Beach Baseline Survey

A Baseline beach surveys sets the baseline condition and benchmark for future surveys. The primary function of the beach surveyis to measure distances, angles and heights of the beach at different points.

Under the Southwest Regional Coastal Monitoring Programme all beach sites receive a full baseline beach survey once every five years, with the exception of beach management plan sites which receive an annual baseline.

The surveys are conducted to a consistent standard, based on a combination of beach profiles at 50m intervals and continuous spot height data collected at approximately 1m intervals across the whole beach to the level of MLWS.

There are two types of surveying instruments used: the total station and the GPS system.

The total station employs the electro-optical distance metering method, emitting laser beams to a target and detecting light reflected off it. It takes measurements by calculating the deviation of the wavelength of the reflected light. Total stations are able to measure distances to an accuracy of 2-3 millimeters per kilometer, and angles to 1-second (1°/360°) accuracy. One second in an angle is equivalent to the width of pencil lead at 100 meters.

With the GPS system, measurements are taken by receiving signals from GPS satellites. Real-Time Kinematic (RTK) GPS is a process where GPS signals are transmitted in real time from a reference receiver at a known location to one or more remote rover receivers.

The use of an RTK capable GPS system can compensate for atmospheric delay, orbital errors and other variables in GPS geometry, increasing positioning accuracy up to within a centimeter. This is a technique employed in applications where precision is paramount. The video below shows the how GPS works.

The surveys are sufficiently detailed to enable development of digital surface models; enabling profiles to be drawn at any location.Below is a digital surface model of Loe Bar, Cornwall, created from the baseline survey data.