Tags
height, NGS, elevation, control, N/A, N/A, NSRS, location, latitude, horizontal, longitude, The geographic limits of Arkansas, benchmark, ellipsoid, orthometric, vertical, geodetic
Provide a base of reference for latitude, longitude and height throughout the United States. Geodetic Data provide the base of reference for latitude, longitude, height, scale, orientation, and gravity measurements used throughout the United States.
This data contains a set of geodetic control stations maintained by the National Geodetic Survey. Each geodetic control station in this dataset has either a precise Latitude/Longitude used for horizontal control or a precise Orthometric Height used for vertical control, or both. The National Geodetic Survey (NGS) serves as the Nation's depository for geodetic data. The NGS distributes geodetic data worldwide to a variety of users. These geodetic data include the final results of geodetic surveys, software programs to format, compute, verify, and adjust original survey observations or to convert values from one geodetic datum to another, and publications that describe how to obtain and use Geodetic Data products and services.
NOAA, National Geodetic Survey and cooperating organizations
Not restricted; Geodetic Data, including software were developed and compiled with U.S. Government funding; no proprietary rights may be attached to them nor may they be sold to the U.S. Government as part of any procurement of ADP products for services.
Extent
| West | -94.615872 | East | -89.668630 |
| North | 36.528707 | South | 32.969476 |
Questions concerning this data may be addressed to Craig Larrimore EMail - Craig.Larrimore@noaa.gov Phone - 301-713-3257 x152
NGS Geodetic data sheets are currently being distributed by CD-ROM. NGS' data sheet CD-ROM contains position, height, and descriptive information for more than 150,000 control points on two compact disks for each of five regions of the United States (updated at approximately 1-year intervals). The five geographic regions and their associated states include: North-Central United States (IL, IN, IA, KS, MI, MN, MO, MT, NE, ND, SD, WI, and WY); Northeast United States (CT, DE, DC, KY, ME, MD, MA, NH, NJ, NY, OH, PA, RI, VT, VA, and WV); Southeast United States, Puerto Rico, and the Virgin Islands (AL, FL, GA, MS, NC, PR/VI, SC, and TN); South-Central United States (AZ, AR, CO, LA, NV, NM, OK, TX, and UT); Western United States and Pacific Territories (AK, CA, HI, ID, OR, WA, and Pacific Territories). Hyperlinks provide access to NGS' continuously updated online data sheets. Please visit http://www.ngs.noaa.gov/CDROM/DScdromInfo.htm or http://www.ngs.noaa.gov/cgi-bin/datasheet.prl for more information on updates and CD-ROM data sheets.
NOAA, National Geodetic Survey and cooperating organizations
retrieval date
8:30am to 5:00pm EST
Prefer EMail
The data herein, including but not limited to geographic data, tabular data, analytical data, electronic data structures or files, are provided "as is" without warranty of any kind, either expressed or implied, or statutory, including, but not limited to, the implied warranties or merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the data is assumed by the user. No guarantee of accuracy is granted, nor is any responsibility for reliance thereon assumed. In no event shall the Arkansas State Land Information Board be liable for direct, indirect, incidental, consequential or special damages of any kind, including, but not limited to, loss of anticipated profits or benefits arising out of use of or reliance on the data. The Arkansas State Land Information Board does not accept liability for any damages or misrepresentation caused by inaccuracies in the data or as a result of changes to the data caused by system transfers or other transformations or conversions, nor is there responsibility assumed to maintain the data in any manner or form. These data have been developed from the best available sources. Although efforts have been made to ensure that the data are accurate and reliable, errors and variable conditions originating from physical sources used to develop the data may be reflected in the data supplied. Users must be aware of these conditions and bear responsibility for the appropriate use of the information with respect to possible errors, scale, resolution, rectification, positional accuracy, development methodology, time period, environmental and climatic conditions and other circumstances specific to these data. The user is responsible for understanding the accuracy limitations of the data provided herein. The burden for determining fitness for use lies entirely with the user. The user should refer to the accompanying metadata notes for a description of the data and data development procedures. Although these data have been processed successfully on computers at the Arkansas Geographic Information Office, no guarantee, expressed or implied, is made by Arkansas State Land Information Board regarding the use of these data on any other system, nor does the act of distribution constitute or imply any such warranty. Distribution of these data is intended for information purposes and should not be considered authoritative for engineering, legal and other site-specific uses.
