Research Global Positioning System

Short Name or Variable Name:

GPS

HAIS Instrument:

Manufacturer or Builder:

Novatel

TABS

Description

Model:

Novatel OEM628

Measurements Provided:

Aircraft GPS position and Earth-relative velocity.

Typical Sampling Rates:

10 samples per second

General Description:

GPS position and velocity reported at 10 samples per second from the Novatel BESTPOS and BESTVEL logs. The NMEA GPGGA and GPRMC logs are also recorded for redundancy. The UTC time is taken from the GPGGA log, since the BESTPOS and BESTVEL logs are stamped with GPS time which ignores leap seconds.

Measurement Characteristics:

Overall estimate of uncertainty: For TerraStar-c, fully converged, Horizontal accuracy = 4 cm (RMS), 5 cm (95%). Vertical Accuracy = 6.5 cm (RMS). Without TerraStar but with WAAS/SBAS corrections the horizontal accuracy is typically 0.6 m. If neither is available the accuracy specification is 1.2 m horizontal.
TerraStar corrections often will not be available near the poles, as the TerraStar transmitting satellites are in a geosynchronos orbit. The basic GPS accuracy is degraded near poles due to the satellite orbits.
Response time: Normally recorded at 10 samples per second. Depending upon the receiver and amount of data being logged, up to 100 samples per second is possible.
Other measurement characteristics (comments on signal/noise, bias limits, etc): Can dropout on sharp turns, accuracy is degraded near the poles and during times of ionospheric disturbances. TerraStar may not be available near the poles. TerraStar coverage maps are available at https://www.novatel.com/products/terrastar-gnss-corrections/terrastar-coverage-map/

History of Significant Changes:

2008-August: Updated C-130 receiver firmware to 2.312. Changed pulse-per-second output to positive polarity.

2008-December: Updated GV firmware to 3.500.

2014 - Moving to the OEM628 in FlexPak6 receivers.

2016: Firmware version 6.730.

Example(s) of Measurement

Two periods of 10 Hz data is below. The data in each 0.1 second record are the NMEA GPGGA, Novatel BESTPOSA, NMEA GPRMC, and Novatel BESTVELA.

$GPGGA,143500.00,0500.0190,N,07926.6451,W,5,08,2.4,13221.96,M,14.40,M,08,TSTR*72
#BESTPOSA,ICOM1,0,59.5,FINESTEERING,2068,52518.000,00000008,b1f6,14392;SOL_COMPUTED,PPP,5.00031594521,-79.44408420409,13221.9644,14.4000,WGS84,0.0283,0.0364,0.0813,"TSTR",8.000,0.000,11,8,8,8,00,01,00,03*a0365974
$GPRMC,143500.00,A,0500.0189567,N,07926.6450522,W,455.131,270.0,250819,0.0,E,D*2D
#BESTVELA,ICOM1,0,59.5,FINESTEERING,2068,52518.000,00000008,10a2,14392;SOL_COMPUTED,PPP,0.050,8.000,234.1396,269.979706,0.0538,0*6cc7c58e\r\n
$GPGGA,143500.10,0500.0190,N,07926.6577,W,5,08,2.4,13221.96,M,14.40,M,08,TSTR*76
#BESTPOSA,ICOM1,0,59.5,FINESTEERING,2068,52518.100,00000008,b1f6,14392;SOL_COMPUTED,PPP,5.00031589384,-79.44429487894,13221.9627,14.4000,WGS84,0.0283,0.0364,0.0813,"TSTR",8.100,0.000,11,8,8,8,00,01,00,03*3246d9fc
$GPRMC,143500.10,A,0500.0189536,N,07926.6576927,W,455.093,270.0,250819,0.0,E,D*2D
#BESTVELA,ICOM1,0,59.5,FINESTEERING,2068,52518.100,00000008,10a2,14392;SOL_COMPUTED,PPP,0.050,8.100,234.1202,269.986150,-0.0174,0*c2f47e74

Contacts

Lead Contact:

Stuart Beaton

Alternate Contact:

Chris Webster

Status/Plans

Current Location:

Installed on GV and C130

Operational Status:

requestable, ready for deployment

Data

External Deployments or Description:

This measurement is typically available on all projects.

Lifecycle

Date Acquired:

January, 2004

Serial Numbers

Inventory Count:

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Manufacturer or Builder:

TABS

Organizational Facilities