THE REFERENCE POINT
News from and of the California Spatial Reference Center

No. 2; Spring 2000

"State of NGS 2000" Meeting Scheduled: Invitational "flyers" are being distributed for the annual "The State of NGS" meeting to be held on Thursday, April 6, 2000, at the Riverside County Flood District Office (1995 Market Street, Riverside, California). The cost is $25 and advance reservations are required by March 30. Lunch is included in the cost. (For more information contact Jay Keller at flood.jkeller@co.riverside.ca.us.) The primary purpose of this meeting is to provide an opportunity for NGS and California surveyors to interact on issues related to geodetic control. Mr. Charles Challstrom, the Director of the National Geodetic Survey (NGS), will be present to discuss NGS's goals and current activities and how they affect California. In addition, officers of the CSRC will provide a status report on the state of CSRC and its activities. And Mr. Michael Pallamary, P & D Consultants, Inc., will be making a presentation on "standard of care" as it relates to surveying. The meeting is scheduled from 9 a.m. to 3:30 p.m.

1998 HPGN Reobservation Results to be Released on April 6: CSRC and NGS intend to release the results of the 1998 HPGN reobservations at the April 6 "The State of NGS 2000" meeting (see above). This resurvey effort included 226 stations - 99 HPGN and other B Order stations, 82 CORS (all "healthy" CORS operating at that time), and about 45 additional stations (mostly HPGN Densification stations and NAVD88 benchmarks). NGS observed 68 "in ground" stations and the remaining in ground stations were observed by interested organizations. CSRC performed the analysis and adjustment for this resurvey. On March 17, CSRC completed its work and submitted the results to NGS for review and approval. Since the Center and NGS have worked closely on the analysis, both organizations expect the results will be available on April 6. In addition to new positions for the reobserved stations, the analysis effort also yielded the following important results regarding secular motions:
a. Computed velocities for the included CORS (based on observational data from the Southern California Integrated GPS Network).
b. Computed velocities for HPGN/other stations that are common to the various survey efforts - the original 1991 HPGN, the 1992 Landers resurvey, and the 1998 resurvey (based on actual observational data).
c. An improved velocity model.
CSRC also has made a "preliminary" adjustment of the original 1991 HPGN stations that were not observed in 1998 and propagated them to the reference epoch of July 1, 1998. These station positions were estimated by applying NGS's HTDP velocity model and the computed coseismic displacements induced by the Landers earthquake based on a dislocation model. NGS will be reviewing the adjustment methods for these stations in the near future.

CSRC Represented at Annual GIS Conference: CSRC Coordinating Council members Greg Helmer and Don D'Onofrio provided a half-hour presentation to a group of about 35 people at the 2000 California Geographic Information Systems (GIS) Conference recently held in Palm Springs. The presentation focused on the benefits of consistent and accurate spatial data that CSRC will enable. These included a single source for reference station coordinates that are consistent (and seamless) statewide, use and availability of CORS data, development of guidelines and specifications for the use of GPS, and training and workshops in GPS applications and related matters. During the conference, Don was approached by Scottie Barnes, editor of the GeoInfo Systems magazine and was asked to submit an abstract (or two) regarding the Center for possible publication. Scottie also offered to provide information to the editor of GPS World for a possible article in this magazine (both magazines are published by Advanstar Communications). Don and Greg will work with Mr. Barnes to provide the requested information and materials.

CSRC Members to Speak at CELSOC Conference: Don and Greg will be giving a similar presentation at the annual Consulting Engineers and Land Surveyors of California (CELSOC) Conference in Monterey on April 7. The presentation will focus on the benefits of the Center to the CELSOC community.

CSRC Members Spoke at CEAS Meeting: CSRC Coordinating Council member John Canas and CSRC Director Yehuda Bock provided an overview of CSRC to members of the Surveying and Land Use Committee of the California Engineers Association of California (CEAS) on March 9 in San Diego.

