General

The purpose of this handbook is to familiarize the reader with the procedures to create a digital cadastral map file for the Ozaukee County Land Information Office. These specifications set forth the requirements of the Land Information Office. Cadastral maps produced under these specifications are an important part of the overall development of the county-wide geographic information system (GIS).

Precision and Accuracy Standards

It is recognized that the recorded dimensions and orientation of real property boundaries to be plotted on the base map sheets may not always agree with the horizontal control survey data shown on those sheets, since most property descriptions were written using field survey data obtained prior to the relocation of section and one-quarter-section corners and completion of the horizontal control survey network tied to the Wisconsin State Plane Coordinate System. Further, the required survey accuracy for the property boundary descriptions for land subdivisions as defined in Chapter 236 of the Wisconsin Statutes and generally adhered to in property boundary surveys is 1 part in 3,000 as compared to the third-order, class I survey accuracy of I part in 10,000 for the horizontal control surveys. As a result, overlapping or separated property boundary descriptions may be expected to exist. The property boundary line maps are to record all dimensions as contained in the official records of the county Register of Deeds, and wherever an overlap or gap of 2.5 feet or more exists, such overlaps or gaps shall be shown as mapped lines. Overlaps or gaps of less than 2.5 feet will be evident only from an examination of the recorded property line dimensions.

Top of Page

Construction of Cadastral Maps

1. General

   It is the intent of the Land Information Office to eventually create a "seamless" digital cadastral map of the entire county. To accomplish this task the cadastral map is created by digitizing the map in divisions based on United States Public Land Survey System (USPLSS) sections. For the purpose of creating a readable hard copy plot, two map scales are used. 1"=200' scale is used for plots covering one quarter USPLSS section and 1"=100' scale for plots covering one quarter quarter USPLSS section. The combination of all section map files will comprise the county's cadastral base. The cadastral base will overlay on to the topographic and planimetric base maps enhancing the cadastral data. Creation of the geodetic reference framework is the initial task in the development of the cadastral base.

   Geodetic Reference Framework

   A reference frame, or survey control network, consisting of section corner and quarter corner monuments having geodetically based coordinates, is necessary for defining the relative spacial locations of all land related data and, as such, comprises the first component for the cadastral map. The reference frame is constructed by precision placement of a monument symbol at all section, quarter section, and meander corners. Computer software generates the section line work and associated textual data. Areas of the quarter quarter sections are computed based on coordinate values of the quarter corners. Coordinate values are obtained from the Control Survey Summary Diagram (maintained by the Land Information Office) or may be extracted digitally from previously prepared topographic base maps. The digital file containing the geodetic reference framework serves as the original or master section file. Files cover a complete USPLSS section. Certified survey maps, subdivisions, and other information is usually digitized in other work files and imported into the section file where it is properly placed and rotated to conform to the reference grid.

   Top of Page
   

   Property Boundary Input

   The construction of the real property boundary lines shall be based upon and include the assembly of all authoritative information such as title documents, subdivision plats, certified survey plats, highway plats, and public and private survey records that may be useful in determining the actual location of the real property boundaries. All of this information must be properly analyzed to determine the sequence which the data will be digitized. In general, platted lands such as certified survey maps and subdivision plats are digitized and imported to the reference grid first. After the platted lands have been digitized, meets and bounds descriptions are placed. Lastly, area description are digitized. Every parcel identified on the cadastral map will have a unique parcel identification number assigned to it (see Exhibit C). This number is the key by which computerized tabular data from the Register of Deeds office is linked to the geographic location of the parcel. Digitization will be performed so as to allow for spacial (polygon) processing and network analysis. All graphic line work in the digital file pertaining to parcel boundaries and road right of way will share adjacent endpoints (snapped). Currently, the software utilized for the input of parcel boundaries and text is PARCEL-IN which runs in the AutoCad environment. For more detail on the function of this software, refer to manual.

The cadastral base map will consist of the following information:

• All real property boundaries
• All road, street, highway right-of-way lines
• All property boundaries as originally platted when identifiable
• All Easement descriptions when found
• All tax key numbers
• All property measurements where available
• Area of parcel in acres when appropriate

Textual information specific to subdivisions will be as follows:

• Subdivision name
• Block number
• Lot number
• Textual information specific to certified survey maps will be as follows:
  
• Certified Survey Map number
• Volume/Page
• Lot number
• Acreage

Mapping Elements Specifications

The data layer scheme is as follows: (AutoCad Format)