Visual Impact of Pylons - Interactive Map

Using computer power and algorithms we have generated a visual impact assessment of the Green Gen Cymru Towy/Usk preferred Pylon route. The resulting map enables us to determine from where the proposed pylons are visible and how many pylons are visible from that exact location. This new map takes into account trees and buildings, giving an evermore accurate impact assessment.

How to read the map

The visual assessment map has been produced at a 1m resolution. This means for every 1m2 an assessment was made as to whether a pylon could be visible from that location. Therefore, any location highlighted in red on the map will have at least one visible pylon. The darker the red the more pylons that are visible from the given location.

The map is similar to Google maps, so please zoom into locations which interest you to see the visual impact.

Please click here to access the map directly on the Google Earth website (opens in new tab)


The map provides evidence of the significant impact that the proposed pylon route will have on our communities.

A few headline facts:

  • 142,503 acres (57,670 Ha) would be visually impacted by the proposed pylons. Around 14% of Carmarthenshire would have sight of at least one pylon.
  • Interesting Fact: If you place each of the 388 proposed pylons on top of each other it would be 10x the height of Pen y Fan and even taller (10,476 m) than Mt Everest (8,849 m)!!

About the data

In order to produce this map, we’ve based it on a number of assumptions - which affect the way you interpret what the map is showing you.

  • The map assumes you can see a pylon at a 5km distance, however, weather conditions and other factors may reduce this distance. 5km is a conservative figure, with other scientific studies in Germany suggesting pylons are visible from 10km away, and studies in the USA suggesting even further.
  • The map is based on terrain data which means that all buildings, trees and other objects in the landscape have been removed. It may be that a building or a large tree would obscure the view of pylons from a given map location, in which case you may in reality see fewer pylons from that spot. However, as the landscape continually changes, for example with trees being felled, and given the average lifespan of a pylon is 80 years, it is important to undertake this analysis using the bare earth only.
  • The map assumes that a pylon is located every 250m along the route. This is an average distance, and the pylons may be situated closer together in places, which would increase the visual impact.
  • The map only accounts for the pylons themselves, not the transmission lines between the pylons. This means the map shows a conservative estimation of overall visual impact.

Given these assumptions, the map should be treated as an indicator of visual impact.


The method used copies the approach taken by development companies in the UK to assess visual impacts of developments, e.g. wind turbines. Our approach is more accurate than most as we have used the 1m resolution LiDAR data set, whilst most other visual assessments use low resolutions Digital Surface Models (DSM) data, such as OS Map Terrain. The approach taken goes as follows:

  • 27m Pylons simulated every 250m as per the Green Gen Cymru proposed preferred route. This equates to around 388 pylons.
  • The pylons were placed along the centroid line of Green Gen Cymru proposed preferred route.
  • The 1m LiDAR DTM collected by Welsh Government in 2020 was used to represent the terrain.
  • A Zone of Theoretical Visibility (ZTV) was assessed for each Pylon using Welsh Government 1m LiDAR DSM. This provides a 1m binary map of where that individual pylon is visible from.