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LiDAR and terrain in QGIS

This exercise starts with one specific source: the New Zealand LiDAR 1m DEM published by Toitū Te Whenua LINZ. A DEM is a raster of ground elevation. For ordinary terrain analysis, use the DEM rather than starting with the raw LiDAR point cloud.

Direct dataset: New Zealand LiDAR 1m DEM

LINZ overview: Access elevation data

1. Download only the area you need​

The national 1 m DEM is very large. Do not try to download all of Aotearoa for a local exercise.

  1. Open New Zealand LiDAR 1m DEM.
  2. Sign in to LINZ Data Service if the site asks you to sign in before exporting.
  3. Click Map + if the dataset is not already displayed on the LDS map.
  4. Zoom to the whenua, marae locality, awa reach or other study area you want to analyse.
  5. Click Crop above the map.
  6. Choose Crop by rectangle.
  7. Draw or resize the crop rectangle around the study area. Include a small buffer around the edges so later terrain operations are not cut off exactly at the boundary.
  8. Click Export.
  9. Choose a raster download format that preserves the DEM, normally GeoTIFF where offered.
  10. Choose NZGD2000 / New Zealand Transverse Mercator 2000, EPSG:2193 if the export dialog asks for a projection.
  11. Start the export and download the resulting ZIP/file.
  12. Extract the download into your project's 01_source/elevation/ folder.
  13. Keep this original download unchanged.

If LDS changes the wording of a button, the current official download process is documented at Getting started with LDS.

2. Add the DEM to QGIS​

  1. Open the QGIS project.
  2. Choose Layer → Add Layer → Add Raster Layer….
  3. Click the browse button beside Raster dataset(s).
  4. Select the downloaded .tif DEM file.
  5. Click Add, then close Data Source Manager.
  6. Right-click the DEM in the Layers panel and choose Zoom to Layer(s).

You should see a greyscale terrain raster. If QGIS asks you to choose a CRS for a LINZ national 1 m DEM file that should already contain CRS information, stop and inspect the file metadata rather than guessing.

3. Check the DEM before analysing it​

  1. Right-click the DEM and choose Properties.
  2. Open Information.
  3. Confirm the horizontal CRS is EPSG:2193 for the national product.
  4. Record the pixel size. The national product is nominally 1 m.
  5. Record the source dataset and access date in the project source register.
  6. Record the vertical datum as NZVD2016 for the current national LINZ product. If you use an older regional dataset instead, read that dataset's metadata because the vertical datum can differ.

The ordinary 2D CRS shown by QGIS does not tell the whole vertical-reference story. Keep the vertical datum in your project notes.

4. Clip the DEM to your exact study boundary​

If the LDS crop already produced a small rectangle, you can work directly with it. If you have a polygon for the actual whenua or catchment and want a tighter analysis raster:

  1. Make sure the boundary polygon is loaded in QGIS.
  2. Open Processing → Toolbox.
  3. Search for Clip raster by mask layer.
  4. Open GDAL → Raster extraction → Clip raster by mask layer.
  5. Set Input layer to the downloaded LINZ DEM.
  6. Set Mask layer to the study-area polygon.
  7. Tick Match the extent of the clipped raster to the extent of the mask layer if available.
  8. Save the result as 02_working/dem_study_area.tif.
  9. Click Run.

Keep the original LINZ DEM in 01_source. Use the clipped copy for the remaining steps.

5. Create hillshade​

  1. Open Processing → Toolbox.
  2. Search for Hillshade.
  3. Open the GDAL hillshade algorithm.
  4. Set Input layer to dem_study_area.tif.
  5. Leave the initial azimuth and altitude at their defaults for the first output.
  6. Save the result as 02_working/hillshade.tif.
  7. Click Run.

Put the hillshade below your important vector layers. Hillshade is a visual derivative. It is not a new source of elevation values.

6. Create slope in degrees​

  1. In Processing Toolbox, search for Slope.
  2. Open the GDAL slope algorithm.
  3. Set Input layer to dem_study_area.tif.
  4. Make sure the output is in degrees, not percent, for this exercise.
  5. Save it as 02_working/slope_degrees.tif.
  6. Click Run.

To inspect a slope value, select Identify Features and click the slope raster.

7. Style the slope layer​

  1. Double-click slope_degrees in the Layers panel.
  2. Open Symbology.
  3. Use Singleband pseudocolor.
  4. Choose a small number of classes appropriate to the exercise.
  5. Put degrees in the legend or layer name so nobody later reads the numbers as percent slope.

For a papakāinga teaching exercise, you might display 0–5°, >5–10°, >10–15° and >15° as comparison bands. Those bands are teaching categories, not automatic engineering or planning thresholds.

8. Create contours​

  1. Open Processing Toolbox and search for Contour.
  2. Open the GDAL contour algorithm.
  3. Set the input raster to dem_study_area.tif.
  4. Set an interval suitable for the scale. Start with 2 metres for a small local example and adjust if the lines are too crowded or too sparse.
  5. Set the elevation attribute name to ELEV if QGIS asks for one.
  6. Save the output into 02_working/course.gpkg or another project GeoPackage as contours_2m.
  7. Run the tool and inspect the result.

The contour interval is a display/derivation choice. It is not the stated accuracy of the source elevation data.

9. Check the outputs​

Before using the terrain layers in a hui map or analysis, confirm:

  • the original LINZ download is still untouched in 01_source
  • the project and terrain data align with parcels and imagery
  • the source is recorded as the New Zealand LiDAR 1m DEM, not simply DEM
  • EPSG:2193 and NZVD2016 are recorded
  • slope units are stated
  • filenames distinguish source data from derived data

A useful final layer stack is:

study boundary / whenua
parcels and other vector context
contours_2m
slope_degrees or hillshade
LINZ aerial basemap

Continue to Terrain derivatives or the QGIS practical course.

Last reviewed: 27 August 2026

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