By Rick Dickman, Sept. 1999

BLM Montana State Office

Email:richard_dickman@blm.gov

Legal description (ACSM definition): a description recognized by law which definitely locates property by reference to government surveys, coordinate systems or recorded maps; a description which is sufficient to locate the property without oral testimony.

Legal area description (FGDC definition): a tabular representation of the attributes that identify a legal description and/or the spatial representation of the location of the described area in the geographic database. However, the legal area description is not necessarily the whole description of a parcel, just individual descriptions which stand by themselves on a plat map, in PLS, or through metes and bounds, adjoiner, or strip description language in a deed.

Parcel legal area description (FGDC): a composite list of all of the legal area descriptions that make up a parcel and can be used to derive the full spatial extent of the parcel.

Several notes on view above: Legal Area Description (LAD) fabric is separate from parcel fabric. Metes and bounds, PLS, and other description types are maintained in the LAD fabric by Measurement Management (MM). The parcel fabric is maintained in PM (i.e. Parcel maintainers choose when and exactly what changes need to be made for a parcel). The layers need to be logically separate for several reasons: (1) not all parcels are described in terms of legal area description(s), and (2) not all legal area descriptions to date have been created in the database through coordinate geometry, section subdivision, or digitizing/ adjustment from a map (data conversion issue). One of the goals of the parcel maintainer is to strive for better control. As stand-alone parcels get created/ updated, additional legal area descriptions will be created (when possible), and the parcel will be defined (or re-defined) in terms of the legal area description(s). The parcel will then be derived from the parcel legal area description. Even though the concepts of LAD and Parcel are logically separate in the FGDC data model, normally it should not be a requirement to display the layers separately.

The "toolkit" for maintenance of LAD and Parcel fabric will be very comparable. The functional requirements and the data elements (which support the functional requirements) for users within MM and PM are very different. As a rule, Parcel Maintainers will concentrate activity on work relating to ownership, land use rights, management, beneficiary, tax assessment, administration, land management, and many other types of parcel right and restriction issues. MM users will concentrate activity within the broad categories of survey/survey maintenance/geodetic control (including maintenance of the LAD fabric).

Pre-condition: User enters into Verify Parcel Use Case and searches for a parcel by its legal area, ID, or other attribute. To meet the requirement of this use case one of the following must occur, (a) the legal area exists or (b) a parcel exists and is selected by the user.

1. (For condition a above). Use case for Legal Area Description (LAD) is accessed. User selects the LAD(s) for the parcel. LAD(s) are "tied" to the parcel as an attribute. Note: There is a one-to-many relationship between parcel and LAD.
2. (For condition b above). Use case for LAD is accessed. User chooses (1) a LAD(s) from a list of available LAD(s) based on the geographic extent of the parcel, or (2) modifies an existing LAD from the list, or (3) enters a new LAD(s) as text (e.g. type in description of land from a deed or other source document). Note: Rules need to be established as to the conditions and/or restrictions placed on users that modify or enter new LAD(s).

Note: There is no requirement that all parcels have a legal area description (LAD). Parcels may have a local label or name that can be added to the parcel as an attribute within the Create/Modify Parcel Attribute Values Use Case. Examples of descriptions that do not meet the definition of a Legal Area Description are identified below:

1. Tax lot number
2. Descriptions that are captured during the digitizing of the parcel (Dean’s example) which includes an initial point, bearings and distance measurement, etc.
3. L&M land descriptions (ALMRS example) which includes textual descriptions such as "all land in section North of Missouri River" or "all land in section outside of Wilderness Area Boundary", etc.

Pre-condition: User enters into Create/Modify Parcel Geometry Use Case. User constructs the geometry or modifies existing geometry to create a new parcel.

1. Use case for Legal Area Description is accessed. A list of available LAD(s) are provided to the user based on the geographic extent of the parcel. User can then (1) select, (2) modify, (3) enter new LAD(s) as text (e.g. type in description of land from a deed or other source document). Note: Rules need to be established as to the conditions and/or restrictions placed on users that modify or enter new LAD(s).

1. Use Case for Legal Area Description is accessed. User selects an Area of Interest. A list of available LAD(s) are provided. User has the ability to create, modify, or delete an existing LAD. Deletion of a LAD would only occur if the description is determined to be invalid or created in error. Note: Rules need to be established as to the conditions and/or restrictions placed on users that modify or enter new LAD(s), or delete and existing LAD(s).

Pre-condition: A Legal Area Description has been created or modified (see Use cases 1 – 3). Note: Even though a new or modified LAD does not necessitate a change in geometry, a change in geometry is common and requires the LAD fabric to be edited.

This use case follows the same primary scenario as Edit Parcel Fabric Use Case.