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Topic: Orthophoto

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	Are all Orthos created equal
		Orthophotos may line up very well with a set of planimetric data, and a GIS user can profitably use the data for years even if both data sets are significantly shifted from true ground position.
		First, when comparing orthophotos to adjacent orthophotos, the relative accuracy specification is based on the absolute accuracy spec (unless a custom specification is put in place dealing specifically with edge matching).
		If one orthophoto may be shifted 2 feet from true ground position, and the adjacent orthophoto may also be shifted the same amount, it is possible that the adjacent orthophotos be shifted in opposite directions, giving a 4 foot relative shift (which is acceptable with the accuracy spec).
	gis.esri.com /library/userconf/proc02/pap0265/p0265.htm (1814 words)

	The terms "digital orthophoto" and "DOQ" are used throughout this
		These inputs are used to register the image file to the scanner and to the sensor platform, to determine the orientation and location of the sensor platform with respect to the ground, and to remove the relief displacement from the image data.
		The ground sample distance of the digital orthophoto is a result of the scanning aperture of the microdensitometer used to capture the digital image and the resampling algorithm.
		The geographic extent of the digital orthophotos is 50+ square miles from M-14 on North to Morgan Road on the South.
	www-personal.umich.edu /~sarhaus/courses/NRE501_F2000/lloyd/orthoph.htm (1108 words)

	True digital orthophoto for architectural and archaeological applications
		Orthophoto is an efficient and economic way of representing photographic information in a 2D-reference system, which is useful when the user has to measure the surveyed object without the interpretation made by an unexperienced operator.
		If one uses the traditional approach to digital orthophoto generation, all the points hidden by the perspective effects are not represented and the visible points are duplicated on the resulting orthophoto.
		The input data for the generation of the true orthophoto of a rough object are: a dense DEM, generated by a laser scanner device, and a series of oriented images containing the radiometric description of all the points to be orthoprojected.
	www.gisdevelopment.net /application/archaeology/general/archg0002pf.htm (2907 words)

	OEEPE Workshop, Practical Aspects of Digital Orthophoto Production
		The use of the collinearity equation for every orthophoto pixel is favourable and even necessary in case of rough terrain and in case man-made objects are included in the surface description.
		Orthophotos with the same pixel size may be computed based on input data differing by decreased scale of aerial imagery (e.g.
		Therefore, a user of orthophoto data should be aware of the effects inherent to orthophotos such as misplacement of objects that are not modelled by the DTM.
	phot.epfl.ch /workshop/wks99/8_1.html (3250 words)

	Digital Orthophotography and GIS
		The key to understanding the orthophoto is first understanding the geometric properties of conventional vertical aerial photography, since this is the source of all orthophoto imagery.
		In the construction of the orthophoto all fluctuations in scale are removed and the image is presented constant scale.
		Since most digital orthophoto mapping projects cover large areas, it may not be possible to take GPS readings for each digital image.
	gis.esri.com /library/userconf/proc95/to150/p124.html (3457 words)

	Digital Orthophoto Quadrangles
		The resolution of the digital orthophoto is a result of the scanning aperture of the microdensitometer used to capture the digital image.
		The geographic extent of the digital orthophoto is equivalent to an orthophoto quarter-quadrangle or quadrangle (3.75- or 7.5-minutes), plus a minimum of 50 meters to 300 meters of overedge, sufficient coverage to encompass the four primary and secondary horizontal datum corner points.
		Digital orthophoto accuracy is expressed as RMSE and is determined by finding the line and sample coordinates in the digital orthophoto and comparing these to their ground coordinates.
	www2.hawaii.edu /~mckay/o/usgsdoq.htm (3373 words)

	Orthophoto maps (Site not responding. Last check: )
		Zavod za fotogrametriju Inc. has been making orthophoto maps since 1974; in the past, they were made in analogue way, by differential photographic rectification, but today they are made by use of modern digital methods.
		Orthophoto mapping procedure is faster and much more economical in relation to classical or digital mapping.
		Orthophoto mapping is based on oriented digital photogrammetric photos and digital relief model.
	www.zzf.hr /eng/en_ort1.html (354 words)

