MEMORANDUM FOR: Clifton S. Middleton
Project Director, Survey Section B
FROM: Charles W. Challstrom
Acting Director, National Geodetic Survey
SUBJECT: INSTRUCTIONS: CALIFORNIA FBN, 1998 (GPS-1288)
Task Numbers: 8K6D2000 (FBN)
8K6D4000 (CORS FBN TIES)
8K6D5000 (HEIGHT MODERNIZATION)
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 FBN. This survey will
observe the 66 FBN stations in California. It will also
incorporate 70 Continuously Operating Reference Stations (CORS)
within the state (10 NGS CORS and 60 CORS coordinated by the
Scripps Institution of Oceanography (SIO)). This campaign will
be continuous and will tie into adjoining states. (Some states
will be skipped for seasonal relocations.)
Stations at 16 tide sites along the Pacific Ocean coast
will also be surveyed in this project. Occupations of these
stations must meet the FBN specifications for this project
(height modernization). (Five of these tide sites had stations
already selected as FBNs, although other stations at some of the
sites may have been selected to replace them. The other 11 tide
sites are in addition to the project.)
In addition, at the Columbia College and Yreka CORS sites, a pair
of CORS reference marks at each site is to be tied to both the
local FBN and the CORS antenna. The names (and descriptions)
of the reference marks at each site will be provided.
To support software tests, a full-wavelength, dual-frequency
Global Positioning System (GPS) receiver is needed to act as a
Central Temporary Continuously Operating Reference Station
(CTCORS) where there are no existing CORS within 150 kilometers
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 72 hours or more, before being relocated.
SIO, which supports the California Spatial Reference Center
(CSRC), is coordinating the co-observing of 53 additional
stations, and NGS will provide project data to SIO personnel
for their own processing use. NGS will obtain CSRC project data
for comparison processing. 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.
FBN fulfills the requirements for this component. NGS is charged
with the Federal responsibility for establishment, observation,
monitoring, and maintenance of FBN. FBN provides the critical
network foundation for an accurate, consistent, reliable NSRS.
NSRS, in turn, provides the common geographic framework for
America's spatial data infrastructure. As such, 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 tide site (height modernization) surveys will provide GPS-
derived ellipsoid heights, accurate to 3 cm, on tide site water-
level marks along the Pacific coast.
The reference marks established at the Columbia College and Yreka
CORS sites will provide a very accurate tie to the antennae as an
aid to reposition the antennae should that become necessary. The
FBN ties to the CORS marks will also provide site station
coordinates relative to the local FBN/CBN, thus reducing the
potential for relative error between the stations and the local
network. It will also provide a check on FBN/CBN, relative to
the CORS coordinates.
SPECIFICATIONS:
Project requirements for the FBN observations are to ensure
3-centimeter local accuracy in the horizontal component, as well
as 3-centimeter local accuracy for the ellipsoid heights.
Data from CORS in the region are to be used in the processing.
There are approximately 70 CORS stations in the state, with 10
(and possibly 14 more) of these being NGS CORS. The 10 NGS CORS
are as follows: Blythe (blyt), Goldstone (gold), Point Loma
(plo1), Point Arguello (par1), Pigeon Point (ppt1), Point Blunt
(pbl1), Cape Mendocino (cme1), Yreka (ybhb), Columbia College
(cmbb), and Quincy (quin). A list of all 70 CORS will be
provided. Positions for CORS should be obtained from Richard
Snay (listed under LIAISON section).
General specifications for the project are as follows. At each
FBN site, three sessions of 5 1/2 hours duration 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 than 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 Columbia College and Yreka CORS sites is that
for the two reference stations at each 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 sites must be
tied to the nearest FBN/CBN stations, FBN stations HPGN CA 10 05
(PID HS5413) (for Columbia College) and GRENADA SOUTH BASE
(PID MX0298) (for Yreka) must be occupied simultaneously with
the two reference marks at each site. Since HPGN CA 10 05 and
GRENADA SOUTH BASE are FBN stations, they need to be occupied
continuously with no break for the full 5 1/2 hour FBN sessions
along with the other stations in the sessions.
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. 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 preliminary list (Table 1) and sketch of
stations have been provided. A final list and sketch will be
provided as soon as possible.
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, with additional windows to
be selected as the project moves into the central and northern
parts of the state.) 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. One
station (D 1420 - PID HS4524) is a bench mark tie only for NGS
purposes and only needs to be occupied by NGS as such, although
it is a station that will be co-observed by the California co-
observers.
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 do not need to be
repeated. Each CORS must be tied to the network in a minimum
of one session. CORS and CTCORS data will be used as needed.
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 OMNI. Vectors
shall be computed in the International Terrestrial Reference
Frame (ITRF) system, using the most current epoch and precise
IGSephemerides. Use 30-second epoch intervals, but 15-second
epoch data may be used if it improves ease of data processing.
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 projects in which the vectors
from the CORS antenna to the other stations at the site are less
than 5 km in length, the final reduction will consist of a L1
fixed solution. For projects which include local FBN/CBN ties,
there may be vectors computed from the CORS antenna to the ties
which are greater than 5 km in length. These vectors will be
computed in a separate processing session from the short (less
than 5 km) vectors.
In general, vectors greater than 30 km in length are to be
computed in an ion-free fixed, or partially-fixed, solution. For
vectors between 5-30 km in length, compare both the L1 and ion-
free solutions to determine which has the best Post-Fit Residual
(PFR) plots. In all cases, integer ambiguities will be fixed for
each vector whenever possible. Refer to Chapter 8 of the OMNI
3.42 manual for techniques on fixing integers.
