Connecticut Coastal Airborne ADS40 Digital Imagery Acquisition and Natural Color and Color Infrared Orthophoto Production collected in September 2004

The NOAA Office for Coastal Management purchased digital ADS40 imagery and digital elevation models of the Connecticut coastline in 2004. 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.

Original contact information:

Contact Name: Harold Rempel

Contact Org: EarthData International, Inc.

Title: Director of Program Management

Phone: 301-948-8550

Email: hrempel@earthdata.com

These data were created to support a research investigation to identify and map invasive Phragmites australis. The data are part of the US government provided resources for a grant to the University of Connecticut. A secondary purpose was to provide a sample dataset to examine the applicability of digital aerial imagery for general purpose coastal management.

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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 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.

Leica ADS40 sensors Push-broom Cameras SP14 50 centimeter pixel resolution Color and color IR

Not Applicable

Users must assume responsibility to determine the usability of these data.

None

None

Leica ADS40 Digital Camera System X Digital Image Processing Software Z/I Imaging Orthopro 4.0 Windows NT/2000 Systems

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

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.

Compliance with the accuracy standard was ensured by the placement of photo identifiable ground control points and the collection of airborne GPS data.

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 angles compared against the aerotriangulation adjustment which is incorporated into the mosaic. Company X 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 aerotriangulated X and Y coordinates. This value represents an estimate of the accuracy of the horizontal coordinate measurements in the tile expressed in meters.