Spatial Data Management System Corner Layer, Surveyed Corners, Alaska

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Frequently anticipated questions:


What does this data set describe?

Title:
Spatial Data Management System Corner Layer, Surveyed Corners, Alaska
Abstract:
This dataset is a spatial representation of the Public Land Survey System (PLSS) in Alaska, generated from land survey records. The data represents a seamless spatial portrayal of land parcels, their legal descriptions, corner positioning and markings, and survey measurements. This data is intended for mapping purposes only and is not a substitute or replacement for the legal land survey records or other legal documents.
Measurement and attribute data are collected from survey records using data entry screens into a relational database. The database design is based upon the FGDC Cadastral Content Data Standard. Corner positions are derived by geodetic calculations using measurement records. Closure and edgematching are applied to produce a seamless dataset. The resultant features do not preserve the original geometry of survey measurements, but the record measurements are reported as attributes. Additional boundary data are derived by spatial capture, protraction and GIS processing. The spatial features are stored and managed within the relational database, with active links to the represented measurement and attribute data.
  1. How should this data set be cited?

    Branch of Spatial Records, Division of Geographic Sciences, 20141119, Spatial Data Management System Corner Layer, Surveyed Corners, Alaska.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -176.381198
    East_Bounding_Coordinate: 173.244792
    North_Bounding_Coordinate: 71.362411
    South_Bounding_Coordinate: 51.744349

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Calendar_Date: unknown
    Currentness_Reference: publication date

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • Entity point (158300)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000027778. Longitudes are given to the nearest 0.000027778. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.

  7. How does the data set describe geographic features?

    corner
    Corner (Source: SDMS)

    cor_id
    Corner ID is the primary key which uniquely identifies each record or occurence in the Corner entity. Each record in the Corner entity has a unique Corner ID. (Source: SDMS - FGDC)

    PIDs are a numbering system for the PLSS rectangular grid, adopted by the BLM GCDB program nationally. PIDs are a six digit integer. The PID identifies the relative position of a point on the rectangular grid, within a given township. 100100 represents the southwest corner of a township. 700700 represents the northeast corner.

    PIDs are a numbering system for the PLSS rectangular grid, adopted by the BLM GCDB program nationally. PIDs are a six digit integer. The PID identifies the relative position of a point on the rectangular grid, within a given township. 100100 represents the southwest corner of a township. 700700 represents the northeast corner.

    Serial value assigned by the SDMS data collection system

    pid
    A PID is a user-specified id of a corner. It provides an alternative means of corner identification, but is not necessarily unique within the system. It provides a means of interfacing with systems. (Source: SDMS - PLSS)

    PIDs are a numbering system for the PLSS rectangular grid, adopted by the BLM GCDB program nationally. PIDs are a six digit integer. The PID identifies the relative position of a point on the rectangular grid, within a given township. 100100 represents the southwest corner of a township. 700700 represents the northeast corner.

    cor_typ_cd
    The Corner Type Code is a system code that defines the class of corner and implies the system usuage of the corner. (Source: SDMS)

    ValueDefinition
    CTLControl
    CORRegular corner
    SYSSystem-generated corner

    cor_mon_typ_cd
    Corner Monument Type Code indicates if a given corner has been monumented. It then describes the physical characteristics of a corner marker; such as post, rod, pipe, rock, tablet, stake, etc. (Source: SDMS - FGDC)

    PIDs are a numbering system for the PLSS rectangular grid, adopted by the BLM GCDB program nationally. PIDs are a six digit integer. The PID identifies the relative position of a point on the rectangular grid, within a given township. 100100 represents the southwest corner of a township. 700700 represents the northeast corner.

    PIDs are a numbering system for the PLSS rectangular grid, adopted by the BLM GCDB program nationally. PIDs are a six digit integer. The PID identifies the relative position of a point on the rectangular grid, within a given township. 100100 represents the southwest corner of a township. 700700 represents the northeast corner.

    PIDs are a numbering system for the PLSS rectangular grid, adopted by the BLM GCDB program nationally. PIDs are a six digit integer. The PID identifies the relative position of a point on the rectangular grid, within a given township. 100100 represents the southwest corner of a township. 700700 represents the northeast corner.

