Building

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Metadata:

Identification_Information:
Citation:
Citation_Information:
Originator: Office of the Chief Technology Officer
Publication_Date: 20110321
Title: Building
Geospatial_Data_Presentation_Form: vector digital data
Publication_Information:
Publisher: DC GIS
Online_Linkage:
Server=10.1.11.144; Service=5151; User=dcgis; Version=SDE.DEFAULT
Description:
Abstract:
Building. The dataset contains polygons representing planimetric buildings, created as part of the DC Geographic Information System (DC GIS) for the D.C. Office of the Chief Technology Officer (OCTO). These features were originally captured in 1999 and updated in 2005, 2008, 2010, and 2013. The following planimetric layers were updated: - Building Polygons (BldgPly)- Bridge and Tunnel Polygons (BrgTunPly)- Grate (GratePly- Horizontal and Vertical Control Points (GeoControlPt) - Obscured Area Polygons (ObsAreaPly)- Railroad Lines (RailRdLn) - Road, Parking, and Driveway Polygons (RoadPly)- Sidewalk Polygons (SidewalkPly)- Stairs (StairPly)- Swimming Pools (SwmPoolPly)- Wooded Areas (WoodPly) All DC GIS data is stored and exported in Maryland State Plane coordinates NAD 83 meters.METADATA CONTENT IS IN PROCESS OF VALIDATION AND SUBJECT TO CHANGE.
Purpose:
This data is used for the planning and management of Washington, D.C. by local government agencies.
Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 20100403
Currentness_Reference: ground condition
Status:
Progress: Complete
Maintenance_and_Update_Frequency: Unknown
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -77.115420
East_Bounding_Coordinate: -76.909576
North_Bounding_Coordinate: 38.995622
South_Bounding_Coordinate: 38.810360
Keywords:
Theme:
Theme_Keyword: structure
Theme_Keyword: building
Theme_Keyword: Planimetrics
Place:
Place_Keyword_Thesaurus: Geographic Names Information System
Place_Keyword: United States of America (USA)
Place_Keyword: Washington, D.C.
Place_Keyword: District of Columbia
Place_Keyword: D.C.
Use_Constraints:
For data terms and conditions, go to <http://dc.gov/page/terms-and-conditions-use-district-data>
Point_of_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: D.C. Office of the Chief Technology Officer
Contact_Person: GIS Data Coordinator
Contact_Address:
Address_Type: mailing and physical address
Address: 441 4th St NW, Suite 930 South
City: Washington
State_or_Province: D.C.
Postal_Code: 20001
Country: USA
Contact_Facsimile_Telephone: (202)727-5660
Contact_Electronic_Mail_Address: [email protected]
Hours_of_Service: 8:30 AM - 5:30 PM
Data_Set_Credit: D.C. Office of the Chief of Technology Officer (OCTO)
Native_Data_Set_Environment:
Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 9.3.1.4000
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report: Validated by source and/or responsible agency.
Logical_Consistency_Report:
OCTO developed and operated a QA/QC program to check the deliverables. Generally, the program consists of various types of processes grouped into visual checks, automated procedures, edge-matching routines, specialized checks, and field verification. Through the application of these processes, the data's spatial and attribute accuracy, usability, data documentation adherence, and specialized characteristics are checked.
Staff identified issues in a shapfile with appropriate descriptions for the vendor to fix. The data was delivered in preliminary format for a thorough review and identification of issues. The vendor fixed the data and delivered final data which OCTO checked to ensure the vendor made the fixes appropriately.
Completeness_Report:
Building: Delineate around roof line showing the building "footprint." Roofbreaks and rooflines, such as between individual residences in row houses or separate spaces in office structures, will be captured to partition building footprints. This includes capturing all sheds, garages, or other non-addressable buildings over 100 square feet throughout the City.
Memorials: Delineate around roof line showing the building "footprint." A list of memorials will be provided for capture and coding.
Void: Atriums and other "holes" in buildings created as part of demarcating the building outline.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
For the 1999 data that was not updated in 2005, it was mapped at a 1:1000 scale. This means that the horizontal accuracy is guaranteed to meet National Map Accuracy standards at 1:1000, which calls for 90% of well defined points to fall within .85 feet of true position. This is slightly more accurate that the 2005 data.
For the 2005 data, the horizontal accuracy of the orthorectified images is mainly determined by the accuracy of the aerotriangulation and digital surface model (DSM). For each rectified image, an RMSE value for all of the standard errors of the tie/pass/control points located in that image and computed by the aerotriangulation solution was calculated. The DSM accuracy assessment was achieved by comparing the aerotriangulation-derived elevation with the elevation of the DSM. In addition, visual examination was employed to assess all tiles and its relative edge match. All results were examined for consistency and its compliance with the ASPRS Standards for Large Scale Mapping at 1 to 1200 which indicates that the orthos will meet 1 foot RMSE at the 95% certainty level.
For buildings with a 5/30/2008 capture year value, approximately 20% of the buildings may not meet the ASPRS Standards for Large Scale Mapping at 1 to 1200. DC GIS staff corrected those buildings to straighten building edge angles and, for the 5% that had major capture issues, redigitized the buildings from the orthos.
