Connecticut 2005 Coastal  Orthophoto Tile Index is a polygon feature class that defines the (rectangular) geographic area covered by each Connecticut 2005 coastal orthophoto image tile.  The 2005 orthophoto data for Connecticut is comprised of 98 orthophoto tiles corresponding to the USGS 3.75 minute quarter quad grid for Connecticut.  These data include a tile footprint polygon feature for each orthophoto based quarter quad in the extent of the project area.  The extent of all the tiles comprise a project area described by:

* all land areas within one-thousand (1000) feet of Mean High Water (MHW) and within one-thousand (1000) feet of state-regulated tidal wetlands; 
* an area of at least two-thousand (2000) feet waterward of the immediate shoreline of Long Island Sound; 
* all offshore islands within the territorial borders of the State of Connecticut including Goose Island and Falkner Island (offshore of Branford); Calf Islands and Great Captain Island (offshore of Greenwich); Norwalk Islands (offshore of Norwalk); Thimble Islands (offshore of Branford); Sandy Point (offshore of Stonington); and all islands in the Connecticut part of Fishers Island Sound; and 
* the main stem of the Connecticut River up to the Massachusetts State line. 

Each polygon feature is identified by a unique ORTHOPHOTO_TILE value, which matches the filename of the corresponding digital orthophoto tile.  All tiles also include basic information on the flight including the year, photography type, tide control, vegetation state, scale, etc.

These data serve as a polygon index to the set of 2005 coastal orthophoto image tiles for Connecticut.

A digital orthophoto is a digital image of an aerial photograph in which displacements caused by the camera and the terrain have been removed. It combines the image characteristics of a photograph with the geometric qualities of a map. A digital orthophoto has the same scale throughout and can be used as a map for measuring distances, calculating areas, determining the shape of features, and reading coordinate locations, for example. Digital orthophotos provide the necessary background (base map) layer information to which other spatial data layers are registered or created.  The process of creating an orthophoto, orthorectification, corrects the geometry of a aerial photo image so that it appears as though each pixel were acquired from directly overhead. Orthorectification uses elevation data to correct terrain distortion in aerial or satellite imagery.

To maximize the quality of the images and their contents, photography for the 2005 Coastal Aerial Survey conformed to the following environmental conditions: 
* photos were only taken during times of no/minimal cloud cover when lighting and weather conditions optimized the color infrared film; 
* solar altitude was more than thirty (30) degrees; 
* the ground detail was not obscured by flooding; 
* the foliage (salt marsh vegetation in particular) was fully developed; 
* seasonal conditions (summer) favored maximum human use/recreation activities (e.g., boats & temporary docks/structures in water, etc.); 
* photo times were planned within one (1) hour window before or after a predicted low tide based on National Oceanic & Atmospheric Administration (NOAA) predicted tide tables. (In instances where this window caused conflicts with the general restricted hours, tide coordination times superceded that limitation); and 
* no photography was flown between the hours 1100 and 1300 Eastern Standard Time (EST) to minimize specular reflection.

The photos exist as 1:12,000 orthorectified color infrared images.  Color infrared photography, often called false color photography because it renders the scene in other than the normal colors seen by the human eye, is widely used for interpretation of natural resources.  Atmospheric haze does not interfere with the acquisition of the image, therefore is well suited to aerial photography.  Because the film is high speed and subject to degrees of degradation in handling before exposure, the aerial photographs can vary in overall tone.  This variability can complicate the interpretation of color tones between photographs, but some general guidelines can be given to aid the inexperienced interpreter. 

* The red tone of color infrared aerial photographs is almost always associated with live vegetation. Very intense reds indicate vegetation which is growing vigorously and is quite dense.  Knowledge of the vigor and density of vegetation is important to the interpretation of the red colors on color infrared aerial photography. 

* As the vigor and density of vegetation decreases, the tones may change to light reds and pinks. If plant density becomes low enough the faint reds may be overcome by the tones of the soils on which the plants are growing. The ground areas in this case will appear in shades of white, blue, or green depending on the kind of soil and its moisture content. As plant vigor decreases, the vegetation will show as lighter shades of red and pink, various shades of greens, and possible tans.  Dead vegetation will often be shades of greens or tans. 

* Bare soils will appear as shades of white, blue, or green in most agricultural regions.  In general, the more moist the soil the darker the shade of that particular soil color. Composition of the soil will affect the color tones shown on the photographs.  Dry sand will appear white and, with more moisture, may be very light gray or possibly light tan.  Clayey soils will generally be darker in color than sands and tend toward tans and bluegreens.  Again, wetter clays will be darker shades of the same tones.  Soils high in organic matter, like silts and loams will be even darker in color, and usually in shades of blues and greens.  Wet organic soils can be very dark blue or green in the aerial photographs. 