	DIGITAL ORTHOPHOTO PRODUCTION ON DESKTOP COMPUTERS
		In particular, digital orthophotos are now recognized as valuable "base map" coverages that can be used to identify ground control, update existing coverages for land use/cover and transportation routes and assess changes in the landscape caused by construction or environmental phenomena (Figure 1).
		The procedures for producing digital orthophotos are well established and were derived from techniques developed in the 1950's and 1960's for generating orthophotos.
		They concluded that where digital orthophotos are produced with the intent of generating hardcopy output products at 3 to 4 times the original photo scale, the total cost, including flying aerial photos, surveying ground control, computing a DEM and generating the digital orthophoto can exceed US$1000 per frame.
	www.uga.edu /~crms/gim.htm (1369 words)

	Orthophoto Technology < Photogrammetry < Technology \| Hansa Luftbild - German Air Surveys
		Projection of the earthâs surface on the film or image surface is distorted both through relief and distance from the centre of the image.
		For high resolution orthophotos (GSD=10cm and smaller) the topographic details (such as civil engineering structures eg bridges, dykes etc) have to be taken into account during rectification.
		Orthophoto projects often cover an extensive area and therefore are tiled at regular intervals.
	www.hansaluftbild.de /en/technologie/photogrammetrie/orthophototechnik.html (296 words)

	Stand Up Straight--A True Ortho Perspective on Downtown Devner
		Digital orthophotos can be used for technically specific needs such as planimetric or cadastral mapping; utility data capture and quality control; and accurate project analysis and design implementations.
		Digital orthophotos can also be used to explain projects and issues to the general public because real-world pictures are easier for the untrained eye to understand.
		To create a digital orthophoto, several key input files are necessary: aerial photos with a high-percentage overlap, scanned imagery, aerotriangulation (A.T.) results, and a digital elevation model (DEM).
	www.esri.com /news/arcuser/1001/standup.html (1686 words)

	GeoWorld - Jul 99 - GIS Fundamentals - Digital Orthophoto Concepts and Applications A Primer for Effective Use (Site not responding. Last check: )
		Updating a digital orthophoto coverage where changes have occurred is merely a matter of obtaining new aerial photography, scanning it at the same resolution, controlling the scan with new aerial triangulation and, if there have been no changes in the DTM, simply using the old DTM to rectify the new image.
		Digital orthophotos also are used by landfill site owners who need current information on their landfills to ensure they meet regulatory requirements.
		The cost of producing a digital orthophoto in rural areas is basically the same as in an urban area, whereas the cost of vector mapping decreases because there is less detail to map.
	www.geoplace.com /gw/1999/0799/799dg.asp (2536 words)

	DOQ
		These five inputs are used to register the image file to the scanner and to the sensor platform, to determine the orientation and location of the sensor platform with respect to the ground, and to remove the relief displacement from the image data.
		The ground sample distance of the digital orthophoto is a result of the scanning aperture of the microdensitometer used to capture the digital image and the resampling algorithm.
		The geographic extent of the digital orthophoto is equivalent to an orthophoto quarter-quadrangle (3.75-minutes of latitude and longitude), plus a minimum of 50 meters to to a maximum of 300 meters of overedge is included, sufficient to offer coverage to encompass the four primary and secondary horizontal datum corner points.
	spatialnews.geocomm.com /education/tutorials/doq1/usgs_doq.html (2385 words)

	Orthophoto, aerial photography, digital mapping, photogrammetric software, remote sensing
		Orthophoto provides perfectly vertical representation of a whole scene and is available in resolutions ranging from 1m to a few cm.
		Orthophoto gives much detail for built-up areas emphasis, while emphasis will be on natural resources and features for customers specializing in agriculture and environment.
		Orthophoto is used to measure the precise dimensions of surface of our Earth, such as the area of a farmer's field, to the heights of buildings or the width of roads.
	www.infoterra.fr /Infoterra/orthophoto.php (327 words)

