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Q1:
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What is LiDAR?
LIDAR
(Light Detection and Ranging) is an optical remote sensing
technology analagous to Radar. The range (distance) to
an object is determined by measuring the time delay between
transmission of a pulse and detection of the reflected
signal. The scanner also measures the horizontal and vertical
'direction' of the laser beam.
Q2:
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Can I still have conventional AutoCad drawings?
Yes.....We
have software that allows us to bring the point cloud
into AutoCAD and using this we can produce conventional
topo surveys, floorplans, elevations and section drawings.
We can also produce 3D models from the point cloud data.
For
topographic work we use the Leica Topo II survey program,
which allows the CAD operator to become a 'virtual surveyor'
and this allows us to produce standard topographic survey
drawings.
Some
examples of our work can be seen in the gallery
Q3:
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Why use Laser Scanning?
Laser
scanning is ideal for many projects, because it is very
fast and can provide a much more complete data set than
conventional survey work. Point clouds can yield higher
levels of detail than would be possible to survey conventionally
and this produces more detailed elevations and more accurate
volumes.
In
our experience, clients have been impressed by the speed
at which additional products can be provided and because
scanning data is more complete, the need to return to
site for additional information is reduced. In scanning
a cliff face for example, our brief was to produce 20
sections through the cliff. After the fieldwork was complete,
the client requested some additional sections. Because
the cliff was laser scanned, we were able to produce the
sections wherever needed without a costly return to site.
As
we do conventional survey work as well, we are ideally
placed to combine techniques in order to reduce costs
and work efficiently.
Q4:
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I know the scanner has a built in camera, what additional
benefits does this offer?
The
scanner has a built in camera, which allows us to colour
the point cloud by the images taken. The built in camera
provides low resolution photography, but Merrett Survey
also use a 10 mega pixel camera to record a 360 degree
panoramic view from the scanner's position after the scan
has finished.
As
well as offering this panoramic image to help clients
to understand the site, we can use the Leica TruView software
to provide an innovative method for taking measurements
from the photograph. This web enabled panoramic point
cloud viewer lets you view, pan, zoom measure and markup
point cloud data over the Web. Instantly sharing data
with your colleagues anywhere in the World.
Q5:
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How accurate is laser scanning?
The
accuracy will depend on the type of scanner that we use
and the specific nature of the job. The Scanstation 2,
for example, delivers survey grade accuracy for each measurement.
Its ultra-fine scanning and small laser spot size allow
for accurate registration (joining together) of scans.
The
distance accuracy of a single point at 50m is 6mm and
for a modelled surface, the accuracy can be increased
to 4mm. The big advantage the Leica ScanStation2 has,
is that it integrates the same one-second resolution,
dual-axis (tilt) compensator as in total stations. It
can be used with traditional traverse and resection workflows
for additional time savings in the field and office.
Highway
surfaces can be surveyed with a vertical accuracy of better
than 7mm.
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