Data Management Plan

This data set consists of 0.5-foot pixel resolution, natural color orthoimages covering Newton County, Georgia. 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. Each orthoimage provides imagery over a 2,500-foot by 2,500-foot block on the ground. There is no image overlap between adjacent files. The projected coordinate system is Georgia State Plane West (FIPS 1002) feet with a NAD83 datum.

A secondary set of GeoTIFF tiles, MrSID tiles, and MrSID mosaic was produced in WGS84 Lat/Long.

Process Steps:

• 2016-01-01 00:00:00 - Digital aerial imagery was obtained using a large format Leica ADS 100 camera system equipped with Airborne GPS/IMU covering the AOI. A total of 64 lines were collected in early 2016 in multi-spectral (RGB and NIR) 16 bits per band format. The imagery was acquired with a 62.5 mm focal length at an altitude above mean terrain of 5,965' to yield a pixel resolution of 0.5-feet suitable for photogrammetric mapping and orthophoto production. The imagery was collected during leaf off conditions in early 2016 under conditions free from clouds and cloud shadows, smoke, fog, haze, light streaks, snow, ice on water bodies, foliage, flooding, and excessive soil moisture. The sun angle threshold was 30 degrees. The imagery consisted of blue, green, red, and near infrared bands.
• 2016-01-01 00:00:00 - Ground based photo control points were established throughout the area of interest 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. This control supplemented the exposure station control obtained from the onboard Airborne Global Positioning System (ABGPS) and Inertial Measurement Unit (IMU). Photo control points established for this project have a combined local and network accuracy at 95% confidence of less than or equal to five (5) centimeters horizontally and vertically as determined by the residuals of the network adjustment.
• 2016-01-01 00:00:00 - Utilizing all four bands [blue (B), green (G), red(R) and near 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 State Plane Zone 1002 Georgia West. The interior and exterior orientation parameters were used to project each pixel into the ground coordinate system, while the ortho grade DEM/DTM 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 tonally balanced to produce a uniform contrast and tone across the entire project. The individual overlapping orthophoto frames were mosaicked together and the final tiles were extracted from the image set to a 2,500 x 2,500 foot tiling scheme consisting of 1,481 individual ortho tiles. Delivery included digital ortho photos at a 0.5-foot pixel ground sample distance in 8 bit, 4 band (RGB and NIR) uncompressed GeoTIFF and MrSID Gen 4 (compression 20:1) files. The ortho photos meet a horizontal accuracy of +/- 2.5-feet or less at 95% confidence level when compared to higher accuracy check points based on NSSDA testing standards.
• 2016-01-01 00:00:00 - A single mosaic of the 4-band orthoimagery was produced using LizardTech GeoExpress software version 9.1. Mosaics were produced in MrSID Generation 4 format at a compression ratio of 20:1.