4.2.1 GPS Hardware for Surveying:

INTRODUCTION

In 1980 there was only one GPS receiver available on the market. Two decades later there are well over 100 different makes and models available, most of them having appeared in the last 5-10 years. Receivers have varied features and capabilities. For example, some are designed for military users; others for civilians; some receivers are intended for navigation, others for the most precise geodetic surveys; some receivers use the C/A code, others additionally track the P/Y code; there are single and dual-frequency receivers; and there are handheld and rack-mounted configurations. However all receivers share a number of common features. A typical GPS receiver comprises the following hardware components (section 4.1.1):

• antenna and preamplifier,
• radio frequency section,
• microprocessor,
• terminal, or control and display unit,
• data recording section, and
• power supply.

In this and the next section the focus is on the total GPS surveying "package", and therefore to the above list must be added the software components:

• survey planning software component,
• data logging, data downloading, pre-processing, editing, etc.,
• phase data processing module, and
• result presentation modules (network combination, transformation, etc.).

In the following sections are highlighted some characteristics of the hardware component of GPS surveying instrumentation, with particular emphasis given to the most popular instrumentation used in Australia, from the three major GPS survey receiver manufacturers: Ashtech, Leica and Trimble. The software component is discussed in section 4.3.

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© Chris Rizos, SNAP-UNSW, 1999