Transportable DGPS reference station Baseline HD by CLAAS for use in satellite-assisted steering systems in modern agriculture

Differential Global Positioning System (DGPS) is an enhancement to Global Positioning System that provides improved location accuracy, from the 15-meter nominal GPS accuracy to about 10 cm in case of the best implementations.

DGPS uses a network of fixed, ground-based reference stations to broadcast the difference between the positions indicated by the satellite systems and the known fixed positions. These stations broadcast the difference between the measured satellite pseudoranges and actual (internally computed) pseudoranges, and receiver stations may correct their pseudoranges by the same amount. The digital correction signal is typically broadcast locally over ground-based transmitters of shorter range.

The term can refer both to the generalized technique as well as specific implementations using it. For instance, the United States Coast Guard (USCG) and Canadian Coast Guard (CCG) each run such a system in the U.S. and Canada on the longwave radio frequencies between 285 kHz and 325 kHz near major waterways and harbors. The USCG's DGPS system is nationwide and comprises 86 broadcast sites located throughout the inland and coastal portions of the United States including Alaska, Hawaii and Puerto Rico.

A similar system that transmits corrections from orbiting satellites instead of ground-based transmitters is called a Wide-Area DGPS (WADGPS)^[1] or Satellite Based Augmentation System.

History[link]

When GPS was first being put into service, the US military was concerned about the possibility of enemy forces using the globally available GPS signals to guide their own weapon systems. Originally, the government thought the "coarse acquisition" (C/A) signal would only give about 100 meter accuracy, but with improved receiver designs, the actual accuracy was 20 to 30 meters.^[2] Starting in March 1990,^[3] to avoid providing such unexpected accuracy, the C/A signal transmitted on the L1 frequency (1575.42 MHz) was deliberately degraded by offsetting its clock signal by a random amount, equivalent to about 100 meters of distance. This technique, known as "Selective Availability", or SA for short, seriously degraded the usefulness of the GPS signal for non-military users. More accurate guidance was possible for users of dual frequency GPS receivers that also received the L2 frequency (1227.6 MHz), but the L2 transmission, intended for military use, was encrypted and was only available to authorised users with the encryption keys.

This presented a problem for civilian users who relied upon ground-based radio navigation systems such as LORAN, VOR and NDB systems costing millions of dollars each year to maintain. The advent of a global navigation satellite system (GNSS) could provide greatly improved accuracy and performance at a fraction of the cost. The accuracy inherent in the S/A signal was however too poor to make this realistic. The military received multiple requests from the Federal Aviation Administration (FAA), United States Coast Guard (USCG) and United States Department of Transportation (DOT) to set S/A aside to enable civilian use of GNSS, but remained steadfast in its objection on grounds of security.

Through the early to mid 1980s, a number of agencies developed a solution to the SA "problem".^{[dubious – discuss]} Since the SA signal was changed slowly, the effect of its offset on positioning was relatively fixed – that is, if the offset was "100 meters to the east", that offset would be true over a relatively wide area. This suggested that broadcasting this offset to local GPS receivers could eliminate the effects of SA, resulting in measurements closer to GPS's theoretical performance, around 15 meters. Additionally, another major source of errors in a GPS fix is due to transmission delays in the ionosphere, which could also be measured and corrected for in the broadcast. This offered an improvement to about 5 meters accuracy, more than enough for most civilian needs.^[1]

The US Coast Guard was one of the more aggressive proponents of the DGPS system, experimenting with the system on an ever-wider basis through the late 1980s and early 1990s. These signals are broadcast on marine longwave frequencies, which could be received on existing radiotelephones and fed into suitably equipped GPS receivers. Almost all major GPS vendors offered units with DGPS inputs, not only for the USCG signals, but also aviation units on either VHF or commercial AM radio bands.

They started sending out "production quality" DGPS signals on a limited basis in 1996, and rapidly expanded the network to cover most US ports of call, as well as the Saint Lawrence Seaway in partnership with the Canadian Coast Guard. Plans were put into place to expand the system across the US, but this would not be easy. The quality of the DGPS corrections generally fell with distance, and largest transmitters capable of covering large areas tend to cluster near cities. This meant that lower-population areas, notably in the midwest and Alaska, would have little coverage by ground-based GPS. As of January 2012 the USCG's national DGPS system comprises 86 broadcast sites which provide dual coverage to almost the entire US coastline and inland navigable waterways including Alaska, Hawaii, and Puerto Rico. In addition the system provides single or dual coverage to a majority of the inland portion of United States.