For the Columbia College and Yreka CORS reference marks, the
CORS antenna at each site will be used as the reference station
in the data processing.
The quality of collected data shall be determined from the plots
generated from OMNI and by analysis of repeated vectors and free
adjustment residuals and/or loop misclosures.
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 units 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.
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.
For each station visited, a visibility obstruction diagram must
be prepared and the TO-REACH description carefully checked for
errors or omissions.
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 June 10, 1998, 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
"caro068d.620". All records in connection with this project
shall be titled "CALIFORNIA FBN, 1998". The project number
(accession number) is GPS-1288.
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, SSMC III, Station 8564
Telephone: 301-713-3215, ext. 117
Fax: 301-713-4327
e-Mail: mclemore@ngs.noaa.gov
Questions and problems concerning adjustment processing should be
directed to:
Maralyn L. Vorhauer
Observation and Analysis Division
N/NGS4, SSMC III, Station 8562
Telephone: 301-713-3176, ext. 104
Fax: 301-713-4327
e-Mail: maralyn@ngs.noaa.gov
Questions and problems concerning vector processing should be
directed to:
Juliana Blackwell
Field Operations Branch
Observation and Analysis Division
N/NGS41, SSMC III, Station 8458
Telephone: 301-713-3215, ext. 108
Fax: 301-713-4327
e-Mail: juliana@ngs.noaa.gov
CORS positions can be obtained from:
Richard Snay
Systems Development Division
N/NGS5, SSMC III, Station 8112
Telephone: 301-713-3205, ext. 155
Fax: 301-713-4322
e-Mail: rich@ngs.noaa.gov
Questions and problems concerning using CORS data in processing
should be directed to:
Neil Weston
Geosciences Research Division
N/NGS6, SSMC III, Station 9830
Telephone: 301-713-2847, ext. 202
Fax: 301-713-4475
e-Mail: nweston@ngs.noaa.gov
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, SSMC III, Station 8853
Telephone: 301-713-3194, ext. 111 (ext. 127)
Fax: 301-713-4316
e-Mail: steve@ngs.noaa.gov (dough@ngs.noaa.gov)
The contact for the project is:
Joseph D. D'Onofrio
NGS, c/o Caltrans
P.O. Box 942874, MS 35
Sacramento, California 94274-0001
Telephone: 916-227-7325
Fax: 916-227-7670
e-Mail: donofrio@trmx3.dot.ca.gov
Federal Express Address:
1801 30th Street, MS 35
Sacramento, California 95816
For tide site information, contact:
Brooks Widder
Oceanographic Products and Services Division
Requirements and Engineering Branch, N/CS41
SSMC4/Station 6342
1305 East-West Highway
Silver Spring, Maryland 20910-3282
Telephone: 301-713-2902, ext. 184
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 FBN/CBN CORS ties will be charged to
task number 8K6D4000. Expenses for the tide sites (height
modernization) will be charged to task number 8K6D5000.
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.
ACKNOWLEDGMENT:
Please acknowledge receipt of these instructions in your Monthly
Report.
Attachment
cc: N/CS - N. Prahl
N/CS41 - B. Widder
N/NGS - S. Misenheimer*
N/NGS1 - G. Mitchell
N/NGS1x1 - J.D. D'Onofrio
N/NGS1x1 - C. Smith
N/NGS11 - S. Cofer
N/NGS2 - J. Till
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 - D. Zilkoski*
N/NGS6 - N. Weston
FGCS Members*
B. Brown, Arizona Department of Transportation
* 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).
---------------------------------------------------------------------
MEMORANDUM FOR: Clifton S. Middleton
Project Director, Survey Section B
FROM: Charles W. Challstrom
Acting Director, National Geodetic Survey
SUBJECT: INSTRUCTIONS: Addendum to CALIFORNIA FBN, 1998
(GPS-1288)
Task Numbers: 8K6D2000 (FBN)
8K6D4000 (CORS FBN TIES)
8K6D5000 (HEIGHT MODERNIZATION)
GENERAL:
These instructions are an addendum to the original instructions
for this project. All data processing for this project will
take place in Silver Spring, and all data for this project is to be sent
via FedEx on a daily basis to Ms. Miranda Chin or
Ms. Linda Nussear of the Geosciences Lab. Their address is as follows:
Ms. Miranda Chin (Ms. Linda Nussear)
Geosciences Research Lab
N/NGS6, SSMC III, Station 9111
1315 East-West Highway
Silver Spring, Maryland 20910-3282
Telephone: 301-713-2845, ext. 109
Fax: 301-713-4475
e-Mail: miranda@tango.grdl.noaa.gov
linda@gracie.grdl.noaa.gov
ACKNOWLEDGMENT:
Please acknowledge receipt of these instructions in your Monthly Report.
Attachment
cc: N/CS - N. Prahl
N/CS41 - B. Widder
N/NGS - S. Misenheimer
N/NGS1 - G. Mitchell
N/NGS1x1 - J.D. D'Onofrio
N/NGS1x1 - C. Smith
N/NGS11 - S. Cofer
N/NGS2 - J. Till
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 - M. Chin
N/NGS6 - M. Morrison
N/NGS6 - L. Nussear
N/NGS6 - D. Zilkoski
N/NGS6 - N. Weston
FGCS Members
B. Brown, Arizona Department of Transportation