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GNSS Technology Update
Speaker: Eric Gakstatter Contributing Editor – GPS World
Editor - Geospatial Solutions Presented at: Association of Petroleum Surveying & Geomatics
Houston, TX April 7, 2015
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Agenda
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- GNSS Infrastructure advancements
- Sources of GNSS corrections
- Space Weather
- Trends
GNSS is the new GPS
GNSS = Global Navigation Satellite System
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GNSS technology is going to advance significantly more in the next 5 years than it has in the past 10
years
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GNSS Infrastructure
ACTIVE GNSS:
-GPS (USA)
-GLONASS (Russia)
-SBAS: WAAS (North America), MSAS (Japan)
EGNOS (Europe), GAGAN (India), Omnistar, RTX, Terrastar, Starfire,
Starfix
-QZSS Regional (Japan)
-BDS Regional (China)
PLANNED GNSS:
-Galileo (Europe)
-BDS Global (China)
-SBAS: SDCM (Russia)
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Augmentation
Regional:
-RTK Networks/Clusters (Public and Commercial)
-Public SBAS (WAAS, etc.)
-Commercial SBAS (Omnistar, RTX, Terrastar)
-DGPS
Global:
-Commercial SBAS (Omnistar, RTX, Terrastar, Starfire, etc.)
-Public PPP (RT GPS)
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• Not only is GNSS receiver technology constantly evolving, so is the GNSS infrastructure (satellites, signals and control).
• This is one of the reasons that the GNSS industry is so dynamic and will be for the foreseeable future.
• These changes will affect the way that GNSS mapping and surveying users perform their work. Better, faster, cheaper.
GNSS is Changing
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GPS Constellation Status
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• Four GPS launches scheduled in FY2015. The most in one year in a long time.
• Oct. 2014, Mar 2015, June 2015, Oct 2015
• After that, one more II-F model left to launch.
• Model IIF = L1 C/A, L1/L2 P(Y), L2C, L5
• Then, it’s time for GPS III satellites.
• Model III = L1C, L1 C/A, L1/L2 P(Y), L2C, L5
GPS Constellation
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• There are currently 31 operational GPS satellites.
• 15 x GPS Block IIA/IIR. L1 C/A, L1/L2 P(Y)
• 7 x GPS Block IIR-M. L1 C/A, L1/L2 P(Y), L2C
• 9 x GPS Block II-F. L1 C/A, L1/L2 P(Y), L2C, L5
• L2C = More robust iono correction for high precision positioning. No need for cross-correlation (semi-codeless).
• L5 = Similar to L2C, but stronger signal @ 1176 • Civil signals (black, red), Military signals (blue)
•
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GLONASS
Russia’s Satellite Navigation System
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• Declared fully operational in December 2011.
• ~24 operational satellites. Most since 1997.
• A valuable augmentation to GPS. Not used as a stand-alone system.
• Valuable to high-precision users (RTK, sub-meter) because it increases productivity.
• Adds ~6-10 more satellites.
• Increases productivity, not necessarily accuracy.
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• Transitioning to CDMA radio design on satellites.
• Glonass-K launched Dec. 2014.
• Up to 9 Glonass-M satellites to launch 2015/2016.
• Ultimate constellation expansion to 30 satellites.
• Transitioning to PZ-90.11 geodetic system. Aligned with ITRF at the mm-level.
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Galileo
Europe’s Satellite Navigation System
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• First four operational Galileo satellites are test sats converted to operational sats (4).
• 1st production launch last Fall. Limited success. A pair injected into the wrong orbit (6).
• 3/27/15 production launch pair successful (8).
• Two more launches scheduled this year (12).
• Constellation of 18 operational Galileo satellites projected in 2016.
• Highly compatible with GPS L1/L5. No L2.
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BDS (Beidou)
China’s Satellite Navigation System
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• More high-precision GNSS receivers are sold in China than the rest of the world combined.
• BDS is currently a regional system of satellites orbiting in a figure eight pattern above China that add ~14 satellites in addition to GPS and GLONASS.
• The RTK environment in China is better than any other place in the world due to the significant number of satellites in view.
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• China plans to offer a 30-satellite constellation by 2020, some speculate they’ll have it complete by 2017.
• Most recent launch was last week (March 30).
