Sect_1.2.1

1.2.1 System Ingredients

INTRODUCTION

WHY SATELLITES?

Satellite-Based Positioning Systems are ideal from a number of points of view:

They transmit signals that can be "seen" over a far larger area than ground-based systems.
With the appropriate technology they can transmit signals through cloud and rain, and can be used day or night.
They recognise no national boundaries, and hence can be used globally wherever they are visible, on the ground, in the air and at sea.
Satellites are tamperproof.
For most national authorities, there is no investment in the necessary space hardware.

However, in order to ensure an appropriate design for the satellite positioning system, there are several issues to be considered:

The system configuration: the "pattern" of satellite deployment (impacting on the availability of the system), and the reference frame definition.

The measurement technology to be used: the nature of the observations, their errors and biases, and suitability for 3-D positioning.

The positioning principles to be employed: influenced to a large extent by the above issues.

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