Clifton S. Middleton
Project Director, Survey Section B

Charles W. Challstrom
Director, National Geodetic Survey

INSTRUCTIONS: ARKANSAS FBN, 2000 (GPS-1411)
Task Numbers: 8K6D2000 (FBN) 8K6D4000 (CORS FBN/CBN TIE)

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 22 FBN stations in Arkansas. This campaign will be continuous and will tie into adjoining states. (Some states will be skipped for seasonal relocations.)

FBN station FB 10+00 is presumed destroyed and is being replaced by station FB 26+37 (PID AA9332).

Stations C 62 (PID DL1088), D 293 (PID FG1566), N 48 (PID FG0055), and Z 294 (PID FG1627) are included in the project to serve as bench mark ties only. Q 299 (PID EK0677) is a bench mark tie that is also a Cooperative Base Network (CBN) station.

In addition, at the DeQueen Continuously Operating Reference Station (CORS) site, a pair of CORS reference marks is to be tied to both the local FBN/CBN and the CORS antenna. The reference marks are DQUA A (PID AE7115) and DQUA B (PID AE7116). The FBN/CBN station to use is HOCHATOWN (PID EK1040) (in Oklahoma). The backup tie station is MENAPORT AZ MK (PID EK1036).

A full-wavelength, dual-frequency Global Positioning System (GPS) receiver is needed to act as Central Temporary CORS (CTCORS) throughout the project. The receiver shall be deployed at relatively secure stations 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.

A total of approximately 53 CBNs will be surveyed in this project and are to meet FBN specifications. Participants include Messrs. Dean Wilkerson and Kit Carson of the Arkansas Highway and Transportation Department, Ms. Mickie Warwick of Petit Jean College, and Mr. Fred Ballard of Tyler Surveying. 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.

The reference marks established at the DeQueen CORS site will provide a very accurate tie to the antenna as an aid to reposition the antenna should that become necessary. The FBN/CBN tie to the reference marks will also provide site station coordinates relative to the local FBN/CBN, thus reducing the potential for relative error between the reference marks and the local network. It will also provide a check on the FBN/CBN, relative to the CORS coordinates.

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 six NGS CORS in the area. There is also a GPS base station (ROUCH) operated by the University of Arkansas - Little Rock. Finally, there is an additional GPS base station in northwestern Louisiana operated by the Northwest Louisiana Council of Governments. It is currently located in Bossier City, although it will be moved to Shreveport sometime in January.

The six NGS CORS are: Conway (CNWN) in Missouri, Sallisaw (SAL1) in Oklahoma, DeQueen (DQUA) in Arkansas, Winfield (WNFL) in Louisiana, Memphis (MEM2) in Tennessee, and Vicksburg (VIC1) in Mississippi.

Positions and data for the NGS CORS are available from the NGS web site. Contact Mr. Jud Rouch, listed under LIAISON, to obtain the University of Arkansas - Little Rock CORS data. Contact Mr. Chris Petro, listed under LIAISON, to obtain the Bossier City-Shreveport 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.

Specific to the DeQueen CORS site is that for the two reference marks at the site, two sessions of 2 hours each shall be observed. In order to provide a check, the equipment shall be broken down and reset with a minimum of 30 minutes between the two sessions. Since the CORS site is to be tied to the nearest FBN/CBN station, FBN station HOCHATOWN (or backup FBN station MENAPORT AZ MK) must be occupied simultaneously with the two reference marks. If station HOCHATOWN is used, break down the equipment there while observing the two 2-hour sessions. If station MENAPORT AZ MK is used and is being occupied during a normal session as part of the overall project, observe the station continuously for the entire 5 1/2 hour session and do not break down the equipment.

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 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 have been 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 - 1545 UTC and 1955 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 two different bench marks. This bench mark tie requirement can be satisfied in one or two sessions. 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. The two bench mark tie requirement also applies to the CBN.

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.

The data will be processed in 24-hour sessions (or slightly longer if the observation session crosses 0000 UTC) in order to utilize the 24-hour data sets collected at the CORS and CTCORS. The "fixed baseline" option in PAGES will be used to compute direct baselines between the CORS and CTCORS. The "fixed baseline" scheme will depend on the location and reliability of the CORS and CTCORS used in this project. Contact Ms. Juliana Blackwell, Field Operations Branch, N/NGS41 (see LIAISON), for specific information relating to this project.

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, if public ownership, the telephone number of the responsible party. Do not include the telephone numbers of private property owners.

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. All co-observers should take a photograph of the setup, if possible, 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 January 4, 2000, 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 "arro010d.711". All records in connection with this project shall be titled "ARKANSAS FBN, 2000". The project number (accession number) is GPS-1411.

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: 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:
Ajit Singh
Observation and Analysis Division
N/NGS4
Telephone: 301-713-3182, ext. 109
Fax: 301-713-4327
E-mail

The coordinators for the CBN are:
Mr. Dean Wilkerson
Arkansas Highway & Transportation Department
Surveys Division
P.O. Box 2261
Little Rock, AR 72203-2261
Telephone: 501-569-2086
Fax: 501-569-2344
E-mail

Mr. Kit Carson
Arkansas Highway & Transportation Department
Surveys Division
P.O. Box 2261
Little Rock, AR 72203-2261
Telephone: 501-569-2341
e-Mail: E-mail

Ms. Mickie Warwick
Petit Jean College
1 Bruce St.
Morrilton, AR 72110
Telephone: 501-354-2465
Fax: 501-354-9948

Mr. Fred Ballard
Tyler Surveying
51 West Cadron Ridge Road
Greenbrier, AR 72058
Telephone: 501-679-2015
E-mail

The contact for the University of Arkansas - Little Rock base station is:
Mr. Jud Rouch
University of Arkansas - Little Rock
2801 South University Ave.
Little Rock, AR 72204-1099
Telephone: 501-569-8204
Fax: 501-569-8002

The contact for the Bossier City-Shreveport, Louisiana, base station is:
Mr. Chris Petro
Northwest Louisiana Council of Governments
509 Market Street, Suite 1000
Shreveport, LA 71101
Telephone: 318-673-5957
Fax: 318-673-5952
E-mail

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. Expenses for the CORS FBN/CBN tie will be charged to task number 8K6D4000.

