Today's new feature series focuses on viewshed maps. Rather than reinvent the wheel, I've republished Leslie McWhirter's article from our newsletter published in July 2015 (Issue 79). Read on for an example of creating and using a viewshed map.
With the release of Surfer 13 comes an exciting new map type: viewshed maps. Viewshed maps show visibility of the surrounding map from a given point location. These maps have a wide range of uses in industries like security, architecture and landscape architecture, military, communications, surveying, wildlife research, and urban planning. Uses include site selection for buildings, radio/cell phone towers, or parking structures based on potential views or openness of the region, selection of survey locations, and discovery of holes in radar coverage. Read on for an example use case, and then contact us to see how viewshed maps can be integrated into your daily workflows and presentations.
An architect in the San Francisco Bay region wishes to build a 5-story apartment building to take advantage of the beautiful water views. His options are the three highest points on the southwest side of the bay. The price of these three pieces of land are the same, so the architect's decision comes down to which location offers the best view of both the ocean and the bay from the penthouse apartment, which offers 360 degree views from the 5th floor.
The three proposed sites for our architect's 5-story apartment building are
on the three highest points on the southwest edge of San Francisco Bay in California.
To make this decision, he creates the following map layers using the instructions below. Each of the three maps shown below represent viewsheds for the three different locations. They are shown in three different colors to make it easier to compare them. The location is shown with a yellow bulls-eye, and everything that can be seen from that location is colored. The coloring is uniform, but may look darker or lighter depending on the coloring of the shaded relief map beneath it.
Comparison of the three viewshed maps for the three location options.
- Click Map | New | Shaded Relief Map.
- In the Open Grid dialog, choose a grid file of the region that uses elevation for the Z values, such as a DEM file, and click Open.
- In the Object Manager, click on the Map to select it.
- Click Map | Add | Viewshed.
- Hover your mouse over the first site location, make note of the Z listed in the status bar, and click to add the viewshed layer.
- In the Object Manager, click the viewshed layer to select it.
- On the General page of the Property Manager, in the Height Above Surface section change the Transmitter height to 20, since the elevation is measured in meters and each floor of a multi-story building is approximately 4 m.
- Add 20 to the Z from step 5, and then calculate the horizon distance manually or using an online calculator like this one.
- Back in Surfer, on the General page of the Property Manager, in the View section change the Radius to the distance calculated in the previous step (note, if you use the suggested online calculator, distance will be given in km, so they must be converted to m to be entered into Surfer).
- If desired, change the line, fill, and transmitter symbol properties in the General section.
Viewshed map of the first possible site location. The bay is almost
completely viewable from this location, however the ocean views are minimal.
- Repeat steps 3-10 for the other two sites.
Viewshed map of the second possible site location. Again, the majority
of the bay is viewable, but from this location a majority of the ocean is also viewable.
Viewshed map of the third possible site location. The majority of the bay is also
viewable from this location, with the exception of the section immediately southeast
of the third location; however, there are no views of the ocean.
From the comparison map, it's easy to see the second site location offers the best view of both the bay and the ocean as represented by the blue viewshed map. Surfer simplifies decision-making so you can make the right decision every time!
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