Tree and building heights from lidar, in Brown County

Who uses this

• Arborists and foresters. Screen tree heights across a property or a stand.
• Planners and neighbors. Get approximate building and tree heights for a shading or view question.

When to use it

• Checking tree heights for shading, view or line-of-sight questions.
• Getting approximate roof heights across a neighborhood.
• Seeing what stands on a property before visiting.

Tools for your job

Object Heights 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. Select a property, draw an area or upload a boundary.
2. Run. Heights are drawn from tan (nothing above ground) to deep blue (tallest).
3. Read the coverage, the minimum, mean and maximum in the panel. For ground elevation use Terrain Stats instead.

Step by step: Lambeau Field in Green Bay

We measure the buildings and trees around Lambeau Field in Green Bay from Brown County’s lidar surface model, the only surface model this site reads.

1.Zoom to the area and run the analysis. Tan is bare ground, deep blue the tallest objects. The panel shows the mean and maximum height above ground.

2.Zoom in and single roofs and trees stand out. The panel warns what share of the area is steeper than 30°, where the readings are less reliable.

What it showed

• Buildings and trees are not told apart; compare with the aerial basemap.
• Heights are from when the lidar was flown. Trees planted or cut and buildings put up since do not show, and outside Brown County the tool has no surface data at all.

How it works

Lidar produces two models: the bare earth with everything stripped off, and the surface, which is the top of whatever the laser hit first. Subtracting one from the other, cell by cell, leaves the height of trees, buildings and other objects.

Cells with no surface data, an obvious no-data value, or a surface below the ground are left blank. The color scale is stretched between the 2nd and 98th percentile so a single tall tree does not wash out the rest.

Reading the results

Values are feet above the ground, not elevation. A low reading in a field is a fence line or a hedge; a reading over 100 ft is a mature conifer.

Buildings and vegetation are not told apart. Use the aerial basemap to see which is which.

Limits and caveats

• Only where the Brown County surface model has usable data, and only as objects stood when it was collected. Other Wisconsin locations have no supported object-height result.
• Over cliffs, rock outcrops and snowfields the two models diverge for reasons unrelated to objects. The tool warns when most of the area is steeper than 30 degrees, and readings there should be ignored.
• The Brown County surface model and 3DEP ground model can come from different dates and processing. Misalignment and terrain change can create false edges or heights; inspect the site before relying on the estimate.

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

• Terrain Stats — Summarizes the minimum, maximum, mean and range of ground elevation across an area, with a chart of how much land sits at each elevation.
• Sunlight — Models hours of direct sun across a site on any day of the year, with shadows from terrain up to 1.86 mi away and, where Brown County’s regional surface model has usable data, from trees and buildings.
• 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.