General

Please submit any additional tips to info@kaarta.com for possible inclusion in future revisions of this page.

1.     If you are doing a lot of indoor scanning in extruded tunnels, tight spaces, and small rooms, consider Kaarta Contour. The Velodyne 3D Lidar scanners have a limited vertical field of view which makes these types of areas problematic.

2.     The less occluded the sensor is, the better the results.

3.     For longer scan times when hand held, consider a holster or support to avoid arm fatigue.

4      Start from a stationary position. Allow five seconds after initiating the scan before moving.

5.     Plan your scan.

        a.  Scout the area to be scanned beforehand and plan your route.

        b.  For more complex scans, consider taking some preliminary scans to see how they come out before committing to a longer scan.

        c.  Shorter paths that cross are better than a longer single path.

        d.  If you can scan a place that you will return to, it will decrease overall map drift. For example, in the diagram below it is better to start at 1, rather than 2. If you start at 2, then move to 1 and back to 2 before proceeding.

6.     It is better to overlap scanning areas than to go for longer distances and coming back to the beginning - similar to a lawnmowing pattern.

7.     If the area is very large (>150 meters), then make sure there is some 3D structure in the field of view at all times.

8.     Scanning will fail if there is insufficient 3D structure to match between laser scans. It is better to do two independent maps and try to connect two areas through the flatter area. If you typically scan environments with less 3D structure, consider purchasing Stencil with the feature tracker option.

9.     Ground control points can be used to improve map accuracy. Ground control points should be physically visible in the point cloud and not a flat reflectance target on the ground.

10.    Better to scan with fewer people or moving objects around. They add unnecessary points to the registered cloud.


Handheld

Indoor:

1.    Rotate the Velodyne by slowly rolling and pitching at the beginning of the scan before moving around.

2.    When transitioning between rooms or turning corners, move a little slower to build up new area before proceeding.

3.    Scanning with the lidar scan planes closer to horizontal is the best. Tilting up to 45 degrees is okay when stationary. Definitely do not combine tilting with rotations while scanning.

4.    Do not start scanning in a corner or near a wall. It is better to start in the center of the room.

5.    When ascending/descending stairs orient the sensor parallel to the pitch of the stairs (also see 1.a above).

6.    For large areas, it is best to hold the scanner above your head to get the overall outline of the room. This will help eliminate any drift while walking around.

Outdoor:

1.    For vertical scanning, tilt the lidar up to 45 degrees while standing still, but do not tilt and move around at the same time.

2.    While scanning vertically, ensure there is structure in front of and behind the scanner.

 


Vehicle or Aerial Platforms

1.     Mount LIDAR horizontally.

2.     Don’t occlude the front or back of the sensor.

3.     Don’t fly too high (<15 meters).

4.     Drive or fly only around or over 3D structure. Flat fields will cause the algorithms to fail.

5.     For vehicle mounted applications in particular:

     a.  Start data collects from a stopped position or a low velocity such a less than 15 mph.

     b.  If data collections are started and stopped in the same place, Kaarta has loop closure software which can correct for drift that occurs during data collection.