Relative
Positioning using
map matching techniques based on Gage and cross level. All referenced to a
reference file. This is Called Geometry
Alignment
Geometry data from
"measurement file" is compared to that of stored reference
file. The Errors between them are used to adjust the relative odometer
correction between them, through a Kalman Filter, modeling odometer and
measurement errors.
Key output is the
Odometer Correction, used to correct measurement file annotation of MP and
ft. with that for reference.
It provides a file
of regions where alignment may be suspect.
Quality plots are
provided to asses if algorithms are working appropriately
Many integrity
Tests to assure system is locked or correlated. And Sophisticated search
algorithms for instances when the algorithm gets lost.
Positions geometry data when geometry alignment is not possible
In a parallel
computation with the Geometry Alignment: A Distance based Kalman filter inputs
GPS, geometry curvature( a type of rate gyro), and odometer in a Kalman filter
estimating position and distance along Track
It Can Reject bad GPS measurements , extrapolate through GPS outages and provide indication of the Quality of
estimation.
It can reset itself if issues arise
It allows for Tie Down points to correct distance along track with
the corridor track map when needed.
It provides data for geometry data positioning in the absence of
Proper alignment
If Geometry alignment not possible, geometry data is positioned
with this within 3-4 ft!
During running of
the alignment program, GPS derived results are used to reinitialize the
geometry alignment quickly and efficiently if alignment gets lost because of
bad data or travel on alternate track
A Final program
then combines the two measures of position.
If Alignment is deemed good, position is corrected first by
the estimated odometer offset, then according to track map, and MP& ft. are
annotated though the Geodetic milepost file.
. If alignment is deemed poor the position
corrections are from the GPS derived Kaman filter.
This competes the annotation of the new.g01 file, where
annotations are now synched to the reference file and referenced to ground
truth.
Synergism's used in the approach include:
Fast recovery of
track alignment when data does not correlate, using GPS positioning in
the search for a "restart".
If geometry
alignment is possible ( that's most of the time) points can be geodetically
positioned to within 2-3 ft.. even if GPS is not working in area
Linear positioning
of data using GPS derived data when alignment for some reason cannot work is
within 3-4 ft
Fewer
"throw-away" Runs. Many of the GPS Faults, and Tachometer Outages, and large scale
factors that may have previously made a run nearly useless will be
corrected