	SE WI Regional Land Information: Aerial Orthophotography
		The Orthophoto Viewer is a mapping application that displays the year 2005 orthophotos for the Southeastern Wisconsin Region.
		Samples of color and fl-and-white orthophotos are included in the 2005 orthophoto samples document (PDF file).
		Digital orthophotos for the year 1995 and 2000 are also available for purchase from the Southeastern Wisconsin Regional Planning Commission.
	www.sewrpc.org /regionallandinfo/orthophotos/default.shtm (840 words)

	Ph.D. Dissertation - John Evans - Chapter 8
		The orthophoto browser is in part an outcome of several years of activity in state and federal governments in the area of geographic data sharing and standards.
		The orthophoto prototype can be evaluated in several ways: its fulfillment of the CCAP project terms, its demonstrated value to researchers, reports of its use, and its performance along the yardsticks set forth for the cases.
		Putting easy access to orthophotos at everyone’s fingertips may offer a more accurate alternative: if field workers were to use highly precise orthophotos as a backdrop to enter observations and measurements, their "events" could be tagged with geographic coordinates (e.g.
	web.mit.edu /jdevans/chapter8.html (6872 words)

	Digital Orthophoto Quadrangle (DOQ).
		It is a photographic map in which ground features are displayed in their true ground position because relief displacements caused by the camera and terrain of an aerial photograph have been removed.
		Since an orthophoto has a uniform scale, it is possible to measure directly on it like other maps.
		An orthophoto may serve as a base map onto which other map information may be overlain.
	tahoe.usgs.gov /DOQ.html (442 words)

	EOM Archives
		The answer is "to a certain extent." The digital orthophoto, dependent on resolution (pixel size), will provide a geographically accurate backdrop of the ground, and further depending on the cost/benefit ratio of producing the digital orthophoto, may well provide value beyongd that initial investment.
		As the population at large is able to easily navigate through what was once complex GIS exercises, the political viability of the technology is assured (i.e., the viewer doesn't need to be a rocket scientist to understand that this is good stuff and it needs to be in place to effectively manage the community).
		Total increase in cost of color digital orthophotos over fl and white is in the range of 60 to 70 percent, but since color orthophotos are without a doubt more interpretable than fl and white, the decision is one of serviceability.
	www.eomonline.com /Common/Archives/March96/nale.htm (1742 words)

	Alabama Water Quality Information System - Digital Ortho Quarter Quadrangles (Aerial Photos)
		The term "digital orthophoto" is used throughout this document to refer to both the "digital orthophoto quadrangle" (DOQ) and "digital orthophoto quarter-quadrangle" (DOQQ) products.
		A digital orthophoto is a digital image which has the properties of an orthographic projection.
		The digital orthophoto is useful as a layer of a geographic information system and as a tool for revision of digital line graphs and topographic maps.
	www.aces.edu /waterquality/gis_data/doqq_metadata.htm (359 words)

	Viewing Orthophoto Imagery and Information
		All Regional Orthophoto Project imagery, elevation data, and more can be viewed using our Pima County MapGuide Maps with either the Main MapGuide Map or the Orthophoto Map.
		The orthophotos are actually a number of layers for different scales (zoom levels), but you only see one orthophoto layer in the legend at a time in the orthophoto group.
		All Grayscale Orthophoto Imagery includes the imagery from the 1998, 2000 and 2002 projects with the latest imagery overlaying portions of older imagery.
	www.dot.co.pima.az.us /gis/data/imagery/viewing.htm (1215 words)

	Orthophoto Data
		An orthophoto is a digital scan of an aerial photo that is controlled for both horizontal and vertical accuracy using several thousand control points obtained from a digital elevation model.
		This data is tiled into approximately 170, 1 km by 1 km tiles.
		As a result we also offer resampled images (25 cm pixel resolution) at a fraction of the size.
	www.oakville.ca /5852.htm (416 words)

