Coastal Connecticut 2004 Color Orthophoto is a raster mosaic of ADS40 natual color digital imagery taken in September 2004 for Connecticut municipalities located along the Long Island Sound coastline. This is a raster mosaic of 122 quarter quadrangle natual color input rasters in GeoTIFF format. An orthoimage is remotely sensed image data in which displacement of features in the image caused by terrain relief and sensor orientation have been mathematically removed. Orthoimagery combines the image characteristics of a photograph with the geometric qualities of a map. This task consists of two primary components, ADS40 digital image acquisition and natural color and color infrared digital orthophoto production. In addition to the orthophotos a reflective surface digital elevation data set covering the project area was produced.
These data have been created as a result of the need for having geospatial data immediately available and easily accessible in order to enhance the capability of the NOAA Coastal Services Center (CSC) and the USGS.
The bounding coordinates provided within the Spatial Domain section represent a rectangle covering the total area in which the project is located. The actual project boundary located within this area is comprised of areas delimited by areas along the coast of the state of Connecticut. The Coastal Connecticut project area is comprised of approximately 930 square miles. A total of 244 orthos (122 natural color and 122 color infrared) were produced to cover this area. Aerial imagery was collected in panchromatic, Red, Green, Blue and Near Infrared which yielded a natural color and false color infrared version of the completed digital orthophotography. In addition to producing the digital ortho imagery a first surface (reflective surface) elevation data set was produced. Imagery was collected at an approximate altitude of 15,750 feet above mean terrain. The ADS40 digital camera system used in this project incorporates the latest in sensor technology, optics, electronics, data transfer, and storage. The ADS40 imagery is generated from seven parallel sensor lines in the focal plane of a single lens system, three panchromatic (forward, nadir, backward), red, green, and blue lines placed next to each other, and one infrared. Each panchromatic channel consists of two lines, each with 12,000 pixels, staggered (shifted with respect to each other) by 0.5 pixels. The viewing angles and characteristics of the sensor are as follows - - Focal length 62.5mm - Pixel size 6.5mm - PAN 2 arrays 12,000 pixels each - R,G,B and NIR,R,G 12,000 pixels - Backward to nadir stereo angle -14.1 degrees - Near infrared to nadir stereo angle -2.05 degrees - Dynamic Range of CCD - 12-bits for all arrays for this dataset, the natural color and color infrared orthoimages were produced at 0.50-meter pixel resolution. Each digital orthorectified quarter quad provides imagery for a nominal 3.75 by 3.75 minute area corresponding to the USGS quarter quad boundaries. The projected coordinate system is UTM (Zone 18) with a NAD83 datum. The naming convention is based on the National Grid. Deliverables include - - 24-Bit Natural Color in GeoTIFF format - 24-Bit False Color Infrared in GeoTIFF format - Reflective surface digital elevation data set in .flt
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EarthData International, LLC
The digital imagery for each acquisition sortie is differentially rectified to produce orthophotography for the Red, Green, and The digital imagery for each acquisition sortie is differentially rectified to produce orthophotography for the Red, Green, and Blue and near infrared channels at a resolution of 0.50-meter per pixel. The orthophoto mosaics are inspected for accuracy issues that fall in the following categories - - Aerotriangulation related - DSM related Accuracy issues will be investigated through review an correction of the DSM or triangulation adjustment. Once the imagery has passed quality control review, final radiometric adjustments are performed to create a uniform overall appearance.
Compliance with the accuracy standard was ensured by the placement of photo identifiable ground control points and the collection of airborne GPS data. Using several tools that are part of the ISTAR workflow, a digital surface model (DSM) was correlated at a post spacing of 2 meters depending on terrain and land cover. The ISTAR correlation algorithm computes the X,Y,Z value for each DSM post utilizing every stereo angle that is available. A series of DSM files were created for each acquisition block, one for each stereo look angle. A mosaic was then created from the separate DSM files where the best vertical value for each posting was selected from all look anglescompared against the aerotriangulation adjustment which is incorporated into the mosaic. EarthData then edited the surface to the level required to support the orthophoto production. An RMS value was calculated based on the imagery utilized in the production of the tile by comparing the AT X and Y coordinates. This value represents an estimate of the accuracy of the horizontal coordinate measurements in the tile expressed in meters.
