Time, Space, Position Information

Time, Space, Position Information

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All testing of avionics and weapons systems requires that the tester prove the performance of the system under test by measuring its performance against some known quantity. This known quantity falls under the heading 'truth data,' or time, space, position information, affectionately known as TSPI. The concept is slightly different from the testing accomplished on the vehicle side of the house. In loads testing for example, the tester relies on instrumented parameters to determine the 'true' bending and torsion on a member. The accuracy of the result depends entirely on the accuracy of the instrumentation system. The tester in this case is measuring the truth and comparing this answer to the predicted results. In avionics and weapons system testing, we still collect instrumented parameters such as latitude, longitude, and altitude, but we compare them to an outside reference, a truth. This truth is generated by calibrated reference systems such as cinetheodolites or an on-board global positioning system (GPS). It is important that our truth system be accurate enough to measure the expected performance of the system under test. Unfortunately, all too often testers use whatever TSPI system is available without considering the impact on the results of the test. In some cases, highly accurate avionics systems are being measured by TSPI systems that are not as accurate as the system under test! This chapter discusses what systems are available, how the results can be improved upon, and defines a common-sense approach for identifying required test assets.

Chapter Contents:

  • 2.0 An Overview of Time, Space, Position Information
  • 2.1 Sources of TSPI
  • 2.2 Ground-Based Tracking Radar
  • 2.3 Radar Characteristics
  • 2.4 Radar Accuracies
  • 2.5 Geometric Dilution of Precision
  • 2.6 Earth Models
  • 2.7 Theodolites
  • 2.8 Theodolite Limitations
  • 2.9 Global Positioning System
  • 2.10 Stand-Alone GPS Receivers
  • 2.11 Inertial-Aided GPS Receivers
  • 2.12 Differentially Corrected GPSs
  • 2.13 Sensor Fusion
  • 2.14 Ranges
  • 2.15 Range Assets
  • 2.16 Unique Services
  • 2.17 Interfacing with the Range
  • 2.18 Time Alignment
  • 2.19 Summary
  • 2.20 Exercises
  • 2.21 Answers to Exercises
  • 2.22 Selected Questions for Chapter 2

Inspec keywords: weapons; avionics; calibration; Global Positioning System

Other keywords: system under test; instrumentation system; on-board global positioning system; TSPI system; GPS; avionics systems; weapons systems; vehicle side; cinetheodolites; true bending; truth system; space information; time information; calibrated reference systems; weapons system testing; position information; common-sense approach; instrumented parameters; truth data

Subjects: Satellite communication systems; Radionavigation and direction finding; Avionics; Measurement standards and calibration

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