Three Fundamental Points To Remember About Cadastral Data
 

1. The focus of cadastral information is legal decisions and legal transactions. 2. The real power of cadastral information is tying records of transactions and status to survey data. 3. Cadastral data in a GIS should show what is on the ground, not what is on the map.

What Is In The Cadastral Data Set
The cadastral data set, like any other GIS data set, consists of spatial components (point, line, and polygon themes) and associated attribute information.
 

Cadastral Spatial Themes

point data	corners, monument locations, other locations, towns
line data	boundaries, PLSS land net, easements, natural features representing boundaries e.g. rivers, streams
polygon data	parcels, lots, blocks, tracts, PLSS townships, sections, section subdivisions, easements, conveyances, claims, zoning, grants, allotments, towns, counties, states, rights-of-ways

Cadastral Data Attributes
Ownership, past ownership, type of ownership, uses, current activities, permits, licenses, rights and restrictions, transactions, land value, purchase price, taxation, legal description, monument description, owner name, administering agency.
 

Valid Uses Of The Cadastral Data Set
Because cadastral information deals with legal decisions and transactions, legal delineation of land, and legally defined rights and restrictions, there are serious precautions with respect to using cadastral data.  The valid uses of cadastral data can be summarized as:

• depicting what is on the ground, not what is on the map
• depicting legal transactions, status and decisions
• showing change in status, rights, easements, conveyances, etc.

• The map is still a picture, and not an exact and authoritative representation of reality.
• GIS users tend to take advantage of the ability to move points (nodes) and lines (arcs), and snap spatial features - editing spatial features for the sake of topology.   Do not do this with cadastral data.  Or, if you do, make sure you realize what you are doing, and don't make the mistake of subsequently representing the data as being more reliable than it is.
• GIS offers the use of air photos and satellite imagery which show what is on the ground.  But what these images do not show is where PLSS lines, property boundaries, and easements and rights exist.  For example, it is easy to look at a fence on an air photo, and think that the fence in the photo follows a legal boundary.  Do not assume that what is on an air photo, a map or an image inherently depicts legal boundaries.
• Do not post any kind of boundary marker on the land based solely on the data you have in the GIS.  Always go to the legal survey record and the legally placed survey monuments for verification.  See the Case Of The Misplaced Boundary Marker below.
• Always know the reliability of your spatial data.  Now that we have, in many places, newly established GPS and control information, it may be too easy to assume that our data is highly reliable.  Always check the reliability information about your cadastral data.  See the Canyon Of The Ancients example later in this section.