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Introducing View Finder, a web tool for evaluating the visual impact of new transmission corridors.

Placing power transmission lines across the landscape is a necessary to transmit energy from source to destination. Until we get a breakthrough in efficiency, distributed and localized generation, new transmission corridors will be needed.

Choosing where to put corridors is contentious and drawn-out - for example, see the well-documented campaign against new corridors in Virginia run by the Piedmont Environmental Council. Reviews take a long time, and require data, expert analysis, public and stakeholder consultation. What if new tools could help make the processes more effective?

Here are two such tools:

• View Finder. A visibility analysis for the entire US, running in your browser. Discussed below.
• Path Finder. A collaborative platform for contributing, assessing and commenting on corridor options.

These two tools alone don’t resolve all the challenges around corridor placement, but they represent small building blocks towards more inclusive and open processes.

What is View Finder?

View Finder uses freely-available datasets to calculate what can be seen from a particular location. While detailed viewshed analysis is expensive and slow, View Finder provides a rough sketch of the same information in seconds, right in your web browser.

From your browser, click a point on a map, or draw a path to represent a transmission corridor (shown green in the screenshot below). View Finder overlays two colors: blue, showing locations that can’t see the point or corridor, and pink for locations that can.

Pre-set options relevant to transmission corridors allow you to specify the height of the pylons. Taller corridor infrastructure increases the size of the possible viewing area.

Vegetation cover data are used to calculate summer and winter views, where the corridor is located in or near a deciduous forest.

The ground cover also affects how likely you are to see the corridor from each location - forest gets in the way more than scrubland, for example.

After tweaking the settings, share, save or print the viewshed.

Behind the scenes, View Finder uses the National Elevation Dataset, and the National Land Cover Dataset. Both are stored in Amazon Elastic Block Storage, and called as needed by a GRASS GIS script running in Amazon Elastic Cloud Compute to calculate the visibility for the current location. Map tiles showing the view shed are generated on the fly by Mapnik and stored for re-use.

View Finder is an integral part of Path Finder - to be covered in a follow-up post.