Introduction

This section discusses the Witness radar and application terminology.

Contents

Radar Terminology

PPI 

The Plan Position Indicator (PPI) is the original name given to very first radar displays. These were based on very early CRT technology and provided a simple way of visualising the raw data produced by a radar. This concept still remains in the Witness software, although we now use a modern digital display to render the radar data. Typically the raw radar data is only used during commissioning or as a diagnostics aid.

STC

Sensitivity Time Control (STC) is used to attenuate (reduce) strong signals from nearby clutter and targets. The filter is based on range and adjusts the level of attenuation dependent on how far objects are from the radar. The further the object, the less the signal is reduced. STC can be very useful to reduce the effect of sea clutter close to the radar.

Application Terminology

Replica Set

Replica Set refers to a collection of at least 3 database servers which are configured to dynamically replicate data between themselves. At any one time, the set has a master server but if this system goes offline, for any reason, then one of the remaining servers in the set automatically takes over. Because each server in the set has a duplicate set of data the replica set can continue operate without consumers of the data ever knowing that one of the servers is unavailable.

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