| 1959 - 1995 |
Prior to the year 2000, DVRPC’s aerial imagery consisted of mylar aerial photo
enlargements or “atlas sheets”. These atlas sheets were produced from 9x9" aerial
photos. The imagery dates from the years 1959, 1965, 1970, 1975, 1980, 1985, 1990,
& 1995. The 1959s and 1965s primarily cover the urbanized portion of
the DVRPC region (the DVRPC region is made up of nine counties: Bucks, Chester,
Delaware, Montgomery, and Philadelphia in Pennsylvania; Burlington, Camden,
Gloucester, and Mercer in New Jersey). Subsequent years provide full coverage of the
region, minus the occasional missing scan.
In order to increase the efficiency of using the historical aerial imagery, the sheets were
scanned into TIFF (Tagged Image File Format) files. Each TIFF file ranges between 35-
40MB in size. Unlike DVRPC’s more recent aerial imagery (2000 and later), the
historical aerials are not “orthorectified” or “orthocorrected”. In other words, they are
simply aerial images with no spatial reference or uniform scale. Through the process of
georeferencing, the scanned images can be assigned a spatial reference which will
enable them to be used more readily in a GIS environment. That said, georeferencing is
not orthorectifying or orthocorrecting. What it does allow is for the scan to be displayed
relative to other spatially referenced GIS layers. A georeferenced scan does not have
the properties of an actual orthoimage. Whereas an orthoimage can be used for making
accurate measurements, a georeferenced image cannot, as it does not have the spatial
accuracy and uniform scale of an orthoimage.
ftp://ftp.pasda.psu.edu/pub/pasda/dvrpc/DVRPC_Historical_Aerials/Indexes/DVRPC_Historical_Aerial_Index_Maps.pdf
https://www.dvrpc.org/webmaps/TileIndex/
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| Delaware Valley Regional Planning Commission |
| 1938 - 1980 |
Penn Pilot, a project sponsored by the Pennsylvania Geological Survey, is an online library of digital historical aerial photography for the Commonwealth of Pennsylvania. Using the interactive map provided on this website, you can browse, view, and download thousands of photos covering the Commonwealth from 1937 to 1942 and 1967 to 1972.
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| The Pennsylvania State University |
| 1993 |
Orthophotos combine the image characteristics of a photograph with the geometric qualities of a map. The primary digital orthophotoquad (DOQ) is a 1-meter ground resolution, quarter-quadrangle (3.75-minutes of latitude by 3.75-minutes of longitude) image cast on the Universal Transverse Mercator Projection (UTM) on the North American Datum of 1983 (NAD83).The geographic extent of the DOQ is equivalent to a quarter-quad plus The overedge ranges a minimum of 50 meters to a maximum of 300 meters beyond the extremes of the primary and secondary corner points. The overedge is included to facilitate tonal matching for mosaicking and for the placement of the NAD83 and secondary datum corner ticks. The normal orientation of data is by lines (rows) and samples (columns). Each line contains a series of pixels ordered from west to east with the order of the lines from north to south. The standard, archived digital orthophoto is formatted as four ASCII header records, followed by a series of 8-bit binary image data records. The radiometric image brightness values are stored as 256 gray levels ranging from 0 to 255. The metadata embedded in the digital orthophoto contain a wide range of descriptive information including format source information, production instrumentation and dates, and data to assist with displaying and georeferencing the image. DOQ images are acquired as a part of the USGS' National Aerial Photography Program (NAPP). Through NAPP imagery for each state is produced on a 7 year cycle. These images are the NAPP III cycle which will run from 1997-2001 These DOQQ's are distributed through PASDA as GeoTIFF images as received from USGS.
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| U S Geological Survey |
| 1999 |
Orthophotos combine the image characteristics of a photograph with the geometric qualities of a map. The primary digital orthophotoquad (DOQ) is a 1-meter ground resolution, quarter-quadrangle (3.75-minutes of latitude by 3.75-minutes of longitude) image cast on the Universal Transverse Mercator Projection (UTM) on the North American Datum of 1983 (NAD83).The geographic extent of the DOQ is equivalent to a quarter-quad plus The overedge ranges a minimum of 50 meters to a maximum of 300 meters beyond the extremes of the primary and secondary corner points. The overedge is included to facilitate tonal matching for mosaicking and for the placement of the NAD83 and secondary datum corner ticks. The normal orientation of data is by lines (rows) and samples (columns). Each line contains a series of pixels ordered from west to east with the order of the lines from north to south. The standard, archived digital orthophoto is formatted as four ASCII header records, followed by a series of 8-bit binary image data records. The radiometric image brightness values are stored as 256 gray levels ranging from 0 to 255. The metadata embedded in the digital orthophoto contain a wide range of descriptive information including format source information, production instrumentation and dates, and data to assist with displaying and georeferencing the image. DOQ images are acquired as a part of the USGS' National Aerial Photography Program (NAPP). Through NAPP imagery for each state is produced on a 7 year cycle. These images are the NAPP III cycle which will run from 1997-2001 These DOQQ's are distributed through PASDA as GeoTIFF images as received from USGS.
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| U S Geological Survey |