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CreateMosaicDataset E:\DCGIS\Projects\Planimetrics2021\Ortho_2021_Review\Ortho_2021_Review.gdb Ortho_2021 PROJCS['NAD_1983_StatePlane_Maryland_FIPS_1900',GEOGCS['GCS_North_American_1983',DATUM['D_North_American_1983',SPHEROID['GRS_1980',6378137.0,298.257222101]],PRIMEM['Greenwich',0.0],UNIT['Degree',0.0174532925199433]],PROJECTION['Lambert_Conformal_Conic'],PARAMETER['False_Easting',400000.0],PARAMETER['False_Northing',0.0],PARAMETER['Central_Meridian',-77.0],PARAMETER['Standard_Parallel_1',38.3],PARAMETER['Standard_Parallel_2',39.45],PARAMETER['Latitude_Of_Origin',37.66666666666666],UNIT['Meter',1.0]] # # None #
AddRastersToMosaicDataset E:\DCGIS\Projects\Planimetrics2021\Ortho_2021_Review\Ortho_2021_Review.gdb\Ortho_2021 "Raster Dataset" E:\DCGIS\Projects\Planimetrics2021\Ortho_2021_Review\GeoTIFF UPDATE_CELL_SIZES UPDATE_BOUNDARY NO_OVERVIEWS # 0 1500 # # SUBFOLDERS "Allow duplicates" NO_PYRAMIDS NO_STATISTICS NO_THUMBNAILS # NO_FORCE_SPATIAL_REFERENCE NO_STATISTICS # NO_PIXEL_CACHE C:\Users\brian.putz\AppData\Local\ESRI\rasterproxies\Ortho_2021
CalculateStatistics E:\DCGIS\Projects\Planimetrics2021\Ortho_2021_Review\Ortho_2021_Review.gdb\Ortho_2021 1 1 # OVERWRITE "Feature Set"
AddRastersToMosaicDataset E:\DCGIS\Projects\Planimetrics2021\Ortho_2021\Ortho_2021.gdb\Ortho_2021 "Raster Dataset" E:\DCGIS\Projects\Planimetrics2021\Ortho_2021\GeoTIFF UPDATE_CELL_SIZES UPDATE_BOUNDARY NO_OVERVIEWS # 0 1500 # # SUBFOLDERS "Allow duplicates" NO_PYRAMIDS NO_STATISTICS NO_THUMBNAILS # NO_FORCE_SPATIAL_REFERENCE NO_STATISTICS # NO_PIXEL_CACHE C:\Users\brian.putz\AppData\Local\ESRI\rasterproxies\Ortho_2021
CalculateStatistics E:\DCGIS\Projects\Planimetrics2021\Ortho_2021\Ortho_2021.gdb\Ortho_2021 1 1 # OVERWRITE "Feature Set"
AddRastersToMosaicDataset E:\DCGIS\Projects\Planimetrics2021\Ortho_2021\Ortho_2021.gdb\Ortho_2021 "Raster Dataset" E:\DCGIS\Projects\Planimetrics2021\Ortho_2021\GeoTIFF\3016.tif UPDATE_CELL_SIZES UPDATE_BOUNDARY NO_OVERVIEWS # 0 1500 # # SUBFOLDERS "Allow duplicates" NO_PYRAMIDS NO_STATISTICS NO_THUMBNAILS # NO_FORCE_SPATIAL_REFERENCE NO_STATISTICS # NO_PIXEL_CACHE C:\Users\brian.putz\AppData\Local\ESRI\rasterproxies\Ortho_2021
CalculateStatistics E:\DCGIS\Projects\Planimetrics2021\Ortho_2021\Ortho_2021.gdb\Ortho_2021 1 1 # OVERWRITE "Feature Set"
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GIS Data Coordinator
D.C. Office of the Chief Technology Officer
GIS Data Coordinator
(202) 727-2277
(202) 727-5660
200 I Street SE, 5th Floor
Washington
DC
20003
dcgis@dc.gov
8:30 am - 5:00 pm
20211202
ArcGIS Metadata
1.0
GIS Data Coordinator
D.C. Office of the Chief Technology Officer
GIS Data Coordinator
(202) 727-2277
(202) 727-5660
200 I Street SE, 5th Floor
Washington
DC
20003
dcgis@dc.gov
8:30 am - 5:00 pm
DC datasets can be downloaded from "https://opendata.dc.gov".
Image Service
Ortho_2021
2021-11-01
GIS Data Coordinator, D.C. Office of the Chief Technology Officer , GIS Data Coordinator
remote-sensing image
2021 Orthophoto - 3 inch resolution: This document describes the processes used to create the orthoimagery data produced for the District of Columbia from 2021 digital aerial photography. It was flown on March 11, 2021. The aerial imagery acquisition was flown to support the creation of 4-band digital orthophotography with a 3 inch/0.08 meter pixel resolution over the full project area covering the District of Columbia which is approximately 69 square miles. The contractor received waivers to fly in the Flight Restricted Zone (FRZ) and P-56 areas. The ortho imagery was submitted to DC OCTO in GeoTiff/TFW format tiles following the tile scheme provided by OCTO. MrSID and JPEG2000 compressed mosaics were delivered as well using a 50:1 compression ratio.
Aerial Photography Image Service (Orthophoto) of Washington, DC at 3 inch resolution. Dated 2021.
https://dcgis.dc.gov
GIS Data Coordinator
D.C. Office of the Chief Technology Officer
GIS Data Coordinator
(202) 727-2277
(202) 727-5660
200 I Street SE, 5th Floor
Washington
DC
20003
dcgis@dc.gov
8:30 am - 5:00 pm
Washington
D.C.
