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GIS Data Types- Part 1:  Rasters & Vector

There are two types of data used by most geographic information systems: Raster and Vector.

In a GIS, raster data is a cell-based representation of map features. Satellite images, aerial photography and scannned images are all stored in raster format.

This is a Digitial Raster Graphic (DRG) of York Pennsylvania NE. A Digital Raster Graphic (DRG) is a raster image of a scanned USGS topographic or planimetric map that is georeferenced to a real-world coordinate system.

A DRG is useful as a source or background layer in a GIS as a means to perform quality assurance on other GIS layers, and as a source for digitizing and and revising vector data. DRGs can also be merged with other digital data, for example, DEMs or DOQs to produce a composite image.

 

This is Digital Ortho Quarter Quaddrangle (DOQQ) of York Pennslyvania. Orthophotos combine the image characteristics of a photograph with the geometric qualities of a map. DOQQ's serve a variety of purposes, from interim maps to field references for earth science investigations and analysis. Like the DRG, the DOQQ is useful as a layer of a geographic information system and as a tool for digitizing and revising new and existing vector data.

 

This raster is SPOT satellite imagery of State College, PA. This data is at a 10-meter resolution in the natural color scheme. PASDA also has available on the web site the 10-meter resolution in Panchromatic (black and white). This imagery will be updated in 2 years to 5-meter resolution and in another 2 years it will be at 2.5 meter resolution. The lower the resolution will increase the quality of the imagery.

Access to the georeferenced Pennsylvania data will be provided to all PA state government agencies; regional, county and local governments within the Commonwealth of Pennsylvania including council of governments; K-12 public schools, state colleges and universities within Pennsylvania. The non-georeferenced JPEG imagery is accessible to anyone for viewing and downloading through PASDA. Users from eligible organizations may register for access to the georeferenced imagery by downloading, printing and submitting an application with PASDA. This form can be downloaded off the PASDA website. By completing this form users are agreeing to the licensing agreement.

 

 


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