9
Processing Data – Range Alignment
Range alignment is used to combine 2 or more scans, taken from 2 or more tripod positions.
Aligning scans provides several important capabilities:
Doing measurements between two points in two different scans – as if they were
from the same scan. You can click on a point in one range data window, then click
on a point in another range data window, and get the real-world distance between the
two points.
Creating a model from more than one scan. This is used frequently – for filling in
spaces in a room with multiple scans, for getting all sides of an object, or for
scanning multiple rooms and connecting them into a single model.
Displaying annotations created in one file at their correct location in another file.
Range alignment requires two range files with overlapping regions. (Multiple range files can be
aligned – but only two at a time.)
9.1
General Approach
We begin by selecting two range data files that have overlapping regions. Typically (though not
always) you’ll need to align multiple range files to cover an entire scene. You’ll do this by
selecting one aligned file and one unaligned file.
When you created the scene, you identified one range file as the ‘reference’ scan – the scan to
which all others will be aligned. You will begin using this scan and choosing a second,
unaligned scan that overlaps it.
Note: If you did not specify a reference scan when creating the scene, you can do
so at any time. In the Edit menu, select Align -> Choose Reference Scan. This
will list the range files from which to choose a reference scan. Once chosen, that
scan is aligned.
Note: It is often helpful to have a 360
°
‘whole room’ scan to use as a reference
scan. This often provides the needed overlap for range alignment with many
scans.
Once the scans are selected, you align them by picking a small number of pairs of
corresponding points (3-6) in the two scans. (This process is described in the next section.)
These are used as starting points for a process that seeks to minimize the distance between the
points in the two scans. In general, the procedure is fast and simple.
9.2
Range Alignment Procedure
This section will guide you through the steps of range alignment. You may want to work
through this with the sample data, or you can read it in preparation for working with your own
data.
DeltaSphere-3000 3D Scene Digitizer
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