Mary L. Johnson | Azavea Atlas

Articles by Mary L. Johnson

Aug 23, 2010

GNSS Coverage Moves Forward in Asia

The China Academy of Launch Vehicle Technology announced the successful launch of the first geosynchronous satellite in China’s Compass constellation on July 31, 2010. China has already launched four geostationary satellites that will provide navigation coverage within the Asia-Pacific region by late 2012. The first geosynchronous satellite is part of China’s proposed plan to provide full global coverage by 2020, similar to what is currently provided by the United States’ GPS constellation.

Japan is also moving ahead with its Quasi-Zenith Satellite System (QZSS). The QZSS will provide navigation coverage for Japan and portions of the surrounding Asia-Pacific region, with full operational status anticipated in 2013. The first satellite was originally scheduled to launch on August 2, 2010, but the launch was postponed due to a suspected defect in the satellite’s reaction-wheel assembly system. The defective part has since been replaced, and the launch has been rescheduled for September 11, 2010.

The QZSS will provide high accuracy positioning to most of Japan, even where urban canyons or mountainous terrain might otherwise be an issue. Following a campaign by the Japanese Aerospace Exploration Agency (JAXA), the satellite has been nicknamed “Michibiki,” which means “guiding star” or “showing the way.” The satellite also has its own mascot as well as a dedicated website that will provide 3-D interaction and information about the satellite beginning on August 23.

The Quasi-Zenith Satellite System Orbit will keep a navigational satellite almost directly overhead at all times, providing greater positioning accuracy for GNSS users in Japan (public domain image courtesy of Wikimedia Commons).

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Jun 15, 2010

Another Point in China’s Compass

By Mary L. Johnson

The fourth navigation satellite in China’s Beidou or Compass constellation was successfully launched on June 2, 2010. This satellite is one of five planned geostationary satellites that will ultimately provide navigation coverage within the Asia-Pacific region. An additional thirty non-geostationary satellites are expected to be in place by 2020 in order to bring the Compass constellation to full global coverage similar to what is currently provided by the GPS constellation. China is planning to have a total of twelve satellites in orbit by the end of 2012 to provide positioning, timing and short messaging communication services for much of Asia and the Pacific region. The system is expected to provide a positioning accuracy of approximately thirty feet for civilian users. A more accurate service will be available to authorized and military users only.

Once all currently planned satellites have been deployed and added to those already in orbit in existing constellations, it is anticipated that positioning services, particularly in “urban canyons” and other locations where signal strength has previously been an issue, will be significantly enhanced for navigation system users around the world.

The Compass Navigation Satellite System will initially provide service to the Asia-Pacific region (public domain image courtesy of Wikimedia Commons).

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May 28, 2010

A New Satellite in the GPS Constellation

By Mary L. Johnson

After a week of delays caused by everything from technical malfunctions to bad weather, the first in a series of GPS IIF satellites was finally launched from Cape Canaveral late in the evening on May 27, 2010. A total of twelve IIF satellites are expected to launch through 2014, with the next launch tentatively scheduled for November 2010.

The IIF satellites are part of the ongoing modernization of the GPS constellation by the United States Air Force. The IIFs have improved atomic clocks used for timing and are therefore expected to provide more accurate navigation signals than those currently available from the rest of the GPS constellation. The IIFs will also broadcast the civil L5 signal for safety-of-life applications, which has the potential to enhance indoor reception with its wider bandwidth and lower frequency. The new satellites will also be compatible with the Galileo, GLONASS and QZSS constellations. In addition, the IIFs will assist the IIRM series already in orbit with military-specific M-code, a unique encryption for military users requiring secure access.

The new satellite, officially known as GPS IIF-1 SV-1, is expected to begin broadcasting its signal to GPS users following a three- to four-month testing period. In addition to being the first in the new IIF satellite series, this launch was significant for another reason as well. GPS IIF 1 SV-1 was carried into orbit on a Delta IV rocket, making it the first GPS satellite since 1985 that was not placed in orbit by an Atlas rocket.

The new IIF satellite series has finally launched. An example of the IIF satellite series. (Public domain image courtesy of http://pnt.gov/public/images/.)

The new IIF satellite series has finally launched. (Public domain image courtesy of http://pnt.gov/public/images/.)

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Apr 12, 2010

AWRA GIS and Water Resources Conference

By Mary L. Johnson

The American Water Resources Association (AWRA) held its Spring Specialty Conference on GIS and Water Resources from March 29-31, 2010 in Orlando, Florida. I had the privilege of attending this event to present a poster on using the Sajara software framework to manage hardcopy infrastructure plans. Azavea also prepared a paper for the conference proceedings to help utility organizations digitize their hardcopy documents and otherwise prepare them for integration in the Sajara software framework.

The AWRA Conference covered a diverse range of subjects involving the use of GIS in the water resources industry. There were presentations on hydrologic modeling, watershed delineation, data sharing, software interface development and land use applications, just to name a few. The poster session added topics such as coastal management, agriculture, community water systems, education and irrigation, as well as document management. Many of the organizations looking at Sajara to manage their infrastructure plans were also interested in using GIS for stormwater management applications, similar to what the Philadelphia Water Department is doing with phillystormwater.org.

