PostGIS Raster : Extending PostgreSQL for The Support of ... - CoDE

2.2.3 Imagery
Figure 2.3: Polygon feature representing parcels [27].
Imagery is organized as a raster data type composed of cells organized in a grid of rows and
columns. In addition to cell values, a raster includes also its cell size and a reference coordinate (the
upper left or lower left corner of the grid). These properties enable a raster to be described by a series
of cell values starting in the upper left row. Each cell location can be automatically located using the
reference coordinate, the cell size and the number of rows and columns.
Figure 2.4: Grid of cells in raster data [27].
Aerial imagery is a raster data structure obtained from various sensors carried in satellites and
aircraft. Digital orthophotography is a typical imagery sources that comes from cameras.
Figure 2.5: Raster data [27].
Imagery is also used to collect data in both the visible and nonvisible portions of the electromagnetic
spectrum. One system is the multispectral scanner carried in landsat satellites that records imagery
in seven bands along with the electromagnetic spectrum. The measures for each band are recorded in
a separate grid. The stack of seven grids makes up a multiband image.
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