FROM: Charles W. Challstrom
Acting Director, National Geodetic Survey

SUBJECT: INSTRUCTIONS: Field Reconnaissance for NEVADA FBN, 1999 (GPS-1356)
Task Numbers: 8K6D2000
 

BACKGROUND:

The National Geodetic Survey (NGS), in accordance with the NGS Strategic Plan, is engaging in a campaign of observing stations of the Federal Base Network (FBN) to complete the ellipsoidal and orthometric height components of FBN. Requirements for field reconnaissance to support the upcoming survey in Nevada are outlined below.

FBN in Nevada consists of 38 stations (list and sketch included) that must be reconned. If a FBN station is not recoverable, a nearby GPS station (bench mark) should be recovered and the office informed. Two additional bench marks (one in the vicinity of station PERSHING and the other in the area formed by stations W 2, COALDALE 2, HAYET, and COVE) need to be reconned as well.

Since Central Temporary Continuously Operating Reference Stations (CTCORS) throughout the state will be used in the GPS portion of the project, the reconn party should note which stations are suitable to serve as such (i.e., a receiver must be able to be left unattended for 24 hours for a several-day period).
 

RECONNAISSANCE SPECIFICATIONS:

Contact the following person in the state of Nevada upon receipt of these instructions to begin coordination of reconnaissance activities:

Mr. Timothy Wolf
Las Vegas Valley Water District
PHONE: (702) 258-7163
FAX: (702) 258-3811
E-mail

The on-site coordinator for the project who also should be contacted will be:

Mr. Gary Fredrick
7600 Sand Point Way, NE
Seattle, WA 98115
PHONE: (206) 526-6842
E-mail

Reconnaissance shall consist of a review of existing control, field recovery and mark maintenance, station selection, and compilation of updated station descriptions in standard NGS Blue Book format.
 

LIAISON:

For concerns regarding survey field operations, contact:

William T. McLemore, Jr.
Chief, Field Operations Branch, N/NGS41
PHONE: (301) 713-3215, ext. 117
FAX: (301) 713-4327
E-mail

For concerns regarding survey design or specifications, contact:

Stephen J. Frakes (Doug Hendrickson)
Chief, Project Development Branch, N/NGS21
PHONE: (301) 713-3194, ext. 111 (ext. 127)
FAX: (301) 713-4316
E-mail (E-mail)
 

DATA:

All records for this project shall be archived under the title "NEVADA FBN, 1999" and accession number GPS-1356. Digital files shall be archived under filename "nvro039d.680".
 

REPORTS:

A summary of reconnaissance activities shall be included in the final project report.
 

ADDRESSES:

Keep N/NGS41 informed of the party's post office, physical address, and telephone number at all times.
 

PUBLICITY:

See NGS Operations Handbook, Section 1.4.1.
 

EXPENSES:

FBN expenses for this project will be charged to task number 8K6D2000.
 

TRAVEL:

Travel and per diem are authorized in accordance with Federal Travel Regulations, Part 301-7, Per Diem Allowances. Current per diem rates were effective January 1, 1998.
 

ACKNOWLEDGEMENT:

Please acknowledge receipt of these instructions in the Monthly Report and Journal.
 

cc:

N/CS - N. Prahl
N/NGS - S. Misenheimer*
N/NGS1 - G. Mitchell
N/NGS1x1 - J.D. D'Onofrio
N/NGS1x1 - D. Minkel
N/NGS1x1 - C. Smith
N/NGS11 - S. Cofer
N/NGS21 - S. Frakes
N/NGS21 - R. Anderson
N/NGS21 - D. Hendrickson*
N/NGS22 - T. Soler
N/NGS3 - E. Allen
N/NGS4 - E. Wade
N/NGS4 - D. Hoar
N/NGS41 - W. McLemore
N/NGS415 - G. Fredrick
N/NGS6 - D. Zilkoski*
FGCS Members*

Dennis Goreham, Utah Automated Geographic Reference Center
Don Bloodworth, Arizona Department of Transportation
Connie Brown, Arizona Department of Transportation
Phil Johnson, Hopi Tribe
Lemont Yazzie, Navajo Nation
Dean Wiese, Bureau of Land Management
J. Lumsden, U.S. Bureau of Reclamation
Bernard Kelly, Idaho Transportation Department
Timothy Wolf, Las Vegas Valley Water District

