Line of sight between any two points in Oregon

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 mountain, the ocean 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 DOGAMI’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: Mount Hood

We check whether a point near Timberline Lodge can see a point further down the mountain.

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 DOGAMI’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 surface model is DOGAMI’s statewide mosaic, which is still being completed. Where it is empty the tool falls back to bare earth, so trees and buildings there do not count.
• Where lidar has not been flown, the USGS 3DEP model falls back to its 1/3 arc-second layer, about 33 ft per pixel, and downloads state what share of the area came from it. That coarser model is not fit for site-scale decisions. DOGAMI reports about 99% of Oregon covered by at least one lidar project. The fallback is rare.

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, and the 1/3 arc-second model, about 33 ft per pixel, elsewhere, with elevations above NAVD 88. The tools with a surface option (Sunlight, Viewshed, Sightline, Object Heights) read DOGAMI’s statewide digital surface model of trees and buildings.

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. DOGAMI lidar products are published by the State of Oregon; credit "DOGAMI / Oregon Lidar Consortium". County taxlot boundaries are the assessor's GIS data, not surveys, and each county publishes its own disclaimer, shown with the parcel. The aerial basemap is from Esri and follows Esri's terms; it is not included in downloads.

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.