Geodetic Data are in the public domain, not restricted from access or distribution.
none
Not restricted; Geodetic Data, including software were developed and compiled with U.S. Government funding; no proprietary rights may be attached to them nor may they be sold to the U.S. Government as part of any procurement of ADP products for services.
Geodetic Data- horizontal positional datum conversion, use program NADCON (version 2.1) Geodetic Data - vertical positional datum conversion, use program VERTCON (version 2.0) These programs provide indirect spatial reference data and are available from NOAA, National Geodetic Survey at <http://www.ngs.noaa.gov/PC_PROD/pc_prod.shtml>
FGCS sponsored testing in cooperation with equipment manufacturers and National Institutes of Standards and Technology, Gaithersburg, MD 20850 Total consistency is maintained throughout the data set by following the "Input Formats and Specifications of the National Geodetic Survey Data Base: The NGS Bluebook. For detailed information about the NGS Bluebook, see: <http://www.ngs.noaa.gov/FGCS/BlueBook/>
This dataset DOES NOT include destroyed marks. All other non-publishable marks are NOT included. Non-publishable criteria is available at <http://www.ngs.noaa.gov/cgi-bin/craigs_lib.prl?HELP_NONPUB=1> New data sets (from backload projects) that are not included in this National data set, will be included in the future as resources permit.
Horizontal control stations (those with precise Latitude, Longitude) were established in accordance with FGDC publications "Standards and Specifications for Geodetic Accuracy Standards" and "Geometric Geodetic Accuracy Standards and Specifications for Using GPS Relative Positioning Techniques" The final Latitude, Longitude of these stations were determined by a least squares adjustments of the horizontal observations. Horizontal control station have Latitude, Longitudes displayed to 5 places and are identified by attribute POS_SRCE = 'ADJUSTED' Lesser quality Latitude, Longitudes may also be preset in the dataset. These are identified by a POS_SRCE attributes HD_HELD1, HD_HELD2, or SCALED. These lesser quality positions are described at: <http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=SCALED> Vertical control stations (those with precise Orthometric Heights) were established in accordance with FGDC publications "Standards and Specifications for Geodetic Accuracy Standards" The final Orthometric Height of these stations were in most cases determined by a least squares adjustments of the vertical observations but in some cases may have been keyed from old survey documents. Vertical control stations have Orthometric Heights displayed to 2 or 3 places and are identified by attribute ELEV_SRCE of ADJUSTED, ADJ UNCH, POSTED,READJUST,N HEIGHT,RESET,COMPUTED Lesser quality Orthometric Heights may also be preset in the dataset. These are identified by a ELEV_SRCE attributes GPS_OBS, VERT_ANG, H_LEVEL, VERTCON, SCALED. These lesser quality orthometric heights are described at: <http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=SCALED> IMPORTANT - Control stations do not always have both precise Latitude, Longitude AND precise Orthometric Height. A horizontal control station may have a orthometric height associated with it which is of non geodetic quality. These types of heights are displayed to 0, 1, or 2 decimal places. Worst case being off by +/- 1 meter. LIKEWISE - A Vertical control station may have a Latitude, Longitude associated with it which is of non geodetic quality. These types of Latitude, Longitudes are displayed to 0, 1 or 2 decimal places. Worst case being off by +/- 180 meter. Refer to <http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=SCALED> for a description of the various type of methods used in determining the Latitude, Longitude, and Orthometric Height. Attribute POS_CHECK and ELEV_CHECK indicate whether or not an observational check was made to the position and/or orthometric height. Care should be taken when using "No Check" coordinates. If attribute ELEV_SRCE = 'VERTCON' then the Orthometric Height was determined by applying NGS program VERTCON to an Old NGVD 29 height. In most areas VERTCON gives results to +/- 2 cm. See <http://www.ngs.noaa.gov/TOOLS/Vertcon/vertcon.html> for a more detailed explanation of VERTCON accuracy. Ellipsoid Heights are also present in the dataset. The ellipsoid heights consist of those determined using a precise geoid model, which are displayed to 2 decimal places and are considered good to +/- .005 meters, and those displayed to 1 decimal place and are considered only good to +/- .5 meters
Geodetic Data are continuously being processed; their standards and specifications are being reviewed for next publication release. "Standards and Specifications for Geodetic Control Networks", 1984 and "Geometric Geodetic Accuracy Standards and Specifications for Using GPS Relative Positioning Techniques," FGCS (formally FGCC) publication version 5.0 1989, are most current published documents.