* first page only

FROM:  Charles W. Challstrom
Acting Director, National Geodetic Survey

SUBJECT:  INSTRUCTIONS:  NEVADA FBN, 1999 (GPS-1356)
Task Number:  8K6D2000 (FBN)
 

GENERAL:

The National Geodetic Survey (NGS), in accordance with the NGS Strategic Plan, is engaging in a campaign of observing stations of the Federal Base Network (FBN) to complete the ellipsoidal and orthometric height components of the FBN.  This survey will observe the 38 FBN stations in Nevada.  This campaign will be continuous and will tie into adjoining states.  (Some states will be skipped for seasonal relocations.)

In addition, two stations have been added to the project as bench mark ties.  Also included in this project is a station (DAVIAN) in northwest Arizona that will complete the FBN in that state.

Lastly, two bench marks (V 172 and K 173) have been included in the project to monitor subsidence in the vicinity of Lake Mead.

A full-wavelength, dual-frequency Global Positioning System (GPS) receiver is needed to act as a Central Temporary CORS (CTCORS) where there are no existing CORS within 300 km of the ongoing observations.  The receiver shall be deployed at a relatively secure station within the vicinity of the ongoing observing sessions.  The receiver shall continuously collect data at a 30- second epoch collection interval for a minimum of 72 hours and for as long as observations are ongoing in the vicinity of the CTCORS.  (Even if there is an existing CORS within 300 km of the ongoing observations, deploy a receiver at a relatively secure station and collect data for 72 hours or more.)

Mr. Gary Fredrick, NGS field coordinator for the project, is coordinating the co-observing by various organizations of approximately 40 (this number could vary significantly) additional Cooperative Base Network (CBN) stations that are also to meet the FBN specifications for this project.  The project will be performed under the technical management of NGS.
 

PURPOSE:

In order to meet America's accelerating positioning and navigation needs, the existing coordinate reference system must be continually enhanced to provide the accessibility and high accuracy required for use with GPS.  The digital revolution in mapping, charting, and surveying requires a National Spatial Reference System (NSRS) consisting of, among other components, a network of monumented points having four-dimensional positions.  The FBN fulfills the requirements for this component.  NGS is charged with the Federal responsibility for establishment, observation, monitoring, and maintenance of the FBN.  The FBN provides the critical network foundation for an accurate, consistent, reliable NSRS.

The NSRS, in turn, provides the common geographic framework for America's spatial data infrastructure.  As such, the NSRS serves as the basis for mapping, charting, navigation, boundary determination, property delineation, infrastructure development, resource evaluation surveys, and scientific applications, including crustal motion monitoring, modeling of flooding, storm surge, pollution trajectories, and agricultural runoff.  A modernized, accurate, consistent, reliable NSRS is of enormous benefit to state, county, tribal, local, and Federal authorities, as well as to the private sector.

SPECIFICATIONS:

Project requirements for the FBN observations are to ensure 2-centimeter local accuracy in the horizontal component, as well as 2-centimeter local accuracy for the ellipsoid heights.

Data from the CORS in the region are to be used in the processing.  There are five NGS CORS in California, one in Utah, and nine Northern Basin and Range (NBAR) CORS in Nevada, Utah, and California combined. (Seven NBAR CORS are in Nevada, and one each is in Utah and California.)  Also, there is one other CORS run by the Las Vegas Valley Water District in Nevada.

The five NGS CORS in California are: China Lake (COSO), Columbia College (CMBB), Goldstone (GOLD), Minaret (MINS), and Quincy (QUIN).  The NGS CORS in Utah is Red Butte (RBUT). The seven NBAR CORS in Nevada are (only id available):  GAR1, TUNG, UPSA, SLID, RUBY, GOSH, and EGAN.  The NBAR CORS in Utah and California, respectively, are (again, only id available): FOOT and SHIN.  The id for the CORS run by the Las Vegas Valley Water District is LVWD.  Positions and data for the NGS CORS are available from the NGS web site.  Contact Mr. Rick Bennett, listed under LIAISON,for the web site address to obtain the NBAR CORS data; contact Mr. Tim Wolf, again, under LIAISON, to obtain data from the Las Vegas Valley Water District CORS.
 

It should be noted that there is a 30-day delay in the availability of the NBAR CORS data.

