Wisconsin Elevation ToolsOpen Slope & Aspect on the map →

Terrain · Select a property, draw a box or polygon, or upload a boundary

Slope map: how steep is my lot?

This slope map shows how steep every part of a Wisconsin lot is, from the USGS 3DEP lidar elevation model, and which way each face points. The panel breaks the site into slope classes, so “how steep is my lot” gets a number instead of a guess.

Slope decides whether a site is easy to build on, where retaining walls and cut and fill will be needed, and whether the county may ask for a geotechnical report. Aspect decides how much winter sun the ground gets.

Free to run · pay to download

See the full result on the map free, with no account. Download the slope or aspect grid as a GeoTIFF with a pass: US$29 for 24 hours, US$99 for 30 days or US$399 for 12 months, a one-off payment in US dollars that never renews. Every download on the site is included while the pass lasts.

Open Slope & Aspect on the map →Pass prices and what’s included

Who uses this

  • Buyers. Know how much of a lot is actually buildable before making an offer.
  • Architects and permit applicants. Describe the site slope for a design brief or a conversation with the county.
  • Farmers, ranchers and foresters. Find the ground too steep for equipment or prone to erosion.

When to use it

  • Checking whether a lot is buildable and where excavation or retaining walls will be needed.
  • Assessing pasture, orchard, vineyard or timber ground for sun and equipment access.
  • Answering a building permit or county planning question about slope.

Tools for your job

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

For the job: Solar panels and sun

Where will panels, a greenhouse or a deck get the most sun?

  1. 1.Sunlight — Hours of direct sun on any date, with terrain shadows from up to 1.86 mi away. Start with December 21.
  2. 2.Slope & Aspect (this tool) — The aspect view shows which faces point south, and the slope view how steep the mounting ground is.
  3. 3.Find Matching Areas — Highlights the ground that is flat enough, faces the right way and gets a minimum of winter sun, all at once.
  4. 4.Object Heights — Tree and building height estimates where Brown County surface data is usable; inspect shading on site elsewhere.

For the job: Choosing a house site

Where on this property should the house go?

  1. 1.Find Matching Areas — Narrows the property to the patches that are flat, sunny and facing the right way.
  2. 2.Slope & Aspect (this tool) — Shows gentler and steeper ground for a designer to assess.
  3. 3.Sunlight — Checks winter sun on the candidate pad, hour by hour.
  4. 4.Cut & Fill — Estimates the excavation to level the pad before you ask for bids.
  5. 5.Viewshed — Models terrain visibility from a chosen eye height; surface blocking is regional.

For the job: Farms, ranches, orchards and timber

Which ground suits which use?

  1. 1.Slope & Aspect (this tool) — Equipment limits and erosion-prone slopes.
  2. 2.Sunlight — Frost pockets and shaded slopes in winter.
  3. 3.Wetness Map — Wet-tolerant planting in the blue, drought-tolerant on the tan.
  4. 4.Landforms — Exposed ridges, sheltered hollows and well-drained spurs.

How to use it

  1. Select a property, draw an area or upload a boundary.
  2. Run the analysis. Switch between the Slope and Aspect views in the panel.
  3. Read the class breakdown in the panel, or download the slope or aspect grid as a GeoTIFF for GIS. Downloading needs a pass.

Step by step: Devils Lake

We map slope across Devils Lake, from the shore up onto the bluffs.

1.Zoom to the area or select a property, then choose Preview on map.

2.Green is gentle, red is steep. The panel gives the mean slope for the area. The red bands are the bluff faces and talus slopes.

3.Zoom in for detail. The maximum is often a few cells on cliffs or road cuts, so read the colors rather than the single maximum figure.

What it showed

  • As a rough guide, under 10° is easy building ground, 10–20° usually means cut and fill or a split-level design, and over 25° calls for a geotechnical engineer.
  • Switch to Aspect to see which faces point south.
Try it yourself on Devils Lake →

How it works

For every terrain cell the tool fits a plane through the eight surrounding cells of the USGS 3DEP bare-earth model. The tilt of that plane is the slope, in degrees and percent; the downhill direction is the aspect, as a compass bearing.

Slope classes and aspect sectors are then tallied as shares of the analyzed area.

Reading the results

As a rough guide, under 10 degrees is easy building ground, 10 to 20 degrees usually means cut and fill or a split-level design, and over 25 degrees calls for a geotechnical engineer. Your county’s rules set the actual requirements.

The flat share is ground too level to have a meaningful aspect, and is reported separately.

In Wisconsin, south-facing slopes get the most winter sun and north-facing slopes the least.

Limits and caveats

  • Areas up to 7.5 miles per side; large areas are sampled more coarsely, which smooths out short steep banks.
  • 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.
  • Slope is of the bare ground. Retaining walls, buildings and vegetation are stripped out of the elevation model.

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

What slope is too steep to build on?

As a rough guide, under 10° is easy building ground, 10–20° usually means cut and fill or a split-level design, and over 25° calls for a geotechnical engineer. Your county or city sets the actual rules for steep-slope development; check with the planning department.

Can I use this slope map for a building permit?

It helps you understand the site and brief a designer. What the permit application itself needs is up to your county or city, and many want slope shown on surveyed plans.

Can I download the slope map?

Yes. The slope or aspect grid downloads as a GeoTIFF for QGIS, ArcGIS or any GIS, with slope or aspect in every cell. Running the analysis and saving a PNG of the view are free; the GeoTIFF needs a pass.

Ready to try it?

Open Slope & Aspect on the map →

Free to use, no account. The analysis runs in your browser on public-domain USGS 3DEP data. Downloading the results needs a pass: see pricing.