* Man-made features will show in the tones that relate to the materials they are made of.  Asphalt roads, for example, will be dark blue or black, gravel or dirt roads will show as lighter colors, depending on the soil materials involved in their composition, and concrete roads will appear light in tone, assuming clean concrete.  The buildings and streets of towns can be considered in a similar manner, their color dependent on the material they are made of. 

* Water will appear as shades of blue, varying from nearly black to very pale blue.  Clear, clean water will appear nearly black.  As the amount of sediment increases, the color becomes increasingly lighter blue.  Very shallow water will often appear as the material present in the bottom of the stream.  For example, a very shallow stream with a sandy bottom will appear white due to the high level of reflection of the sand. 

* Degraded film will result in photographs which have an overall blue or green cast.  When that occurs, the interpretation must consider what that overall cast will do to a "normal" rendition of the scene. 

(Description and guidelines for color infrared photography taken from the United States Geological Survey Aerial Photo FAQ web page, http://edc.usgs.gov/guides/news/aerialfaq.htmlt#A10)

James W. Sewall Co. of Old Town, Maine was contracted by the State of Connecticut to perform the 2005 Connecticut Coastal Color Infrared Aerial Photography Project.   All imagery and data products were defined under State of Connecticut contract award number 05PSX0128AA.

Date of photography

None. No restrictions or legal prerequisites for accessing the data. The data is in the public domain and may be redistributed.

None. No restrictions or legal prerequisites for using the data after access is granted. The data is suitable for use at appropriate scale. When printing this data on a map or using it in a software application, analysis, or report, please acknowledge the State of Connecticut, Department of Environmental Protection  as the source for this information. For example, include the following data source description when printing this layer on a map: Photo index - From the Connecticut 2005 Coastal Orthophoto Tile Index layer, published by CT DEP.

Information encoded about the tile area polygon features includes the name of the corresponding orthophoto image (ORTHOPHOTO_TILE) and identification of the quadrangle number (QUAD_NO), quadrangle name (QUADRANGLE), and quadrangle section (QUAD_SEC) the center of the orthophoto is located on.  Additional information describes various aspects of the aerial survey flight.

Orthophoto tile footprint. One polygon feature per orthophoto tile covering the project area as defined in the abstract.

State of Connecticut, Department of Environmental Protection

Polygon features conform to the following topological rules. Polygons are single part. There are no duplicate polygons. Polygons do not self overlap. Polygons do not overlap other polygons. The tests of logical consistency were performed by the State of Connecticut using ESRI ArcInfo software to maintain feature topology in ArcInfo coverage format. The data is topologically clean. The ArcInfo Clean function was repeatedly used following edits to verify topology and enforce a minimum distance between vertices of 4 feet (fuzzy tolerance) and a minimum allowed overshoot length of 0 (zero) feet (dangle length).

The completeness of the data reflects the feature content of the data sources, which were mosaic of the 2005 coastal orthophotos and a tile index of USGS Quarter Quad index tiles created by the State of Connecticut Department of Environmental Protection.

All attributes have valid values. Values are within defined domains. No rigid attribute accuracy tests were conducted. However, assignment of quadrangle number, quadrangle name, and quadrangle section values were conducted through spatial joins with previously quality checked quadrangle and quarter quadrangle index spatial data, followed by a visual inspection for expected results to ensure overall accuracy.

The horizontal positional accuracy of this data complies with the United States National Map Accuracy Standards for 1:24,000 scale maps. According to this standard, not more than 10 percent of the locations tested are to be in error by more than 1/50 inch (40 feet) measured on the publication scale of a USGS 7.5 minute topographic quadrangle map.

Connecticut 2005 Coastal Orthophoto Tile Index

Although these data have been used by the State of Connecticut no warranty, expressed or implied, is made by the State of Connecticut as to the accuracy of the data and or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the State of Connecticut in the use of these data or related materials. The user assumes the entire risk related to the use of these data. Once the data is distributed to the user, modifications made to the data by the user should be noted in the metadata.

Geographic information sytem (GIS), computer-aided drawing or other mapping software is necessary to display, view and access the information.

The data distributor does not provide custom GIS analysis or mapping services. Data is available in a standard format and may be converted to other formats, projections, coordinate systems, or selected for specific geographic regions by the party receiving the data.

None. No restrictions or legal prerequisites for accessing the metadata.

None. No restrictions or legal prerequisites for using the metadata after access is granted.