Line of sight between any two points in Wisconsin

Who uses this

• Wireless and radio installers. Confirm terrain clearance for a point-to-point link.
• Buyers and owners. Check a specific view from a deck or a window.

When to use it

• Will this deck see the lake, the bluffs or the neighbor’s new barn?
• Is there line of sight for a wireless link or a camera between two places?
• How much would a building need to rise to clear a ridge?

Tools for your job

Sightline is one step in a bigger question. These are the jobs it helps with, and the tools that go with it.

How to use it

1. Open Sightline and tap the observer, then the target.
2. Set the observer and target heights above ground.
3. Choose bare ground, or terrain with trees and buildings so Brown County’s surface model can block the line.
4. Finish the line. The panel draws the terrain profile with the sightline over it and reports clear or blocked.

Step by step: Devils Lake

We check whether a point on the East Bluff can see a point on the far shore of Devils Lake.

1.Open Sightline and tap the observer (A), then the target (B). Choose Done.

2.The panel shows the ground elevation at A and B, whether B is visible and, if not, how far from A the view is blocked and by how much the terrain rises above the line.

What it showed

• If the view is blocked close to A, raising the eye height a little or stepping to the edge of the slope is often enough.
• The same check works for a radio link or a camera: put A and B on the two masts.

How it works

The terrain, or with the surface option Brown County’s surface model of trees and buildings, is sampled along the straight line between the two points and compared with the line joining the two eye heights, with earth curvature and refraction applied. The first place the ground rises above that line is the blocking point, and the height by which it blocks is reported.

Reading the results

A block of 10 ft at a given distance means raising the observer or the target by about 10 ft would just clear the terrain there.

The profile shows every bump along the way, so you can see whether the block is a ridge or a small rise close to one end.

Limits and caveats

• With bare ground, trees and buildings along the line are not tested. With the surface option they are, but only as they stood when the lidar was flown.
• The optional surface model covers Brown County only. Outside usable Brown County data, Sunlight, Viewshed and Sightline fall back to bare earth, so trees and buildings do not count. Object Heights needs usable surface data. Its source date can differ from the 3DEP ground model.
• Outside the finest lidar work units, 3DEP can use older lidar at about 9.8 ft per pixel or a coarser model at about 33 ft per pixel. Fine output spacing cannot recover missing source detail. Lidar coverage and source dates vary across Wisconsin. Check your site against the USGS 3DEP work-unit index; an unavailable lookup means coverage is unknown.

Data and attribution

Results come from the USGS 3D Elevation Program (3DEP) bare-earth elevation model: lidar at 3.3 ft per pixel where it has been flown, with older lidar at about 9.8 ft per pixel and coarser sources at about 33 ft per pixel elsewhere, with elevations above NAVD 88. The optional surface model is limited to Brown County. Outside usable regional data, Sunlight, Viewshed and Sightline fall back to bare earth; Object Heights needs usable surface data. Surface and ground source dates can differ.

USGS 3DEP elevation data and USGS maps are U.S. Government works in the public domain: you may use the results, including commercially. A credit to the USGS 3D Elevation Program is appreciated, and every file you download carries it. Wisconsin parcel boundaries are aggregated local-government data, not legal surveys; the parcel disclaimer accompanies the selection. Brown County surface data is credited separately when used. The Esri aerial basemap follows Esri’s terms and is display-only; downloadable aerial photos use USGS NAIP.

Questions

Related

Related tools

• Viewshed — Shows which ground can be seen from a point, out to a radius you pick from 0.5, 1, 2 and 5 miles, for a chosen eye height, with earth curvature and refraction allowed for and, optionally, trees and buildings blocking the view.
• Elevation Profile — Produces a cross-section of the ground along any line, with distance, total climb and descent, and grade.

Guides

• Line of Sight Between Two Points in Wisconsin