	Orthophoto images - One step further... (Site not responding. Last check: )
		For the non-technical users, orthophoto images could be another term for photo-maps, that images is geometrically correct and usually display more data then conventional maps.
		Because all of that, orthophoto images are more easily used for non-technical people - it's kind of WYSIWYG in the cartographic terms.
		Digital Terrain Model is prerequisite and post product of orthophoto image making, so it's a time to use it for something else then just making orthopohoto images.
	www.inet.hr /cad_studio/references/ref22.htm (302 words)

	Interoperable Web-based delivery of digital orthophoto imagery
		Digital orthophotos are scanned aerial photographs whose pixels have been precisely aligned with a planar ground coordinate system.
		This is because few end-users ever want an entire orthophoto file at a time: most want either a low-resolution overview, or a detailed view of a small area.
		Queries to orthophoto servers may also be embedded in HTML pages, or word-processing documents, or formulated by handheld devices, vehicle navigation systems, or any HTTP-enabled piece of software.
	tull.mit.edu /jpers (3264 words)

	Dissertation (Abstract): Fahmi Amhar (Site not responding. Last check: )
		The increasing importance of large and medium scale orthophotos (for instance as database in a GIS in particular for urban planning purposes) is obvious.
		For the time being usual orthophotos do not place general 3D objects (buildings, bridges, etc) on their geometrically correct positions because conventional algorithms are based on 2.5D digital terrain models (DTM) thus limiting significantly the possibility of describing the real 3D shape of the objects and inhibiting the correct calculation of visibility.
		The orthophoto of the terrain (that contains only the terrain surface) and the orthophoto of the buildings (that contains the correctly mapped 3D objects) are generated separately with the help of a 2.5D DTM and a 3D DBM, respectively.
	www.ipf.tuwien.ac.at /phdtheses/diss_fa_a.html (627 words)

	U of A Orthophotos
		An orthophoto is an photograph that has been orthogonally corrected to remove distortions based upon viewing angle.
		Orthophotos are very useful because they are really a model and a map, beyond being just a picture.
		The orthophoto is scaled down to be viewable on this webpage.
	ag.arizona.edu /agnet/icac/real/ortho.htm (205 words)

	Metadata: Digital Orthophoto Quadrangles: 10 Meter County Files, Minnesota
		A digital orthophoto is a raster image of remotely sensed data in which displacement in the image due to sensor orientation and terrain relief have been removed.
		Radiometry is verified by visual inspection of the digital orthophoto quadrangle with the original unrectified image to determine if the digital orthophoto has the same or better image quality as the original unrectified input image.
		The area of coverage for a standard USGS digital orthophoto is either a quarter-quadrangle (3.75-minutes of latitude by 3.75-minutes of longitude plus overedge) or quadrangle (7.5-minutes of latitude by 7.5-minutes of longitude plus overedge).
	www.lmic.state.mn.us /chouse/metadata/doq10m.html (3136 words)

	CT DEP: USGS Digital Orthophoto Quarter Quadrangles
		The USGS Digital Orthophoto Quarter Quadrangle (DOQQ) Images are published by the U.S Geological Survey through a cooperative program between the U.S. Department of Agriculture, Agricultural Stabilization and Conservation Service (ASCS); U.S. Department of Agriculture, Natural Resources Conservation Service (NRCS), and the U.S. Geological Survey, National Mapping Division (NMD).
		After receiving the original orthophoto images from the USGS on CD-ROM, the Enviromental and Geographic Information Center of DEP projected them to Connecticut State Plane, NAD 83, reduced the image overlap to a minimum in order to reduce file size, and coverted them to TIFF and MrSID format.
		The orthophoto images on CDs 5-7 are in MrSID (.sid) format and each file is named according to its quadrangle number and quadrant - NW, NE, SE, and SW.
	dep.state.ct.us /gis/dataguides/dep/layers/doq.htm (465 words)

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