The description of tests are explained in "Geometric Geodetic Accuracy Standards and Specifications For Using GPS Relative Positioning Techniques," FGCS (formally FGCC) publication version 5.0, 1989.
Horizontal positional accuracy statements pertain to horizontal control stations only. i.e. Those with geodetic quality Latitude, Longitudes. Positional Accuracy explanation contained in "Geometric Geodetic Accuracy Standards and Specifications For Using GPS Relative Positioning Techniques," FGCS (formally FGCC) publication version 5.0, 1989, (See table 1, p6). with the exception of Order A and Order B which have an accuracy of as described at: <http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=HORZ%20ORDER>
The description of tests are explained in "Geometric Geodetic Accuracy Standards and Specifications for Using GPS Relative Positioning Techniques," FGCS (formally FGCC) publication version 5.0, 1989, (See table 1, p6).
Vertical positional accuracy statements pertain to vertical control stations only. i.e. Those with geodetic quality Orthometric Heights. Orthometric Height accuracy explanation is contained in FGDC publication "Standards and Specifications for Geodetic Control Networks" with the exception of vertical control of class 0 POSTED and READJUSTED Heights which are described at: <http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=VERT%20ORDER> Ellipsoid height accuracy explanation contained in "Geometric Geodetic Accuracy Standards and Specifications for Using GPS Relative Positioning Techniques," FGCS (formally FGCC) publication version 5.0, 1989. (see table 1, p6). The accuracies for ellipsoid heights are described at: <http://www.ngs.noaa.gov/cgi-bin/ds_lookup.prl?Item=ELLP%20ORDER>
The geodetic data must be submitted in the digital formats specified in the FGCS (formally FGCC) publication "Input Formats and Specifications of the National Geodetic Survey Data Base" which describes the formats and procedures for submission of data for adjustment and assimilation into the National Geodetic Survey Data Base. Separate volumes of this publication refer to horizontal (volume 1), vertical (volume 2), and gravity (volume 3) control, and are available from NOAA, National Geodetic Survey, 1315 East-West Hwy, Code N/CGS1, Silver Spring, MD, 20910 (1-301-713-3242). Note guidelines for submission of three-dimensional Global Positioning System (GPS) relative positioning data are contained in annex L to volume 1.
N/A
publication date
Internal feature number.
ESRI
Sequential unique whole numbers that are automatically generated.
Longitude Coordinates in decimal degrees
Arkanas Geographic Information Office
Latitude coordinates in decimal degrees
Arkansas Geographic Information Office
Indicates how orthometric height was determined
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Sequential unique whole numbers that are automatically generated.
Date these data were retrieved from NGS data base
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Indicates how horizontal coordinates were determined
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Agency that described or recovered station
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Unique "permanent identifier" assigned to the station
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
The county location of the station.
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Latitude in degrees, minutes, seconds N or S of equator, referenced to horizontal datum
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Survey control ellipsoid-order class
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
URL String for source of feature
Arkansas Geographic Information Office
Description of station recovery
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Survey control horizontal order.
