Related Topics; Gnss Management: Velocity & Displacement Engine; Background Information - Leica GR30 Online Help Manual

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GNSS management: Wake-up sessions
GNSS management / Site name and coordinates
GNSS management: Velocity & Displacement Engine

Background Information

Leica VADASE also referred to as Velocity & Displacement Engine (V&DE) allows detecting velocities and displacements of the
receiver's antenna position on the order of some cm/s and cm, respectively, without the need of using any kind of real time correction
streams or services. If enabled, the estimated velocities and displacements can be streamed or logged using two new NMEA-type
messages referred to as Leica Geosystems velocity measurement – LVM and Leica Geosystems displacement measurement –
LDM message. In addition, while the V&DE is enabled, for each detected displacement, the start time, end time and total amount of
displacement during this period will be reported in the Event log messages.
The Velocity & Displacement Engine requires an accurate (≈ cm) receiver reference position for precise
velocity and displacement calculations.
The Velocity & Displacement Engine cannot be used in parallel with an activated incoming real time data
stream.
To enable the Velocity & Displacement Engine the "GRL 124 Velocity & Displacement Engine" license option
is required.
The idea behind the Leica Velocity & Displacement Engine relates to the research of the University of Rome "La Sapienza" Geodesy
and Geomatics division and is known as the "Variometric Approach for Displacement Analysis Standalone Engine (VADASE )" and is
subject to a patent. This is to estimate in real-time and in the global reference frame the three dimensional (3D) displacement that a
single GNSS receiver undergoes within 2 consecutive epochs. This displacement, if divided by the interval between the 2 consecutive
epochs, is equal to the (mean) velocity over the interval itself: as such, the "variometric" approach uses the GNSS receiver as a
velocimeter. Multiple tests performed on synthetic and real data attest that VADASE is capable of detecting velocities higher or equal
than 1 cm/s in the horizontal components and 2 cm/s in the vertical component. As a further step, provided that continuous data have
been acquired, the time series of the estimated 3D velocities can be integrated over a certain interval to retrieve the dynamic
movements (waveforms) of the receiver in a global reference frame.
The algorithm is based upon a so called "variometric" solution that requires the observations collected by a unique, stand-alone GNSS
receiver and the standard GNSS broadcast products (orbits and clocks), which are ancillary information routinely available in real-time
as a part of the broadcast satellites navigation message.
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