USCG DGPS coverage plot via USCG Navigation Center

Instead, the FAA (and others) started studies for broadcasting the signals across the entire hemisphere from communications satellites in geostationary orbit. This has led to the Wide Area Augmentation System (WAAS) and similar systems, although these are generally not referred to as DGPS, or alternatively, "wide-area DGPS". WAAS offers accuracy similar to the USCG's ground-based DGPS networks, and there has been some argument that the latter will be turned off as WAAS becomes fully operational.

By the mid-1990s it was clear that the SA system was no longer useful in its intended role. DGPS would render it ineffective over the US, precisely where it was considered most needed. Additionally, experience during the Gulf War demonstrated that the widespread use of civilian receivers by U.S. forces meant that leaving SA turned on was thought to harm the U.S. more than if it were turned off.^{[4][citation needed]} After many years of pressure, it took an executive order by President Bill Clinton to get SA turned off permanently in 2000.^[5]

Nevertheless, by this point DGPS had evolved into a system for providing more accuracy than even a non-SA GPS signal could provide on its own. There are several other sources of error that share the same characteristics as SA in that they are the same over large areas and for "reasonable" amounts of time. These include the ionospheric effects mentioned earlier, as well as errors in the satellite position ephemeris data and clock drift on the satellites. Depending on the amount of data being sent in the DGPS correction signal, correcting for these effects can reduce the error significantly, the best implementations offering accuracies of under 10 cm.

In addition to continued deployments of the USCG and FAA sponsored systems, a number of vendors have created commercial DGPS services, selling their signal (or receivers for it) to users who require better accuracy than the nominal 15 meters GPS offers. Almost all commercial GPS units, even hand-held units, now offer DGPS data inputs, and many also support WAAS directly. To some degree, a form of DGPS is now a natural part of most GPS operations.

Operation[link]

A reference station calculates differential corrections for its own location and time. Users may be up to 200 nautical miles (370 km) from the station, however, and some of the compensated errors vary with space: specifically, satellite ephemeris errors and those introduced by ionospheric and tropospheric distortions. For this reason, the accuracy of DGPS decreases with distance from the reference station. The problem can be aggravated if the user and the station lack "inter visibility"—when they are unable to see the same satellites.

Accuracy[link]

The United States Federal Radionavigation Plan and the IALA Recommendation on the Performance and Monitoring of DGNSS Services in the Band 283.5–325 kHz cite the United States Department of Transportation's 1993 estimated error growth of 0.67 m per 100 km from the broadcast site^[6][7] but measurements of accuracy across the Atlantic, in Portugal suggest a degradation of just 0.22 m per 100 km.^[8]

Variations[link]

DGPS can refer to any type of Ground Based Augmentation System (GBAS). There are many operational systems in use throughout the world, according to the US Coast Guard, 47 countries operate systems similar to the US NDGPS (Nationwide Differential Global Positioning System).

A list can be found here 300KHz DGPS stations

European DGPS Network[link]

The European DGPS network has been mainly developed by the Finnish and Swedish maritime administrations in order to improve safety in the archipelago between the two countries.

In the UK and Ireland, the system was implemented as a maritime navigation aid to fill the gap left by the demise of the Decca Navigator System in 2000. With a network of 12 transmitters sited around the coastline and three control stations, it was set up in 1998 by the countries' respective General Lighthouse Authorities (GLA) — Trinity House covering England, Wales and the Channel Islands, the Northern Lighthouse Board covering Scotland and the Isle of Man and the Commissioners of Irish Lights, covering the whole of Ireland. Transmitting on the 300 kHz band, the system underwent testing and two additional transmitters were added before the system was declared operational in 2002.^[9][10]

Trinity House - DGNSS Stations: UK and Ireland

Effective Solutions (Data Products) - European Differential Beacon Transmitters - Details and map

United States NDGPS[link]

The United States Department of Transportation, in conjunction with the Federal Highway Administration, the Federal Railroad Administration and the National Geodetic Survey appointed the Coast Guard as the maintaining agency for the U.S. Nationwide DGPS network (NDGPS). The system is an expansion of the previous Maritime Differential GPS (MDGPS), which the Coast Guard began in the late 1980s and completed in March 1999. MDGPS only covered coastal waters, the Great Lakes, and the Mississippi River inland waterways, while NDGPS expands this to include complete coverage of the continental United States.^[11] The centralized Command and Control unit is the USCG Navigation Center, based in Alexandria, VA.^[12] There are currently 86 NDGPS sites in the US network, and there are plans for up to 128 total sites to be online within the next 15 years.^{[citation needed]}

Canadian DGPS[link]

The Canadian system is similar to the US system and is primarily for maritime usage covering the Atlantic and Pacific coast as well as the Great Lakes and Saint Lawrence Seaway.

