Digital Orthophoto

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A Digital Orthophoto is a photographic map. It is possible to measure directly on the map because it has a uniform scale. It can be a base layer in a Geographic Information System (GIS) that can be overlayed with other information and data layers.[1]

Initially, orthophotography (first used in the 1960's) incurred exorbitant financial costs and a high volume of man hours to produce a usable product. Technological improvements in the early 1970's made this data more affordable. The individual computer and improved software of today have replaced the old technology. It is said that the orthophoto of today, "can stand alone on its own visual merits or be integrated and employed within a geographic information system."[2]

Digital orthophotos are inexpensive, and efficient. They are used to represent the actual (correct) shape of any object on earth.[3]

The National Digital Orthophoto Program (NDOP) consists of Federal agencies for the purpose of managing national orthoimagery for the public through Federal, State, local agencies and tribal organizations.[4]

A Digital Orthophoto Quad or DOQ is a digitized image of an aerial photograph or other remotely sensed data in which the displacement caused by camera tilt and terrain relief has been removed. The USGS has produced many DOQ's since 1991 using 1:40,000 scale aerial photographs from the National Aerial Photography Museum. The quads are georeferenced to NAD83 UTM coordinates. USGS DOQ's are available in either a 3.75 or 7.5 minute quadrangle in black and white, color infrared, or natural color with 1m ground resolution.[5]

DOQ's are useful because they combine the image characteristics of a photograph with the geometric qualities of a map. With a 1m ground resolution and pixel values representing 256 gray levels DOQ's can be very effective in a variety of GIS applications as a background for digitizing or updating.[6]

Sources

  1. <http://online.wr.usgs.gov/ngpo/doq/doq_basics.html>
  2. <http://proceedings.esri.com/library/userconf/proc95/to150/p124.html>
  3. <http://www.gisdevelopment.net/application/archaeology/general/archg0002.htm>
  4. <http://www10.giscafe.com/nbc/articles/view_weekly.php?section=Magazine&articleid=216288>
  5. Chang K. (2008)'Introduction to Geographic Information Systems'
  6. Chang K. (2008)'Introduction to Geographic Information Systems'
Authors Laurie H.
Editors Jarom Randall, Karl Yorgason
BoK Topics DM3
311 Weeks 3
Tags photo, raster, digital
Facts about "Digital Orthophoto"RDF feed
311 Week3 +
AuthorLaurie H. + and Jarom Randall, Karl Yorgason +
BoK TopicDM3 +
Tagsphoto +, raster + and digital +