    Values as determined from the survey record.

    cor_reliab_cd
    Corner Reliability Code is a numeric code identifying the accuracy of a survey corner in terms of maximal position error; such as 1 foot or less, 3 feet or less, 10 feet or less, 40 feet or less, etc. (Source: SDMS)

    Values as determined from the survey record.

    Each survey has an implied reliability based on the perceived accuracy of the control used. Each corner in the survey then, inherits the survey's implied reliability.

    geod_cd
    Geodetic Reference ID identifies an established representation of the Earth's surface. (Source: SDMS - FGDC)

    ValueDefinition
    N27North American Datum 1927

    source_id
    Source ID is the system-generated primary key for a Source. Source ID may be used as a reference to record the basis of a survey meaurement or legal description. It implies the authority under which a measurement or legal description was defined. (Source: SDMS - FGDC)

    Each survey has an implied reliability based on the perceived accuracy of the control used. Each corner in the survey then, inherits the survey's implied reliability.

    Each survey has an implied reliability based on the perceived accuracy of the control used. Each corner in the survey then, inherits the survey's implied reliability.

    Each survey has an implied reliability based on the perceived accuracy of the control used. Each corner in the survey then, inherits the survey's implied reliability.

    Source ID is the system-generated primary key for a Source.

    survey_org_cd
    Monumenting Organization Code identifies the organization that last monumented a corner. The default organization is the organization that conducted the survey. (Source: SDMS - FGDC)

    Survey organization as identified from survey records.

    cor_desc_txt
    Corner Legal Description is a name or identifier describing relative location. For Public Land Survey System corners these are names for corners on the base land net. Other labels relate to corners of special surveys or private sector land subdivision surveys. (Source: SDMS - FGDC)

    Corner Legal Description is a system-generated field constructed by concatenating all the corner aliases (corner-land descriptions) to form a single narrative style description of the corner.

    cor_lat_meas
    Coordinate Latitude is the angle between the plane of the reference ellipsoid's equator and a normal to the ellipsoid surface. It is formatted by direction, degrees, minutes, decimal seconds (60 24 32.56 N). This item is analogous to the 'Y' value of a rectangular coordinate system. (Source: SDMS - FGDC)

    Range of values
    Minimum:49.657833099365234375
    Maximum:71.37645721435546875
    Units:decimal degrees

    cor_long_meas
    Coordinate Longitude is the dihedral angle between the meridian of an ellipsoidal normal and an arbitrary initial meridian (usually Greenwich). It is formatted by direction, degrees, minutes, decimal seconds (149 24 32.56 W). This item is analogous to the 'X' value of a rectangular coordinate system. (Source: SDMS - FGDC)

    Range of values
    Minimum:-179.9916534423828125
    Maximum:179.9892730712890625
    Units:decimal degrees

    cor_lat_dec_meas
    Decimal Degreees Latitude is the calculated Y axis measurement of a corner's position. It is either calculated from record input, or from angle measurement. (Source: SDMS - FGDC)

    Range of values
    Minimum:49.657833099365234375
    Maximum:71.37645721435546875
    Units:decimal degrees

    cor_long_dec_meas
    Decimal Degrees Longitude is the calculated X axis measurement of a corner's position. It is either calculated from record input, or from angle measurement. (Source: SDMS - FGDC)

    Range of values
    Minimum:-179.9916534423828125
    Maximum:179.9892730712890625
    Units:decimal degrees

    cor_elev_meas
    Coordinate Elevation is the recorded elevation for a Corner. Elevation is the measured vertical distance from a datum, usually mean sea level, to the Corner's position on the Earth's surface. This item is analogous to the 'Z' value of a rectangular coordinate system. (Source: SDMS - FGDC)

    Corner Legal Description is a system-generated field constructed by concatenating all the corner aliases (corner-land descriptions) to form a single narrative style description of the corner.

    Elevation as determined from survey records.

    meas_source_cd
    Measurement Source defines the source of a measurement. For instance, a corner's position may be generated by COGO calculations, or input from record. It indicates how a survey measurement was arrived at. (Source: SDMS - FGDC)

    The source of the measurement.

    pos_control_id
    Position Control is a system field to identify a land unit that controls the corner's position. When the identified land's corners are being calculated/adjusted, this flag grant's postion update. Other lands utilizing that corner, cannot affect the corner's position. A corner can only be controlled by one land unit. (Source: SDMS - FGDC)

    A system field to identify a land unit that controls the corner's position

    pos_hold_cd
    Position Hold Code tracks whether a position can be updated by system calculation, or should be "held" at the current position. This field is used in conjunction with Position Control Id and Measure Source Code to record how a position was determined, and under what conditions it can be updated. (Source: SDMS)

    A system field that tracks whether a position may be updated.

    cor_systat_cd
    Corner System Status Cd is a system field that flags a corner's status within the system as follows: (Source: SDMS)

    ValueDefinition
    VALIDCorner describes the geometry of one or more land units. All requisite relationships exist.
    ORPHANCorner does not describe the geometry of any land unit, but remains related to one or more land units. An Orphan corner may become Valid if is utilized to describe a land unit's geometry. If an Orphan corner is not used within a certain timeframe, it is administratively removed from the system.
    PENDINGCorner that has no relationships to any land, but may become a Valid corner at some point. Examples of this are raw data from other organizations, imported control stations, etc.
    ZOMBIECorner has no relationships with any land, and is not marked as Pending. A corner will not by explicitly labeled by this status, but will be apparent during an administrative search. Zombie corners should be immediately removed from the system.

    cor_mon_oset_date
    Monument Original Date is the date a monument was originally set in the field, identified by the date stamped on the marker. (Source: SDMS - FGDC)

    Original set date from survey records.

    cor_mon_cset_date
    Monument Current Date is the most current date a monument was re-observed in the field, identified by the last date stamped on the marker. By default, the Monument Current Date should reflect the Monument Original Date until the Monument Current Date is updated. (Source: SDMS- FGDC)

    Current date from survey records.

    cor_northerr_meas
    Corner Northing Error Measurement is the estimated deviation along the Y axis related to a Corner's position. It is required for GMM/SFF compatibility. (Source: SDMS)

    Estimated deviation along the y-axis.

    cor_easterr_meas
    Corner Easting Error Measurement is the estimated deviation along the X axis related to a Corner's position. It is required for GMM/SFF compatibility. (Source: SDMS)

    Estimated deviation along the x-axis.

    user_id
    The system User ID of the person who entered the original data for this record. (Source: SDMS)

    User ID of person that entered the original data for this record.

    entered_date
    The system date that the original data was entered for this record. (Source: SDMS)

    System date.

    modified_user_id
    The system User ID of the person who modified the original data for this record. (Source: SDMS)

    User ID of the person that modified the data for this record.

    modified_date
    The system date that the original data for this record was modified. (Source: SDMS)

    System date.

    pro_pt_id
    Protraction Point Id is a system-generated id to uniquely identify a protracted point. (Source: SDMS)

    System generated id.

    objectid
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    Jarad Bond
    Branch of Information Resources Management
    Information Technology Specialist
    222 W. 7th Ave. #13
    Anchorage, AK 99513
    USA

    (907) 271-3255 (voice)
    j05bond@blm.gov


Why was the data set created?

This dataset was created to provide an accurate, seamless portrayal of the PLSS network, based upon survey records. The dataset is intended for use as a base layer for mapping purposes, and as a framework for the portrayal of land ownership


How was the data set created?

  1. From what previous works were the data drawn?

  2. How were the data generated, processed, and modified?

    Date: Not complete (process 1 of 1)
    Two columns added to the corner table: objectid int, shape st_point
    These must be managed by the SDMS data collection application or a trigger that is fired when a new record is created or the lat/long of a point is changed.
    Objectid (type int) must be set equal to cor_id
    To update object id programatically or in a trigger, use:
    update corner set (objectid, shape) = (cor_id, '2 point(' || cor_long_dec_meas || ' ' || cor_lat_dec_meas || ')')
    This updates all corners. Add the appropriate where clause to update a single corner.