General specifications for the project are as follows.  At each FBN site, three sessions of 5 1/2 hours duration for each session shall be observed.  The observing scheme shall be arranged so that for each station, the start time of one of the observing sessions shall be at least 4 hours different from the other two.  The observing scheme shall be arranged to ensure that adjacent FBN stations are directly connected in at least one observing session, and at least half of all base lines are repeated.

In general, station occupation and observing procedures must be carried out according to appropriate sections of the "NGS Operations Handbook" and the current applicable receiver field manuals.  Data formats and digital file definitions are given in "Input Formats and Specifications of the National Geodetic Survey Data Base," Volume I. Horizontal Control Data, Federal Geodetic Control Subcommittee, September 1994, revised and reprinted November 1998.  Success in meeting the accuracy standards will be based on repeatability of measurements, analysis of loop misclosures, and adjustment residuals.

General specifications for the project are given in "Geometric Geodetic Accuracy Standards and Specifications for Using GPS Relative Positioning Techniques," Version 5.0:  dated May 11, 1988, reprinted with corrections August 1, 1989.  Specific project criteria and deviations from the general specifications are given in the following sections.

Project Network - A list (Table 1) and sketch of stations involved in this project will be provided.

Data Acquisition - Data collection must be accomplished as specified in the appropriate dual-frequency receiver field manuals in the compressed mode at a 15-second epoch collection interval.  The GPS receivers must be dual-frequency and full- wavelength.  Track satellites down to a 10-degree elevation angle.

The satellite observing scenario has been provided in Table 2. (Sessions will generally begin at two observing windows at least 4 hours apart - 1605 UTC and 2010 UTC.  Vectors between the project stations shall be measured by single sessions consisting of continuously and simultaneously tracking for 5 1/2 hours.

Each FBN station must be occupied at least three times - twice at one observing window and once at the other.  Each FBN station must be tied to a bench mark in at least two sessions.  A different bench mark must be used for each of the two ties.  Adjacent FBN stations must be directly connected in at least one observing session, and at least one-half of all FBN base lines must be repeated.  The CORS base lines will be repeated.  CORS and CTCORS data will be used throughout the project.

For this project, each CBN station must also be occupied three times as described above.  However, CBN stations can be tied to adjacent FBN stations (if the FBN station is closer than a CBN station), and a base line consisting of a CBN station and a FBN station can be used in the repeated-base line requirement mentioned above for the CBN portion of this project.

Record weather data just before, immediately after, and at the mid-point of each session.  Meteorological data shall also be collected immediately after an obvious weather front passes during a session and immediately before it passes, if possible.  Pressure and relative humidity measurements must be made near and at about the height of the GPS antenna phase center.  Indicate in the log the location of the barometer and psychrometer.

Survey operations shall be conducted with due regard to the safety of personnel and equipment.  Contact with the airport traffic control tower is mandatory during surveys at any controlled airports.

Vector Computations - Data management, quality review of collected data, and final vector processing for the FBN survey will be accomplished by the field party using PAGES.  Vectors shall be computed in the International Earth Rotation Service Terrestrial Reference Frame (ITRF) system, using the most current epoch and precise IGS ephemerides.  Use 30-second epoch intervals for data processing.  Monument positions will be used for CORS when available, otherwise, antenna reference point (ARP) positions will be used.   For stations where weather data are not available, or are suspect, predicted values computed based on the station's latitude, height above mean sea level, and time and day of year will be used.  Use 15 degrees as the cutoff elevation angle in data processing.  A cutoff angle of 10 degrees may be used when necessary to improve results.

The type of final solution, L1 versus ion-free, will depend on the length of the vectors.  For vectors which are less than 10 km in length, the final reduction will consist of a L1 fixed solution.  These vectors will be computed in a separate processing session from the longer vectors computed in an ion- free solution.

In general, vectors greater than 10 km in length are to be computed in an ion-free fixed, or partially-fixed, solution.  In all cases, integer ambiguities will be fixed for each vector whenever possible.

The quality of collected data shall be determined from the plots generated from PAGES, by analysis of repeated vectors and/or comparison of station positions, and free adjustment residuals and/or loop misclosures.  In addition, a constrained adjustment constraining all CORS will be performed.