Australia[link]

Australia runs three DGPS systems: one is mainly for marine navigation, broadcasting its signal on the longwave band;^[13] another is used for land surveys and land navigation, and has corrections broadcast on the Commercial FM radio band. While the third at Sydney airport is currently undergoing testing for precision landing of aircraft (2011), as a backup to the Instrument Landing System at least until 2015. It is called the Ground Based Augmentation System. Corrections to aircraft position are broadcast via the aviation VHF band.

Post processing[link]

Post-processing is used in Differential GPS to obtain precise positions of unknown points by relating them to known points such as survey markers.

The GPS measurements are usually stored in computer memory in the GPS receivers, and are subsequently transferred to a computer running the GPS post-processing software. The software computes baselines using simultaneous measurement data from two or more GPS receivers.

The baselines represent a three-dimensional line drawn between the two points occupied by each pair of GPS antennas. The post-processed measurements allow more precise positioning, because most GPS errors affect each receiver nearly equally, and therefore can be cancelled out in the calculations.

Differential GPS measurements can also be computed in real-time by some GPS receivers if they receive a correction signal using a separate radio receiver, for example in Real Time Kinematic (RTK) surveying or navigation.

The improvement of GPS positioning doesn't require simultaneous measurements of two or more receivers in any case, but can also be done by special use of a single device. In the 1990s when even handheld receivers were quite expensive, some methods of quasi-differential GPS were developed, using the receiver by quick turns of positions or loops of 3-10 survey points.

See also[link]

• Global Positioning System (GPS)
• Wide Area Augmentation System (WAAS) - A space-based augmentation system (SBAS) primarily for aviation usage
  • European Geostationary Navigation Overlay Service (EGNOS) and Multi-functional Satellite Augmentation System (MSAS)
• Local Area Augmentation System (LAAS) - Another type of ground-based augmentation system (GBAS), but designed primarily for aviation usage
• Assisted GPS (A-GPS) - System used primarily in GPS equipped cellular devices to improve startup performance
• StarFire
• OmniSTAR (DGPS)

References[link]

External links[link]

Wikimedia Commons has media related to: Differential Global Positioning System

• SiReNT information page
• US NDGPS fact sheet
• USCG Navigation Center National DGPS system
• USCG coverage maps
• Canadian Coast Guard DGPS information (English)
• Canadian Coast Guard DGPS information (French)
• Product Survey on RTK DGPS receivers for (mainly) hydrographic use
• DGPS Decoding Software
• Useful DGPS Links, Databases and Resources
• Worldwide database of IALA DGPS Reference stations on an interactive map

Tommy Thompson
19th United States Secretary of Health and Human Services
In office February 2, 2001 – January 26, 2005
President	George W. Bush
Preceded by	Donna Shalala
Succeeded by	Mike Leavitt
42nd Governor of Wisconsin
In office January 5, 1987 – February 1, 2001
Lieutenant	Scott McCallum
Preceded by	Tony Earl
Succeeded by	Scott McCallum
Personal details
Born	Tommy George Thompson (1941-11-19) November 19, 1941 (age 70) Elroy, Wisconsin
Political party	Republican
Spouse(s)	Sue Ann Mashak (m. 1968)
Alma mater	University of Wisconsin–Madison University of Wisconsin Law School
Religion	Roman Catholic
Military service
Service/branch	United States Army
Rank	Captain

Tommy George Thompson (born November 19, 1941), a United States Republican politician, was the 42nd Governor of Wisconsin, after which he served as U.S. Secretary of Health and Human Services. Thompson was a candidate for the 2008 U.S. Presidential Election, but dropped out early after a poor performance in polls.^[1] He is currently running for the United States Senate election in 2012.^[2]

Early life, education, and military service[link]

Thompson was born in Elroy, Wisconsin, where his father, Allan, owned and ran a gas station and country grocery store, and his mother, Julia, was a teacher.^[3] He is a former captain in the United States Army and United States Army Reserve, and holds a law degree from the University of Wisconsin Law School.

