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GIS Glossary

parcel data – Data representing the geographic limits of property ownership as defined by some legal instrument. It is normally a multi purpose public record designed to show real property ownership within a jurisdiction, the basis for property valuation, and other data used by government officials.

pavement edges – The line demarcating the end of an impervious ground cover and the beginning of unconsolidated materials along a traveled path.

photo laboratory process – The chemical process of converting a latent image in an emulsion layer to a visible, stable image. It involves developing, fixing, washing, and drying the photograph.

planimetric data – Data about features on the Earth surface that are represented only by their correct horizontal position. Distinguished from a topographic map by the omission of relief in a measurable form.

quarter quad – One-quarter area of a four-sided quadrangle that depicts 7.5 minutes of latitude and 7.5 minutes of longitude on a side. Used as a standard surface area mapping unit by the U.S. Geologic Survey.

rectification – The process of eliminating photo scale variations and relief displacement. In digital image processing, it also refers to correcting for geometric distortions, radiometric calibrations, and noise removal.

ridgeline – A line representing the intersection or top between opposite slopes. Commonly used as a parcel line.

satellite imagery – Imagery that is collected using a space-borne remote system that is in orbit around the Earth.

street centerline – A real or imaginary line that is equidistant from the sides (usually pavement edges) of a travel path. Typically, these are the basis for network routing applications.

surface data – Information about variations in the surface of the Earth that are referenced to a known coordinate system and vertical datum. A required component of the orthophoto rectification process.