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Feature geometry.
ESRI
Coordinates defining the features.
Longitude in degrees, minutes, seconds E or W of Greenwich meridian, referenced to horizontal datum
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Coordinates defining the features.
Name of geodetic control station; this name does not usually exactly match the marker stamping
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Survey control ellipsoid order
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
The U.S. Geological Survey quad location of the station. This is the name of the USGS 7.5 minute series
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Last recieved
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Height of the station above the ellipsoid; always referenced from NAD 83
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Horizontal datum reference for station's horizontal coordinates.
Arkansas Geographic Information Office
Year- Horizontal datum reference for station's horizontal coordinates.
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Method by which the ellipsoidal height was determined
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Survey control ellipsoid-order class
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
Feature geometry.
Esri
Coordinates defining the features.
Feature geometry.
ESRI
Coordinates defining the features.
Survey control ellipsoid order
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
The vertical datum of the station. The orthometric vertical datum in use is the North American Vertical Datum of 1988 (NAVD 88). NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums. Care should be taken not to "mix" current datum(s) with past datum(s) within a project.
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
The state location of the station.
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
first recieved
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
The station height in meters.
National Oceanic Atmospheric Administration/National Ocean Service/National Geodetic Survey
The current attributes and their meaning are shown below. #FeatureId Temporary unique ID assigned to this station. DATA_DATE- The date when this information was retrieved from the NGS database. DATA_SRCE- Data Source where the information for the mark came from. You should use this link to obtain a full datasheet for the mark or obtain the datasheets from <http://www.ngs.noaa.gov/cgi-bin/datasheet.prl> if you intend to use the data for survey control. DEC_LONG- Decimal equivalent of the LONGITUDE Always displayed to 10 decimal places, but you should see POS_SRCE and POS_ORDER to determine the true accuracy. DEC_LAT- Decimal equivalent of the LATITUDE PID- Permanent Identifier assigned by NGS to each mark NAME- Station Name (a.k.a. Designation) STATE- State Code COUNTY- County Name QUAD- USGS Topographic Quad Map Name LATITUDE- Latitude in Deg-Min-Sec format LONGITUDE- Longitude in Deg-Min-Sec format POS_DATUM- Datum of the LATITUDE,LONGITUDE Should always be NAD83 DATUM_TAG- Datum Tag of the LATITUDE,LONGITUDE NAD83 (1986) indicates positions on the NAD83 datum for the North American Adjustment, completed in 1986. NAD83 (nnnn) indicates positions on the NAD83 datum for the North American Adjustment, but readjusted to a State High Accuracy Reference Network (HARN) on the date shown in (nnnn). NAD83 (CORS) indicates positions which are part of the CORS network. POS_SRCE- Position Source for the LATITUDE,LONGITUDE ADJUSTED = Least squares adjustment. (Lat,Lon Rounded to 5 decimal places.) HD_HELD1 = Differentially corrected hand held GPS observations. (Lat,Lon Rounded to 2 decimal places.) HD_HELD2 = Autonomous hand held GPS observations. (Lat,Lon Rounded to 1 decimal places.) SCALED = Scaled from a topographic map. (Lat,Lon Rounded to 0 decimal places.) ELEVATION- Present if available. The Orthometric Height in METERS indicating the height above the Geoid. ELEV_DATUM- Datum of the ELEVATION ELEV_SRCE- Elevation Source for the ELEVATION ADJUSTED = Direct Digital Output from Least Squares Adjustment of Precise Leveling. (Rounded to 3 decimal places.) ADJ UNCH = Manually Entered (and NOT verified) Output of Least Squares Adjustment of Precise Leveling. (Rounded to 3 decimal places.) POSTED = Pre-1991 Precise Leveling Adjusted to the NAVD 88 Network After Completion of the NAVD 88 General Adjustment of 1991. (Rounded to 3 decimal places.) READJUST = Precise Leveling Readjusted as Required by Crustal Motion or Other Cause. (Rounded to 2 decimal places.) N HEIGHT = Computed from Precise Leveling Connected at Only One Published Bench Mark. (Rounded to 2 decimal places.) RESET = Reset Computation of Precise Leveling. (Rounded to 2 decimal places.) COMPUTED = Computed from Precise Leveling Using Non-rigorous Adjustment Technique. (Rounded to 2 decimal places.) LEVELING = Precise Leveling Performed by Horizontal Field Party. (Rounded to 2 decimal places.) H LEVEL = Level between control points not connected to bench mark. (Rounded to 1 decimal places.) GPS OBS = Computed from GPS Observations. (Rounded to 1 decimal places.) VERT ANG = Computed from Vertical Angle Observations. (Rounded to 1 decimal place; If No Check, to 0 decimal places.) SCALED = Scaled from a Topographic Map. (Rounded to 0 decimal places.) U HEIGHT = Unvalidated height from precise leveling connected at only one NSRS point. (Rounded to 2 decimal places.) VERTCON = The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height. (Rounded to 0 decimal places.) ELLIP_HT- Present if available. The ellipsoid height in METERS referenced to GRS80 ellipsoid. ELLIP_SRCE- Ellipsoid Ht Source for the ELLIP_HT Should always be GPS_OBS when present. POS_ORDER- Order of accuracy for the LATITUDE,LONGITUDE Should be one of the following- A,B,1,2,3 Order and class for Orders 1, 2, and 3 are defined in the Federal Geodetic Control Committee publication "Standards and Specifications for Geodetic Control Networks". In addition- Order A stations have a relative accuracy of 5 mm +/- 1-10,000,000 relative to other A-order stations. Order B stations have a relative accuracy of 8 mm +/- 1- 1,000,000 relative to other A- and B-order stations. POS_CHECK- Y=Observational Check was made for the position, N=NO Observational Check was made for the positions ELEV_ORDER- Order of accuracy for the ELEVATION Should be 1,2, or 3 for Vertical Control Stations. Will be blank for stations used for Horizontal Control only. Also see attribute DIST_RATE which is used for some vertical control stations. Elevation order and class for 1, 2, and 3 are defined in the Federal Geodetic Control Committee publication "Standards and Specifications for Geodetic Control Networks". In addition- Vertical control which were determined only for the purpose of supplying a height for Horizontal Distance Reductions are assigned an order of 3. Class 0 is used for special cases of orthometric vertical control as follows- Vertical Order/Class Tolerance Factor -------------------- ---------------- 1 class 0 2.0 mm or less 2 class 0 8.4 mm or less 3 class 0 12.0 mm or less ELEV_CLASS- Should be 0, 1, or 2 See details under ELEV_ORDER ELEV_CHECK- Y=Observational Check was made for the orthometric height, N=NO Observational Check was made for the orthometric heights VERTCONED- Y=Orthometric Height was determined by applying VERTCON to an old NGVD 29 height. N=Orthometric