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A mathematically based process for converting locations on the three-dimensional earth surface into two dimensions. Spherical coordinates are converted to planar. Different projections will have different impacts on various aspects of area, distance, and shape.
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Geographic Information Systems (GIS) is an assembly of computer hardware, software and geographic data for capturing, managing, displaying and querying various forms of spatial referenced information. In GIS all information has a geographical or spatial component. GIS is often used as an analysis tool to combine mapping with multiple databases, which in turn allow people to make educated, precise and efficient decisions.
Geographic Information Systems support the following:
The City of Newburgh's GIS obtains spatial-referenced data from a number of sources, including the following:
Data types range from aerial photo imagery to designated wetland areas. Many of the City-maintained GIS data layers and attributes are created and enhanced internally, such as housing, proposed zoning, building vacant registry, property value, neighborhood, water supply protection zone and landmark.
Scale is defined as the relationship between a distance measured on the map and the true distance on the ground. It can be presented in three different ways:
An aerial photograph processed to remove the effect of planimetric shift. It has the correct scale throughout.
An attribute table is a database table containing information about geographic features in a GIS dataset. One column typically contains a primary geographic identifier while others might contain additional information. It can often be linked to excel or DBF files as well as PDF or JPG files based on a common ID.
Shapefile, DEM, TIFF, Dwg, Sid, Mdb. Many of these formats are binary and therefore readable only with GIS software.
Vector data is the storage of X, Y, and Z coordinates connected to define points, lines, areas, or volumes. They are best suited to store discrete, well-defined data that can clearly be delimited.
Raster data consists of rows and columns of cells where in each cell is stored a single value from 0 to 255. They are characterized by pixel values. For example, orthoimagery, aerial photography, digital elevation models, and digital raster graphic (USGS Topo DRG) are often stored as raster data.
A mapsheet is a geographic unit or identifiable spatial area for which one or more data themes are available. Mapsheets are grouped into a spatial series. For example, there are more than 900 7.5 minute quadrangles that include the 62 New York counties as a whole.
Global Positioning System (GPS) is a radio emitting and receiving Satellite Navigation System that measures location, velocity and time on earth. Different GPS devices are often used in navigation, mapping, or surveying. For more information, view the Introduction to GIS (PDF) or the slide presentation slides How GPS Works (PDF).
Metadata are data about data, used to evaluate digital databases. They document the origin and characteristics of: