The 2010 Connecticut Multispectral Coastal Digital Orthophotography is 1:12,000-scale, 4-band (red, green, blue, and near infrared) tide controlled orthorectified imagery. These data were compiled from a set of 821 individual vertical aerial images taken over 3 distinct days during a June 15 to September 15, 2010 flight window. The indivudual orthophotos have been subsequently mosaicked into a composite that can be configured to show either true color or color infrared versions of the coastal landscape. The geographic extent (~320 sq mi) of the photography includes: * 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 in order to clearly depict the interface between the shorelands and coastal waters; * 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. To maximize the quality of the images and their contents, photography also conformed to the following flight specifications: * photos were only taken during times of no/minimal cloud cover when lighting and weather conditions optimized the data collection; * solar altitude was no more than 65 degrees and no less than 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 1 hour window before or after a predicted low tide based on National Oceanic & Atmospheric Administration (NOAA) predicted tide tables. * Forward overlap is 60% and side image overlap is 30% * Crab and Tilt do not exceed 5 degrees. The individual aerial photos were first orthorectifed and mosaicked into grid-based system provided by the State of Connecticut Department of Environmental Protection. Adjacent tiles are edgematched with no gaps. Temporal and seasonal differences between source images were minimized to avoid incongruence across join lines. When a mosaic of source images was made, the image judged by visual inspection to have the best contrast was used as the reference image. The brightness values of the other images were adjusted to match that of the reference image. The join lines between the overlapping images were hosen to minimize tonal variations. Localized adjustment of the brightness values were performed to minimize tonal differences between join areas. Subsequent mocaicking took the individual orthophotos and combined them into a project-wide composite. The ground resolution of the imagery is approximately 1 ft per pixel. Data is compiled at 1:12,000 scale. This data is not updated.
The imagery exists as 1:12,000 4-band (red, green, blue, near infrared) multispectral images. When bands are configured as follows: red = 1, green = 2, blue = 3, the imagery will render as true color - the same color the human eye naturally discerns. When bands are configured as follows: red = 4, green = 1, blue = 2, the imagery will render as color infrared. 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. 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)
ground condition
Color orthophotos are comprised of RGB and NIR bands. (Source: None)
Photoscience, Inc., of Lexington, KY performed the 2010 Connecticut Multispectral Coastal Imagery Project via an MOU between the State of Connecticut Department of Environmental Protection and the NOAA Coastal Services Center as part of the Coastal Geospatial Services Contract (CGSC), a FAR Part 36, Architectural and Engineering Contract vehicle to provide geospatial services.
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The 2010 Connecticut Multispectral Coastal Digital Orthophotography is 1:12,000-scale 4 band (red, green, blue, & near infrared) tide controlled imagery. It depicts land use, natural resources, vegetation, and other features and characteristics in the immediate shoreline areas of Connecticut during the summer of 2010 within one hour of a predicted low tide both in true color or color infrared, depending on the band configuration. Use this layer as photo representation for depicting coastal features/landscapes or to analyze the landscape, features, or activities of the coastal area. NOTE: This data is georeferenced, so it can be combined with other GIS data with real world coordinates. An un-rectified version of this data (2010 Connecticut Multispectral Coastal Imagery) constituting the source data for the orthophtography is also available for use.
Planned Photo Centers.
Digital stereoscopic aerial imagery was obtained using a large format Zeiss/Intergraph Digital Mapping Camera (DMC) over 3 flight dates comprised of 4 missions. Aerial imagery was supplemented with the simultaneous acquisition of airborne GPS/IMU data, which captured the ground coordinate for the nadir point of each photograph. Aerial imagery was exposed at an altitude of approximately 9800' above mean terrain yielding an approximate GSD of 1 ft. The aerial images are used to AT the project and in the production of orthophotos.