Height determined by observations. DIST_RATE- Distribution rate for POSTED and READJUSTED benchmarks which do not have an Order and Class are as follows "Posted bench marks" are vertical control points in the NGS data base which were excluded from the NAVD 88 general adjustment. Some of the bench marks were excluded due to large adjustment residuals, possibly caused by vertical movement of the bench marks during the time interval between different leveling epochs. Adjusted NAVD 88 are computed for posted bench marks by supplemental adjustments. A range of mean distribution rate corrections is listed for each posted bench mark in the data portion of the publication. A summary table of the mean distribution rates and their codes is listed below. The mean distribution rate corrections which were applied to the original leveling observations is a good indication of the usefulness of the posted bench marks' adjusted NAVD 88 heights. Distribution Distribution Rate Code Rate Correction ------------ --------------- "a" 0.0 thru 1.0 mm/km "b" 1.1 thru 2.0 " "c" 2.1 thru 3.0 " "d" 3.1 thru 4.0 " "e" 4.1 thru 8.0 " "f" greater than 8.0 mm/km POSTED BENCH MARKS SHOULD BE USED WITH CAUTION. As is the case for all leveling projects, the mandatory FGCS check leveling two-mark or three-mark tie procedure will usually detect any isolated movement (or other problem) at an individual bench mark. Of course, regional movement affecting all the marks equally is not detected by the two- or three-mark tie procedure. ELLP_ORDER- Order of accuracy for the ELLIP_HT Should be 1,2,3,4, or 5 if present. The following ellipsoid height order and class relative accuracy standards have not yet been adopted by the Federal Geodetic Control Subcommittee, but are currently in use by NGS- Ellipsoid Height Maximum Height Classification Difference Accuracy ------------------ ------------------- 1 class 1 0.5 (mm)/sqrt(km) 1 class 2 0.7 2 class 1 1.0 2 class 2 1.3 3 class 1 2.0 3 class 2 3.0 4 class 1 6.0 4 class 2 15.0 5 class 1 30.0 5 class 2 60.0 The ellipsoid height difference accuracy (b) is computed from a a minimally constrained correctly weighted least squares adjustment by- b = s / sqrt(d) where b = height difference accuracy s = propagated standard deviation of ellipsoid height difference in millimeters between control points obtained from the least squares adjustment. d = horizontal distance between control points in kilometers ELLP_class- Class of accuracy for ELLIP_HT Should be 1 or 2 See details under ELLP_ORDER 1_RECV- Date when the station was first monumented or in the case of landmarks, first observed. LAST_RECV- Date when the station was last recovered. LAST_COND- Last recovered condition of the mark. Should be one of the following- MONUMENTED 1 OBSERVED GOOD POOR MARK NOT FOUND SEE DESCRIPTION DESTROYED LAST_RECBY- Agency who reported the last condition of the mark. STABILITY- The stability of the mark may have 1 of 4 codes as indicated below- A = MOST RELIABLE AND EXPECTED TO HOLD POSITION/ELEVATION WELL B = PROBABLY HOLD POSITION/ELEVATION WELL C = MAY HOLD, BUT OF TYPE COMMONLY SUBJECT TO SURFACE MOTION - E.G. FROST HEAVE, ETC D = MARK OF QUESTIONABLE OR UNKNOWN STABILITY
All values were obtained from the NGA Datasheet available at <http://www.ngs.noaa.gov/cgi-bin/datasheet.prl>
8:30am to 5:00pm EST
Prefer EMail
Last metadata review date: 20051108
Geodetic Data are in the public domain, not restricted from access or distribution.
none
not restricted; Geodetic Data, including software were developed and compiled with U.S. Government funding; no proprietary rights may be attached to them nor may they be sold to the U.S. Government as part of any procurement of ADP products or services.
