Consensus Reference Concept

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GPS IN SITU REFERENCE SYSTEM (ISRS)
PRESENTED BY J. FACUNDO, C. BOWER,
J.FITZGIBBON NOAA/NWS
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Why do we need ISRS?

• Observing technologies taking measurements above
  the surface to the Ionosphere are becoming more
  dependent on GPS
• COTS vendors are using a wide range of GPS
  engines/techniques
• NOAA/other agencies/industry require a
  lower-cost/excellent performing reference system
  for in situ applications aloft

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Evaluating the Performance of Upper Air GPS Data
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GPS-derived Pressure/Heights
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GPS Geopotential Height Differences vs
Hypsometric calculations

• GPS height measurements agreed on average to
  within 20 m from the surface to 34 km.
• At 30 km pressure sensors were in error by values
  between -70m (Vaisala) up to 120m (SRS).
• The pressure sensors considered were of extremely
  good quality compared to earlier generations of
  sensors, but were unable to provide very reliable
  heights at pressures lower than 10 hPa.

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Computing Radiosonde Winds
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IN SITU (GPS) REFERENCE SYSTEM
MOBILE-ISRS IN-SITU TIME (1-sec),
POSITION VALUES SENT TO ISRS
5-METERS
LAT, LONG, HTGEOM, TIME, u, v
1-SEC
u
u
v
v
BASE STATION (LOCAL GPS)
OPUS
DUAL CORS
NGS Benchmark
ISRS
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National Geodetic Survey Benchmark
Future CORS Site
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Possible Flight-train Configuration
M-ISRS
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BLOCK DIAGRAM
BALLOON
M-ISRS
LAUNCH POINT CORRECTION
HI-RES GPS ENGINE CLOCK
403-MHz ANTENNA
TELEMETRY
ISRS GROUND SYSTEM
DUAL CORS
RECEIVER
GPS-PITS
OPUS
GPS-SIM
GRAPHICS/DISPLAY
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GPS-PITS GRAPHICS DISPLAYS
Reference Flight Path and Smoothed Wind Speed
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Position Error Profiles
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Velocity Error Profiles
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GPS SIMULATOR
TEST INSTRUMENT
GPS-SIMULATOR
GPS-PITS
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Conclusions

• GPS has become increasing critical for measuring
  the upper atmosphere
• Demonstrates great reliability and measurement
  accuracy/precision.
• In the future, new applications could be derived
  directly from high-resolution in situ
  GPS-computed measurements.
• Can serve as an independent reference for a wide
  range of legacy and new technologies.
• NOAA LEADING THE WAY!