geoscientificInformation, North Dakota, Intermediate, Index, environment, Contours, Bismarck, Coverage, Mandan
Horizons, Inc. was contracted by the Bismarck-Mandan Metropolitan Planning Organization to provide an update 2 1/2 sections of existing 2' contour data and collect new DTM data for the generation on 2' contours on 39 new sections. A Leica ADS40 Digital Camera system including an inertial measuring unit (IMU) and a dual frequency airborne GPS receiver was used for the digital image acquisition. Imagery acquisition was performed on April 17th and April 22nd of 2005 at 4800' AMT. Ground control survey was conducted by Kadrmas, Lee and Jackson of Bismarck, North Dakota. A survey report summarizing methodology and results was submitted in hardcopy and a digital file in PDF format. GPS data was collected on two new monuments and 11 existing MPO monuments. The resulting coordinates for each new station are referenced to NAD 83(96) datum in North Dakota State Coordinate System South Zone (3302). The horizontal units were international feet. The GPS Orthometric Heights were determined by calculating the Ellipsoid-Geoid separation using Geoid 99 model and are based on NGVD 1929 international feet. The existing DTM data which Horizons had collected in 2001 was updated to support 2' contours where requested. New mapping was performed on 25 sections and an additional 30 sections of DTM collection was done for ortho rectification only. Contour were generated from the updated and new DTM data and delivered in ESRI shapefile format. The DTM data including breaklines, random points and spot elevation points were also delivered in ESRI shapefile format.
The purpose of collecting this data was to provide engineers and planning personnel valuable topographic information.
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The collection of significant topographic breaks, mass points, and spot elevations to accomodate 1"=100' scale mapping and comply with National Map Accuracy Standards. A ground control network of 14 targeted points was established. The control was tied to the North Dakota State Plane coordinate system NAD83 datum. The vertical control was based on the NGVD 1929 datum. GPS phase data was post processed with continuous kinematic survey techniques using "On the Fly" (OTF) integer ambiguity resolution. The GPS data was processed with forward and reverse processing algorithms. The results from each process, using the data collected at the airport, were combined to yield a single fixed integer phase differential solution of the aircraft trajectory. The differences between the forward to reverse solution within the project area were within project specifications (<10cm) in both the horizontal and vertical components, indicating a valid and accurate solution. An IMU was used to record precise changes in position and orientation of the ADS40 Digital Camera System. All IMU data was processed post flight with a filter to integrate inertial measurements and precise phase differential GPS positions. The resulting solution contains geodetic position, omega, phi, kappa, and time for digital image processing.
The horizontal RMS from the aero-triangulation for the project was: X - RMS = .045 feet, Y - RMS = .034 feet.
The vertical positional accuracy of this data meets NMAS for 2 feet contours. The vertical RMS from the aero-triangulation for the project was: Z - RMS = .034 feet.
The Leica GeoSystems GPro software was used for downloading and preparing imagery collected with the ADS40 Airborne Digital Sensor for softcopy photogrammetric use. The raw image was download in the field with GPro to a portable workstation. This enabled a quick look at image quality and coverage. Using the Applanix POSgps software package the GPS data was differentially processed against a base station. After the differential GPS solution was checked and verified the Applanix POSproc program was used to compute an integrated GPS/IMU navigation solution at one-second intervals. Using the GPS/IMU trajectory computed by the Applanix POSproc software and the camera calibration, GPro computed a full x,y,z, omega,phi,kappa exterior orientation of each scan line. Using the orientation data file produced the L0 imagery was resampled. The resampling removes most aircraft motion and provides epipolar geometry imagery for stereo viewing, automated aerotriangulation and automated DEM extraction. The Level 1 epipolar-resampled and georeferenced imagery usually will provide a pixel?s true ground location to within a few pixels without any additional processing. To improve accuracy, a fully automatic aerotriangulation process was performed to minimize the residual errors in the GPS/IMU derived exterior orientations. The aerotriangulation also allowed the introduction of ground control and checkpoints to ensure the accuracy specifications were achieved. Automated aerotriangulation of ADS40 imagery was performed with the Socet Set Automatic Point Measurement (APM) tool. A digital elevation model (DEM) was required for orthophoto production. Using L1 imagery new DTM data was collected as well as existing DTM data was updated using KLT softcopy plotters with superimposition. The resulting updated and new DTM data was used for the generation of new 2' contours as well as DTM data to support the ortho only areas. Contours were generated utilizing ARC-VIEW 3.2. Graphic Edit and GIS technicians reviewed the contours generated and edited the DTM data where necessary to produce accurate 2' contours. The final reviewed map files were delivery in ARC Shape files with delivery on CD-ROM.
Date of Photography
Horizons - 1"=100' Compilation Specification
Internal feature number.
Sequential unique whole numbers that are automatically generated.
Coordinates defining the features.
The data set contains contours on a 2' interval. A 'type' field identifies the contour as index, intermediate (intermed), obscured index (index_obs), or obscured intermediate (intermed_obs). An 'elevation', 'elevation_dxf' field indentifies each contour segments elevation.
(See Data Quality - Completeness Report))
Last metadata review date: 20051222