Basic GIS coordinates

Coordinates are the foundation of GIS, cartography, and surveying, to name just a few fields. Computers have an astounding capacity for repetition and they possess a superior ability to handle the mathematics behind coordinate manipulation¿but they are very bad at interpreting coordinates and coordinate systems.

Basic GIS Coordinates, Second Edition clearly illustrates the basic principles of coordinate systems, covering ellipsoids, datums, and plane coordinates as they are used in GIS and GPS. Keeping in mind that it is ultimately incumbent on humans to ensure the correct use of coordinate systems, this book explains complex topics in a logical progression, presenting them in a way that is neither too complicated nor oversimplified. This new edition of a bestseller expands the material with updates on what has occurred in the field during the past five years, especially in the World Geodetic System and International Terrestrial Reference Frame. It also addresses the upcoming GNSS constellations and coordinate implications.

Details how to build a coordinate system Addresses different methods of leveling, as well as measuring and modeling of height and gravity Explores two-coordinate (state-plane, UTM) systems Discusses initial points and other aspects of the rectangular system Covers the geoid and the concepts of elevation

There are thousands of horizontal geodetic datums and Cartesian coordinate systems currently sanctioned by governments around the world to describe our planet electronically and on paper. Even if a computer has done nothing wrong, coordinate errors can often occur and lead to potentially disastrous miscalculations. This book is a valuable tool to help readers develop an understanding of how coordinate systems work¿and how they sometimes don¿t.

Preface	p. ix
Author	p. xi
1 Foundation of a Coordinate System	p. 1
Uncertainty	p. 1
Datums to the Rescue	p. 1
René Descartes	p. 2
Cartesian Coordinates	p. 2
Attachment to the Real World	p. 4
Cartesian Coordinates and the Earth	p. 4
The Shape of the Earth	p. 7
Latitude and Longitude	p. 9
Between the Lines	p. 11
Longitude	p. 12
Latitude	p. 14
Categories of Latitude and Longitude	p. 14
The Deflection of the Vertical	p. 16
Directions	p. 20
Azimuths	p. 20
Bearings	p. 20
Astronomic and Geodetic Directions	p. 22
North	p. 23
Magnetic North	p. 23
Grid North	p. 24
Polar Coordinates	p. 25
Summary	p. 28
Exercises	p. 31
Explanations and Answers	p. 34
2 Building a Coordinate System	p. 39
Legacy Geodetic Surveying	p. 39
Ellipsoids	p. 41
Ellipsoid Definition	p. 42
Ellipsoid Orientation	p. 45
The Initial Point	p. 46
Five Parameters	p. 46
Realization of a Geodetic Datum	p. 48
Terrestrial Reference Frame	p. 48
New Geocentric Datum	p. 49
Geocentric Three-Dimensional Cartesian Coordinates	p. 53
The IERS	p. 56
Transforming Coordinates	p. 58
Common Points	p. 60
Molodenski Transformation	p. 60
Seven-Parameter Transformation	p. 61
Surface Fitting	p. 63
Exercises	p. 65
Explanations and Answers	p. 68
3 Heights	p. 73
Ellipsoidal Height	p. 73
Trigonometric Leveling	p. 75
Spirit Leveling	p. 77
Sea Level	p. 79
Evolution of the Vertical Datum	p. 82
Zero Point	p. 82
Geoid	p. 84
Measuring Gravity	p. 86
Orthometric Correction	p. 87
Ellipsoidal, Geoidal, and Orthometric Heights	p. 89
NGS GEOID Models	p. 91
Dynamic Heights	p. 93
References	p. 94
Exercises	p. 95
Explanations and Answers	p. 98
4 Two Coordinate Systems	p. 101
State Plane Coordinates	p. 101
Map Projection	p. 101
Polar Map Projections	p. 104
Choices	p. 109
SPCS27 to SPCS83	p. 113
Geodetic Lengths to Grid Lengths	p. 116
Geographic Coordinates to Grid Coordinates	p. 123
Conversion from Geodetic Azimuths to Grid Azimuths	p. 125
SPCS to Ground Coordinates	p. 129
Common Problems with State Plane Coordinates	p. 130
UTM Coordinates	p. 130
Exercises	p. 137
Explanations and Answers	p. 141
5 Rectangular System	p. 147
Initial Points	p. 148
Quadrangles	p. 150
Townships	p. 153
Sections	p. 157
Subdivision of Sections	p. 160
Township Plats	p. 160
Fractional Lots	p. 161
Naming Aliquot Parts and Corners	p. 165
References	p. 171
Exercises	p. 172
Explanations and Answers	p. 175
Index	p. 179

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