GNSS/GPS Update Eric Gakstatter GPS World magazine Presented July 14, 2009 ESRI International User Conference San Diego, CA ©Copyright 2009

GNSS/GPS Current Events United States -GAO report on GPS -SVN 49 report -SBAS (WAAS) -NDGPS International -Solar Cycle 24 -GLONASS -Galileo -SBAS (EGNOS/MSAS/GAGAN)

GAO Report on GPS health Government Accountability Office -In April 2009, released a report entitled.. “Global Positioning System Significant Challenges in Sustaining and Upgrading Widely Used Capabilities”. -Full report available at:

GAO Report on GPS health Currently, there are 31 healthy satellites. The DoD is only committed to a 24-satellite constellation. A number of satellites are well- beyond their design life. Delays in new satellite development have raised concerns about the medium/long-term health of GPS.

GAO Report on GPS health

Is there a legitimate concern? -For consumer GPS users, very minimal. -For GIS and survey GPS users, there’s a legitimate concern.

GAO Report on GPS health Why be concerned? -GIS and survey GPS receivers are “satellite-hungry”. They need satellite signals to perform well. -Even a drop of 2-3 GPS satellites will affect performance. A drop of 4-5 satellites would be very significant. -Field productivity would be significantly reduced.

GAO Report on GPS health What to Do? -Monitor constellation status. -If the constellation is reduced by 2- 3 satellites, utilize mission planning software. -Survey receivers utilizing GLONASS (in addition to GPS) will likely not be affected. -GIS (mapping-grade) receivers generally don’t utilize GLONASS.

GAO Report on GPS health Further comments -Three older satellites are available to return to service and are tested every six months. -Full GAO report available at: -Univ. of New Brunswick analysis of GLONASS compensating for a loss of GPS satellites. d+Test+News

SVN 49 Report SVN 49 (PRN01) Report

SVN 49 Report The 7 th (of 8) Block IIR-M satellite was launched March 24, It hasn’t been declared healthy. SVN 49 includes a unique L5 demonstration payload to secure the L5 frequency with ITU. L5 payload is interfering with the normal operation of the IIR-M satellite.

SVN 49 Report – cont. Ionospheric refraction corrected pseudoranges Relative to a “best fit” orbit determined early in the test program Roughly a 4+ meter spread from 10 to 80 degrees

SVN 49 Report – cont. Design flaw essentially means it will never perform as well as the previous IIR-M satellites, but likely still falls within contract specification. Department of Defense is investigating possible “patches” and seeking user community input. There is no plan to declare SVN-49 healthy in the immediate future.

Solar Cycle 24 Solar Cycle 24 Report

Solar Cycle 24 -On May 8, 2009, the National Oceanic and Atmospheric Administration’s (NOAA) Solar Cycle 24 Prediction Panel (consisting of 12 international experts) released a statement revising their predictions for Solar Cycle You can read the press release here… _solarstorm.html

Solar Cycle 24 Solar Cycle 24 will be the weakest solar cycle since 1928.

Solar Cycle 24 Why do we care? -11 year cycle. -Geomagnetic storm activity affects GPS receivers by altering the density of the electrons in the ionosphere. The density of electrons is referred to as the Total Electron Content (TEC). -Real-time TEC can be viewed at:

Solar Cycle 24 Why do we care? -GPS L1 (single frequency) receivers rely on a rough TEC model to estimate the ionospheric delay. -DGPS (real-time or pp) largely mitigates the delay. -Dual frequency receivers can more precisely mitigate the TEC. -A dynamically changing TEC is very difficult to model.

Solar Cycle 24 Why do we care? -GPS L1 receivers are affected the most by a dynamic TEC. -Sunspot count isn’t necessarily an indicator of geomagnetic activity and therefore the low Sunspot Number Prediction isn’t an indicator that GPS will be affected less than Solar Cycle 23. -In practical terms, a TEC value of 1 = ~15cm of GPS L1 error.

Solar Cycle 24 How bad can it get? -During the late October 2003 geomagnetic event, simulations showed that L1 DGPS accuracy reached 18 meters (95% horizontal) and L1 WAAS accuracy reached 25 meters (95% horizontal). -Extreme events can last for several days.

Solar Cycle 24 What to do? -Sign up to receive alerts at: ?ReturnUrl=%2fproductsubscriptionservice% 2fMainMenuWebForm.aspx -Don’t operate mission-critical GPS L1 receivers during predicted periods of geomagnetic storm activity. -Geomagnetic storms affecting GPS typically occur 1-2 years after the solar cycle peak.

GPS Modernization

GPS Launch Schedule -Last Block IIR-M satellite launch scheduled for August/September. -First Block IIF satellite launch delayed until Spring 2010 at earliest. Introduces L5 signal.

GLONASS status -Russian GNSS

GLONASS status -Currently 18 operational satellites, effectively adding 3-6 observables in addition to GPS. -Six more planned to launch by end of Still considered an augmentation for high precision users until GLONASS quality reaches GPS.

Galileo status -European GNSS

Galileo status European Union Transport funding the initial 3.4B Euro development with public funds. Planned 30 satellite constellation. Two Galileo test satellites in orbit. June 16, Contract signed to launch the first four operational Galileo satellites (two at a time) by the end of Full constellation is proposed to be 2013.

SBAS SBAS status -Satellite-Based Augmentation System

GPS SBAS systems WAAS – Covers North America, AK, HI EGNOS – Covers most of Europe and Northern Africa. Not officially operational for aviation users be usable for ground users. MSAS – Covers region around Japan. GAGAN – Covers India. Not operational yet. Limited availability for ground users. OmniSTAR – World-wide coverage. Subscription-based.

Worldwide SBAS Coverage Map Courtesy: Geneq, Inc.

DGPS – Radio beacon corrections Used internationally for marine navigation. Used in the US for marine navigation and inland applications such as transportation, mapping, etc. Referred to as NDGPS. The correction is free. Requires a “beacon receiver” to use. NDGPS budget is under intense scrutiny.

Current US DGPS coverage

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