Using Targets

When capturing data of a site there must be known scale targets or survey point targets placed within the scene. These targets are used to set an accurate scale, reduce drift in the final output, and allow for alignment of the model. We provide a set of scale plates which should always be used, an optional origin plate to define a local coordinate system, and a set of control point markers which can be used when three or more control points are available.

We recommend always using surveyed control points when attempting larger captures of over 1000 square metres.

Note: With all markers it is vital they do not move during a scan. They must be stationary to prevent geometric errors in the final model. Do not collect any of the targets until capture of the scan has finished and place them in locations where they will not be moved by accident.

Scale plates - easy use

Our standard set of eight unique scale plates should be placed as evenly as possible around the site. We suggest trying to ensure the distances between targets are no more than 20 metres to minimise accumulation of drift in the scan. They may be placed in any convenient location. Leaning them against a wall can help maximise visibility.

If you are using the optional square origin plate, it can be placed flat on a level surface to define an origin point for the scan and vertical direction when not using a supported 360 camera.

For improved accuracy on larger captures and around repeating structures such as stairwells you may also use the control point targets described below, but without surveyed ground truth positions . These should be placed in locations with good visibility as shown below. It is important that these markers be secured if you are in a windy outdoor environment to prevent them moving during the capture.

If you are using an Insta360 camera with the Sensori app, Insta360 app, or GPS remote, the captured geometry will be georeferenced using approximate GPS data.

Control point targets - advanced use

These markers allow the captured geometry to be aligned with surveyed control points, providing accurate geo-referencing and drift correction. They should be placed around existing retro markers or bolts in the scene with known accurate positions. When uploading the captured video data for a scan, you will also need to provide a csv file listing the coordinates and target ID for each control point marker (described on the control point format page). We recommend leaving these markers in place if possible so that successive scans can be captured without updating the marker coordinates.

Notes on target placement:

• You might need to secure the targets to the ground or other surface to prevent them moving in the wind for outdoor captures.

• Using double sided tape is useful when fixing control point markers to walls, though if left too long this may rip off paint, so take care.