    Person who carried out this activity:

    Jarad Bond
    Branch of Information Resources Management
    Information Technology Specialist
    222 W. 7th Ave. #13
    Anchorage, AK 99513
    USA

    (907) 271-3255 (voice)
    j05bond@blm.gov

  3. What similar or related data should the user be aware of?


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    A. Attribute records are input from approved survey records - this process results in a 100% review of existing survey records. Errors in existing survey records are forwarded to the Review Section for corrections.
    B. Spatial Data Management System validation: 1. Self-validation through data collection application a. SDMS data collection application creates legal description from well-known alias names within the context of the land being collected;
    b. Geometry Checks: can't modify geometry in one land without also changing geometry of adjacent land;
    c. Automation of input processes ensures standardization of things like legal land descriptions and corner descriptions.
    d. Spatial data are generated by position calculations from the survey record attributes. All inaccuracies found in the spatial features are fixed in the attribute record information and then spatial data is re-generated. An error is never "fixed" by spatial edits.
    e. All input is validated by the system to verify observance of Cadastral Survey business rules and integrity of the data. For instance, no two corners can share the same position. A corner cannot exist in the system more than once. There cannot be significant breaks in the bearing along a fixed boundary, etc.
    2. Print out and review reports: a. Print land, boundary, tie, and corner reports to review for accuracy against survey record;
    b. Establish limit of closure and run closure report against the established limit of closure.
    3. Geometry is exported in the largest possible 'network' possible. Networks are defined as those land units that are adjacent to one another or are connected through ties to nearby land units. Edge-matching of adjacent land units are resolved at the coordinate level through the data collection application. a. Special Survey land unit networks are defined as the largest possible 'grouping' of land units (defined by adjacency or by tie).
    b. Rectangular land unit networks are defined by township. Edge-matching of townships are defined at the coordinate level within the data collection application.
    C. Spatial validation: 1. Review land spatially - check arc/info generate "shape" against existing land net;
    2. Review land net imported into SDE layer against existing SDE land net;
    3. Spatial errors are forwarded to data collection staff for correction within the SDMS application. Spatial data is never edited spatially.
    D. Spatial land unit polygon completion: 1. Special Survey land unit polygons are usually 'self-contained' land descriptions. These descriptions include metes and bounds descriptions of all boundaries, including hydrographic boundaries.
    2. Rectangular survey land unit polygons may be composites of both rectangular and non-rectangular descriptions (hydrography meanders).

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Data collection is complete as of the date of publication. This metadata describes a snapshot of the data, current as of the date of publication.

  5. How consistent are the relationships among the observations, including topology?

    All fields in the corner table are system-generated by the SDMS data collection system. The sole exception is the cor_lat_meas and the cor_lon_meas fields. These fields may be used when the source coordinates are known for the point-of-beginning the this corner is defined as the point-of-beginning.
    Corners positions are based on either known or derived corners (points) determined through geodetic calculations. Corners are used to construct boundaries. The resulting boundaries are used to construct polygons.


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints:
Discretionary, contains no sensitive information - generally considered releaseable.
Use_Constraints:
Accuracy published on or derived from BLM's official survey records. Please refer to BLM's official survey records for specific bearing and distance information.
Any hardcopies or published datasets using these data shall clearly indicate their source. Any users wishing to modify the data are obligated to describe the types of modifications they have performed. User specifically agrees not to misrepresent the data, nor to imply that changes made were approved or endorsed by the BLM. Any discrepancies or errors in this data should be reported to John_Montgomery@ak.blm.gov

  1. Who distributes the data set? (Distributor 1 of 1)

    Tim Varner
    Alaska State Office, Bureau of Land Managment,
    IT Specialist
    222 W. 7th Ave #13
    Anchorage, AK 99513
    USA

    (907) 271-5799 (voice)
    (907) 271-4549 (FAX)
    tvarner@blm.gov

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    No warranty is made by the Bureau of Land Management as to the accuracy, reliability, or completeness of these data for individual use or aggregate use with other data.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 15-Jun-2004
To be reviewed: 05-Jun-2005
Metadata author:
Branch of Information Resource Managment
Attn: Tim Varner
Information Technology Specialist (GIS)`
222 W. 7th Ave #13
Anchorage, AK 99513
USA

(907) 271-5799 (voice)
(907) 271-4549 (FAX)
Tim_Varner@ak.blm.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:


Generated by mp version 2.9.12 on Thu Mar 09 14:07:51 2017