Terrestrial Laser Scanning Software

RiMTA 3D

for Automated Resolution of Range Ambiguities••automatic resolution of range
ambiguity in time-of-flight
ranging••unlimited number of MTA zones

Acquiring data in terrestrial laser scanning with highmeasurement rates over long ranges frequently resultsin range ambiguities. Instruments with multiple-timearound capability (MTA), like the RIEGL VZ-4000,
include information in the provided data which thepost-processing software can utilize in to resolve theseambiguities. Instead of asking the user to manuallyspecify the correct MTA zone for each data set or evensubset, RiMTA 3D calculates the most probable MTA
zone for each measurement automatically.

••processes data acquired withRIEGL VZ-4000 and VZ-6000
laser scanners

In order to correctly determine the range to the target with LIDAR••smoothly integrated in theRIEGL data processing workflow

pulses requires to correctly determine the correlation of each

instruments using time-of-flight measurements with short laser
received echo pulse to its causative emitted laser pulse. However, at high pulse repetition rates (PRR) and large target ranges
this definite allocation becomes ambiguous due to a limiting
factor which may not be tweaked by engineer‘s skills: the speedof light. At a PRR of 300 kHz the range of unambiguity is limited
to only 500 meters, a measurement distance which is routinely
exceeded by RIEGL terrestrial laser scanners (TLS).
In case of ambiguities, received target echoes may not necessarily be associated with the immediately preceding laser pulse
emitted (MTA-zone 1). Instead, they may be associated withany of the laser pulses emitted previously. For correct
ranging it is therefore mandatory to correlate eachpulse echo with its correct originating laser pulse.

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Ri Software

Preliminary Data Sheet

RiMTA 3D - For Automated Range Ambiguity Resolution
Terrestrial scanning, compared to airborne laser scanning,
introduces an additional level of complexity in the resolutionof ranging ambiguity. It is possible that a single laser pulse
hitting multiple targets, e.g., a nearby target only partly obscuring the propagating laser beam and a remote target,
thus causing echoes in multiple MTA zones. Therefore, theresolution of the ambiguity has to be carried out strictly onan echo to echo basis and not simple on a laser shot basis.
Each target echo is subject to a congruence test measuring also the confidence for the association with the selectedFig. 1

MTA zone. This confidence value, an additional point attri-

Profile of scan data physically present in MTA
zone 1 shown as processed in MTA zones 1-4

bute to each point of the resulting point cloud, allows theuser to filter the data and thus to clean up the point cloud byrejecting statistical outliers.
RIEGL utilizes a novel modulation scheme to the train of emitted laser pulses and unique techniques in high-speed signal
processing thus enabling range measurements without any
notable gaps between the MTA zones within the instrument‘smaximum measurement range.
For an optimized workflow, RiMTA 3D is seamlessly integrated
into RiSCAN PRO, thus maintaining fast processing speeds formass data production.

Fig. 2Top view of data acquired by RIEGL VZ-6000
at 50 kHz with data from 3 different MTA zones

Fig. 3

Data visualized by (from left to right) reflectance, target range, multiple
echoes ID, MTA confidence, true color, and pulse shape deviation

RIEGL Laser Measurement Systems GmbH, 3580 Horn, Austria
Tel.: +43-2982-4211, Fax: +43-2982-4210, E-mail: office@riegl.co.atRIEGL USA Inc., Orlando, Florida 32819, USA
Tel.: +1-407-248-9927, Fax: +1-407-248-2636, E-mail: info@rieglusa.com
RIEGL Japan Ltd., Tokyo 1640013, Japan
Tel.: +81-3-3382-7340, Fax: +81-3-3382-5843, E-mail: info@riegl-japan.co.jp

www.riegl.com
Information contained herein is believed to be accurate and reliable. However, no responsibility
is assumed by RIEGL for its use. Technical data are subject to change without notice.

Preliminary Data Sheet, RiMTA 3D, 08/10/2012