Velocity & Displacement Engine: Data Rate Relationship - Leica GR30 Online Help Manual

Appendix I: Velocity & Displacement Engine
Velocity & Displacement Engine: Data Rate Relationship
Velocity & Displacement Engine rate and NMEA LVM/LDM rate
The Velocity & Displacement Engine computation rate is always equal to the position update rate of the
receiver.
The position update rate of the receiver can be found on the page Status: Position.
The position update rate of the receiver is the rate at which the receiver calculates its position. Per default this is one second (1s). In
case an incoming real time data stream or an outgoing NMEA data stream is configured with a faster (higher) data rate, the highest
configured data rate is automatically also applied for the position update rate.
It is not allowed to log or stream NMEA messages in a rate higher than the position update rate of the receiver.
In case the user configures and activates LVM and/or LDM streams or logging sessions, two cases are possible:
Case 1:
The user sets a LVM and/or LDM stream or logging session with a rate equal to the current receiver position update rate. The velocity
and displacement in the LVM and LDM messages at each epoch are equal to the velocity and displacement in the Velocity &
Displacement Engine at the same epoch.
Case 2:
The user sets a LVM and/or LDM stream or logging session with a rate lower than the current receiver position update rate, and thus
lower than the computation rate of the Velocity & Displacement Engine. The velocity and displacements for the lower rate LVM and LDM
messages are then computed as follows:
•
The velocities in the LVM message at epoch 't' are the result of averaging all velocities between epochs 't' and 't- ΔtLVM'
computed from the Velocity & Displacement Engine, where 'ΔtLVM' is the time between two consecutive epochs of the LVM
message.
•
The displacements in the LDM message are the result of sampling all the displacements computed from the Velocity &
Displacement Engine with a sampling rate equal to the user selected LDM message rate. This means that the displacement at
epoch 't' in the LDM message is equal to the displacement computed from the Velocity & Displacement Engine at epoch 't'.
Examples:
The position update rate is 20 Hz. The user configures a LVM stream with 1 Hz data rate. This means that
the Velocity & Displacement Engine will compute a velocity every 0.05 s, and the LVM stream will output a
velocity every 1 s. In this case, at every epoch of the LVM stream, i.e. every 1 s, the velocities generated
from the Velocity & Displacement Engine between the same epoch and the previous epoch of the LVM
stream, i.e. 20 epochs of the Velocity & Displacement Engine, are averaged and the result is streamed in the
LVM stream.
The position update rate is 10 Hz. The user configures a LDM stream with 2 Hz data rate. This means that
the Velocity & Displacement Engine will compute a displacement every 0.1 s, and the LDM stream will output
a displacement every 0.5 s. In this case, at every epoch of the LDM stream, i.e. every 0.5 s, the
displacement computed in the Velocity & Displacement Engine at the same epoch of the LDM stream is
streamed out.
The position update rate is 5 Hz. The user configures a NMEA LDM logging session with 2 Hz data rate. The
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