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2019 Technical Seminar

Center of Population Monument
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Al Vedder, GA Power Company

Thank you for all who stopped by the exhibit table at the recent SAMSOG Annual Technical seminar held at Southern Tech on January 23-25, 2003.   There was a lot of interest, and we had many sign up to help either with the setting of the monument and GPS observations or by donating to cover expenses.

Al Vedder with GPC    Closeup of Monument

The Center of Population project was initiated by the Census Bureau, NGS and ACSM.  The project is intended to be a public relations opportunity for the land surveying profession.  It provides an opportunity to showcase improvements in GPS technology, the adaptation of this technology by surveyors, and the ability to develop cooperative initiatives between the private sector, Federal, state and local surveying and mapping professionals.  The location of Georgia’s Center of Population based on the Year 2000 U.S. Census Bureau data is located in Butts County near Lake Jackson.  In the majority of cases, the Census location will fall at a location that for a variety of reasons would not be a good area to establish a geodetic control point.  A nearby site has been chosen which is suitable for GPS measurements and will be easily accessible to the public.  The geodetic control monument will be set approximately one mile southeast of the computed Census location at the Georgia Power Company’s Lloyd Shoals Park public use area. 

For a location map, click here..

The dedication ceremony, set for Friday, April 25, 2003, will begin at 11:00 am, followed by a BBQ lunch.  We will have Curt Sumner, ACSM Executive Director, as our guest speaker.  Many others will be participating in the ceremony, including several of our own prestigious SAMSOG leadership, local and state representatives and others.  We  hope that all of you will plan to attend.   

For those of you who would like to help, the preparation dates leading up to dedication day are as follows:

Saturday February 22, 2003            9:00-12:00noon         Dig hole, mix & pour concrete, set monument

Thursday, March 6, 2003                 9:00am-3:00pm        GPS – First 5.5 hr session

Friday, March 7, 2003                      9:00am-3:00pm        GPS – Second 5.5 hr session

Saturday, March 8, 2003                  9:00am-3:00pm        GPS – Third 5.5 hr session

Information gathered will then be submitted to David Doyle at  NGS to be “Blue-Booked”.

Guidelines for the project are listed below and are also posted on the ACSM website at :  


The U.S. Census Bureau recently completed the compilation and analysis of the 2000 decennial census data. From these data, they have computed the Center of Population for the United States, and the population centers of each state and the District of Columbia. This event provides an opportunity to showcase improvements in GPS technology, the adaptation of that technology by surveyors, and the ability to develop cooperative initiatives between the private sector, Federal, state and local surveying and mapping professionals.

The National Geodetic Survey (NGS), in cooperation with the individual state professional surveying associations, the American Congress on Surveying and Mapping (ACSM), the National Society of Professional Surveyors (NSPS), and the American Association for Geodetic Surveying (AAGS) would like to encourage the setting of a commemorative geodetic control monument at or near the computed location of each states' population center (hereafter referred to as the "Center Station") as determined by the U.S. Census Bureau and listed in Attachment A.

For this project, NGS has streamlined the process of adding information into the National Spatial Reference System (NSRS) by providing the guidelines listed below. Under this arrangement, the local organizing group need only perform those observations necessary to ensure the Center Station achieves a positional accuracy of 1-2 cm horizontally relative to the network of Continuously Operating Reference Stations (CORS) and/or High Accuracy Reference Network (HARN) stations. In the majority of cases the Census location will probably fall at a location that for a variety of reasons would not be a good location to establish a geodetic control point. A nearby location that is suitable for GPS measurements, and will be easily accessible to the public should be chosen instead. This project should be viewed as both a technical and a media event to highlight the achievements of Surveyors, Geodesist, and Geographers. Organizing groups are encouraged to include media contacts as part of their activities.

Site selection and mark setting requirements

The site selection should conform to the following criteria as much as possible

1. As close to the computed coordinate as possible
2. A "GPS-able" site (e.g., clear of obstructions 15° above the horizon)
3. Located on a publicly accessible site (e.g., town park, road right of way, etc.)

Once a suitable location has been selected for the Center Station, the mark should be set in accordance with "General Specifications for Aeronautical Surveys," Attachment 7-9 as listed at

Given the unique nature of this project, it is recommended that a special commemorative mark be produced of at least 8" in diameter. The mark can have whatever logo or design the organizing committee decides. NSPS and Berntsen International have designed a disk that can be used. The design and contact information is provided in the attached information package. The costs of the survey mark will be the responsibility of the State Survey Society/Association

GPS equipment and observation requirements

All observations must be performed using dual-frequency, full-wavelength GPS receivers. All antennas must be of a make and model that have been calibrated by NGS - see:

Fixed height GPS tripods (quadpods) are highly recommended, but not required. If fixed height poles are not used, special effort should be made to ensure an accurate height of the GPS antenna is measured at the start and end of each session. These measurements should be recorded and diagramed on the "Illustration for Antenna Height Measurements" page of the GPS observation log sheet describes below.

GPS network design will include 3 CORS and/or HARN stations. If there are 3 CORS within 300 km, then there is no requirement for connections to HARN stations. However, it is recommended that at least 1 HARN and 1 North American Datum of 1988 (NAVD 88) bench mark (BM) published by NGS and within 50 km also be observed. If convenient the HARN station and the BM should be the same station.

GPS observation at the Center Station will consist of 3 each 5.5 hour sessions, with the start time of one session offset from the other 2 by at least 4 hours. Sessions do not all need to be on separate days. (i.e., 2 sessions can be on the same day).

If there are not 3 CORS within 300 km, then the observations at the HARN station(s) should be coincident with all Center Station observations. If a separate BM tie is performed it should be at least a single 4 hour session coincident with the observations at the Center Station. It is recommended but not required that there be 2 each 4 hours sessions to the BM. A separate NGS GPS observation log sheet, visibility obstruction diagram and station description/recovery form must be completed for each station in the project. GPS observation log sheets must be completed for each session. Copies of all forms can be found at:

Data processing requirements

Data at all stations should be processed through the OPUS GPS processing website:


For the data to be "Blue-Booked", the following data must be submitted to NGS

1. All GPS data files in RINEX format.
2. Copy of OPUS output.
3. Original observation log sheets, visibility diagrams and description/recovery forms.
4. 4-5 digital photos clearly showing the monument and the surrounding area.
5. A brief report describing the project, including the site selection, personnel involved and equipment used. Report can be provided in either Microsoft Word (.doc) or Corel Wordperfect (.wpd) format.

All data should be sent to:

David Doyle
National Geodetic Survey, N/NGS2
1315 East-West Highway, #8826
Silver Spring, MD 20910
(301) 713-3178

Population and Population Centroid by State: 2000
 FIPS Name               Population    Latitude     Longitude
 13   Georgia               8186453    33.332208   -83.86888

Center of Population Monumentation Guidelines
Guidelines have been developed for the joint ACSM, Census Bureau, NGS, NSPS, and state surveying societies program to set a marker at or near the center of population in each state.
Information contacts include:
ACSM - Curt Sumner -
Census Bureau - David McMahon -
NGS - David Doyle -
NSPS - Gary Thompson -


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