Early political career (1966-1987)[link]

Wisconsin Assembly[link]

Thompson was elected to the Wisconsin State Assembly in 1966; he became the Assembly's assistant minority leader in 1973 and minority leader in 1981. He was famous for aggressively utilizing parliamentary procedure to give his minority party some limited say in the legislative process. Since this use of procedure was invariably one of delay and obstruction, he soon received the nickname "Dr. No" by the frustrated majority.^{[neutrality is disputed]}

1979 congressional election[link]

Incumbent Republican U.S. Congressman William Steiger of Wisconsin's 6th congressional district died at the age of 40 from a heart attack. There was a special election in 1979. In the February 1979 Republican primary, he was defeated by Tom Petri 35%-19%.^[4] Petri won the general election and still represents the 6th district today.

Governor of Wisconsin (1987-2001)[link]

Thompson served as the 42nd Governor of Wisconsin, having been elected to an unprecedented four terms. While serving as governor, he was elected Chairman of the Midwestern Governors Association in 1989 and 1990.

The American Legislative Exchange Council identifies Thompson in the form of one of its success stories, being important to the organization in its formative years.^[5]

Elections[link]

1986

Thompson decided to run for Governor of Wisconsin in 1986 against incumbent Democrat Anthony Earl. He ran and won the Republican primary with 52% of the vote in a five candidate field.^[6] He defeated Earl 53%-46%.^[7]

1990

Thompson won re-election to a second term defeating Democrat Thomas Loftus, the Speaker of the Wisconsin State Assembly, 58%-42%.^[8]

1994

Thompson won re-election to a third term defeating Democrat State Senator Chuck Chvala 67%-31%. He won every county in the state except Menominee County.^[9]

1998

Thompson won re-election to a fourth term defeating Democrat Ed Garvey, the Wisconsin Deputy Attorney General, 60%-39%.^[10]

Tenure[link]

Thompson's initiatives during his 14 years as governor of Wisconsin were his Wisconsin Works welfare reform and school choice programs.^[11] In 1990 Thompson pushed for the creation of the country's first parental school-choice program, allowing low-income Milwaukee families to send children to the private or public school of their choice at taxpayer expense. He created the BadgerCare program, designed to provide health coverage to those families whose employers don't provide health insurance but make too much money to qualify for Medicaid. Through the federal waiver program, Thompson helped replicate this program in several states when he became Secretary of Health and Human Services.

Post-gubernatorial career[link]

Health and Human Services Secretary[link]

Thompson at the 2004 HealthierUS summit

Thompson left office when he was appointed by President George W. Bush as HHS Secretary. Thompson announced his resignation from HHS on December 3, 2004, and served until January 26, 2005, when the Senate confirmed his successor, Michael O. Leavitt.

Business career[link]

He was a member of the Amtrak Board of Directors and had an Amtrak locomotive named for him.^[12][13][14]

Thompson is a partner at Akin Gump, a Washington, D.C., law firm, and was formerly senior adviser at the consulting firm Deloitte and formerly the independent chairman of the Deloitte Center for Health Solutions.^[15] Thompson taught a class in the fall of 2005 at Harvard University's Kennedy School of Government on medical diplomacy.^[16]

Shortly after leaving his Bush Cabinet post, Thompson joined and served for two years on the board of directors of Applied Digital Solutions, makers of the controversial VeriChip: a glass-encapsulated RFID chip that can be injected into human flesh for various database-driven identification purposes.

He was formerly the co-host for their television series, Plain Talk About Health.^[17]

2008 Presidential campaign[link]

After first announcing the formation of an exploratory committee in late 2006, Thompson announced his candidacy for the 2008 presidential election on April 1, 2007.^[18]

During a May 3, 2007, presidential debate at the Ronald Reagan Presidential Library Thompson said in response to a question from moderator Chris Matthews that a private employer opposed to homosexuality should have the right to fire a gay worker.^[19] He said, "I think that is left up to the individual business. I really sincerely believe that that is an issue that business people have got to make their own determination as to whether or not they should be." He called CNN the following morning to say he didn't hear the question correctly. He apologized, saying, "It's not my position. There should be no discrimination in the workplace."

Thompson had stated he would drop out of the race if he did not finish either first or second in the Ames straw poll on August 11, 2007. Thompson finished sixth, with just 7% of the vote, despite the fact that some major contenders were not competing in the poll. On August 12, Thompson officially announced he would drop out of the race.

