Sunlight

When to use it

• Checking winter sun on a house site, a deck or a garden before you buy or build.
• Comparing sunny and shaded parts of a block for planting or stock.
• Seeing when the sun first reaches a valley floor and when it leaves.

How to use it

1. Select a property, draw an area or upload a boundary.
2. Pick a date: the shortest day, an equinox, the longest day, or any date you type.
3. Choose bare ground, or the LiDAR surface so trees and buildings cast shadows too.
4. Run. Read total hours, first and last sun, and step through the day half an hour at a time to watch the shadows move.

How it works

The sun's position is computed for the chosen date at each half-hour step. For every cell the tool traces a ray toward the sun and checks whether any terrain within 3 km rises above it. If nothing blocks the ray the cell is lit for that step.

Hours of sun are the count of lit steps. With the surface option the LiDAR surface model, which includes canopy and roofs, is used as the blocking surface instead of bare ground.

Reading the results

Winter (21 June) is the test that matters for a house site. A north-facing slope with an open northern horizon will show the most hours.

First and last sun are the clock times the sun first clears and finally drops behind the horizon for that cell.

Limits and warnings

• Direct sun only. Cloud, haze and diffuse light are not modelled.
• Shadows from things further than 3 km away, such as a distant range, are ignored. In deep valleys the true horizon may be further out.
• The surface model is only available where LiDAR has been flown, and shows trees as they were on the capture date.

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

Related

Neighbouring tools

• 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.
• 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.
• Viewshed — Shows which ground within 1 to 10 km can be seen from a point, for a chosen eye height, with earth curvature and refraction allowed for and, optionally, trees and buildings blocking the view.