Photo Science, Inc. established a combination of photo identifiable and limited targeted ground control points to create a digital control file and control report used in the ortho production and QA processes. Predefined points within each collection block were measured using a combination of GPS and conventional survey techniques. These points along with their precise coordinates and elevations were used in the AT process and to check the horizontal accuracy of the resulting orthophotos. The X and Y coordinates were expressed in CT SPCS NAD83, US Survey Feet and Z elevation were expressed in NAVD 1988, US Survey Feet. A total of 41 control points were. Details of the Ground Control Survey Phase can be found in Photo Science's full control report.
Exterior Orientation (EO) Parameters (x,y,z,omega,phi,kappa) are produced to provide precise photocenter locations for each frame of imagery.
SoftCopy Aerotriangulation is a computer process of densifying the ground control network from locations in a few of the digital images to numerous points in each digital image that is to be used in the mapping process. This process is dependent on the location and coordinate positions of the ABGPS and GPS photo control points as well as a precise camera calibration for the DMC camera used to capture the images.
The LIDAR elevation data used for the rectification of the orthophotos was provided by NOAA Coastal Services Center for the Connecticut Department of Environmental Protection.
The tiled orthophoto is the result of mosaicking orthorectified imagery and using the tile definition to cut into manageable, usable orthophotos.
The orthophoto mosaic is the result of mosaicking orthorectified imagery into a composite project wide dataset.
Imagery Acquisition: A set of 821 individual aerial photos were taken over 3 distinct days during a June 15 to September 15, 2010 flight window. The geographic extent (~320 sq mi) of the photography includes: * 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 in order to clearly depict the interface between the shorelands and coastal waters; * 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. To maximize the quality of the images and their contents, photography also conformed to the following flight specifications: * photos were only taken during times of no/minimal cloud cover when lighting and weather conditions optimized the data collection; * solar altitude was no more than 65 degrees and no less than 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 1 hour window before or after a predicted low tide based on National Oceanic & Atmospheric Administration (NOAA) predicted tide tables. * Forward overlap will be 60% and side image overlap will be 30% * Crab and Tilt will not exceed 5 degrees. All flight plans were approved by CTDEP prior to flight operations. Flight Info: Flight # 1 on 6/15/2010 * Date: 06/15/2010 * Time: 8:10AM - 11:47 (EST) * Aircraft #: N62923 * Camera Type: DMC * Camera Serial #: 131 * Focal Length (mm): 120 * # Flight Lines: 10 lines were flown (see flight logs) * AbGPS and IMU were used to obtain the omega, phi and kappa values Flight #1 on 6/18/2010 * Date: 06/18/2010 * Time: 8:38 - 11:20 (EST) * Aircraft #: N62923 * Camera Type: DMC * Camera Serial #: 131 * Focal Length (mm): 120 * # Flight Lines: 14 lines were flown (see flight logs) * AbGPS and IMU were used to obtain the omega, phi and kappa values Flight #2 on 6/18/2010 * Date: 06/18/2010 * Time: 2:00 - 3:29 (EST) * Aircraft #: N62923 * Camera Type: DMC * Camera Serial #: 131 * Focal Length (mm): 120 * # Flight Lines: 4 lines were flown (see flight logs) * AbGPS and IMU were used to obtain the omega, phi and kappa values Flight # 1 on 6/19/2010 * Date: 06/19/2010 * Time: 10:43 - 11:25 (EST) * Aircraft #: N62923 * Camera Type: DMC * Camera Serial #: 131 * Focal Length (mm): 120 * # Flight Lines: 3 lines were flown (see flight logs) * AbGPS and IMU were used to obtain the omega, phi and kappa values All flight data was QA/QC inspected by PhotoScience Inc. and the NOAA Coastal Services Center prior to shipment to the State of Connecticut, Department of Environmental Protection for final QA/QC. No areas were required to be reflown.
