hsgps hsgps ins (1)
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High Sensitivity GPS Tracking Performance inIndoor Environment with Moderate Pedestrian
Traffic Conditions
Nadezda SokolovaBrje [email protected]
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
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N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
GPS Signal Challenges Indoors (1)
Extremely weak LOS signal
Shadowing and Fadingeffects
Heavy attenuationMultipath (short delay
multipath)
Signal level differencesCross-correlation problems
Interference from other RFsystems
Cellular transmissionWireless internet
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N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test Description (1)
-Same test equipmentsetup.
-Same satellite geometry(tests performed in 23hours 56 minutesperiod).
-Same test path.
-Warm start outside thebuilding.
Test A
Test B
Performed during a weekday, people present in thebuilding and along thetest path.
Performed during a weekend, no people presentalong the test path.
Two tests were performed to investigate effects of humanbody interference effects on the tracking performance of aHSGPS receiver in the indoors environment.
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N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test Description (2)
Construction materials in the
Electro- block.
Electro block views from the outside, passage inside the building, entrance .
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N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Description of the Test Equipment Setup
Parameter Value
Tracking L1, C/A code
Channels 16
Protocol UBX binary, NMEA
Tracking Sensitivity -158 dBm
Hot Start Sensitivity -148 dBm
Cold Start Sensitivity -142 dBm
Field test setup.
Main operating parameters of u-blox SuperSense HSGPSreceiver.
Measurement path inside the Electro block, NTNU.
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N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test results (1)
Signal strengths at theentrance varied from -136dBm down to -144 dBm.
C/No levels between 38
dBHz and 23 dBHz.
6 satellites acquired andtracked.
Test A - two studentspassed by the receive
antenna in about 1.5meter distance. Result -loss of lock and necessityto reacquire the signals.
Test initialisation outside
SVs C/No levels outside, at the entrance to the Electro block, test B, nopeople present.
SVs C/No levels outside, at the entrance to the Electro block, test A,people present.
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N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test results (2)
C/No average levels measuredfor each particular satelliteduring both tests were almostthe same, varying from 30.1dBHz to 18.3 dBHz.(giving signal levels of-156dBmto -144.2dBm).
Signal losses due to change intype of material above the testpath experienced in both tests.
Test A- the receiver often loseslock on satellite signals.
Test B- the receiver was able tocontinue tracking for longerperiods.
Inside the Electro block
C/No diagrams for each SV available under the tests inside the building.
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N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test results (3)
Test A- navigationsolutions put the receiverall the time at and around
the entrance where thetest was initialised.
Test B- the receiver wasable to producenavigation solutions whichwere spread along the
test path.
SuperSense LEA-4H position solutions, test A (no people present).
SuperSense LEA-4H position solutions, test B (people present).
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N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test results (4)
As stated by the manufacturer, the HSGPS receiver used in the testshad tracking sensitivity like -158dBm and acquisition sensitivity (hotstart) like -148dBm.
GPS signal strength levels measured inside the Electro block were
varying from -144,2dBm to -156dBm.
With so extremely low signal strengths, signal attenuation caused bypeople in the building blocking the satellite signal paths or justpassing by in close distance to the antenna can result in loss ofsignals even if the receiver has such a good tracking sensitivity asstated.
More complex measurements and analyses should be performed toidentify the exact degree of influence of this effect.
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N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Conclusions
A person blocking the satellite signal path or just passing by in closedistance to the receive antenna can cause loss of signal and degradedaccuracy in indoor and other degraded signal environments.
Standing and moving people are additional and very unpredictable
obstructions and sources of multipath that should be considered incombination with other effects degrading the GPS performance inpedestrian traffic environments.
A user of a handheld GPS device should be aware of such limitationsin order to use his device in the best way to get satisfactory results.
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N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
References
[1] R.M.Allnutt, A.Dissanayake, K.T.Lin, C.Zaks, Propagationconsiderations on L-band handheld communication service offeringsvia satellite, IEEETrans. on Antenna and Propagation, Vol.2, 1993,pp.800-803.
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Integrated Low-Cost MEMS INS+HSGPSPerformance for Pedestrian Navigation in a
Signal Degraded Environment
Nadezda Sokolova
Brje [email protected]
N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance
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High- Sensitivity GPS
Signals are integrated over a longer period of time, (tens of ms
instead of just a few ms) to improve SNR.