District of Columbia
United States of America (USA)
Geographic Names Information System
orthophotography
planning
imagery
orthos
aerial photography
imageryBaseMapsEarthCover
imageryBaseMapsEarthCover
ISO 19115 Topic Categories
orthophotography
planning
imagery
orthos
aerial photography
imageryBaseMapsEarthCover
imageryBaseMapsEarthCover
Washington
D.C.
District of Columbia
United States of America (USA)
This work is licensed under a Creative Commons Attribution 4.0 International License.
See access and use constraints information.
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Quality control procedures were implemented and documented at each step of the project to ensure that all services required by the contract are completed to specification; they include visual (manual) inspections, automated routines, and technical reviews.
Acquisition
The aerial imagery acquisition for DC OCTO was flown to support the creation of 4-band digital orthophotography with 8 cm pixel resolution over the full project area covering the District of Columbia. Due to the security requirements in the area, waivers were needed to fly in the Flight Restricted Zone (FRZ) and P-56 areas.
The aerial photographic mission was completed by Keystone Aerial Surveys and was composed of two flight areas: DCM3 Red Area (25 flight lines) and DCM3 Blue Area (114 flight lines) at an average altitude of 4,000 feet above mean sea level. Data was collected on March 11, 2021 in one lift.
All data were collected with censor type DCM III, serial sensor 545. Aerial photography was collected in conjunction with airborne GPS.
Ground Control and Aerotriangulation
Rice Associates, under contract to Fugro Geospatial, Inc. successfully established ground control for the DC OCTO project area. Ground control for the DC OCTO project area consisted of a total of 25 points: six new ground control points and 19 previously collected ground control points collected by Wiles Mensch Corporation in 2017 and Rice Associates in 2019. GPS was used to establish the control network. The horizontal datum is provided in NAD83/HARN91. The vertical datum was the North American Vertical Datum of 1988 (NAVD88) using GEOID12B.
Catalyst Ortho Engine software was used for downloading and preparing imagery collected with the DCM III Sensor for softcopy photogrammetric use. The data was differentially processed against a base station. After the differential GPS solution was checked and verified, the software computed an integrated GPS/IMU navigation solution. The GPS/IMU trajectory was computed to a full x, y, z, omega, phi, kappa exterior orientation of each scan line.
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. Stereo imagery (level 1 georeferenced imagery) was created by applying the aerotriangulation solution to the raw imagery. This resampling removes aircraft motion and provides epipolar geometry imagery for stereo viewing. Low resolution images were created to determine the radiometric correction for each lift of imagery. Those settings were then used to create full resolution imagery strips.
Processing
Ground Orthoimagery
Upon the completion of the Aerotriangulation, a DEM was generated for the rectification of the imagery. The ortho-rectified strips (each flight line) were mosaicked together using proprietary image database and mosaicking software. The database was edited using Photoshop and QA/QC'ed for coverage, seam lines, smears, and other artefacts. The imagery was clipped out of the database into the sheet layout generated based on OCTO requirements. In the clipping stage, the coordinate system and georeferencing was embedded into the header of the files.
True Orthoimagery
GXL is a server-side high volume geospatial image-processing system designed to leverage modern computing technology, and Geomatica is PCI’s visualization and analytical desktop platform. GXL was utilized for generating the DSM Ortho products, and Geomatica was used for Quality Assurance (QA) purposes.
The workflow was executed to produce the final products:
• DSM Extraction
• DSM Orthorectification
• Mosaic Prep/Generation
• Post Mosaic Editing
GXL’s DEM Extraction workflow automatically scans an input directory for all valid stereo pairs, computes the epipolarized images and extracts the Digital Surface Model (DSM) for each stereo pair. Elevation values in a DSM are determined by matching points in a left and right epipolar input image using image correlation. The image disparity for the point pair is computed and this value, combined with the geometric model for each image, is used to compute the scene elevation for the corresponding scene point. After all DSMs in the batch are extracted, the GXL automatically merges them together to create a seamless multiview DSM. Using a “Pattern Suppression” algorithm helps to reduce or eliminate blunders in the output digital surface model (DSM).
Quality Assurance (QA) was performed on the derived DSM using Geomatica’s DEM Editing toolset. Utilizing the Live Ortho Preview capability, users can generate ortho images on the fly to check the quality of the DEM. Blunders and artifacts can be removed/fixed using Geomatica’s DEM editor.
The DSM Orthorectification operation is a straightforward process that orthorectifies the aerial imagery using the derived DSM. Occlusion zones that are created during the ortho process are detected for each ortho image and filled by retrieving optimal visible pixels from the adjacent overlapping ortho images.
The Mosaic Preparation processing module is responsible for automatically normalizing the images, calculating color balancing and generating the seamlines (cutlines). The output is a very lightweight mosaic preview that can be viewed and edited using the GXL’s Mosaic Tool. The Mosaic Preview does not generate an actual mosaic image, but rather it stores all the necessary information for future full resolution mosaics. Fugro used DC OCTO’s collected building footprints as a “cutline mask” forcing the mosaicker to avoid buildings eliminating an extreme majority of known buildings. Mosaic editing was conducted in the Mosaic tool to adjust cutlines and perform color balancing.
Deliverables
The ortho imagery was submitted to DC OCTO in GeoTiff/TFW format tiles following the tile scheme provided by OCTO. MrSID and JPEG2000 compressed mosaics were delivered as well using a 50:1 compression ratio.
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