Preface
Why have we written this book and who should read it?
Leica manufactures, amongst other things, GPS hardware and software.
This hardware and software is used by many professionals in many applications.
One thing that almost all of our users have in common is that they are not GPS scientists or experts in Geodesy.
They are using GPS as a tool to complete a task. Therefore, it is useful to have background information about what GPS is and how it works.
This book is intended to give a novice or potential GPS user a background in the subject of GPS and Geodesy. It is not a definitive technical GPS or Geodesy manual. There are many texts of this sort available, some of which are included in the reading list on the back pages.
This book is split into two main sections.
The first explains GPS and how it works.
The second explains the fundamentals of geodesy.

Contents
Preface ........................................................... 4
1. What is GPS and what does it do ? .......... 5
2. System Overview ....................................... 6
2.1 The Space Segment ............................................... 6
2.2 The Control Segment .............................................. 8
2.3 The User Segment ................................................. 9
3. How GPS works....................................... 10
3.1 Simple Navigation .................................................. 11
3.1.1 Satellite ranging .................................................... 11
3.1.2 Calculating the distance to the satellite ................. 13
3.1.3 Error Sources ........................................................ 14
3.1.4 Why are military receivers more accurate ? ........... 18
3.2 Differentially corrected positions (DGPS) ................19
3.2.1 The Reference Receiver ........................................ 20
3.2.2 The Rover receiver ................................................. 20
3.2.3 Further details ....................................................... 20
3.3 Differential Phase GPS and Ambiguity Resolution ...22
3.3.1 The Carrier Phase, C/A and P-codes .................... 22
3.3.2 Why use Carrier Phase? ....................................... 23
3.3.3 Double Differencing ............................................... 23
3.3.4 Ambiguity and Ambiguity Resolution ...................... 24
4. Geodetic Aspects..................................... 26
4.1 Introduction ...........................................................27
4.2. The GPS coordinate system .................................28
4.3 Local coordinate systems ......................................29
4.4 Problems with height .............................................30
4.5 Transformations .....................................................31
4.6 Map Projections and Plane Coordinates .................34
4.6.1 The Transverse Mercator Projection ...................... 35
4.6.2 The Lambert Projection ......................................... 37
5. Surveying with GPS ................................ 38
5.1 GPS Measuring Techniques ..................................39
5.1.1 Static Surveys ........................................................ 40
5.1.2 Rapid Static Surveys .............................................. 42
5.1.3 Kinematic Surveys ................................................. 44
5.1.4 RTK Surveys .......................................................... 45
5.2 Pre-survey preparation ...........................................46
5.3 Tips during operation .............................................46
Glossary ....................................................... 48
Further Reading .......................................... 59
Index ............................................................. 60