Survey Section B will perform all quality checks for conformance with NGS format standards such as executing software programs COMPGB, OBSCHK, and OBSDES.  The final ITRF vectors will be assessed and transformed to the NAD 83 coordinate system using program ADJUST.

The data and results will be submitted to the Observation and Analysis Division.  All B-files and G-files must be complete, including *25* and *27* records.
 

Station Descriptions - Station recovery notes must be submitted in computer-readable form using DDPROC software.  Include the name, address, and telephone number of a property owner or other contact.

Special Requirements - Antenna set-up is critical to the success of this project.  Fixed-height tripods are preferred for all receivers.  The plumbing bubbles on the antenna pole of the fixed-height tripod must be shaded when plumbing is performed.  They must be shaded for 3 minutes before checking and/or re- plumbing.  Also, the perpendicularity of the poles must be checked at the beginning of the project and any other time there is suspicion of a problem.

When a fixed-height tripod is not used, the height of the antenna must be carefully measured to prevent station set-up blunders from occurring.  Tribrachs used for these set-ups must be checked and adjusted when necessary.  Totally independent measurements of the antenna height above the mark in both metric and English units must be made before and after each session.  Someone other than the observer must check the measurement computations by carefully comparing measurements and then entering his/her initials on the log.

Some GPS antennas have detachable ground planes and radomes.  In order to help identify what exactly was used at a particular site, it would be useful to have a snapshot of the setup.  If possible, please take a photograph of the setup with a close-up   of the antenna as viewed from the side.

In addition, a rubbing of the stamping of the mark must be made at each visit to a station.  If it is impossible to make a rubbing of the mark, a plan sketch of the mark must be substituted, accurately recording all markings.

Also, for each station visited, a visibility obstruction diagram must be prepared and the TO-REACH description carefully checked for errors or omissions.

Lastly, the following must be recorded at each occupation of a station:

     (1) receiver manufacturer,
     (2) antenna manufacturer,
     (3) receiver model number (part number),
     (4) antenna model number (part number),
     (5) the complete serial number of the receiver, and
     (6) the complete serial number of the antenna.

Success of this project requires that the highest quality GPS data be collected.  Therefore, during each station occupation, the operators shall carefully monitor the operation of the receivers.  Any irregularities in the data due to equipment malfunction, DOD adjustment of the satellite orbit, obstructions, etc., must be reported to the Field Operations Branch, N/NGS41, as soon as possible and noted on the observing log.  If the quality of observations for an observing session is questionable, notify the Field Operations Branch immediately.

The survey team shall not depart the project area until they have quality reviewed all data, advised N/NGS21, and notified N/NGS41.
 

GPS DATA:

Visibility tables and plots of the present satellite constellation for April 26, 1999, have been reviewed and two observing windows selected.  For operational use, current data must be generated with Trimble mission planning software or from program SATMAP.

Project report and data listed in Annex L of "Input Formats and Specifications of the NGS Data Base" and in the attached addendum for the adjustment portion must be transmitted.  Any data considered suspect as to quality in achieving accuracy standards should be sent via FedEx immediately for office review.  Backup of transmitted data must be held until notified by the Field Operations Branch, N/NGS41.

The data set collected during the project shall be named "nvro039d.680".  All records in connection with this project shall be titled "NEVADA FBN, 1999".  The project number (accession number) is GPS-1356.
 

LIAISON:

Liaison must be maintained with designated offices at the National Geodetic Survey headquarters located at:
          1315 East-West Highway
          Silver Spring, Maryland  20910-3282

Questions and problems concerning survey field operations should be directed to:

          William T. McLemore, Jr.
          Chief, Field Operations Branch
          Observation and Analysis Division
          N/NGS41
          Telephone:  301-713-3215, ext. 117
          Fax:  301-713-4327
           E-mail

Questions and problems concerning adjustment processing should be
directed to:

          Maralyn L. Vorhauer
          Observation and Analysis Division
          N/NGS4
          Telephone:  301-713-3176, ext. 104
          Fax:  301-713-4327
            E-mail

Questions and problems concerning vector processing should be directed to:

          Juliana Blackwell
          Field Operations Branch
          Observation and Analysis Division
          N/NGS41
          Telephone: 301-713-3215, ext. 108
          Fax: 301-713-4327
           : E-mail

Questions and problems concerning using CORS data in processing should be directed to:

