Registration with Survey Targets

Registration to a survey control points using survey targets is achieved by one of two methods: scan-to-scan or scanproject-to-control.

	Import a survey control network
Import a .csv file containing survey coordinates acquired using standard survey equipment and methods. See more about Survey Control Points. (A control network may be created from identifiable features located in a Computer Aided Design model.)
	Import survey target locations
Import a csv file containing survey target coordinates captured by reality capture data methods. This data eliminates the need to "mark" the targets manually before registration.
	Compute the registration
Once enough targets on each each scan are marked, select some or all of the scans and compute the registration. If some scans fail to register, use "Ctrl+Z" to undo the registration transform. Confirm the position of the targets, mark additional targets that overlap adjacent scans, and recompute the registration.
	Results and reporting
Registration results are reported in excel. For each survey point the number of markers used in registration and the RMS variance is recorded.

"scan-to-scan" registration

In the scan-to-scan method, a collection of unregistered LIDAR scans, with visible survey targets, are located onto an imported survey control network achieving scan-to-scan registration with survey control over a large area.

Start by placing markers on visible targets in each scan. Use the ScanData Cycler button on top of objectlister to setup each scan one-by-one. Only scans visible in the Object Lister, are cycled through, others are ignored. Once a scan is loaded, zoom into the survey targets using mouse wheel. Use the "Alt" key to place the registration marker at the cursor location. Manual entry of the Target ID is optional.

Once enough targets on each each scan are marked, select some or all of the scans and compute the registration. If some scans fail to register, use "Ctrl+Z" to undo the registration transform. Confirm the position of the targets or mark additional targets that overlap the adjacent scans and recompute the registration.

"scanproject-to-control" registration

A scan project containing multiple LIDAR range images previously registered, or any unified point cloud model, can be located to a survey control network by marking three or more corresponding targets within the scan data model.

With a typical registered LIDAR project, begin by selecting all scans and lock the transform, then group the scan under one node. Registration of the group is as a single scan or unified model. select this group node when calculating the registration. After transform to the control point the cloud-to-cloud registration will be maintained.

Place corresponding markers on visible targets in a selected scan using the ScanData Cycler button on top of objectlister. Once a scan is loaded, zoom into the survey target using mouse wheel. Use the "Alt" key to place the registration marker at the cursor location. Manual entry of the Target ID is not required.

Object selection for workflows

Scans with survey targets and survey control network

Select the unlocked scans and make the survey control network visible.

Scans with Spherical targets

Select the scans with spherical targets. If all the scans are unlocked, then first scan is considered locked and others are registered to it.

Scans with Mix of Spherical targets and Survey targets

The survey targets and spherical targets can be freely mixed together to compute registration.

Registered Scans with another set of Registered Scans

Register, a set of scans registered together (Set1) with another set of registered scans (Set2). Follow this workflow:

Group scans of set1 together (Group1), and also group scans of set2 together (Group2).
Lock Group1 and keep Group2 unlocked. As a check verify that both Group1 and Group2 now contain scans inside that are registered to each other within the set and locked.
Select both Group1 and Group2, and calculate.

Note that either of set1 or set2 could have been registered with spherical targets, survey targets or mix of both. Also when Group1 is locked, there can be other groups such Group3, Group4 etc that can be registered together.

Registered Scans with Survey Control Network

Group each set of registered scans into its own group node in objectlister. Keep each group unlocked, select the unlocked group node and calculate registration.

Advanced topics

Often the scandata from sensor mounted on a drone or non-terrestrial scanners is noisy, or has considerable distortion. In such cases, you may need to increase the matching tolerance. The current maximum tolerance is 0.010m (10mm). Say if you need to increase it to 0.2m for drone data, you can type this command in the command prompt in the bottom left corner of main window (ensure there are no extra spaces):

SystemVar --key "Registration/Stitching_Tol" --value 0.200 --type_float

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