elevation/Bouldin_Island_DEM_20171130 (ImageServer)

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Service Description: The purpose of this project was to produce 1"-40' topographic mapping and orthophoto imagery of Bouldin Island. The orthophotography encompassed the entire island and topographic mapping was produced for an area approximately 1850 acres near the center of the island. This work was performed under MWD Task Order 164106-1-104740. Survey Control Ground control survey for this project was established by Towill, Inc. based on RS 39-36 supplied by Metropolitan. Details of the control survey are available in the report file named “15133-101_Bouldin_Island_Flight_Panel_Report_v1”. In addition, Towill’s field survey crews collected additional ground truth points in widely dispersed locations which were used to verify the vertical accuracy of the LiDAR dataset. LiDAR Acquisition The LiDAR survey was accomplished using an Optech Orion M300 LiDAR system operating from a fixed wing aircraft (Partenavia C-68 Tail #N6602L). The mission was performed on November 30, 2017. The mission plan was based on the following: Aircraft Flight Altitude: 750m FT AGL Aircraft Speed: 120 knots Number of Flight lines: 20 Flight Line Spacing: 380m Nominal Point Density: 9 Points Per Square Meter (PPM^2) LiDAR Data Post-Acquisition Processing Airborne GPS Data Processing - Using Novatel, Inc.’s Grafnav version 8.20 software, the differential kinematic data was processed from two base stations, and the solutions compared. This procedure is intended to verify the integrity of the base station coordinates and elevations. Each processing session was computed in both the forward and reverse temporal directions. The comparison of these solutions is intended to provide insight into the quality of the kinematic ambiguity resolution. The horizontal and vertical datums of the LiDAR data set were realized by adjusting the coordinates of the base station points and the relative application of the geoid model to the final data set. IMU Data Processing and Best Estimated Trajectory - The post-processed ABGPS trajectory was combined with the raw, high-frequency IMU observations in a loosely-coupled Kalman filter-based processing algorithm to produce the final high-frequency Smoothed Best Estimated Trajectory (SBET) using Applanix’s POSPac software, version 4.3. Optech’s LiDAR Mapping Suite (LMS) –The ABGPS and integrated IMU data files were used as inputs to process the laser range files collected during the mission. The LMS software package assembles each of these three components and outputs fully georeferenced LAS strip files. The overlap between adjacent strip files are analyzed and if elevation differences exist, these values are used as feedback and the process is repeated. LiDAR Data Classification Terrasolid’s Terrascan V.1.2 software was used to tile the LAS strip files into manageable size files and to run macro routines which assist in the ground classification. Bridges and other structures were manually reclassified as non-ground classes. Following a thorough QA/QC review by an analyst, ground points comprising the “bare-earth” surface were used to generate separate deliverables. Aerial Imagery Aerial imagery was acquired for the study area simultaneously with the LiDAR using a PhaseOne 4-Band 100 megapixel camera. The imagery was aerotriangulated using INPHO’s MATCH-AT software and used to generate 4-band orthophoto imagery with a 0.25ft pixel resolution. The imagery was delivered as GeoTIF tiles and MrSID mosaics. Photogrammetric Mapping Planimetric features were stereo-digitized from the imagery using DATEM software and incorporated into the MicroStation DGN file. The mapping scale is 1”-40’ and has a one-foot contour interval. DWR makes no warranties or guarantees — either expressed or implied — as to the completeness, accuracy, or correctness of the data. DWR neither accepts nor assumes liability arising from or for any incorrect, incomplete, or misleading subject data. This is an official DWR Image Service, published on June 13, 2018 by Stephanie Baker of the Division of Engineering, Geodetic Branch, Geospatial Data Support Section, who may be contacted at stephanie.baker@water.ca.gov, or 916-653-9815.

Name: elevation/Bouldin_Island_DEM_20171130

Description: The purpose of this project was to produce 1"-40' topographic mapping and orthophoto imagery of Bouldin Island. The orthophotography encompassed the entire island and topographic mapping was produced for an area approximately 1850 acres near the center of the island. This work was performed under MWD Task Order 164106-1-104740. Survey Control Ground control survey for this project was established by Towill, Inc. based on RS 39-36 supplied by Metropolitan. Details of the control survey are available in the report file named “15133-101_Bouldin_Island_Flight_Panel_Report_v1”. In addition, Towill’s field survey crews collected additional ground truth points in widely dispersed locations which were used to verify the vertical accuracy of the LiDAR dataset. LiDAR Acquisition The LiDAR survey was accomplished using an Optech Orion M300 LiDAR system operating from a fixed wing aircraft (Partenavia C-68 Tail #N6602L). The mission was performed on November 30, 2017. The mission plan was based on the following: Aircraft Flight Altitude: 750m FT AGL Aircraft Speed: 120 knots Number of Flight lines: 20 Flight Line Spacing: 380m Nominal Point Density: 9 Points Per Square Meter (PPM^2) LiDAR Data Post-Acquisition Processing Airborne GPS Data Processing - Using Novatel, Inc.’s Grafnav version 8.20 software, the differential kinematic data was processed from two base stations, and the solutions compared. This procedure is intended to verify the integrity of the base station coordinates and elevations. Each processing session was computed in both the forward and reverse temporal directions. The comparison of these solutions is intended to provide insight into the quality of the kinematic ambiguity resolution. The horizontal and vertical datums of the LiDAR data set were realized by adjusting the coordinates of the base station points and the relative application of the geoid model to the final data set. IMU Data Processing and Best Estimated Trajectory - The post-processed ABGPS trajectory was combined with the raw, high-frequency IMU observations in a loosely-coupled Kalman filter-based processing algorithm to produce the final high-frequency Smoothed Best Estimated Trajectory (SBET) using Applanix’s POSPac software, version 4.3. Optech’s LiDAR Mapping Suite (LMS) –The ABGPS and integrated IMU data files were used as inputs to process the laser range files collected during the mission. The LMS software package assembles each of these three components and outputs fully georeferenced LAS strip files. The overlap between adjacent strip files are analyzed and if elevation differences exist, these values are used as feedback and the process is repeated. LiDAR Data Classification Terrasolid’s Terrascan V.1.2 software was used to tile the LAS strip files into manageable size files and to run macro routines which assist in the ground classification. Bridges and other structures were manually reclassified as non-ground classes. Following a thorough QA/QC review by an analyst, ground points comprising the “bare-earth” surface were used to generate separate deliverables. Aerial Imagery Aerial imagery was acquired for the study area simultaneously with the LiDAR using a PhaseOne 4-Band 100 megapixel camera. The imagery was aerotriangulated using INPHO’s MATCH-AT software and used to generate 4-band orthophoto imagery with a 0.25ft pixel resolution. The imagery was delivered as GeoTIF tiles and MrSID mosaics. Photogrammetric Mapping Planimetric features were stereo-digitized from the imagery using DATEM software and incorporated into the MicroStation DGN file. The mapping scale is 1”-40’ and has a one-foot contour interval. DWR makes no warranties or guarantees — either expressed or implied — as to the completeness, accuracy, or correctness of the data. DWR neither accepts nor assumes liability arising from or for any incorrect, incomplete, or misleading subject data. This is an official DWR Image Service, published on June 13, 2018 by Stephanie Baker of the Division of Engineering, Geodetic Branch, Geospatial Data Support Section, who may be contacted at stephanie.baker@water.ca.gov, or 916-653-9815.

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