When to use it

Finding candidate house sites or building platforms on a rural block.
Locating flat, sunny ground for a shed, a glasshouse, an orchard block or solar panels.
Screening a large property down to the few places worth walking.

How to use it

Select a property, draw an area or upload a boundary.
Set the maximum slope in degrees, the facing direction (or Any), and the minimum winter sunlight in hours.
Run analysis. Matching ground is drawn in green; everything else is grey.
Tighten or loosen the criteria and run again until the highlighted patches are a useful size.

How it works

Slope and aspect are computed for every terrain cell from the 1 m LiDAR bare-earth model. Direct sun hours are modelled for 21 June, the shortest day, by tracing the sun across the sky and checking whether terrain up to 3 km away blocks it at each step.

A cell matches only when all three tests pass: slope at or under the limit, aspect within 45 degrees of the chosen direction, and sun hours at or above the minimum. Flat ground has no aspect, so it only passes the direction test when Any is chosen.

Reading the results

Matching area is the total in square metres and as a share of the analysed ground. Small isolated green cells are noise; look for connected patches big enough for what you are planning.

Because sun is modelled on bare ground, a patch shaded by a shelterbelt or a neighbour's house can still show as sunny.

Limits and warnings

Terrain criteria only. Not a check of zoning, setbacks, geotechnical stability, access, services or flood hazard.
Areas up to 12 km across. Larger areas are sampled more coarsely, so small platforms can disappear; select a smaller area for detail.
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.

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

Slope & Aspect — Maps how steep every part of your area is and which compass direction each face points, with a full breakdown of slope classes and aspect shares.
Sunlight — Models hours of direct sun across a site on any day of the year, with shadows from terrain up to 3 km away and, where LiDAR has been flown, from trees and buildings.
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.
Saved Properties — Keeps up to five places in your browser and compares their elevation, slope, winter sunlight and drainage side by side.

Guides

Slope Maps for Building on Sloping Land

Find Matching Areas