Graphics Programs Reference
In-Depth Information
Deciding on an exterior or Interior Scan
Knowing whether you need an exterior or interior scan is important because it will largely
determine the type of scanning equipment you should use or request from your service
provider. If your project is exterior in scope or requires you to collect information that is more
than 80ʹ (24 m) away from the scanner, then you will want to use a time-of-flight scanner. If your
project is an interior space that is limited to shorter lines of sight, you will want to use a phase-
shift scanner because of the high-speed data-collection capabilities at short range.
Scanner Interoperability
There is no rule that says that you can't use a time-of-flight scanner in an interior environment or
a phase-based scanner in an exterior setting. however, the scanners are somewhat purpose-built
for optimal operation within the environments that suit them. The recommendation is to use the
right scanner for the right project to achieve the best return on your investment.
Determining the Level of Detail
This is typically the most difficult factor to determine. This is also one of the largest cost drivers
for a LiDAR project, and if it's misunderstood or specified incorrectly, there is a risk that the
scan won't meet your needs. Not planning for enough detail might lead you to scan again,
while planning for too much detail will result in receiving way too many points, huge files, and
unwieldy point clouds.
There are two levels of detail in LiDAR project delivery:
Point Cloud Level of Detail
This will affect the amount of field collection time. A higher
level of detail = more field time = higher cost.
Level of Detail of the Derivatives
What is the smallest scale of things you'll want in the
scan? This will affect the amount of processing and modeling time and typically refers to
the lowest level of modeling detail. An example would be specifying scanning all pipes
greater than or equal to 6ʺ (150 mm) diameter. Again, a higher level of detail = more modeling
time = higher cost.
You must have a good grasp of your project needs when planning for LiDAR data collection
and modeling so that you can convey the requirements to those conducting the scan. Unclear
direction to a service provider can cause enormous blows to schedule and budget. For example,
if you call a LiDAR service provider and say, “I need to have LiDAR collected on my project and
I need it delivered as a 3D as-built model,” that can mean many different things. You need to
take the time to clearly specify the project requirements so that the provider doesn't spend two
months modeling an entire building when you needed only the door and window openings.
Using Imagery
Some scanners have built-in digital cameras that take panoramic photos and stitch them
together. The colors from the photos can then be draped onto the point clouds to give
them a “true-color” appearance. Some scanners do not have a built-in camera and will deliver
a point cloud in black-and-white pixels. This requires the service provider to collect the imagery
