3.1 Scope

This chapter looks at surveying and profiling essential first requirements for any new line construction or for refurbishment. Traditional ground-based techniques are covered first, followed by a description of the increasing trend to use helicopters and laser profiling. The chapter is split into three main areas:

1. traditional surveying /profiling for a proposed new green field route

2. refurbishing an existing line

3. laser profiling using helicopters.

3.2 Introduction

Before any new line is built, or any major changes made to an existing line, it will need to be surveyed and profiled. Essentially, surveying means going along the line and making a detailed note of:

• every pole (height, age, condition)

• span length

• conductor type

• nearby tree growth

• land heights relative to the conductor

• land height relative to mean sea level (normally to a local Ordnance Survey (OS) datum point)

• road, rail, river or footpath crossing

• fences, houses etc. near to the line.

Indeed, anything that may be in any way remotely affected by the existence of the overhead line. Surveying is essential as new estates are built and land changes use in ways that could affect safety or normal operation of the line. The OHL engineer does not have to do this there are specialist surveying companies to carry out the tasks. The output of all this will be a profile of the land within, say, ten metres either side of the existing or planned line route, which includes the clearance values under the conductor along each span.

It is important to realise...