Dec 2020
Gas Transmission
Analytical Approach for Vegetation Management
Dec 2020
Mar 2021
National Grid Gas Transmission
Graham Harvey
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Network Innovation Allowance
GT - Safety and emergency, GT - Reliability and maintenance and GT - Environment and low carbon
Gas Transmission Networks
RSK Orbital currently conduct detailed aerial photography of the NTS network over a four year rolling programme for the purposes of TD1 population density and Building Proximity Analysis.

The survey output is a digital report identifying building and population change since the last survey (four years previously), categorized into severity. The photography captured for this purpose is delivered via the RSK Orbital Visivi tool. Consecutive photographs have been captured with considerable overlap, with an effective orientation to identify usage, type and condition of the buildings in the corridor. This potentially also lends itself to creating 3D models of the pipeline route from the same data.

Generating 3D models we propose to then analyse a central corridor spanning three metres either side of the pipeline centreline to create a Digital Surface Model (DSM). Using the DSM, We propose to identify the precise mapped whereabouts of vegetation ingress. The results can be reported against the Network length, Pipeline or sub sections thereof.

In addition to providing the visual evidence which will clearly show the colour and shape of the vegetation, we also propose to report on the following:
  1. Self-seeded vegetation locations, Using DSM against a wider area Digital Terrain Model (DTM)
  2. Sub-Metre Vegetation (not on a hedge row), using GIS analysis
  3. Sub-Metre Vegetation (on a hedge row), using GIS analysis
  4. Height of vegetation, using the DSM
  5. Volume of vegetation, using our software tools
  6. Vegetation Species - For this trial using our in-house arboriculturalists
  7. Criticality of vegetation ingress delivered via a thematic map
  8. Comparison analysis for year-on-year showing differences in vegetation volume and location
All applicable outputs will be ESRI Shape file Map layers for use with your corporate GIS systems. Otherwise the data will also be displayed and be accessible via the Visivi tool.
We propose to utilise data from a pipeline flown during the 2020 survey runs for the purpose of the trials, but also propose to refly the same line with the new camera and camera rigs which we will be using for the 2021 surveys. This will give an interesting idea of how the technology is developing and can be honed to provide the best possible data for the purposes at hand.
Determine whether historic oblique aerial photography, captured for one specific application (population density), can be appropriately adapted to fulfil an alternative application (vegetation survey).
The benefits are that the data is already being collected for the TD1 so no additional flights will be required, with the associated improvements to safety, increases in efficiency, lessening impact on the environment and possible tie-ins to future developments for data gathering and surveillance.