Capable to maintain a position fix in degraded GPS signalenvironments, (can track down to signal levels approaching
-160dBm).
Price to pay...
Reduced positioning accuracy due to weak signals and interference.
Increased acquisition times. Limited dynamic responsiveness.
N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance
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N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance
HSGPS Performance Indoors: Examples
3 tests performed in a 2-hourperiod.
Same test path
Different satellite constellations.
Significant variance in positioningresults.
Results indicate the need ofexternal aiding to improve thequality of the navigation solution.
HSGPS solutions indoors, Electro block, sept.07.
Satellite visibility indoors, Electro block,sept.07.
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Low-Cost MEMS INS+HSGPS Integration
Loosely coupledintegration algorithm.
2 decentralized Kalmanfilters.
At least four GPSsatellites recquired toprovide GPS updates
for INS corrections.
N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance
Loosely coupled INS/GPS integration algorithm.
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Description of the Field Tests
The integrated system performance was evaluated in two different test
areas:
-Semi-urban area
-Indoor area
Operating scenario for all performed tests: walking mode.
Inertial sensor placement: in the users hand, kept close to the body.
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Equipment Setup for the Field Tests (1)
N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance
Field test setup.
Parameter Value
Tracking L1, C/A code
Channels 16
Protocol UBX binary, NMEA
Tracking Sensitivity -158 dBm
Hot Start Sensitivity -148 dBm
Cold Start Sensitivity -142 dBm
Sensor Gyro Accelerometer Magnetometer
Operating range +/- 1200 deg/s +/-17 m/s +/-750 mGauss
Scale factor linearity(% of operating range)
- 0.05% 0.5%
Bias stability (1) 5 deg/s 0.02 m/s 0.5 mGauss
Noise (RMS) 0.1 0.001m/s / 0.5 mGauss
Alignment error (deg.) 0.1 deg 0.1 deg 0.1 deg
2
Main operating parameters of u-blox SuperSense HSGPSreceiver and Xsens MtxIMU.
2
Hz2
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Equipment Setup For the Field Tests (2)
It is inefficient to useheading information derivedfrom magnetometer
measurements in indoorenvironments.
Magnetic field inside abuilding is strongly disturbedby building structure,electrical equipment, mobile
phones, computers.... etc
Magnetic field measurements, outdoors, NTNU
Magnetic field measurements, indoors, Electro block, NTNU.
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Field Test in a Semi-Urban Area (1)
N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance
Measurement path, semi-urban area, Trondheim.
Satellite visibility, semi-urban area test.
Measurement path, semi-urban area test, Trondheim.
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Field Test in a Semi-Urban Area (2)
HSGPS navigation solution with simulated 30seconds of GPS outage.
Rapid error
accumulation by INSduring absence ofGPS navigationsolutions, about150m horisontalerror.
In order to investigate the performance of the integrated system duringGPS outage periods, a 30-second GPS outage was introduced.
HSGPS-only navigation solution. Integrated HSGPS/MEMS INS navigation solution.
Integrated HSGPS/MEMS INS navigation solutionwith simulated 30 seconds of GPS outage
N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance
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Field Tests in an Indoor area
Construction materials of the
Electro- block.
Electro block views from the outside, passage inside the building, entrance .
N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance
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HSGPS-only: Results
N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance
Measurement path inside the Electro block, NTNU.
HSGPS-only results, Test 1 and Test 2.
Satellite visibility inside the Electro block, Test 1 and Test 2.
To illustrate the integrated systemperformance, two tests were chosen:
Test 1 good HSGPS results, GPS available for95 seconds out of 121.
Test 2 poor HSGPS results, GPS availableonly for a few short periods, for 43 seconds outof 125 in total.
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Integrated MEMS INS+HSGPS: Results
Integrated system accuracy isdependant on accuracy ofHSGPS navigation solutions.
Integrated system rapidlyaccumulates errors in absenceof GPS updates.
Integrated system availability isbetter, but errors in navigation
solution are very large.
N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance
Integrated MEMS INS/HSGPS results, Test 1.
Integrated MEMS INS/HSGPS results, Test 2.
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Conclusions and Future Work
Use of tight HSGPS+MEMS INS coupling algorithm.
Use of other additional sensors.
Use of an additional barometric sensor to strengthen the INSvertical component.
N.Sokolova, B.Forssell, Integrated Low-Cost MEMS INS/HSGPS Performance