The current attributes and their meaning are shown below. #FeatureId Temporary unique ID assigned to this station. DATA_DATE- The date when this information was retrieved from the NGS database. DATA_SRCE- Data Source where the information for the mark came from. You should use this link to obtain a full datasheet for the mark or obtain the datasheets from <http://www.ngs.noaa.gov/cgi-bin/datasheet.prl> if you intend to use the data for survey control. DEC_LONG- Decimal equivalent of the LONGITUDE Always displayed to 10 decimal places, but you should see POS_SRCE and POS_ORDER to determine the true accuracy. DEC_LAT- Decimal equivalent of the LATITUDE PID- Permanent Identifier assigned by NGS to each mark NAME- Station Name (a.k.a. Designation) STATE- State Code COUNTY- County Name QUAD- USGS Topographic Quad Map Name LATITUDE- Latitude in Deg-Min-Sec format LONGITUDE- Longitude in Deg-Min-Sec format POS_DATUM- Datum of the LATITUDE,LONGITUDE Should always be NAD83 DATUM_TAG- Datum Tag of the LATITUDE,LONGITUDE NAD83 (1986) indicates positions on the NAD83 datum for the North American Adjustment, completed in 1986. NAD83 (nnnn) indicates positions on the NAD83 datum for the North American Adjustment, but readjusted to a State High Accuracy Reference Network (HARN) on the date shown in (nnnn). NAD83 (CORS) indicates positions which are part of the CORS network. POS_SRCE- Position Source for the LATITUDE,LONGITUDE ADJUSTED = Least squares adjustment. (Lat,Lon Rounded to 5 decimal places.) HD_HELD1 = Differentially corrected hand held GPS observations. (Lat,Lon Rounded to 2 decimal places.) HD_HELD2 = Autonomous hand held GPS observations. (Lat,Lon Rounded to 1 decimal places.) SCALED = Scaled from a topographic map. (Lat,Lon Rounded to 0 decimal places.) ELEVATION- Present if available. The Orthometric Height in METERS indicating the height above the Geoid. ELEV_DATUM- Datum of the ELEVATION ELEV_SRCE- Elevation Source for the ELEVATION ADJUSTED = Direct Digital Output from Least Squares Adjustment of Precise Leveling. (Rounded to 3 decimal places.) ADJ UNCH = Manually Entered (and NOT verified) Output of Least Squares Adjustment of Precise Leveling. (Rounded to 3 decimal places.) POSTED = Pre-1991 Precise Leveling Adjusted to the NAVD 88 Network After Completion of the NAVD 88 General Adjustment of 1991. (Rounded to 3 decimal places.) READJUST = Precise Leveling Readjusted as Required by Crustal Motion or Other Cause. (Rounded to 2 decimal places.) N HEIGHT = Computed from Precise Leveling Connected at Only One Published Bench Mark. (Rounded to 2 decimal places.) RESET = Reset Computation of Precise Leveling. (Rounded to 2 decimal places.) COMPUTED = Computed from Precise Leveling Using Non-rigorous Adjustment Technique. (Rounded to 2 decimal places.) LEVELING = Precise Leveling Performed by Horizontal Field Party. (Rounded to 2 decimal places.) H LEVEL = Level between control points not connected to bench mark. (Rounded to 1 decimal places.) GPS OBS = Computed from GPS Observations. (Rounded to 1 decimal places.) VERT ANG = Computed from Vertical Angle Observations. (Rounded to 1 decimal place; If No Check, to 0 decimal places.) SCALED = Scaled from a Topographic Map. (Rounded to 0 decimal places.) U HEIGHT = Unvalidated height from precise leveling connected at only one NSRS point. (Rounded to 2 decimal places.) VERTCON = The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height. (Rounded to 0 decimal places.) ELLIP_HT- Present if available. The ellipsoid height in METERS referenced to GRS80 ellipsoid. ELLIP_SRCE- Ellipsoid Ht Source for the ELLIP_HT Should always be GPS_OBS when present. POS_ORDER- Order of accuracy for the LATITUDE,LONGITUDE Should be one of the following- A,B,1,2,3 Order and class for Orders 1, 2, and 3 are defined in the Federal Geodetic Control Committee publication "Standards and Specifications for Geodetic Control Networks". In addition- Order A stations have a relative accuracy of 5 mm +/- 1-10,000,000 relative to other A-order stations. Order B stations have a relative accuracy of 8 mm +/- 1- 1,000,000 relative to other A- and B-order stations. POS_CHECK- Y=Observational Check was made for the position, N=NO Observational Check was made for the positions ELEV_ORDER- Order of accuracy for the ELEVATION Should be 1,2, or 3 for Vertical