Designing on a Drone Capture

Overview

Bring a point cloud of the real site, from a drone or a laser scan, and see your design on it: the actual ground, the neighbouring buildings and the trees, rather than what public data says about them. The capture is cropped to the site, placed on the map in the right spot, and shown behind your design.

The Check and the pipe designs measure from it: the ground levels, the neighbours' heights and the existing trees. In the City of Melbourne, the Check already has the neighbours' measured heights and the council trees without a capture (see Rules and checks).

Adding One

1. In Build, open a site and find Drone capture. Choose Add a drone capture. You need to be signed in.
2. Pick the file: LAS, LAZ, E57 or PLY, up to 2 GB.
3. Say what its heights are:
   • As the file says: converted to AHD when the file names its height datum. Otherwise they're kept as they are.
   • Already AHD: the capture was processed with ground control or survey marks on AHD.
   • GPS heights: flown without ground control, so heights are on the ellipsoid. They're converted to AHD with AUSGeoid2020, about 5 m lower in Melbourne.
4. Upload. Big files go up in pieces; if the connection drops, choosing the same file again picks up where it stopped.
5. Our server converts it, which takes a few minutes for a large capture:
   • it puts it on MGA2020 (the site's zone) with AHD heights;
   • it crops it to the site plus 50 m;
   • it removes stray points, and thins it evenly if it's over 40 million points.
6. Show on this site.

If the file doesn't say which coordinate system it's in, you'll be asked. It's in the drone software's export settings or its project report. A capture in a local grid, with no coordinate system at all, can't be placed yet.

Sites in the City of Melbourne: the City's Own Capture

The City of Melbourne publishes a point cloud of the whole municipality: photogrammetry from May 2018 at 7.5 cm, with colour and AHD heights, accurate to about 25 cm. For a site inside the municipality, Drone capture offers Use the City's 2018 capture, so you don't need a drone.

• Only the pieces around your site are fetched: the city comes in 500 m tiles, and a site usually needs one to four of them.
• They go through the same steps as an upload: cropped to the site plus 50 m, put on MGA2020, and shown behind your design.
• The capture is credited to the City wherever it shows.

It's from 2018, so anything built since isn't in it.

Showing It

Under the site, Drone capture has:

• Show: turn it on or off.
• Colour:
  • Photo (the capture's own colours, when it has them);
  • Height (purple low to yellow high);
  • Class (ground, vegetation, buildings, when the capture is classified).
• Fade: see the design and the map through it.
• Remove: takes it off the site and deletes it from our server.

The capture stands on the ground like your design: its ground level (the lowest points across the site) is put at the map's ground.

Each account has 5 GB for captures.

What It Measures

Once converted, the capture is also measured. You'll find these under the site's Drone capture:

• The ground. The capture's own ground classes when it has them. Otherwise, the points that lie on the best ground model we hold for the site, which is Geoscience Australia's 5 m LiDAR terrain (the City of Melbourne's 1 m terrain where it covers). So a big flat roof can't pass for ground. Where neither is available, PDAL's cloth simulation filter is used. Ground the capture couldn't see, under roofs, is filled from the reference terrain.
• Contours every 0.5 m and spot levels every 10 m (AHD). Turn Ground contours on to see them on the map. They're also on the site plan, inside the site, with heavier lines every 2.5 m, in the PDF and in the DXF, where each contour sits at its height.
• Trees. Crowns are found where the height above ground forms a round dome at least 3 m high; with a coloured capture, it must also be green. Add the trees found on the site adds them as existing trees with their crown spread, kept, so the Check counts their canopy and protects them. Trunk diameters can't be measured from above, so the protection zone is estimated from the crown.

Two more things use what the capture measured:

• The neighbours' heights. The Check measures each neighbouring building's height from the capture (the roof, not the chimney) and uses it for overshadowing and overlooking. The Check says how many heights came from the capture. The City's 2018 capture only fills in buildings the City's 2023 footprints didn't measure, because those are newer.
• Stormwater and sewer levels. Pipe depths start from the capture's ground, rather than the 5 m public terrain, and the design's sources say so.

A capture shows the site as it was when it was flown. The City's 2018 capture of a lot that's vacant now may still show the buildings that stood there then.

Exporting From Drone Software

Ground control points on MGA2020 and AHD give the best result. Without them a drone's GPS can be a metre or two out sideways.

Sources