Line of sight between any two points in North Carolina

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. Finish the line. The panel draws the terrain profile with the sightline over it and reports clear or blocked.

Step by step: Grandfather Mountain

We check whether a point on Grandfather Mountain’s upper flank can see a point further down toward the Parkway.

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 bare-earth terrain 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

• Trees and buildings along the line are not tested, so a line the tool calls clear can still be blocked by a tree line or a roof on the ground.
• Every tool on this site is bare earth: trees and buildings are not in the elevation model for North Carolina, so shade and views come from the shape of the ground alone.
• 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. USGS 3DEP serves lidar-derived elevation across North Carolina: 3.3 ft per pixel where a full-resolution lidar survey exists, about 9.8 ft per pixel where the model is built from older lidar. 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. Every tool is bare earth: trees and buildings are not in the elevation model for North Carolina, so Sunlight, Viewshed and Sightline work from the terrain alone.

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. County parcel boundaries are the assessor's GIS data compiled by NC OneMap, not surveys, and the county that published each parcel is named with it. 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, on the bare-earth terrain.
• Elevation Profile — Produces a cross-section of the ground along any line, with distance, total climb and descent, and grade.