Connecticut 2004 Orthophoto Tile Index is a polygon feature class that defines the (rectangular) geographic area covered by each Connecticut 2004 orthophoto image tile. The 2004 orthophoto data for Connecticut is comprised of 3,413 orthophoto tiles and these data include a tile footprint polygon feature for each tile. Each tile measures approximately 1.17 miles east-west by 1.5 miles north-south, covering a geographic area of approximately 1.755 square miles. The 2004 digital orthophotos are organized in a regular grid pattern with 36 orthophoto tiles per 7.5 minute quadrangle area or 9 per 3.75 minute quarter quadrangle area. The overlap between adjacent photos is approximately 350 to 450 feet. Each polygon feature is identified by a unique ORTHOPHOTO_TILE value, which matches the filename of the corresponding digital orthophoto tile.
These data serve as a polygon index to the set of 2004 orthophoto image tiles for Connecticut. Use it to determine the name of orthophoto image file for a particular tile.
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.
Date of photography
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, Departments of Environmental Protection and Transportation 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 2004 Orthophoto Tile Index layer, published by CT DEP and CT DOT.
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Aero-Metric, Inc. of Sheboygan Wisconsin was contracted by the State of Connecticut to provide the 2004 Statewide Aerial Survey of Connecticut. Contract deliverables include digital orthohotos, two sets of non-rectified prints for stereoscopic viewing, photo indexes, and LIDAR data. The scale of the accuracy of imagery, data and products meets horizontal National Map Accuracy Standards (NMAS) for 200-scale mapping. Photography is black and white and flown under clear sky conditions when deciduous trees and shrubs are in leafless condition ("leaves off") and the ground is free from ice, snow, cloud shaddows, and floodwaters. The Spring of 2004 was particulary wet, making it extremely difficult to arrive at conditions ideal for conducting a statewide aerial survey. Consequently, portions from 2000, 2005 and 2006 aerial surveys were used for orthophotographic production where there was unacceptable Spring 2004 orthophotography. All 2004 Statewide Aerial Survey imagery and data products defined under State of Connecticut contract award number RFP-990-A-14-0518-C (dated Feb 22, 2000), including contract award supplement #1 (dated Feb 28, 2002), contract award supplement #2 (dated Nov 4, 2004), contract award supplement #3 (dated Nov 26, 2004) and contract award supplement #4 (dated May 13, 2005).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.
Polygon features conform to the following topological rules. Polygons are single part. There are no duplicate polygons. Polygons overlap along their edges, corresponding to the expected overlap between adjacent images. The overlap between adjacent photos is approximately 350 to 450 feet. Establishment of logical consistency was performed by the State of Connecticut, Department of Environmental Protection using ESRI ArcGIS software to derive these polygon features from a photo index in CAD format supplied by the State of Connecticut, Department of Transportation. No automated procedures or tests were performed to guarantee desired topology other than visual inspection.
The completeness of the data reflects the feature content of the data sources, which is a photo index for the 2004 orthophotos in CAD format from the State of Connecticut, Department of Transportation.
The horizontal positional accuracy of this data is unknown.
Quarter_Quadrangle_Index_NAD83_Area.shp is in ESRI Shapefile format with polygon features.
These data serve as a polygon index to the set of 2004 orthophoto image tiles for Connecticut.
Orthophoto tile boundary information in CAD format from the State of Connecticut Department of Transportation (source 1) was used as the basis for creating a center point feature for each orthophoto tile. Attributes such as ORTHOPHOTO_TILE were transferred from the polygon data in CAD format to individual point features. Additional center point attribute information such as quadrangle number, quadrangle name, and quadrangle section values were subsequently determined and assigned to individual point features through spatial joins with quarter quadrangle index spatial data published by the State of Connecticut, Department of Environmental Protection (source 2). The resulting point feature class was named Ortho_2004_Index_Point (source 3). These point features recorded the name of each orthophoto tile and indentified which quarter quadrangle the center of each orthophoto tile is located on. A spatial join was subsequently used to assign the orthophoto center point attributes (source 3) to the corresponding orthophoto tile polygon features (source 1). The resulting polygon feature class was named Ortho_2004_Index (source 4), containing 3,413 orthophoto tile features.
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Internal feature number.
ESRI
Feature geometry.
ESRI
Quadrangle Number - An ID number designated by the State of Connecticut, Department of Environmental Protection, Natural Resources Center in the 1980's to uniquely identify individual 7.5 minute 1:24,000-scale USGS topographic quadrangle maps. The Quadrangle Number value of each point feature identifies the USGS topographic quadrangle map that the orthophoto center point is located on.
State of Connecticut, Department of Environmental Protection
Quadrangle Section - There are 4 sections per 7.5 minute quadrangle, each one corresponding to a 3.75 minute quarter quadrangle area. The Quadrangle Section value of each point feature identifies the (NE, NW, SE, SW) section of the 7.5 minute 1:24,000-scale USGS topographic quadrangle map that the orthophoto center point is located on.
State of Connecticut, Department of Environmental Protection
Northeast quarter quandrangle
Northwest quarter quandrangle
Southeast quarter quandrangle
Southwest quarter quandrangle
Old Orthophoto tile name - Name assigned by CT DEP to an initial, draft set of orthophoto image files first used by state agencies and distributed to the public. This set of imagery was subsequently replaced by a final set of orthophoto image files that were named according to the values in the ORTHOPHOTO_TILE field. The OLD_ORTHOPHOTO_TILE field is included as a cross-reference for backward compatibility with the initial draft set of orthophoto files.
State of Connecticut, Department of Environmental Protection
Orthophoto tile name - Unique name assigned to each orthophoto tile, which is the basis for individual image files names such as 0400731161_2.tif and 0400731161_2.sid for data in TIF and SID format, respectively. The first 9 digits (e.g. 040073116) identify the USGS 7.5 minute quadrangle map the orthophoto is located on. These first 9 digits are a concatenation of latitude, longitude, and quadrangle numbers. Digits 1 to 3 and 4 to 6 (e.g. 040073) correspond to latitude and longitude values for the quadrangle. Digits 7 to 9 (e.g. 116) represent the quadrangle number. Appended to the first 9 digits is a tenth digit, ranging from 1 to 4, that identifies the 3.75-minute quarter quadrangle area the orthophoto is located on. Appended these first 10 digits is a second sequence number, ranging from 1 to 9 (_1, _2, _3… _9), that identifies the tile section for the orthophoto image (e.g. 0400731161_2). There are 9 possible tile sections per 3.75-minute quarter quadrangle area.
State of Connecticut, Department of Transportation
Feature geometry.
ESRI
Quadrangle Name - Name of the 7.5 minute 1:24,000-scale USGS topographic quadrangle map published by the USGS that the orthophoto center point is located on.
US Geological Survey
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.
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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.
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.
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