Compliance with the accuracy standard was ensured by the placement of photo identifiable ground control points and the collection of airborne GPS data.
The horizontal accuracy of the orthorectified images is mainly determined by the accuracy of the aerotriangulation and digital surface model (DSM). For each rectified image (lift), an RMSE value for all of the standard errors of the tie/pass/control points located in that image (lift) and computed by the aerotriangulation solution was calculated. The DSM accuracy assessment was achieved by comparing the aerotriangulation-derived elevation with the elevation of the DSM. In addition, visual examination was employed to assess all tiles and its relative edge match. All results were examined for consistency and its compliance with the NMAS accuracy standard.
Accuracy assessment determined by evaluating the horizontal accuracy obtained during the aerotriangulation process for each lift.
CheckDEM is a program designed to compare a list of controls against DEM file(s) and therefore to check the accuracy of the DEM file(s). For each control point, first, the program selects all the DEM points that fall into a given radius from the position of the control point. Second, the program calculates a weighted average of the DEM points to interpolate an elevation at the position of the control point. And last, the program computes the difference between the elevation of the control point and the interpolated elevation. After all the control points have been checked, the program computes several statistics on the differences between controls and interpolated DEM elevations. The statistics include RMSE, Standard Deviation, Minimum Difference, Maximum Difference, and Mean Difference. In the output report, the program prints out elevation differences for every control points and the statistics. Raw elevation measurements have been determined to be vertically accurate to within 0.328 meters.
Terrasurv Inc. established ground control to support the aerotriangulation process. A total of 16 points were surveyed to support the AT process.
Used to provide ground elevations for the orthorectification process.
The digital imagery mission was composed of a total of 2 lifts. Imagery was obtained at an altitude of 15,750 feet above mean terrain. The mission was flown with a Leica ADS40 digital camera with ABGPS and IMU. Imagery was acquired on the following dates - Lift Date 26404B 09/20/2004 26604A 09/22/2004 Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 18 Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.9996 Longitude_of_Central_Meridian: -075.000000 Latitude_of_Projection_Origin: +00.000000 False_Easting: 500000.0 False_Northing: 0.0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: row and column Coordinate_Representation: Abscissa_Resolution: 0.50 Ordinate_Resolution: 0.50 Planar_Distance_Units: Meters Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1983 Ellipsoid_Name: Geodetic Reference System 80 Semi-major_Axis: 6378137 Denominator_of_Flattening_Ratio: 298.2572221
Statewide raster mosaic of all input rasters. The raster mosaic is in the Connecticut State Plane Coordinate System, North American Datum of 1983 (NAD83).
