RSR GNSS Transcoder™ User Manual
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© 2017 Jackson Labs Technologies, Inc.
to the next simulated position are placed so that these maximum dynamics are not exceeded. Limits
are also placed on the velocity so that the simulated position will stop on and not overshoot the input
position due to the acceleration and jerk limits.
Dynamic filtering is useful to match the expected dynamics of the target receiver and avoid loss of
lock due to large jumps in position or velocity--both of which can result in loss of GPS satellite
tracking. Dynamic filtering is also useful when simulating with fixed position mode so that the
simulated position will move to the new position with limited dynamics, which is useful for creating
simple dynamic simulations.
In the Dynamic position filtering mode, limits are placed on the maximum velocity, acceleration and
jerk to move towards the newly received reference position as quickly as possible. The set of
commands for configuring the maximum dynamics include:
SIMulation:POSition:FILTer:VMAX
SIMulation:POSition:FILTer:AMAX
SIMulation:POSition:FILTer:JMAX
The target receiver also often has configuration options for maximum expected dynamics. In
transcoding applications, the reference PVT input should be expected to have a maximum dynamics
because of the configuration of the PVT source and the maximum dynamics expected in the given
application. So in general for transcoding applications, the dynamics should be in the order:
Application expected dynamics <= PVT source maximum dynamics
<= RSR GNSS Transcoder™ maximum dynamics <= Target receiver maximum dynamics
In the INS position filtering mode and transcoding position mode, the onboard IMU provides
additional filtering and interpolation between input position as well as short periods of dead
reckoning in the cases of short (<60 second) loss of the input PVT source. This is useful in
interpolating the external GNSS reference 1-position-fix-per-second to 10Hz or higher to provide a
smoothly varying RF simulation output to the target receiver. The INS unit will interpolate and create
intermediate fixes at a 10Hz rate in-between two externally-supplied 1Hz PVT NMEA reference
fixes.
The maximum dynamics expected by the INS system is also affected by maximum velocity,
acceleration and jerk commands used to control the Dynamic filtering mode. Additional INS/IMU
features are provided with the SCPI GYRO commands.
In the filtering OFF mode, the input transcoded position or input fixed position is applied
immediately. This may be useful for some applications where it is OK for fixed position input to
immediatly jump from one position to the next. However this can cause tracking problems and
conditions of loss-of-lock in the target receiver that can be difficult or impossible for the target
receiver to recover from. So it is highly recommended that either Dynamic or INS position filtering
be enabled for most usage scenarios.
Position filtering on the RSR GNSS Transcoder™ can be configured using the following command:
SIMulation:POSition:FILTer:MODE <OFF | DYNAMIC | INS >
as described in Section
. The filtering does not affect the simulated position when playing
back motion commands since the motion commands have built-in definitions for dynamics that
override the position filtering settings.
Summary of Contents for RSR GNSS Transcoder
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