In October 2007, Thompson endorsed Rudy Giuliani. Thompson told the Associated Press in a statement that "Rudy Giuliani has shown that he is a true leader. He can and will win the nomination and the presidency. He is America's mayor, and during a period of time of great stress for this country he showed tremendous leadership." He then endorsed Senator John McCain after Giuliani's withdrawal from the presidential race.^[20] However, in a New York Times article published October 11, 2008, Thompson is quoted in response to a question regarding whether he was happy with McCain's campaign as saying, "No. I don't know who is."^[21]

2012 U.S. Senate election[link]

On September 19, 2011, Thompson officially launched his campaign to run for the Wisconsin senate seat vacated by Sen. Herb Kohl.^[22] On December 1, 2011, he formally announced his candidacy.

Criticism[link]

Medicare controversies[link]

After leaving office, Thompson promoted changes to Medicare that some complained would benefit companies Thompson has a financial stake in (including Centene and the Deloitte Center for Health Solutions).^[23]

Additionally, while in office, Thompson was involved in a dispute over whether the Center for Medicare and Medicaid Services had to share cost estimates to Congress for legislation that would create a prescription drug benefit. Critics accused HHS of downplaying the true cost of the law by $150 billion. CMS Administrator Tom Scully threatened to fire the actuary if he revealed to Congress his estimate. Investigators determined that the data was improperly hidden from Congress, but did not conclude whether laws had been broken.^[24]

Treatment of Ojibwa spearfishers[link]

During his 1986 gubernatorial campaign, Thompson suggested abrogating the right of Wisconsin's Ojibwa tribe to engage in traditional spearfishing.^[25] Once in office, Thompson called on the tribe to sell their rights to spearfish in off-reservation lakes and streams, which is guaranteed by treaties with the United States, for $42 million dollars to the Lac du Flambeau Band of Lake Superior Chippewa and $10 million to the Mole Lake Band of Lake Superior Chippewa.^[25] Thompson and anti-spearfishing organizations Protect Americans' Rights and Resources and Stop Treaty Abuse-Wisconsin tried unsuccessfully to challenge the 1983 "Voigt Decision" of the Seventh Circuit Court of Appeals—which prohibited Wisconsin from regulating fishing on Ojibwe land.^[25] The decision was upheld by the Supreme Court of the United States in 1983.^[25][26] Thompson claimed that Native Americans' lives were in danger from protesters associated with PARR and STA if they continued spearfishing.  In 1989, federal judge Barbara Crabb refused the request and chastised the state for attempting to avoid violence by punishing the Ojibwa, who had broken no laws, since it was violence by non-Native American protesters that was threatening.^[26] Crabb issued an injunction against violent anti-spearfishing protests in 1991, and made it permanent in 1992.^[27] On May 20, 1991, the Thompson administration declared it would no longer attempt to appeal the 1983 Voight Decision.^[25]

Statements about Jews, Israel[link]

In April 2007, Thompson was compelled to apologize for remarks he made about Jews and Israel during an address to an assembled crowd of Jewish social activists in Washington, D.C.^[28] On April 18, 2007, appearing before a conference organized by the Religious Action Center of Reform Judaism, Thompson made reference to his lucrative transition from public service to the private sector by stating: "You know that's sort of part of the Jewish tradition and I do not find anything wrong with that."^[29] After the conclusion of his address, Thompson was reportedly pulled aside privately by the RAC's Rabbi David Saperstein, and then returned to the podium to issue a clarification,^[30] adding: "I just want to clarify something because I didn't (by) any means want to infer or imply anything about Jews and finances and things. What I was referring to, ladies and gentlemen, is the accomplishments of the Jewish religion. You've been outstanding business people and I compliment you for that."^[29]

Later, Thompson told Politico that his remarks could be blamed on fatigue and a persistent cold.^[28]

Thompson made a variety of other lesser gaffes, including referring to the Anti Defamation League as the fringe Jewish Defense League, and to Israel bonds as "Jewish bonds".^[31][32][33] He also discussed his connections to politically conservative Israeli and Jewish leaders while speaking to the mostly liberal leaning group.^[31]

Conference organizers avoided comment on the faux pas, instead praising Thompson's decision to appear before the group.^[34]

Politicizing of science[link]

In 2001, early in his term as Secretary of Health and Human Services, Thompson's office rejected 19 of 26 people recommended for seats on the advisory board for the NIH developing nations unit, including a Nobel laureate, by the unit's director.^[35] In return, Thompson's office sent résumés for other scientists that Gerald Keusch, the director of the Fogarty International Center, described in an interview as "lightweights" with "no scientific credibility". Keusch relayed to the Nobel laureate, Torsten Wiesel, that he was rejected for having "signed too many full-page letters in The New York Times critical of President Bush." ^[36] This incident was cited by the advocacy group Union of Concerned Scientists as part of a report detailing their allegations of politicization of science under President George W. Bush's administration.^[37][38]

