A total of 200 ground based photo control points including 40 blind QC ground based photo control points were established throughout New Jersey 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. Ground control collection followed requirements set forth in USGS Contract No. G10PC00026; USGS Task Order: G12PD00392; Requisition Reference Number: 0040035232, and were modified as appropriate to accommodate the specifications related to ABGPS collection specific to these end photogrammetric mapping requirements. All horizontal and vertical control was prepared under the supervision of State of New Jersey licensed Professional Land Surveyors. Date is approximate.
Digital aerial imagery was obtained using a large format Z/I Digital Mapping Camera system (DMC) equipped with Airborne GPS/IMU covering the entire State of New Jersey. A total of 139 flight lines with 11157 frames were collected in the spring of 2012 in multi-spectral (RGB and NIR) 16 bits per band format. This includes the acquisition of supplemental imagery over the cities of Atlantic City (4 Flight Lines; 141 Frames), Jersey City (6 Flight Lines; 158 Frames), Newark (5 Flight Lines; 120 Frames), and Trenton (7 Flight Lines; 200 Frames) that was used to minimize building lean in the orthophotography production process. The imagery was acquired with a 4.7244" (120 m/m) focal length at an altitude above mean terrain of 9,600' to yield a raw pixel resolution of 0.96' suitable for photogrammetric mapping and orthophoto production. The imagery was collected during leaf off conditions in the spring of 2012 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 35 degrees south of US Highway 1 and 30 degrees north of US Highway 1. Due to a compression of the acquisition window caused by an abnormally warm spring flying season these sun angle requirements were relaxed after consultation with USGS and the state of New Jersey. The imagery consisted of panchromatic, blue, green, red and near infrared bands. The three color bands and near infrared bands have been pan sharpened and archived as frame imagery. Imagery for the photogrammetric mapping and digital orthophotos was captured according to the USGS Contract No. G10PC00026; USGS Task Order: G12PD00392; Requisition Reference Number: 0040035232 regarding, snow, haze and cloud cover, and modified as appropriate to accommodate the requirements specific to Z/I DMC camera technologies and as specified in this scope of work.
Softcopy aerotriangulation was performed on three large blocks of imagery 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 frame to support the photogrammetric process and orthophoto production. The adjusted Root Mean Square Error (RMSE) of all horizontal and vertical control points used for any single block adjustment was 1.0 foot or better. At the same time, residuals on each refined image coordinate remain less than 12 microns and residuals on any horizontal or vertical control point did not exceed plus or minus 2.0 feet. Within each block, the blind QA ground survey coordinates were within two times the RMSE (two feet) of the corresponding AT derived coordinates. Date is approximate.
This process involved the development of seamless topographic landform elevation dataset utilizing existing LiDAR derived public domain elevation data sets to support the production of digital orthophotography that meet or exceed required orthophoto horizontal accuracy. Existing terrain surfaces utilized for this project included the maximum utilization of government supplied airborne topographic LiDAR bare earth data sets of various vintages, accuracies and post spacing as well as DEM data from the 2012 New Jersey Orthophoto Project as needed to complete a 2012 Statewide orthophoto DEM source. 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 DTM is suitable for orthophoto production only (not suitable for contour generation). The DTM is used to then generate a Triangulated Irregular Network (TIN) to support orthophoto production. Date and time are approximate.
Utilizing all four pan-sharpened bands [blue (B), green (G), red(R) and near infrared (IR)] digital orthorectification was performed using cubic convolution algorithms resulting in a spatial and radiometric transformation of the digital image from line/sample space into the New Jersey State Plane Coordinate System, NAD 83, US Survey Feet. 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/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 adhere to the New Jersey 5,000' x 5,000' tiling scheme consisting of 9,202 individual ortho tiles within the State Plane Delivery and 9831 within the UTM Delivery. State Plane Delivery included digital ortho photos at a 1' pixel ground sample distance in the following formats: 16 bit, 4 band (RGB and NIR) uncompressed GeoTIFF; and 8 bit, 4 band (RGB) compressed MrSID. UTM Delivery produced for the USGS was created from the State Plane GeoTIFFs via Global Mapper, included 8 bit, 3 band (RGB) GeoTIFFs. The ortho photos meet a horizontal accuracy of four (4) feet or less at 95% confidence level when compared to higher accuracy check points based on NSSDA testing standards. Date and time are approximate.
GeoTIFF imagery tiles were reprocessed using LizardTech GEOEXPRESS 8.5 to create MrSID MG4 format. These images were indexed to create a WMS using Lizardtech Express Server.
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A digital number from 1 to 4096 will be assigned to each pixel. This number refers to a color look-up table which will contain the red, green, blue, and Near Infrared values, each from 1 to 4096, for that digital number.