Connecticut 2004 Orthophoto is a raster mosaic of primarily spring 2004 orthophotography for Connecticut. It represents a mosaic of over 3,400 input rasters. Some input rasters from 2000 and 2005 aerial surveys were used for orthophotographic production in areas of unacceptable quality of spring 2004 orthophotography. The spring of 2004 was particularly wet, making it extremely difficult to arrive at conditions ideal for conducting a statewide aerial survey. For example, stream levels were high and deciduous trees were not leafless in certain regions. Consequently, in some areas, the raster mosaic includes features photographed on one input raster that do not appear on an adjacent input raster of a different vintage. The geographic extent of individual input rasters is equivalent to 1/36 of a 7.5 minute quadrangle area.
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 shadows, and floodwaters. The raster mosaic is not color balanced, and the input rasters were in Tagged Image File Format (TIFF) format. The normal orientation of the raster 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 radiometric image brightness (pixel) values are stored as 256 gray levels, ranging from 0 to 255. Note, pixel values in the raster mosaic result from a resampling of pixels values from individual input rasters due to the difference in alignment of input and mosaic (target) pixels. Areas where othophotography was not captured either outside of Connecticut or in Long Island Sound are assigned pixel values of zero (0) in the input rasers and were converted to NoData pixels in the raster mosaic.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. Refer to a data source named Connecticut 2004 Orthophoto Tile Index published by the State of Connecticut, Department of Environmental Protection for the geographic extent covered by individual input rasters. The 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 Connecticut 2004 Orthophoto raster mosaic is comprised of 3,413 orthophoto input rasters. The Connecticut 2004 Orthophoto Tile Index includes a polygon feature for the geographic extent (footprint) of each input raster. Each tile footprint 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 (input raster). Refer to a data source named Connecticut 2004 Aerial Photo Center Point Index published by the State of Connecticut, Department of Environmental Protection for aerial photo date and time (flight line) information.
ground condition
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. All 2004 Statewide Aerial Survey imagery and data products are 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).
79 Elm Street
An orthophoto combines the image characteristics of a photograph with the geometric qualities of a map. Orthophotography serves a variety of purposes, from interim maps to field references for Earth science investigations and analysis. It is useful as a layer of a geographic information system and as a tool for revision of base maps. It can be incorporated into any geographic information system (GIS) that can manipulate raster images. It can function as a cartographic base for displaying, generating, and modifying associated digital planimetric data. Other applications include vegetation and timber management, routing and habitat analysis, environmental impact assessments, emergency evacuation planning, flood analysis, soil erosion assessment, facility management, and ground-water and watershed analysis. The accuracy and detail provided by orthophography allow users to evaluate their data for accuracy and completeness, make real-time modifications to their data, and create new spatial data.
Source imagery for tile production. The original flight index negatives are made at the proper altitude (6,000 feet AGL) to yield contact or plotter prints at a scale of 1:12,000 (1 inch = 1,000 feet), enlargeable to a scale of 1:1,200 (1 inch = 100 feet).
Used to provide ground elevations for orthorectification process. The DEM was generated using LiDAR data collected by TerraPoint. LiDAR and photography data were collected separately. LiDAR data was primarily collected during April-July of 2000, with some collected in January-April 2001. The flight altitude was 3000 feet AGL at a nominal flight speed of 140 knots. The scanner model was ALTMS 2036, scan width 18+/- degrees at rate of 20 kHz shot rate and 49Hz scan rate. the standard deviation is 0.6'+/- RMS. The elevation datum is NAV 88.
Used to provide photo exterior orientations for orthorectification process.
Used to provide ground check points for the QC and orthorectification process.
Individual orthophoto image tiles (input rasters). These original input rasters are in Connecticut State Plane Coordinate System, North American Datum of 1983 - NAD83 (HARN). The original flight index negatives are made at the proper altitude (6,000 feet AGL) to yield contact or plotter prints at a scale of 1:12,000 (1 inch = 1,000 feet), enlargeable to a scale of 1:1,200 (1 inch = 100 feet). Naming Convention for Input Rasters - Individual orthophoto image tiles are uniquely named 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, _3Â… _9), that identifies the tile section for the orthophoto image (e.g. 0400731161_2). There are 9 tile sections per 3.75-minute quarter quadrangle area.
Statewide raster mosaic of all ORTHOPHOTO input rasters. The raster mosaic is in the Connecticut State Plane Coordinate System, North American Datum of 1983 (NAD83).