• The launch is believed to be the first Beidou-3 M1 satellite and the beginning of Beidou’s Phase III program, which is a 30-satellite global constellation.
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• GPS+Galileo = 20 average satellites in view.
• Add 30 more from BDS and 24 from GLONASS.
• 30-40 satellites in view using 4 constellations.
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SBAS
Satellite-Based Augmentation System
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• SBAS – WAAS/EGNOS/MSAS/GAGAN. Free source of GPS L1 corrections.
• SBAS was designed for aviation, but used widely by geospatial professionals as an accurate source of GPS L1 corrections.
• SBAS was designed primarily for integrity, but can be optimized for accuracy to achieve sub-meter precision.
Public SBAS (sub-meter)
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• Commercial PPP SBAS (decimeter world-wide subscription services):
- RTX, Omnistar
- Starfire
- Terrastar
• Public PPP SBAS (free decimeter world-wide service):
• IGS RT <rt.igs.org>
PPP SBAS (decimeter)
OmniStar/Starfire/Terrastar
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• Commercial RTK Networks • - Surveying equipment dealers
• - GNSS eq. manufacturers – Trimble/Leica/Topcon
• Commercial RTK Clusters • - Agriculture
• Public RTK Networks • - State agencies (eg. Dept of Transportation)
• Public RTK Clusters • - Plate Boundary Observatory (PBO)
RTK
Leica SmartNet RTK Bases
South Plains RTK Cluster – 12m acres
TxDOT RTK Bases
PBO RTK Bases
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• Omnistar – ITRF08 current day epoch
• WAAS – ITRF08 current year epoch
• DOT RTK Networks – NAD83/2011 2010.0
• NGS CORS streaming (discontinued) – ITRF00 1997.0
• PBO RTK bases - ???
• Commercial RTK Networks (surveying) - ??? Localize?
• Commercial RTK Clusters (ag) – WGS-84??
Disparate Geodesy
Public RTK Base Stations in the U.S.
Two recent examples of using Public RTK bases:
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Public RTK Base Stations in the U.S.
Case #1. Colorado.
-Windows Mobile data collector w/AT&T SIM card for internet connectivity
-~12 mile baseline
-Accuracy: 1.9cm horizontal RMS. Adjusted from ITRF00 1997.0 to NAD83.2011 2010.0 using HTDP
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Public RTK Base Stations in the U.S.
Case #2. California (SF Bay Area)
-Samsung Note smartphone (Android) running AutoCAD 360.
-~5 mile baseline, 0.75” precision
- Accuracy: ????
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Trending towards real-time decimeter (PPP) and centimeter positioning (RTK)
Never in history has real-time, high-precision technology been so available and affordable.
And we’re only just beginning…………………….
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Trends
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High-Precision GNSS Technology
The Next 5 Years
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The Next 5 Years
• Complete hybrid L5 constellation (GPS/Galileo/BDS).
• Cheaper/more accurate GNSS receivers.
• Initial deployment of Europe’s Galileo and Chinese BDS.
• Continued proliferation of RTK Networks.
• Further refinement of PPP real-time services (eg. Trimble RTX, IGS-RT, others).
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• The new GPS L5 signal will result in very low-cost L1/L5 receivers capable of cm-level horizontal/vertical precision.
• High-precision GPS receivers trending towards commoditization.
• RTK on your mobile phone by 2020?
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• GNSS performance around obstructions such as tree canopy, buildings, terrain blockage.
• Geodesy – datums, coordinate velocities. Combining disparate data sets.
• Communication for real-time GNSS corrections.
Three Gotchas
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Velocities
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• Don’t know what you have.
• Simplicity vs. accuracy. Geospatial software operators follow the path of least resistance.
• Transformation workflows are not simple or understandable.
• Velocities are a difficult concept for the average geospatial specialist.
• Mainstream workflows to deal with velocity models are largely non-existent.
• Velocity models are a work in progress.
The Geodesy Headache
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• The ability to collect high-accuracy geospatial data is cheaper and easier than ever before.
• Stewards of geospatial data are largely ill-equipped to accurately deal with disparate data sets.
• Geospatial workflows are largely ill-equipped to accurately deal with disparate data sets.
• Velocities are a foreign concept to most geospatial data stewards.
• Velocity models are a work in progress.
Geodesy Takeaways
Comments?
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Questions?
Eric Gakstatter
Contact Information: [email protected]
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