Ground Surveying: Ground Control points were collected from July 10, 2010 to July 14, 2010 by P. Hrabak of Photo Science, Inc.. A total of 41 Photo Identifiable (PID's) features were collected for this project. Static GPS observation sessions were of 30 minutes apiece, using a Trimble 5700 receiver and a Zephyr Geodetic antenna on a 2.0 meter fixed height tripod. PDOP prediction was accomodated, only collecting data when values were predicted to be less than 4.0 and with 6 or more satellites, using an elevation mask of 15 degrees. A data log sheet was filled out on each occupation. Four photographs were taken of each point from four different directions. High-contrast corners of pavement, especially concrete adjoining dark asphalt or grass, were favored, and were selected in evenly-spaced, open, well-exposed areas where the planned aerial imagery footprints had maximum overlap. See the full Survey Report for more details.
Aerotriangulation: Softcopy aerotriangulation was performed by Photo Science to supplement and extend ground control and ABGPS / IMU control data. Aerotriangulation constructs a detailed model of the position of each pass point and provides residuals (and blunders) at all photo control locations. The end result is not only the referenced image, but also a coordinate listing of all of the points and corresponding residuals. This process enabled photogrammetric production of the orthophotography requirements. According to the scope of work, accuracy is stated: Positional Accuracy should be at least as good as the National Map Accuracy Standards for the nominal scale of the output. The AT computations were based on a projection of the Conneticut State Plane Coordinate System and a datum of NAD83. Vertical computations were based NAVD88. All final coordinate and elevation values were expressed in US Survey Feet. A digital image of the aerial photography was utilized to compare and measure the coordinates of selected pass points, (min. 9 per image) with the exception of end images, which have a minimum of 6 per image. Pass points were either dark spots on the ground, corner intersections of sidewalks, rocks, or road lines to name a few. These pass points and any ground based photo control points were measured using the calibration statistics to adjust measurements for the specific camera characteristics. Computer routines (relative and absolute) provide analysis of all pass points, tie points, ABGPS and photo control points. Once all strips were checked for completeness, the strips were assembled into a block where a second degree block adjustment was run along with the full least squares bundle adjustment. Once the last set of blunders and adjustments are complete, a final block bundle adjustment is run to produce the final solution using a rigorous simultaneous least squares bundle adjustment. The bundle adjustment was then run with minimal ground control to test the photogrammetric measurements for consistency. Next, the full ground control data set, including the ABGPS data, was added to the adjustment. The horizontal control was then tightened and the effect on the vertical control and the photogrammetric residuals were inspected. Results of the Aerotriangulation Phase can be found in Photo Science's AT reports.
Digitial Orthophoto Processing: The ortho rectification process required as input a digital elevation model (DEM), imagery (RAW), camera calibration and aerotriangulation exterior orientation file (AT Report). The orthorectified imagery was produced using Intergraph OrthoPro software. It uses ImageStation Photogrammetric Manager (ISPM) for photogrammetry project setup, file management, and importing triangulation data from a user defined ASCII file (EO). The ortho project recorded all the operations, including all the parameters that are defined through the OrthoPro workflow, such as the project area coordinates, pixel size, rotation angle, ISPM project and its unorthorectified source images, product areas (index) orthorectification settings, seamlines and so on. The results were single frame images ready for mosaicking into manageable tiled orthos. The single frame orthos were checked for accuracy against the surveyed ground control before further image editing. Orthorectified imagery was mosaicked, locally color-balanced and cut to the tile definition boundaries using Intergraph OrthoPro software. Tiled orthophotos undergo a rigorous manual QC process to evaluate for remaining hotspots (sun reflectance over water), tone quality, color balance and the feathering area along seamlines. Any imperfections at this point were manually edited. Radiometry is verified by visual inspection of the digital orthophoto. Slight systematic radiometric differences may exist between adjacent orthoimage files; these are due primarily to differences in source image capture dates and sun angles along flight lines. These differences can be observed in an image's general lightness or darkness when it is compared to adjacent orthoimage file coverages. Tonal balancing may be performed over a group of images during the mosaicking process which may serve to lighten or darken adjacent images for better color tone matching. The final 1' GSD, tiled, 4 band (R,G,B), 16 bit, ortho images were then converted to the required GeoTIFF file format. Each TIF was processed to replace 0 values with 1 values inside valid imagery files, then pixels not inside the valid imagery were converted to 0,0,0,0 to represent NoData values.
