When to use it

Checking whether a site is buildable and where earthworks or retaining will be needed.
Assessing pasture, orchard or vineyard ground for sun and machinery access.
Answering a building consent or resource consent question about slope.

How to use it

Select a property, draw an area or upload a boundary.
Run the analysis. Switch between the Slope and Aspect views in the panel.
Read the class breakdown in the panel, or download the raster for GIS.

How it works

For every terrain cell the tool fits a plane through the eight surrounding cells of the 1 m LiDAR bare-earth model. The tilt of that plane is the slope, in degrees; the downhill direction is the aspect, as a compass bearing.

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

Reading the results

Under 10 degrees is generally easy building ground. Ten to 20 degrees usually means cut and fill or a split-level design. Over 25 degrees expect geotechnical input.

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

North-facing slopes get the most winter sun in New Zealand; south-facing slopes the least.

Limits and warnings

Areas up to 12 km across; large areas are sampled more coarsely, which smooths out short steep banks.
Where 1 m LiDAR has not been flown the tool falls back to the national 8 m elevation model, and the result says what share came from the fallback. The 8 m model was interpolated from 20 m map contours and is not fit for site-scale decisions.
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 LINZ national 1 m LiDAR bare-earth elevation model, read in your browser, with the national 8 m model filling any gaps. Tools that use the surface model (Sunlight, Viewshed, Object Heights) read the matching LiDAR surface tiles.

Elevation and cadastral data is sourced from the LINZ Data Service and licensed for re-use under the Creative Commons Attribution 4.0 International licence. Copyright in each LiDAR survey belongs to the body that commissioned it — a regional or district council, Waka Kotahi, NIWA and around thirty others — rather than to LINZ, which hosts and processes the national dataset. Every file exported from this site names the licensors whose surveys cover the area, and anything you publish from those files carries the same attribution requirement. See https://www.linz.govt.nz/products-services/data/licensing-and-using-data/attributing-elevation-or-aerial-imagery-data

Find Matching Areas — Highlights every patch of ground inside your area that is flatter than a chosen slope, faces a chosen direction and gets at least a chosen number of hours of winter sun.
Contour Lines — Draws topographic contours at any interval from 0.5 m upward across your area and exports them for GIS, CAD, Google Earth, print or laser cutting.
Cut & Fill — Estimates how much earth would be cut and how much filled to level your area to a flat platform, at a height you set or at the height that balances the two.
Landforms — Classifies every part of your area into one of ten landforms, such as ridge, spur, slope, hollow and valley, at a scale you choose.

Guides

Slope Maps for Building on Sloping Land

Slope & Aspect