Electoral history[link]

References[link]

External links[link]

Official sites

• U.S. Senate Campaign Website

Documentaries, topic pages and databases

• Federal Election Commission - Tommy G. Thompson (President) campaign finance reports
• On the Issues - Tommy Thompson issue positions and quotes
• PBS NewsHour with Jim Lehrer - Vote 2008: Tommy Thompson
• "Tommy Thompson and the Conservative Revolution"; primary source material compiled by the Wisconsin Historical Society
• Tommy Thompson at the Open Directory Project
• Tommy G. Thompson Collection, 1957-ongoing Special Collections & Archives, Marquette University (archive of materials donated by Thompson and others)
• Appearances on C-SPAN

Media coverage

• New York Times - Tommy G. Thompson news stories and commentary

v t e United States Secretaries of Health and Human Services (previously United States Secretary of Health, Education, and Welfare) Secretaries of Heath, Education, and Welfare Hobby Folsom Flemming Ribicoff Celebrezze Gardner Cohen Finch Richardson Weinberger Mathews Califano Harris Secretaries of Health and Human Services Harris Schweiker Heckler Bowen Sullivan Shalala Thompson Leavitt Sebelius

v t e Governors of Wisconsin Territory (1836–1848) Dodge Doty Tallmadge Dodge State (since 1848) Dewey Farwell Barstow MacArthur Bashford Randall Harvey Salomon Lewis Fairchild Washburn Taylor Ludington Smith Rusk Hoard Peck Upham Scofield R. La Follette Davidson McGovern Philipp Blaine Zimmerman Kohler Sr. P. La Follette Schmedeman P. La Follette Heil Goodland Rennebohm Kohler Jr. Thomson Nelson Reynolds Knowles Lucey Schreiber Dreyfus Earl Thompson McCallum Doyle Walker

v t e Cabinet of President George W. Bush (2001–2009)   Cabinet Secretary of State Colin Powell (2001–2005) Condoleezza Rice (2005–2009) Secretary of the Treasury Paul O'Neill (2001–2002) John W. Snow (2003–2006) Henry Paulson (2006–2009) Secretary of Defense Donald Rumsfeld (2001–2006) Robert Gates (2006–2009) Attorney General John Ashcroft (2001–2005) Alberto Gonzales (2005–2007) Michael Mukasey (2007–2009) Secretary of the Interior Gale Norton (2001–2006) Dirk Kempthorne (2006–2009) Secretary of Agriculture Ann Veneman (2001–2005) Mike Johanns (2005–2007) Ed Schafer (2008–2009) Secretary of Commerce Donald Evans (2001–2005) Carlos Gutierrez (2005–2009) Secretary of Labor Elaine Chao (2001–2009) Secretary of Health and Human Services Tommy Thompson (2001–2005) Mike Leavitt (2005–2009) Secretary of Education Rod Paige (2001–2005) Margaret Spellings (2005–2009) Secretary of Housing and Urban Development Mel Martinez (2001–2003) Alphonso Jackson (2003–2008) Steve Preston (2008–2009) Secretary of Transportation Norman Mineta (2001–2006) Mary Peters (2006–2009) Secretary of Energy Spencer Abraham (2001–2005) Samuel Bodman (2005–2009) Secretary of Veterans Affairs Anthony Principi (2001–2005) Jim Nicholson (2005–2007) James Peake (2007–2009) Secretary of Homeland Security Tom Ridge (2003–2005) Michael Chertoff (2005–2009)   Cabinet-level Vice President Dick Cheney (2001–2009) White House Chief of Staff Andrew Card (2001–2006) Joshua Bolten (2006–2009) Administrator of the Environmental Protection Agency Christine Todd Whitman (2001–2003) Mike Leavitt (2003–2005) Stephen L. Johnson (2005–2009) Director of the Office of Management and Budget Mitch Daniels (2001–2003) Joshua Bolten (2003–2006) Rob Portman (2006–2007) Jim Nussle (2007–2009) Director of National Drug Control Policy John P. Walters (2001–2009) Trade Representative Robert Zoellick (2001–2005) Rob Portman (2005–2006) Susan Schwab (2006–2009)