Control Stations. Will be blank for stations used for Horizontal Control only. Also see attribute DIST_RATE which is used for some vertical control stations. Elevation order and class for 1, 2, and 3 are defined in the Federal Geodetic Control Committee publication "Standards and Specifications for Geodetic Control Networks". In addition- Vertical control which were determined only for the purpose of supplying a height for Horizontal Distance Reductions are assigned an order of 3. Class 0 is used for special cases of orthometric vertical control as follows- Vertical Order/Class Tolerance Factor -------------------- ---------------- 1 class 0 2.0 mm or less 2 class 0 8.4 mm or less 3 class 0 12.0 mm or less ELEV_CLASS- Should be 0, 1, or 2 See details under ELEV_ORDER ELEV_CHECK- Y=Observational Check was made for the orthometric height, N=NO Observational Check was made for the orthometric heights VERTCONED- Y=Orthometric Height was determined by applying VERTCON to an old NGVD 29 height. N=Orthometric Height determined by observations. DIST_RATE- Distribution rate for POSTED and READJUSTED benchmarks which do not have an Order and Class are as follows "Posted bench marks" are vertical control points in the NGS data base which were excluded from the NAVD 88 general adjustment. Some of the bench marks were excluded due to large adjustment residuals, possibly caused by vertical movement of the bench marks during the time interval between different leveling epochs. Adjusted NAVD 88 are computed for posted bench marks by supplemental adjustments. A range of mean distribution rate corrections is listed for each posted bench mark in the data portion of the publication. A summary table of the mean distribution rates and their codes is listed below. The mean distribution rate corrections which were applied to the original leveling observations is a good indication of the usefulness of the posted bench marks' adjusted NAVD 88 heights. Distribution Distribution Rate Code Rate Correction ------------ --------------- "a" 0.0 thru 1.0 mm/km "b" 1.1 thru 2.0 " "c" 2.1 thru 3.0 " "d" 3.1 thru 4.0 " "e" 4.1 thru 8.0 " "f" greater than 8.0 mm/km POSTED BENCH MARKS SHOULD BE USED WITH CAUTION. As is the case for all leveling projects, the mandatory FGCS check leveling two-mark or three-mark tie procedure will usually detect any isolated movement (or other problem) at an individual bench mark. Of course, regional movement affecting all the marks equally is not detected by the two- or three-mark tie procedure. ELLP_ORDER- Order of accuracy for the ELLIP_HT Should be 1,2,3,4, or 5 if present. The following ellipsoid height order and class relative accuracy standards have not yet been adopted by the Federal Geodetic Control Subcommittee, but are currently in use by NGS- Ellipsoid Height Maximum Height Classification Difference Accuracy ------------------ ------------------- 1 class 1 0.5 (mm)/sqrt(km) 1 class 2 0.7 2 class 1 1.0 2 class 2 1.3 3 class 1 2.0 3 class 2 3.0 4 class 1 6.0 4 class 2 15.0 5 class 1 30.0 5 class 2 60.0 The ellipsoid height difference accuracy (b) is computed from a a minimally constrained correctly weighted least squares adjustment by- b = s / sqrt(d) where b = height difference accuracy s = propagated standard deviation of ellipsoid height difference in millimeters between control points obtained from the least squares adjustment. d = horizontal distance between control points in kilometers ELLP_class- Class of accuracy for ELLIP_HT Should be 1 or 2 See details under ELLP_ORDER 1_RECV- Date when the station was first monumented or in the case of landmarks, first observed. LAST_RECV- Date when the station was last recovered. LAST_COND- Last recovered condition of the mark. Should be one of the following- MONUMENTED 1 OBSERVED GOOD POOR MARK NOT FOUND SEE DESCRIPTION DESTROYED LAST_RECBY- Agency who reported the last condition of the mark. STABILITY- The stability of the mark may have 1 of 4 codes as indicated below- A = MOST RELIABLE AND EXPECTED TO HOLD POSITION/ELEVATION WELL B = PROBABLY HOLD POSITION/ELEVATION WELL C = MAY HOLD, BUT OF TYPE COMMONLY SUBJECT TO SURFACE MOTION - E.G. FROST HEAVE, ETC D = MARK OF QUESTIONABLE OR UNKNOWN STABILITY
All values were obtained from the NGA Datasheet available at <http://www.ngs.noaa.gov/cgi-bin/datasheet.prl>