Source Imagery - ADS40 Digital Camera Imagery. Control - Airborne GPS/IMU supplemented with photo identifiable field control. Aerotriangulation - ISTAR software package. Elevation Model - ISTAR software package. Radiometric Balancing - ISTAR software package and COTS Software (PhotoShop). Orthorectification - ISTAR software package. Mosaic - ISTAR software package and Z/I Imaging OrthoPro software package. The following section describes the ISTAR digital image production sequence. This is a mature, stable workflow and incorporates all production components into an integrated series of tools to accomplish photogrammetric mensuration, aerotriangulation, elevation model development, ortho production and finishing. Production processes are fully documented in accordance with ISO9001 mandates. The following is a step-by-step description of the ISTAR workflow to develop digital orthophoto quarter quads. Step 1 The unprocessed ADS40 data and accompanying GPS and IMU data for one or more sorties was downloaded from the portable hard disks and checked to verify that no files were corrupted and that all data could be downloaded. Digital aerial imagery that was used for this project includes the Red, Green, Blue, Near Infrared channels as well as the S1 pan, S2 pan and nadir green channels. Sample segments of the imagery were inspected in an uncorrected state to verify the integrity of each data sortie. Step 2 The GPS/IMU parameters for each sortie were optimized using the ground control points and the error calibration map. The horizontal and vertical positions of all ground control points in the block were observed in each channel (R,G,B, IR, R, G, S1 Pan, S2 Pan). Step 3 Aerotriangulation was accomplished using the CLB tool that is a component of the ISTAR process. The ground control, GPS and IMU information were ingested and tie points between strips were identified. Normally, only 3 tie points are needed between adjacent flight lines. Step 4 CLB produces a bundle adjustment for each data sortie. The results of the adjustment were verified through the development of a sub-sampled panchromatic mosaic for the data sortie. The mosaic was corrected using the aerotriangulation points only. This mosaic was inspected by the photogrammetric technician to identify any gross errors in the adjustment as well as the identification of any voids or image quality problems. Step 5 Using several tools that are part of the ISTAR workflow, a digital surface model (DSM) is correlated at a post spacing of 2 meters depending on terrain and land cover. The ISTAR correlation algorithm computes the X,Y,Z value for each DSM post utilizing every stereo angle that is available. A series of DSM files are created for acquisition block, one for each stereo look angle. A mosaic is then created from the separate DSM files where the best vertical value for each posting is selected from all look angles compared against the aerotriangulation adjustment which is incorporated into the mosaic. EarthData will then edit the surface to the level required to support the orthophoto production. Step 6 The digital imagery for each acquisition sortie was differentially rectified to produce digital orthophoto mosaics in natural color and false color infrared renditions at a resolution of 0.50-meter per pixel. The orthophoto mosaics were inspected for accuracy issues that fall in the following categories - - Aerotriangulation related - DSM related Accuracy issues were investigated through review and correction of the DEM or triangulation adjustment. Once the imagery passed quality control review, final radiometric adjustments were performed to create a uniform overall appearance. The final DOQQ tiles were organized for nominal 3.75 by 3.75 minute areas corresponding to the USGS quarter quad boundaries and were clipped out with the specified overage of a minimum of 30 meters beyond the quarter quad boundaries. Imagery was output in the folowing formats - 24-bit natural color GeoTIFF images 24-bit false color infrared GeoTIFF images Step 7 The completed digital orthophotos were checked for image quality. Minor artifacts were corrected using Adobe Photoshop in an interactive editing session. Digital files were assigned final names based on the National Grid. Step 8 Project level metadata describing the orthophoto production process was developed to support the task.
Using ESRI ArcGIS 9.2 software, an empty raster dataset was created and subequently populated with input rasters to create a raster mosaic of all imagery along the Connecticut coast. 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 90. 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\10.18.8.94.depgisraster@DEP.sde" Ortho_2004_Coast_Color # 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]] 3 DEPRASTER "PYRAMIDS 8 BILINEAR" "128 128" "JPEG 90" "687800 1015180" "Database Connections\10.18.8.94.depgisraster@DEP.sde\depgisraster.DEP.Ortho_2004_Coast_Color STEP 2 - Mosaic 122 input rasters. 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. Additionally, the Ignore Background Value was set to one (1). This causes pixels along the borders of the input rasters with values of 1 to be set to NoData pixels along the borders of the output raster mosaic when they are projected from UTM to the Connecticut State Plane Coordinate System as part of the mosaic process. Below is an example usage of the ESRI Geoprocessing Mosaic command and arguments used to mosaic 6 quarter quadrangle input rasters. Mosaic P:\tif_format\18TXL048464.tif P:\tif_format\18TXL049394.tif; P:\tif_format\18TXL100534.tif; P:\tif_format\18TXL101464.tif; P:\tif_format\18TXL102395.tif; P:\tif_format\18TXL103326.tif "Database Connections\10.18.8.94.depgisraster@DEP.sde\DEPGISRASTER.DEP.ORTHO_2004_COAST_COLOR" LAST FIRST 1 # NONE 0 "Database Connections\10.18.8.94.depgisraster@DEP.sde\DEPGISRASTER.DEP.ORTHO_2004_COAST_COLOR"
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