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M. Gende, C. BruniniUniversidad Nacional de La Plata, Argentina.
Improving Single Improving Single Frequency Positioning Frequency Positioning
Using SIRGAS Ionospheric Using SIRGAS Ionospheric ProductsProducts
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
2
OutlookOutlook
Goal and motivationsWhy in South America?WorkflowResults for a test bedConclusions
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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GoalGoal
Increase precise positioning accuracy for single frequency receivers.
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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MotivationMotivation
A large part of the GNSS technology users in Latin American have access only to single frequency receivers.
These receivers can not eliminate the ionospheric bias by combining signals.
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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Basic FactsBasic Facts
The ionosphere delay is the main error factor in positioning.This delay can be mitigated with a differencing technique.The technique lose effectiveness as the baseline increases.
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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Context in South AmericaContext in South America
Because of the size of the continent, the GNSS continuously operating reference stations (CORS) are usually more than 300 kilometers from each other.Under this condition the relative positioning method is less effective.
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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Our proposalOur proposal
Use the CORS network already installed in order to produce ionospheric corrections for single frequency receivers.
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
9
MethodologyMethodology
Determine the slant total electron content (STEC) from dual frequency CORS.Estimate STEC in the place the user is located.Correct the single frequency observations. Process the observations in a regular way.
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
10
11stst step: calculate STEC step: calculate STEC using LPIMusing LPIM
Absolute STEC must be determined. Receiver calibration The estimation is done at the zero difference
level
We assume a thin shell model.
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
11
22ndnd step: Estimate STEC step: Estimate STEC
Estimate STEC For each receiver – satellite observation For each epoch
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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33rdrd step: Correct the step: Correct the observationsobservations
We can correct measurements Corrected C/A and Corrected L1
We can generate new measurements Simulated P2 and Simulated L2
The user has a new RINEX file with less ionospheric bias
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
13
44rdrd step: Conventional step: Conventional processingprocessing
Positioning is performed using the software that the user usually uses.
We have extended the CORS – user’s distance.
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
14
EvaluationEvaluation
In the position domain Code and phase Static and cinematic
Comparison Single frequency solution Corrected solution Ion free solution
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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Test bedTest bed
10 days, 24 hours. Mid latitude. Non disturbed solar conditions. Distance between GPS receivers 200 to
300 Km.
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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Standalone positioningStandalone positioning
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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HorizontalHorizontal coordinatescoordinates
C/A code
C/A code + corrections
Ion-free
Delt
a N
ort
h (
mete
rs)
Delta East (meters)
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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Vertical componentVertical component
P1 Simulated ion-free Ion-free
Delt
a U
p (
mete
rs)
Local Time (hours)
Differential positioning Differential positioning using codeusing code
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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HorizontalHorizontal coordinatescoordinates
C/A code
C/A code + corrections
Delt
a N
ort
h (
mete
rs)
Delta East (meters)
C/A
C/A + corrections
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
22
Vertical componentVertical component
C/A C/A corrected
Delt
a U
p (
mete
rs)
Local Time (hours)
Differential positioning Differential positioning using carrier phaseusing carrier phase
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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Local Time (hours)
Delta North (meters)
Delta East (meters)
C/A
C/A + corrections
C/A
C/A + corrections
HorizontalHorizontal coordinatescoordinates
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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Vertical componentVertical component
Local Time (hours)
C/A
C/A + corrections
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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ConclusionsConclusions It is possible to:
Mitigate the ionospheric effect on L1.Extend the separation between the user and a
CORS station. When corrections are applied:
The horizontal errors are reduced more than 40%. The vertical errors are reduced almost 60%.
95% of the time the corrected observations present errors below. 1 centimeter for the horizontal coordinates. 10 centimeters for the height.
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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Extended utilityExtended utility
4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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4 September 2009. Buenos Aires, Argentina.
IAG Scientific Assembly: Geodesy For Planet Earth.
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