Use of CORS Data Explained at CLSA Workshop: On March 9, Michael Duffy (CSRC Coordinating Council member) and Cecilia Whitaker, both of Metropolitan Water District, conducted a workshop on accessing and processing CORS data. About 50 individuals from three southern California CLSA chapters attended the workshop, which was held in Anaheim. The workshop included an explanation of CORS - what are CORS, who establishes and maintains them, where are CORS currently established, the availability of data, and step-by-step procedures to extract raw CORS data. The practical use of CORS on actual projects was demonstrated. During the workshop, Mike and Cecilia explained the role of CSRC in establishing and maintaining a California spatial reference system, which has a primary reliance on CORS. The workshop was well received.

Local Congresspersons Representatives Contacted: CSRC Chairperson Bill Young and Gary Magnuson from the National Oceanic and Atmospheric Administration (NGS's parent organization) met with staff from Senator Feinstein's office on March 7. The primary purpose of this meeting was to gain support for release of the "National Height Modernization Study" report that NGS prepared and submitted to Congress in March 1999. Although this report has not been released to the public to date, it is anticipated that this report contains justification for modernizing the nation's vertical network through GPS technology and recommendations for funding such program. A similar meeting was held the next day with staff from Congressman Cunningham's (from Escondido) office. Staff members from both offices were encouraging and agreed to assist in "freeing up" the report. These meetings also provided opportunities for Bill to explain the purpose and goals of the CSRC.

Planning Underway for the Hector Mine Reobservations: On October 16, 1999, a 7.1 magnitude earthquake occurred in the Mojave desert near Hector Mine, disturbing a number of geodetic control stations. Using data developed by the earth scientists, Marti Ikehara (representing NGS) and Don D'Onofrio (representing the CSRC) have compiled an initial list of stations that will require reobservation. In addition, they have requested interested surveying organizations to participate in the reobservations. To date (March 22), agreement has been received from NGS (four receivers/observers), San Bernardino County (3 receivers and observational support), and Riverside County Flood Control and Water Conservation District (five receivers/observers). Tentative agreement also has been obtained from Caltrans District 11 (San Diego) to provide observational support for the stations in San Diego and Imperial Counties. Several other requests for support were sent out with a request for response by March 24. The survey is scheduled to begin about May 1 and will include about 46 stations that were observed in the 1991 HPGN survey, the 1992 Landers earthquake reobservations, or the 1998 HPGN resurvey. The total time required for the reobservations will depend on the type of support provided by the participating organizations. Marti Ikehara plans to spend the week of March 27 recovering the stations proposed for the survey and updating, if necessary, the station descriptions. NGS headquarters office will develop the observing schedule. USGS, Menlo Park, plans to perform a survey concurrently at about a dozen stations in the vicinity.

Chairperson Young to Brief SCIGN and CLSA Board Members: CSRC Chairman, Bill Young, is scheduled to provide briefings on the status and activities of the Center to the following organizations: * On April 12, Bill will brief the Southern California Integrated GPS Network (SCIGN) Coordinating Board members at their annual meeting in San Diego. (SCIGN is a multi-million dollar earthquake research effort that is in the process of establishing 200 to 250 CORS. This endeavor is greatly benefiting California's geodetic control efforts and, in general, the surveying community. Bill is a member of SCIGN's Executive Board.) * Bill also will present a brief update on CSRC to the CLSA Broad members at their quarterly meeting in Burlingame on May 13. At this meeting, the primary focus of the briefing will be funding issues. (CLSA has been a long-standing supporter of CSRC and is assisting CSRC in developing funds at the state level.)

Next CSRC Coordinating Council Meeting Scheduled: The next meeting of the CSRC Coordinating Council members will be held in Sacramento on Tuesday, May 16, 2000 revised to Wednesday, May 17, 2000 . Mark your calendar. More information will be distributed as the meeting date approaches. If you have suggested agenda topics, contact Chairperson Bill Young at byoung@deltanet.com.

This Issue Editor: Larry Fenske (lfenske@jps.net) Contributing Author: Don D'Onofrio