The opening plenary session featured Jack Dangermond with additional details on his vision for GIS in the cloud” and web services to enable data sharing. He particularly referenced CUAHSI HIS (Consortium of Universities for the Advancement of Hydrologic Science Inc.), an organization representing over 100 United States universities. CUAHSI has received National Science Foundation support to develop a web API and the HydroDesktop software application. The desktop application has been released as open source and available at no cost to users to help them download and manage available water data. But the web API and the database behind it are most interesting parts of the project. CUAHSI harvests sensor feeds of water data from 1000’s of sites across the United States. This data is archived and made available through a SOAP interface Dangermond collaborated with David Maidment on a paper for the AWRA proceedings that outlined the integration of water resources data using GIS and the web more generally and the CUAHSI project specifically. Maidment is the Director of the Center for Research in Water Resources at the University of Texas in Austin and heavily involved in the CUAHSI project. Both of them were also part of a panel discussion on the future of water resources information.

In addition to discussing Sajara with various organizations, one of the highlights of the conference for me was a presentation by the U.S. Army Corps of Engineers regarding GIS past, present and future for water resources applications. Part of their vision for the future includes augmented reality applications, enabled by smart phones, special glasses or potentially car windshields, which would augment the reality experience of approaching a well or other infrastructure asset, for example, with critical descriptive information, or even diagrams and engineering plans overlaid on the reality view. The potential for these projects is very exciting to me, particularly since the Philadelphia Department of Records recently received funding from the National Endowment for the Humanities under its Digital Humanities Startup Grant program to develop an augmented reality application for PhillyHistory.org that would enable smart phone users to view historic photographs of the city as an overlay on their camera displays by simply pointing their smart phone cameras at selected buildings.

AWRA will be holding this year’s annual conference right here in Philadelphia beginning on November 1, 2010. They will be addressing regional topics of interest to Mid-Atlantic water resources organizations. Perhaps Azavea will see you there.

The Poster Session at the AWRA Conference demonstrated Sajara’s ability to organize, search and retrieve infrastructure documents in a single web interface. Azavea’s poster was one of more than forty posters showcasing various aspects of GIS for the water resources industry.

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Mar 26, 2010

GLONASS Constellation Update

By Mary L. Johnson

Russia launched three additional GLONASS satellites on March 1, 2010. The launch was originally scheduled for September 2009, but had to be postponed when problems emerged with a similar satellite already in orbit and sent the three new satellites back to the factory for pre-launch repairs. The GLONASS constellation now includes 23 operational satellites, two of which are being used in a reserve capacity. A 21-satellite constellation provides 98.5% global availability. With three additional satellites expected to launch in August and another launch scheduled for November, the GLONASS constellation could reach 99.5% global availability by the end of 2010.

As a comparison, the current GPS constellation maintained by the United States includes 32 satellites and reached full operational capacity in 1995. It takes a minimum of 24 operational satellites to provide complete global availability.

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Feb 22, 2010

Solar Activity May Impact GPS Users

By Mary L. Johnson

A solar flare that occurred on February 12, 2010 may signal a return to high solar activity after several months of sustained low activity. Intense solar flares can cause temporary disruptions in GPS signals due to the high levels of radiation they release into the Earth’s atmosphere.

Solar activity generally occurs in eleven-year cycles, with the next peak expected by 2012. Increased solar activity is particularly troublesome for the navigation devices many drivers reference in their vehicles. GPS blackouts may last for a number of minutes during periods of peak solar activity and may occur several times each year. In addition to GPS blackouts, the atmospheric charge can impact the amount of time it takes for a GPS signal to make it to a GPS receiver, which causes inaccurate readings. Positioning may be off by as much as thirty feet during these periods, which will have the greatest impact on GPS survey equipment.

For iPhone users that want to keep track of solar activity, NASA has helped implement a new app called “3D Sun” that allows users to access a live global view of the sun. Data is provided in near real-time fashion by NASA’s STEREO mission, a pair of satellites that provide coverage of both sides of the sun simultaneously. More information on the app is available at http://3dsun.org/.

A high resolution 2D image of the sun taken by NASA's STEREO mission. STEREO is monitoring solar activity that may interfere with GPS and other signals. (Public domain image courtesy of NASA.)

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Jan 22, 2010

The Third Point in China’s Compass

By Mary L. Johnson

China launched the third satellite in its Compass Navigation Satellite System on January 17, 2010. This satellite is one of five planned geostationary satellites that will ultimately provide navigation coverage within the Asia-Pacific region. An additional 30 non-geostationary satellites are expected to be in place by 2020 in order to bring the Compass constellation to full global coverage.

Also known as the Beidou system, the geostationary satellites will provide free open service within the local service area. A second level of service will provide greater accuracy to authorized users only.

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