Data Management Plan

This orthoimagery data set includes 0.3 meter digital orthoimages in 8-bit 4-band (RGB-IR) GeoTIFF tiles. Geographic Extent: 4 counties in Maryland, covering approximately 628 total square miles. Dataset Description: The Chesapeake Bay NOAA Option 1 project called for the planning, acquisition, processing, and derivative products of imagery data to be collected at a ground sample distance (GSD) of 0.3 meter. Project specifications are based on the American Society of Photogrammetry and Remote Sensing (ASPRS) standards. The data were developed based on a horizontal projection/datum of NAD 1983 2011 UTM Zone 18N, Meter. Imagery data were delivered as 0.3 meter 8-bit 4-band (RGB-IR) GeoTIFF tiles. Tiled deliverables contained 181 individual 3000 m x 3000 m tiles. Ground Conditions: Imagery was collected in fall 2018 and spring 2019, while no snow was on the ground and rivers were at or below normal levels. In order to post process the imagery data to meet task order specifications and meet ASPRS horizontal accuracy guidelines, Quantum Spatial, Inc. utilized a total of 3 ground control points to assess the horizontal accuracy of the data.

Lineage Statement:
Aerial imagery was acquired using a UltraCam Eagle camera with a flight design that included a total of 16 flight lines. 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 13100 feet above mean terrain. Softcopy aerotriangulation was performed utilizing the airborne GPS/IMU data, GPS ground control and image coordinate measurements allowing the direct computation of the exterior orientation parameters for each image of the project. A compilation of topographic land form elevation datasets developed using in-house LiDAR data and data from the National Elevation Dataset for use in developing digital ortho imagery. Quantum Spatial performed a geodetic control survey in support of the digital orthophoto production project. A total of 3 points were used for QC testing.

Process Steps:

• 2019-11-19 00:00:00 - Imagery Acquisition: Digital aerial imagery was obtained using a UltraCam Eagle camera equipped with Airborne GPS/IMU. A total of 16 flight lines were collected in the fall 2018 and spring 2019 in multi-spectral (RGB-IR) format. The 0.3 meter imagery was acquired at an altitude above mean terrain of 13100 feet to yield a pixel resolution suitable for photogrammetric mapping and orthophoto production. The imagery was collected under conditions free from clouds and cloud shadows, smoke, fog, haze, light streaks, snow, ice on water bodies, flooding, excessive soil moisture, and foliage. The imagery consisted of blue, green, red, and infrared bands. Imagery for the photogrammetric mapping and digital orthophotos was captured according to task order specifications regarding, snow, haze, and cloud cover.
• 2019-11-19 00:00:00 - Ground Control Point Collection: A total of 3 control points were established throughout the project area using a combination of conventional and GPS survey methods in order to support softcopy aerotriangulation and photogrammetric mapping meeting the accuracies specified in this Scope of Work. Ground control collection followed requirements set forth in the task order specifications. Please see the survey report for more information
• 2019-11-19 00:00:00 - Aerotriangulation: Softcopy aerotriangulation was performed on one large block of imagery. The airborne GPS/IMU data, GPS ground control, and image coordinate measurements were utilized to allow the direct computation of the exterior orientation parameters for each image frame to support the photogrammetric process and orthophoto production.
• 2019-11-19 00:00:00 - Surface Creation: This process involved the development of seamless topographic landform elevation dataset utilizing in-house LiDAR data and data from the National Elevation Dataset to support the production of digital orthophotography that meet or exceed required orthophoto horizontal accuracy. The topographic features included a grid of elevation points and may include break lines that define ridges, valleys, edge of water, transportation features and abrupt changes in elevation. The final DEM is suitable for orthophoto production only (not suitable for contour generation). The DEM is used to then generate a Triangulated Irregular Network (TIN) to support orthophoto production. The final DEM used for orthophoto production was delivered in countywide rasters in a file geodatabase.
• 2019-11-19 00:00:00 - Orthophoto Processing: Utilizing all four bands [blue (B), green (G), red (R), and infrared (IR)] digital orthorectification was performed using bilinear interpolation algorithms resulting in a spatial and radiometric transformation of the digital image from line/sample space into NAD 1983 2011 UTM Zone 18N, Meter. The interior and exterior orientation parameters from the aerotriangulation process were used to project each pixel into the ground coordinate system, while the ortho grade DEM was used to correct for relief displacement. Radiometric correction software and techniques were used to create orthophoto files that minimize the appearance of image seams and without loss of feature signature. Orthophotos are checked for geometric accuracy, image quality, and are tonally balanced to produce a uniform contrast and tone across the entire project. The individual overlapping orthophoto frames were mosaicked together. The ortho photos meet ASPRS horizontal accuracy standards.

Data is available online for custom downloads