This step combines all of the indivdual orthophoto tiles into a composiet mosaic using the following procedure: 1. Create File Geodatabase (FGB) 2. Create a new raster dataset (theMosiac) to mosaic into: a. Output location/name = FGB/theMosaic b. Cellsize = 1 c. Pixel Type = 16 bit unsigned d. Spatial Ref = CTSP NAD83 ft e. Bands = 4 f. Environment settings/Raster Storage: i. Config Keyword = omit, leave blank ii. Build Pyramids = yes iii. Pyramids Levels = 1 2 iv. Pyramid resampling = Bilinear v. Tile Size: accept defaults vi. Compression = JPEG2000 vii.Compression Quality = 40 viii. Pyramid Reference Pt: 687800, 1015180 3. From theMosaic, load reprocessed TIFFs: a. Mosiac Method = Last (default) b. Mosaic Colormap = First (default) c. Background value = 0 d. No Data value = omit, leave blank e. Convert 1 bit to 8 bit = omit, leave blank f. Mosaic tolerance = 0 (default) g. Color matching = none (default) h. Environment settings/Raster Storage: i. Build Pyramids = yes ii. Pyramid Levels = 12 iii. Pyramid resampling = Bilinear iv. Calculate statistics = yes, accept defaults v. Compression = JPEG2000 vi. Compression Quality = 40 vii. Tile Size = accept defaults
RMSE Requirements needed here.
Spatial Information Solution's Accuracy Analyst was used to check 36 ground control points. The generated report is available upon request.
There is no vertical component for this set of orthoimagery.
The 2010 Connecticut Multispectral Coastal Digital Orthophotography is complete in the sense that it accurately reflects the content from the 2010 Connecticut Multispectral Coastal Imagery Project available at the time Photoscience, Inc. created the data. However, compared to current conditions, the 2010 Connecticut Multispectral Coastal Digital Orthophotography may be incomplete. This data is not updated.
Compliance with the required horizontal accuracy standard is supported by the placement of photo identifiable ground control points and the collection of airborne GPS and IMU data during the aerial missions. Horizontal accuracy was validated by comparing the ground control values (X,Y) of each photo identifiable ground control point obtained using survey grade GPS with its corresponding values (X,Y) measured from the final orthophoto. An overall horizontal RMSE x or y value was then calculated to verify compliance with the required horizontal accuracy not to exceed 4 foot RMSE X or Y. All GeoTIFF tagged data and image file sizes are validated using commercial GIS software to ensure proper loading before being archived. This validation procedure ensures correct physical format and field values for tagged elements. Seamlines and tile edges are visually inspected.
No restrictions or legal prerequisites for using the data. The data is suitable for use at appropriate scale, and is not intended for maps printed at scales greater or more detailed than 1:12,000 scale (1 inch = 1,000 feet). Although this data set has been used by the State of Connecticut, Department of Environmental Protection, no warranty, expressed or implied, is made by the State of Connecticut, Department of Environmental Protection 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, Department of Environmental Protection 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. 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: "2010 Connecticut Multispectral Coastal Digital Orthophotography, compiled by PhotoScience, Inc. and published by the State of Connecticut, Department of Environmental Protection. Source map scale is 1:12,000."
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The data is in the public domain and may be redistributed. No restrictions or legal prerequisites for using the data. The data is suitable for use at appropriate scale, and is not intended for maps printed at scales greater or more detailed than 1:12,000 scale (1 inch = 1,000 feet). Although this data set has been used by the State of Connecticut, Department of Environmental Protection, no warranty, expressed or implied, is made by the State of Connecticut, Department of Environmental Protection 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, Department of Environmental Protection 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. 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: "2010 Connecticut Multispectral Coastal Digital Orthophotography, compiled by PhotoScience, Inc. and published by the State of Connecticut, Department of Environmental Protection. Source map scale is 1:12,000."
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in format RPF Size: 0.000
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| Network links: | dep.gisdata@po.state.ct.us |
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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