SU 4100 GEODETIC POSITIONING Instructor: Indra Wijayratne

INTRODUCTION

What is the course about ? This course covers topics relating to higher order surveying by positioning techniques

Geodetic positioning is the determination of precise locations of one or more points on earth in a predefined reference coordinate system

The locations of points are generally determined by making measurements between points such as angles, distances, azimuths, or by astronomical or space techniques or a combination of such measurement techniques

The precise locations of a group of points can be established to form a geodetic network and such networks provide high order survey control for subsequent survey projects

Higher order surveying control is needed in  Control for large scale mapping, e.g. base maps for GIS  Boundary demarcation such as international or provincial boundaries  Large Construction Projects, e.g. Bridges, Highways

 County-wide re-monumentation projects where coordinates of position of corners are computed  Siting of transmission lines, pipelines, etc.  Hydrographic and bathymetric surveys, e.g. harbor surveys

 Scientific studies, e.g. particle accelerators  Deformation and plate tectonic studies  Geophysical studies, etc.

Until the advent of satellite and other positioning methods, geodetic control surveys were done by conventional ground survey techniques They utilized a combined process of triangulation/trilateration and occasionally other techniques such as precision traversing

Conventional Control Surveying Methods  Traversing  Intersection  Resection  Triangulation  Trilateration

Inertial navigation systems provided establishment of control with very limited accuracy Photogrammetry also provided a viable method for densification of existing control in a limited sense

Elevation control was exclusively done by geodetic leveling Trigonometric or barometric leveling was used to measure large elevation differences over long distances

Control by Positioning  What is positioning  Point Positioning vs. Relative Positioning

As defined earlier, positioning is the determination of precise locations of one or more points on earth in a predefined reference coordinate system In addition to conventional methods, following positioning techniques have been used in the past

Positioning Methods  Astronomy  Lunar Laser Ranging  Satellite Laser Ranging  Very Long Baseline Interferometry (VLBI)  Electronic Positioning (RADAR, SHORAN, HIRAN)

Very Long Baseline Interferometry Signal from two quasars are received at two points on earth Difference in transmission time is used to determine accurate distance between points

In modern surveying applications, satellite positioning has become the common and only technique being used

Except electronic positioning, all other positioning methods enable the determination of the position of a point independently, that is, without reference to another known point

This type of positioning is called point positioning as opposed to relative positioning when the location of a point is determined relative to another point such as in traversing

All of the above positioning methods, except astronomical techniques, yield three-dimensional positions in a pre- defined coordinate frame

Objectives of this course are  Overview of standards of accuracy, classification, specifications for equipment and field techniques, and datums and coordinates systems used in geodetic control surveys

 Understand the theory behind positioning using Global Positioning System satellites  Survey applications of GPS positioning

 Advantages and limitations of GPS positioning in surveying  Understand the field techniques, data processing, and analysis of results

In order to fully understand the methods employed in conventional geodetic control survey computations as well as concepts behind satellite positioning techniques and related data processing, the student is expected to have a good understanding of the following topics in geodesy, data processing and analysis

Geodetic Datums and Coordinate Systems  geoid, ellipsoid  geodetic datums  North American Datum e.g. NAD27 and NAD83  satellite datum(s), e.g. WGS84  North American Vertical Datum, e.g. NGVD29, NAVD88

 geodetic coordinates (latitude, Longitude)  normal sections and geodetic lines (geodesic)  geodetic and astronomic azimuth/ coordinates  azimuth change due to convergence of meridians, that is, forward and back azimuth of a line

 slope, horizontal, and geodetic lengths of lines  geoid undulations, geodetic heights and orthometric heights (mean sea level elevation)  geoid models

Related Topics  National Spatial Reference System  Federal Base Network (FBN)  Continuously Operating Reference Stations(CORS)  U.S. State Plane Coordinates System

Data processing in GPS uses Least Squares Adjustment techniques, and therefore, an understanding of the following is essential

 general error theory and error propagation  statistical distributions related to measurement errors  principle of Least Squares Adjustment

Students are expected to be skilled in the use of personal computers and general software such as word processors and spread sheets

They should also be skilled in using the Internet and World Wide Web for additional information needed in this course Please review the material covered in SU3150 and SU3250 and try to answer the questions given in class notes