          Neil Weston
          Geosciences Research Division
          N/NGS6
          Telephone:  301-713-2847, ext. 202
          Fax:  301-713-4475
           : E-mail

Questions and problems which could affect the technical adequacy of the project should be directed to:

  Stephen J. Frakes (Douglas Hendrickson)
          Chief, Project Development Branch
          Spatial Reference System Division
          N/NGS21
          Telephone:  301-713-3194, ext. 111 (ext. 127)
          Fax:  301-713-4316
           : E-mail (E-mail)

The field coordinator for the project is:

          Mr. Gary Fredrick
          7600 Sand Point Way, NE
          Seattle, Washington 98115
          Telephone: 206-526-6842
            E-mail
 

Contacts for the CBN are:

          Mr. Tim Wolf
          Las Vegas Valley Water District
          1001 South Valley View
          Las Vegas, Nevada 89107
          Telephone: 702-258-7163
          Fax: 702-258-3811
            E-mail

          Mr. Larry Grube
          Summit Engineering
          5405 Mae Anne Avenue
          Reno, Nevada 89523
          Telephone: 775-747-8550

          Mr. Dan Harmening
          All Points North
          P.O. Box 1990
          Elko, Nevada 89803
          Telephone: 702-753-4142

The e-Mail and web site addresses for obtaining NBAR CORS data are:

          Mr. Rick Bennett,    E-mail or E-mail, web site: http://lox.ucsd.edu/permanentGPSSites
 

Names and telephone numbers of local contacts are given in the station description material.

ADDRESS:

Keep N/NGS41 informed of the party's post office, physical address, and telephone number at all times.

PUBLICITY:

See "NGS Operations Handbook," Section 1.4.1.

EXPENSES:

FBN expenses for this project will be charged to task number 8K6D2000.

TRAVEL:

Travel and per diem are authorized in accordance with Federal Travel Regulations, Part 301-7, Per Diem Allowances.  Current per diem rates were effective January 1, 1999.
 

ACKNOWLEDGMENT:

Please acknowledge receipt of these instructions in your Monthly Report.

Attachment

cc:  N/CS   - D. MacFarland
     N/NGS - D. Zilkoski*
     N/NGS - S. Misenheimer*
     N/NGS1 - G. Mitchell
     N/NGS1x1 - D. Minkel
     N/NGS1x1 - C. Smith
     N/NGS11 - S. Cofer
     N/NGS21 - S. Frakes
     N/NGS21 - R. Anderson
     N/NGS21 - D. Hendrickson*
     N/NGS22 - T. Soler
     N/NGS3 - E. Allen
     N/NGS4 - E. Wade
     N/NGS4 - M. Vorhauer
     N/NGS4 - D. Hoar
     N/NGS41 - W. McLemore
     N/NGS41 - J. Blackwell
     N/NGS5 - R. Snay
     N/NGS6 - N. Weston
     Dennis Goreham, Utah Automated Reference Center
     Don Bloodworth, Arizona Department of Transportation
     Connie Brown, Arizona Department of Transportation
     Dean Wiese, Bureau of Land Management
     Jerry Lumsden, U.S. Bureau of Reclamation
     David Domico, Central Arizona Project
     Bernard Kelly, Idaho Transportation Department
     Tim Wolf, Las Vegas Valley Water District
     Larry Grube, Summit Engineering
     Dan Harmening, All Points North
     FGCS Members*
 

* first page only
 

      DATA TO BE SENT TO HEADQUARTERS RELATING TO THE ADJUSTMENT PORTION OF THE PROJECT

Note that all except specified files or listings can be paper printouts or ASCII files on disk; be sure to keep backups until notified that the data base is loaded.

Free adjustment. [For A- and B-order projects, the data are not scaled.  First- order projects would also have a free adjustment using the modified G-file.]
Constrained horizontal adjustment holding previously published A- and B-order stations and ellipsoid heights (optional).
Constrained vertical adjustment holding NAVD 88 heights.
Final combined Blue Book file (ASCII required).
Free adjustment with accuracies.
Accuracy listing (output of BBACCUR).  (Paper required).
ELLACC output.
OBSCHK output*.
CHKDESC output*.
OBSDES output*.
*any errors or warning messages must be explained.
Copies of data used to determine fixed control, both horizontal and vertical.
Final description file (ASCII required).
Final G file (ASCII required).