ZTV & ZVI Assessments

Zone of Theoretical Visibility (ZTV) & Zone of Visual Influence (ZVI) Assessments

ZTV Assessments for Verifed Views and Photomontages

What are ZTV & ZVI assessments?

Zone of Theoretical Visibility (ZTV) and Zone of Visual Influence (ZVI) assessments are computer generated using specialist software to identify the visibility of a scheme or development. The elevation point (or a multiple elevation points) of a development are tested against a virtual 3D terrain model. This provides a 'heat map' of visibility around the site.

Types of 3D Terrain Model

There are different types of terrain model to test against. The most basic is a bare-earth Digital Surface Model (DSM), giving the least accurate impression of visibility. This only shows the landform without any landscape features such as trees or buildings in it. To increase pertinance, blocks of elevations can be added to the basic DSM model; for example, all houses in the area can be shown at 9 metres. This creates barriers to visibility and provides a more accurate evaluation of the visibility of a development. Finally, a Digital Terrain Model (DTM) can be used through the increasingly available LiDAR datasets. Dependent on the resolution used, a very detailed 3D elevation map of a landscape with features as small as 25cm across can be assessed.

What are ZTV and ZVI assessments for?

ZTV & ZVI assessments are a part of the LVIA (Landscape and Visual Impact Assessment) output. They provide a robust desktop study method for determining viewpoint locations. Along with on-site checks, they allow viewpoints to be selected accurately and appropriately, based on actual and not assumed visibility. Further, they give context and transparency to the planning authority, as they can see exactly why a verified view is being presented from a particular viewpoint whilst others have been excluded, providing complete transparency.

Why choose RBMP for your ZTV & ZVI Assessments?

We have years of experience providing cost effective ZTV & ZVI assessments for all types of projects; including:

  • Residential Developments
  • Listed Buildings and Estates
  • Historic Sites
  • Landmark Towers
  • Commercial Schemes
  • High Sensitivity Sites
  • Blenheim Palace ZTV Bare Earth

    Visibility of listed buildingZTV Assessment.

    ZTV using OS Digital Surface Model (DSM). This is effectively a 'bare-earth' assessment, and doesn't take into account features in the landscape above ground level, that may obscure a view.

    Blenheim Palace ZTV Bare LiDAR

    Visibility of listed buildingZTV Assessment.

    ZTV using the newly availble liDAR Digital Terrain Model (DTM) to give an accurate impression of visibility including landscape features such as trees, hedges, and buildings.

    Nine Acres Bungalow ZTV with Viewpoints

    Visibility of proposalsZTV Assessment.

    A ZTV combined with digital terrain model that shades and hightlights the undulating topography. Here it is used to show how viewpoints have been selected from local highpoints, and surrounding conurbations.