Seven thousand and sixty four photos were acquired to support the State of Connecticut Statewide Digital Ortho program. Airborne GPS and IMU data was provided by AERO-METRIC, Inc and the ground checkpoint data as acquired during the acquisition of the 2000 Department of Environmental Protection (DEP) Statewide program. The project was referenced to the North American Datum of 1983 (NAD83), Connecticut State Plane Coordinates horizontally and to the North American Vertical Datum of 1988 (NAVD88) vertically. Units were measured in United States Survey Feet. The scanned images (21 microns), airborne GPS and IMU data, camera calibration data, and the LiDAR data were used as inputs in developing the Orthophotos, rectified to 0.83 feet pixel resolution. These images were then dodged and cut into final image sheets. The final sheets were viewed and artifacts were removed as well as other edits performed. The final review included the measuring of the ground checkpoints as compared with the surveyed positions to develop a quantitative horizontal positional accuracy assessment. This assessment was reported at a 95% confidence level in United States Survey Feet.
4020 Technology Parkway
Using ESRI ArcGIS 9.2 software, an empty raster dataset was created and subequently populated with input rasters to create a statewide raster mosaic. STEP 1 - Create Raster Dataset - The Coordinate System for the raster dataset is NAD_1983_StatePlane_Connecticut_FIPS_0600_Feet. The image compression type is JPEG with a compression quality of 75. The Pyramid Reference Point X and Y coordinate are 687800 and 1015180, respectively. Pyramids: 8 Bilinear. The Pixel Type is 8_BIT_UNSIGNED, which supports index values from 0 to 255. Raster statistics were not built. Below is a record of the ESRI Geoprocessing CreateRasterDataset command and arguments that created the empty raster dataset. CreateRasterDataset "Database Connections\depdbs11_depraster_DEP_DirectConnect.sde" ORTHOPHOTO_2004 # 8_BIT_UNSIGNED PROJCS['NAD_1983_StatePlane_Connecticut_FIPS_0600_Feet', GEOGCS['GCS_North_American_1983', DATUM['D_North_American_1983', SPHEROID['GRS_1980',6378137.0,298.257222101]], PRIMEM['Greenwich',0.0], UNIT['Degree',0.0174532925199433]], PROJECTION['Lambert_Conformal_Conic'], PARAMETER['False_Easting',999999.999996], PARAMETER['False_Northing',499999.999998], PARAMETER['Central_Meridian',-72.75], PARAMETER['Standard_Parallel_1',41.2], PARAMETER['Standard_Parallel_2',41.86666666666667], PARAMETER['Latitude_Of_Origin',40.83333333333334], UNIT['Foot_US',0.3048006096012192]] 1 DEPRASTER "PYRAMIDS 8 BILINEAR" "128 128" "JPEG 75" "687800 1015180" "Database Connections\depdbs11_depraster_DEP_DirectConnect.sde \ DEPgisraster.DEP.ORTHOPHOTO_2004" STEP 2 - Mosaic approximately 3,400 input rasters. Areas where othophotography was not captured either outside of Connecticut or in Long Island Sound are assigned pixel values of zero (0) in the input rasers and are treated as NoData pixels in the raster mosaic. The Mosaicking Tolerance value was set to zero (0). Consequently, pixel values in the raster mosaic resulted from a resampling of pixels values from individual input rasters due to the difference in alignment of input and mosaic (target) pixels. Below is an example usage of the ESRI Geoprocessing Mosaic command and arguments used to mosaic 8 tif input rasters geographically located in the southeast quarter quadrangle (section 2) of USGS quadrangle No 1. Mosaic :\tif_format\quad0001_to_0014\0420730012_1.tif; Z:\tif_format\quad0001_to_0014\0420730012_2.tif; Z:\tif_format\quad0001_to_0014\0420730012_3.tif; Z:\tif_format\quad0001_to_0014\0420730012_4.tif; Z:\tif_format\quad0001_to_0014\0420730012_5.tif; Z:\tif_format\quad0001_to_0014\0420730012_6.tif; Z:\tif_format\quad0001_to_0014\0420730012_7.tif; Z:\tif_format\quad0001_to_0014\0420730012_8.tif; Z:\tif_format\quad0001_to_0014\0420730012_9.tif "Database Connections\depdbs11_depraster_DEP_DirectConnect.sde \ DEPGISRASTER.DEP.ORTHOPHOTO_2004" LAST FIRST # 0 NONE 0 "Database Connections\depdbs11_depraster_DEP_DirectConnect.sde \ DEPGISRASTER.DEP.ORTHOPHOTO_2004"
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Fourteen (14) QC points were controlled during the the year 2000 statewide flight aquisition. All of the QC points were at well-defined locations. The locations of the 14 QC ground points were compared to their positions on the rectified ortho images. The resulting X and Y residuals were used to calculate the NSSDA horizontal accuracy at the 95% confidenence level in feet.
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79 Elm Street
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 these 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.
| Data format: | in format Raster Dataset (version ArcGIS) |
|---|---|
| Network links: | http://www.ct.gov/deep |
| Media you can order: | disk |
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.
79 Elm Street