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Track geometry measurement - TQM accuracy
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In order to have a broader picture of possible and attainable accuracy of TQM track geometry readings a typical track geometry measurement accuracy expectancy goal needs to be set.
Track geometry measurement accuracy goal:
As TQM aims to replace laborious hand versine measurements, the accuracy of Generated Versine (derived from recorder measurements) must match a hand versine measurement accuracy of +/-2mm. Table A indicate (projection scale derived) expected track geometry singular measurement accuracy related to different chord lengths SB (short bases).
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+/-2mm
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+/-2mm
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HV Accuracy Goal
for 10 and 20m chord
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+/-2mm
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+/-2mm
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10m
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20m
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10m
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20m
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10m
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20m
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10m
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20m
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1m
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1m
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2m
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2m
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Length of Measuring Base
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3m
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3m
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4m
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4m
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100
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400
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25
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100
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Projection Scale
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11
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44
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6
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25
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+/-
0.02
mm
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+/-
0.005
mm
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+/-
0.08
mm
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+/-
0.02
mm
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Required Accuracy
of a TQM Singular Measurement
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+/-
0.18
mm
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+/-
0.05
mm
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+/-
0.32
mm
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+/-
0.08
mm
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System Precision
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System Calibration
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System Corrections
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Design
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Engineering
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Ref. Blocks
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Temp.Control
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Design
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Correction
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Table A. Track geometry - expected accuracy of TQM typical measurement
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[mm]
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Curve Radius [in metres]
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Compiled measurement accuracy on curve of 1000m radius
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HV
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1m SB
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2m SB
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3m SB
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4m SB
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Short base
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Horiz. Versine magnitude
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Single measur. accuracy
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Gen. Versine
on 20m chordG
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2.0
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62
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250
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562
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1000
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1.0
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125
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500
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1125
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2000
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1m
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0.12 mm
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+/- 0.005 mm
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50 +/- 2mm
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0.5
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250
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1000
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2250
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4000
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2m
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0.50 mm
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+/- 0.02 mm
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50 +/- 2mm
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0.2
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625
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2500
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5625
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10000
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3m
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1.12 mm
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+/- 0.05 mm
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50 +/- 2mm
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0.1
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1250
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5000
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11250
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20000
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4m
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2.00 mm
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+/- 0.08 mm
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50 +/- 2mm
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Table B. Versines and Radius
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Table C. SB measurements on 1000m radius
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