TRAVEL:
 
 

Travel and per diem are authorized in accordance with Federal Travel Regulations, Part 301-11, Per Diem Allowances. Current per diem rates were effective January 1, 2000.

ACKNOWLEDGMENT:

Please acknowledge receipt of these instructions in your Monthly Report.
 

cc: N/NGS - D. Zilkoski*
N/NGS - S. Misenheimer*
N/NGS1 - G. Mitchell
N/NGS1x1 - K. Shinkle
N/NGS1x1 - R. Zurfluh
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 - A. Singh
N/NGS4 - M. Vorhauer
N/NGS4 - D. Hoar
N/NGS41 - W. McLemore
N/NGS41 - J. Blackwell
N/NGS5 - R. Snay
N/NGS6 - N. Weston
FGCS Members*
Frank Howard, Texas Department of Transportation
Dean Wilkerson, Arkansas Highway & Transportation Department
Kit Carson, Arkansas Highway & Transportation Department
Michael Flowers, Missouri Department of Natural Resources
James Zeigler, Tennessee Department of Transportation
Gordon Johnson, Oklahoma Department of Transportation
Larry Reser, Oklahoma Department of Transportation
Everett Rowland, Arkansas State Surveyor
Jud Rouch, University of Arkansas - Little Rock
Mickie Warwick, Petit Jean College
Fred Ballard, Tyler Surveying
Chris Petro, Northwest Louisiana Council of Governments

* first page only

Free adjustment in NAD 83 (UNIX run).

Plots of the free adjustment created by running "plotres_prompt.bsh" on a UNIX server. Plots require a printer that supports postscript. The output file (long.out) contains a list of residuals which may be sorted using the following commands:
vi long.out
:1,$ !sort +0.47 (sorts horizontal residuals)
:1,$ !sort +0.71 (sorts vertical residuals)

(OPTIONAL) Constrained horizontal adjustment holding NGS CORS positions and ellipsoid heights.

Final combined Blue Book file (ASCII required) with *86* records (GEOID99).

Final description file (ASCII required.)

Final G-file (ASCII required.)

OBSCHK output.*

CHKDDESC output.*

OBSDES output.*

*Any errors or warning messages must be explained.

Clifton S. Middleton
Project Director, Survey Section B

Charles W. Challstrom
Director, National Geodetic Survey

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 the FBN.  Requirements for field reconnaissance to support the upcoming survey in Arkansas are outlined below.

The FBN in Arkansas consists of 22 stations (list and sketch attached) that must be reconned.  If a FBN station is not recoverable, a nearby station (preferably a bench mark) suitable for GPS should be recovered and the office informed.

Five additional bench marks need to be reconned as well.  They need to be located in the following areas:

(1) between stations HOPEPORT, AP 1970 STA A3 HOT, and MENAPORT AZ MK
(2) between stations MENAPORT AZ MK, AP 1970 STA A3 HOT, RUSSPORT, and AHTD FS 2
(3) between stations AP 1970 STA A3 HOT, AHTD LR 1, HEBEPORT, and RUSSPORT
(4) between stations RUSSPORT, HEBEPORT, and TRI-COUNTY
(5) between stations RUSSPORT, TRI-COUNTY, AHTD HAR 1, and OZARPORT

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 a day for a several-day period).

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

              Mr. Dean Wilkerson
              Arkansas Highway and Transportation Department
              Surveys Division
              P.O. Box 2261
              Little Rock, Arkansas 72203-2261
              PHONE: (501) 569-2086
              FAX:   (501) 569-2344
              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.

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: E-mail

For concerns regarding survey design or specifications, contact:

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

All records for this project shall be archived under the title "ARKANSAS FBN, 2000" and accession number GPS-1411.  Digital files shall be archived under filename "arro010d.711".

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

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

See NGS Operations Handbook, Section 1.4.1.

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

Travel and per diem are authorized in accordance with Federal Travel Regulations, Part 301-11, Per Diem Expenses, and Appendix A to Chapter 301.  Current per diem rates were effective January 1, 1999.

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

cc: N/NGS - D. Zilkoski*
     N/NGS - S. Misenheimer*
     N/NGS1 - G. Mitchell
     N/NGS1x1 - D. Rexrode
     N/NGS1x1 - R. Zurfluh
     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
     FGCS Members*
     Michael Flowers, Department of Natural Resources - Missouri
     Gordon Johnson, Oklahoma Department of Transportation
     Frank Howard, Texas Department of Transportation
     James Zeigler, Tennessee Department of Transportation
     Jud Rouch, University of Arkansas - Little Rock
     Everett Rowland, Arkansas State Surveyor
     Dean Wilkerson, Arkansas Highway and Transportation Department

* first page only