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Ad Valorem- According to its value. Ad Valorem tax means a charge imposed upon the value of real property.

Aerial Photography- Precision photographs taken from aircraft. The photography is taken with special cameras which produce the necessary accuracy and other characteristics required for use in tax mapping.

Base Manuscripts- Large color coded drawings to scale showing all pertinent and usable data which can be seen in the aerial photography. These drawings are prepared from the aerial photography by precision stereo plotting instruments.

Block- A designated area on a section map preferably bounded by natural boundaries such as streets, roads, waterways or other prominent features.

Coordinate Locator Number- An east and north reading in feet or meters from the point of origin of the appropriate zone of the New York Coordinate System to the visual center of each parcel.

Dense Areas- Sections of land usually in cities or other highly developed areas where aerial photography taken from a lower altitude and highly detailed base manuscripts are required.

Digital Data- Data that has been captured in a computerized environment and can be electronically displayed.

Digitizing- Digitizing is the process of converting the features on a paper map into digital format. When you digitize a map, you use a digitizing tablet connected to your computer to trace over the features you are interested in. The x, y coordinates of these features are automatically recorded and stored as spatial data.

Errata List- A compilation, usually by city, town and village, of the problem or unsolvable situations accumulated during the tax mapping program.

Grantee Index- An alphabetical listing of the book and page of all deeds recorded in the County Clerk's Office. The grantee books are indexed by the buyers' last name.

Grantor Index- An alphabetical listing of the book and page of all deeds recorded in the County Clerk's Office. The grantor books are indexed by the sellers' last name.

Horizontal Datum- The base from which all the mapping is computed. For tax mapping the required base is the appropriate zone of the New York Coordinate System.

Special District- A district established for the purpose of carrying on, performing or financing one or more improvements or services (sewer, fire, etc.) intended to benefit the inhabitants of such district.

Index File- A cross reference file showing property owners' name and parcel number which may also include other pertinent cross-reference information by parcel number.

Index Map- A map prepared to serve as a key by which a section map in a city, town or village may be readily located.

Instrument of Title Or Conveyance- An instrument in writing by which some estate or interest of land is transferred from one person to another. In most cases it is the deed of the property owner.

Lot- A separately assessed parcel of land.

Libers- Books in which the county clerk's record deeds presented to their office. The complete deed is recorded and assigned page numbers. There are no duplications of the book numbers. Therefore, each deed is located in a unique position.

Model Technical Specifications- Detailed suggested tax mapping specifications prepared by the State Board of Real Property Services. They are designed to result in a tax map that will meet the State's Rules for the Preparation of a Tax Map for Real Property Assessment Purposes.

Modular Units- Specific rectangular mapping units based on the New York Coordinate System. These units are the basis for determining the section map coverage limits. Their location, orientation and size are prescribed by the State Board's rules. 

New York Coordinate System- A mathematical system used for land surveying and mapping projects. It was enacted by the Laws of 1938, Chapter 545. Chapter 605, effective September 7, 1995, amends Chapter 545 of the laws of 1938, in relation to a system of coordinates for the State of New York. It establishes a plane coordinate system that is based upon the North American Datum of 1983, which was compiled by the National Geodetic Survey.

Parcel Number- A numerical designation of each section, block and separate lot assigned in sequence.

Parcel Split- Refer to Parcel Subdivision

Parcel Subdivision- A change occurring in parcel boundaries requiring alteration of a parcel number using a decimal suffix system.

Photometry- The art of taking aerial photographs and producing accurate maps from them.

Plot Sheet- A form upon which is listed the relevant tax map information contained in a deed. The information is presented as a rough map or sketch with appropriate notations.

Progress Report- A report, usually prepared monthly, which verbally or graphically displays the work progress on each item of the tax mapping project.

Rural Areas- Sections of land usually containing farming or timber areas where high altitude aerial photography is used and less detailed base manuscripts are required.

Section Map- A map covering a specific area which may be mapped on one sheet of a tax map at the scale selected.

Semi-Rural Areas- Sections of land usually on the edges of cities of villages where an intermediate altitude of aerial photography is used and relatively detailed base manuscripts are required.

State Board- The New York State Board of Real Property Services.

Tax Map- A map prepared primarily for assessment purposes and approved for use by the State Board. Such map or maps will be drawn to scale and delineated for property lines, with dimensions or areas and identifying numbers for all delineated lots of parcels.

Topographical Features- Items or objects visible in an aerial photograph or reproduced on a map showing the physical features of any place or region. These include relief, position of woods, streams, orchards, swamps, agricultural fields, cities, towns, villages, other cultural features, etc.

Visual Center- A point lying within the boundaries of a parcel and which appears virtually to be in the center of the parcel.