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Scan Network Creation

This article explains building the scan network, the concept behind the network pairs and how they are defined in setup of a job.

Currently the registration algorithm must be told which pairs of scans to use for registration (in practice, the scans would contain overlapping regions of the scanned scene). This information is provided to the algorithm by the user through the scan network tool during project setup. This process is easiest done by recording the rough placement of scans in the field and then using that sketch map to define the pairs in the tool, which allows the import.

The Scan Network can be edited after the initial project setup, when needed, from the ‘Edit Scan Network’ button by ‘Start’ on the Configuration tab or from the Tools menu.

Add Scans

From the New Project dialog select a project location and then press ‘Add Scans…’.

This will open the Scan Network Creation window as below:

Firstly, add some scans to the project by clicking Add Scan(s) and picking the required data from your file system in any of the supported file formats. They should appear in the right-hand list ready to be formed into a network. All scans included in this list must be added to the network to continue, so if some are not required select them and press delete scan to remove them from the project.

To remove a scan from a level, right-click on the scan and select ‘Remove’. This will send it back to right-hand list so it can be placed on a different level or removed from the project.

Adding Underlay Image

To make placing the scans easier, an underlay image can be added to each level either on creation of a new one or by editing the level.

Create Network

To create the network, drag scans onto the level view on the left or double-click in the level view to add the scan at the top of the list.

If the markers are too large they can be scaled with the slider at the top.

Right-Click and drag = Pans the level

Mouse Wheel = Zooms the level

When the scan positions are laid out you can draw connections between them to create the network. Creation and removal of links can be done in three ways. Either:

  1. Right-click and drag between scans
  2. Right-click -> Connect To -> [Level Name] -> [Scan Name]
  3. Double-Click one scan to select it, then double click the second scan to create a connection to it

The rules governing the network are fully described below and must be followed for a successful job creation. The software will give an error if saying how to correct it if these rules are violated.

The main rule is:

  • The network must form a tree, so loops or isolated separate fragments are not currently allowed.

Once the network is completed, click ‘Finish’ which will bring up the configuration options and start button.

Tooltips
Hovering over a scan allows you to see the connections in a tooltip.

Connecting between levels

Sometimes it is necessary to connect between levels, such as a project with multiple floors.

To do this right-click on the scan that needs to be connected select ‘Connect to’ and then the Level Name and then Scan Name to be connected to:

Once the connection is made the scan icon will have a multi-floor tag and the tool tip will state the scan and floor of the link as well.

Setting the root or home scan

Vercator will automatically calculate the optimal root or home scan. However a user may require a specific scan to be the origin of the coordinate system. In this case the user can manually force the root scan by right-clicking and selecting ‘Set as root’. This will change the icon to a house to indicate the selection.

Scan Pairs Concept

The linkages between scans when building the network must conform to certain rules as described in this section. Below is an example of building the network:

Vercator - Scan Pairs Diagram
Consider the scene shown above. This consists of a room connected to a corridor, with some obstruction in the centre of the room. Ten scans whose locations are indicated by the circles with letters A-J are taken. The arrows connecting the circles show the pairwise scans used for registration and the connections chosen between them to form the network following the rules below, especially about not loops.

Scan Pairs Rules
– The scan pairs must form a single “tree” or network with one or more branches. Currently multiple trees, or disconnected sub-trees/scans are not supported.
– The “tree” must contain one root or home scan (scan E in the above example). This is the “root” of the “tree” and can be considered the global origin. Ideally this should be fairly central to the network so that the branches of the tree are fairly equal. This is calculated automatically but can be forced by the user if needed.
– The tree or network cannot contain loops.