plane Coordinate Systems characterizes the types of distortions that occur with the Transverse Mercator and Lambert Conformal systems. The concepts of “scale greater than true,” “…less than true,” and “true” are discussed. The concept of the mapping angle is presented and demonstrated qualitatively for both types of projection systems. Typical SPCS constants for a selected number of zones for Transverse Mercator types and Lambert Mercator are shown, using them to reinforce the concept of the Central Meridian. The concept of the geoid is briefly reviewed before proceeding through the computational processes for reducing a ground distance to its geodetic equivalent using the sea level factor and then, using the scale factor to its grid distance equivalent. The process of computing the mapping angles for both types of projections is then covered, concluding with a discussion of how to apply them.
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 precision 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 precision with shortening initialization times.
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 requires 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 effects on the signal, referencing NGS guidelines that can aid in achieving precise and accurate GNSS positions.
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.
Unlike static GNSS positioning methods, real time procedures require the geospatial practitioner in the field to perform the data collection correctly with 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 percent confidence level will be highlighted. Ultimately, the control is at the pole.
Geospatial 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.
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.
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.
The science of Geodesy is at the heart of all accurate horizontal and vertical positioning. The development of the NAVSTAR Global Positioning System (GPS) and other space-based positioning and global navigation satellite systems (GNSS) provides us with capacity to locate virtually anything, anywhere at any time to within a few centimeters. Understanding the basic principles of physical and geometric geodesy is vital to being able to accurately describe the vast amounts of high accuracy positioning information that is being collected and shared all around the world. This course will review the historical development of our knowledge of the size and shape of the Earth and the fundamental design of horizontal and vertical datums and their realization.
Accurate descriptions of horizontal positions are defined with respect to a reference surface or datum. This course will describe the general architecture of a horizontal/geometric datum and how that process has evolved since the early nineteenth century, including the evolution of the agencies now represented by the National Geodetic Survey (NGS), the process of triangulation and space-based positioning.
Developments in space-based positioning, especially the NAVSTAR Global Positioning System (GPS) have revolutionized the ability to capture high accuracy positions anywhere in the world. The impact on the design and maintenance of classical horizontal datums has been unprecedented in history of geodesy. The transition from locally defined datums to those that are more globally referenced and provide considerably higher positional integrity has been a challenge for national geodetic institutions around the world. This course will outline the various efforts by the National Geodetic Survey to adapt to these changes and provide improved realizations and products and services to support the increasing demands of diverse disciplines.
The demise of the cold war and the development of the internet have vastly expanded international collaboration and partnership in many scientific endeavors. The science of geodesy has benefit immensely from these efforts. Significant advancements in space and terrestrial measurement systems such as the Global Navigation Satellite Systems (GNSS), Very Land Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR) and Doppler Orbitography and Radio Positioning Integrated by Satellite (DORIS), have greatly improved our knowledge of earth orientation parameters including the knowledge of the location of Earth geocenter, Polar Wobble (Chandler Wobble) and tectonic plate velocities. National geodetic surveying and mapping agencies along with government and academic research institutes from across the globe now share vast amounts of positioning information with the International Earth Rotation and Reference System Service (IERS) headquartered in Paris, France. Periodically the IERS releases updated positional and velocity information for the network of stations providing this foundational information. From this network national organizations can ensure that their respective geodetic reference frames are kept up to date and consistent with the most current understanding of the motions of the planet. This class will review the efforts of the IERS and how NGS and the National Geospatial-Intelligence Agency (NGA) ensure the integrity of NAD 83 and WGS 84.
Describing the location of a point is a critical part of its geodetic realization. This presentation describes the three general ways to show a point’s coordinate location. These include: Earth-Centered Earth Fixed (ECEF) coordinates, geographic coordinates (latitude, longitude, ellipsoid height) and plane coordinates such as the State Plane and Universal Transverse Mercator grid systems.
The need for accurate, consistent and reliable height information is one of the most important set of attributes for any local, regional or national geodetic system. Planning for inundation and flood modeling, ecosystem risk assessment, civil engineering, topographic mapping and charting are vital elements of our national infrastructure. Vertical datums provide the foundation to which all of these activities can be related. This presentation explores the relationship between tidal and geodetic datums and the most general types of heights that are encountered and how they relate to each other. In addition, the presentation reviews how heights are determined and the National Ocean Service (NOS) VDatum transformation tool.
The development of a geodetic vertical datum for the United States traces its history to 1877. Since that time the U.S. Coast & Geodetic Survey, now called the National Geodetic Survey has conducted high accuracy leveling across the country including the island areas of Hawaii, American Samoa, Guam, Northern Marians, Puerto Rico and the U.S. Virgin Islands. This presentation will discuss the historical development of those efforts along with the evolution of the computation of increasingly more accurate geoid models to support GPS-derived heights. The class will also briefly discuss some of the limitations of GPS-derived heights.
During 2008, the National Geodetic Survey conducted an in-house study of the ability of the National Spatial Reference System to support the increasing demands for high accuracy positioning services and capabilities. One of the significant conclusions of that effort was that NAD 83 and NAVD 88 (and other island vertical datums) have sufficient deficiencies that will likely make them unable to support the potential for improved positioning technologies in the near future. To meet these challenges NGS has embarked on an effort to replace these datums with a more contemporary reference frame that will bring the United States geometric datum into closer alignment with the International Terrestrial Reference Frame and provide for a vertical datum based on gravity observations instead of geodetic leveling and the reliance on passive geodetic marks (i.e. bench marks). This class will discuss the rational for these changes, the on-going program of Gravity for the Redefinition of the American Vertical Datum (GRAV-D) and the changes in position and heights that will result from these new datums.
As part of their work, surveyors, engineers and other disciplines use information published on data sheets published by the National Geodetic Survey (NGS). However many have difficulty finding the information they want in these data sheets. In this course former NGS Chief Geodetic Surveyor Dave Doyle, explains the many types of data sheets. He goes through the entire sequence of information and provides many helpful tips so that this course can serve as the “secret decoder ring” for many. In addition, Dave discusses DSWORLD, a program contributed toNGS that all users can access to view control mark locations against a Google Earth backdrop, but to also participate in a crowd sourcing activity that NGS encourages, but which is not widely known, to update mark location information and to add photographs to aid future mark visitors. Copious example data sheets that are discussed in the course are part of the downloadable materials that come with this course.