2013 Massachusetts Department of Environmental Protection Natural Color Imagery

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Image Acquisition: Overview-The study area consists of approximately 77,600 hectares of Massachusetts coastline. Imagery was collected using GeoPod multispectral aerial imaging sensors. Splayed 5184 pixel X 3456 pixel single frames were acquired using two sensors in a direct digital manner combined into 10000 pixel X 3456 pixel single frames. Each GeoPod sensor has an integrated inertial measurement unit (IMU) to record sensor attitude while collecting frame nadirs with an integrated airborne GPS. Positional data are refined and optimized utilizing multiple sets of Continuously Operating Reference Station (CORS) basestation data. GeoVantage's proprietary Geoimage post-processing application was used to process the individual single frames into orthophoto mosaics recified to 7.5 min Digital Elevation Model (DEM) grids at 1 arc-sec (~30m) resolution. Data collection times were selected to optimize conditions for viewing nearshore benthic habitat including: tidal stage, season, wind, cloud cover/shadow, sun elevation, and recency of precipitation.

Image Rectification: Mosaics were generated from orthorectified single frames corrected to USGS 1 arc-sec DEM using multiple CORS stations to control airborne GPS and IMU data. In order to maximize spatial accuracy, all data collected went through the following process: Navigation solution: processed GPS and CORS data to plot coordinates of single frame nadirs for mosaic generation. If navigation solution residuals were in excess of an error tolerance of +/- 1.5m in any of the three axes of rotation, data were reprocessed following a systematic series of quantitative adjustments to processing parameters including the following: incremental manipulation of the gps elevation mask (usually sufficient), blocking and /or substitution of corrupt or confounding CORS data, blocking data from specific individual satellites from the solution, and/or truncation of full mission time. If, after iterating through each of the preceding systematic quantitative adjustments, the navigation solution failed to return residuals within tolerance, The target was submitted for recapture. Mosaic Generation: Proprietary GeoImage software projected single frames to DEM of 1 arc-sec resolution. Single frames were inspected for uniquely identifiable coincident tie points by which to mosaic to adjacent frames.