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report: N/A
Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Originator: EarthData International, Inc
Publication_Date: 08/04/06
Publication_Time: Unknown
Title: Aerial Photography of Washington, D.C.
Geospatial_Data_Presentation_Form: raster digital data
Type_of_Source_Media: filmstrip
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 20050404
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: Aerial Photography
Source_Contribution:
This aerial photography was composed of 24 flight lines and a total of 1023 exposures. Imagery was obtained at an altitude of 1,100 meters above mean terrain (AMT) 7200.
The mission was flown with two Wild RC30 cameras serial no. 5368 with 153.743 mm lens serial number 13413 and serial no. 5324 with 153.247 mm lens serial number 13365 with ABGPS.
Source_Information:
Source_Citation:
Citation_Information:
Originator: TerraSurv, Inc
Publication_Date: 08/01/05
Title: Report of Survey Washington, DC Area
Geospatial_Data_Presentation_Form: model
Type_of_Source_Media: electronic mail system
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 20050404
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: GPS ground control
Source_Contribution:
TerraSurv established 30 photo identification control points to support the aerotriangulation process. Continuously Operating Reference Station (CORS) station USNO (PIDAI7403) was used as the control for this project. The horizontal datum was the North American Datum of 1983, CORS adjustment (NAD 1983 CORS). The vertical datum was the North American Vertical Datum of 1988 (NAVD 1988).
Source_Information:
Source_Citation:
Citation_Information:
Originator: Sanborn Corporation
Publication_Date: 20090612
Title: Aerial Photography of Washington, D.C.
Geospatial_Data_Presentation_Form: raster digital data
Type_of_Source_Media: filmstrip
Source_Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: 20080530
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: aerial photography
Source_Contribution:
New aerial photography was collected in the Spring of 2008 to support new orthoimagery and planimetric updates. This aerial photography was composed of approximately 52 flight lines and a total of 1552 exposures. Imagery was obtained at an altitude of 8,900 ft above mean terrain (AMT). The mission was flown with one Vecxel Ultracam X camera and collected ABGPS and IMU for each exposure.
Process_Step:
Process_Description:
This process describes data originally captured in 1999 and applies to features not updated in 2005. The CAPTUREYEAR field contains the data of origin for the feature.
Earthdata Maryland (EDMD) transferred control points, pass and tie points from the 1995 analytical aerotriangulation solution. Control was transferred from 1995 working diapositives to diapositives of the new photography. Control points were transferred optically using a Wild PUG 4-point transfer device equipped with a 60-micron drill.
EDMD acquired new aerial photography of the District of Columbia in the spring of 1999 prior to the emergence of deciduous foliage. Aerial photography was exposed at an altitude of 7,200' AMT using a Wild RC-20 or RC-30 camera system that is equipped with forward motion compensation and a 12" (300mm) focal length lens cone 600'.
The flight design developed in 1995 was duplicated. The design calls for an approximate total of 1,000 frames in 24 North-South oriented flight lines. Forward overlap between frames within each flight line was 80%. Sidelap between adjacent flight lines was 48%. Aerial photography was captured in natural color using Kodak Aerocolor negative film type 2445. Aerial photography was not exposed using airborne GPS due to the existence of an existing control network created in 1995.
EDMD produced 2 full sets of contact prints. The prints were separated into a total of 4 sets of prints, 2 sets of even frames and 2 sets of odd frames. Three of these sets were delivered to NCPC for distribution to the District. One set was held by EDMD for reference purposes. The project manager determined if an odd or even set was withheld for work purposes. The planimetric mapping was developed using a set of stable base color film diapositives that are created from the 1999 photography. EDMD produced a flight line index of the completed photography. The positions of the photographs as recorded by the ASCOT navigation/control system was plotted over an existing raster or vector map of the District of Columbia. EDMD delivered 3 plots of the completed index to NCPC.
Planimetric Data Capture and Edit:
The following is a step-by-step description of the steps involved in the collection of planimetric features from the aerial photography.
Step 1 Planimetric data is captured within each flightline proceeding in an North-South or South-North progression. The diapositives and contact prints for each of the priority production areas are assigned to photogrammetric technician for data collection. All planimetric data is collected using Wild BC-2 first order analytical stereoplotting systems.
Step 2 The photogrammetric supervisor establishes the data collection conventions to be used for data capture. All planimetric data is initially collected in the Microstation environment. The photogrammetric supervisor establishes data collection conventions and establishes the data-layering schema, global origin and working units to be used for data collection. These preferences are programmed into Microstation to ensure continuity.
Step 3 Planimetric data is collected and saved to the designated network subdirectory. As data is collected, the technician reviews the planimetric information on the stereoplotter monitor to ensure that collection is complete and that the required features are depicted and assigned to the correct layer in the CAD design file. EDMD has developed an in-house CAD application to prepare the planimetric features for conversion to polygons once the data has been migrated into ARC/INFO. The technician collects planimetric features in a clockwise direction, which create centroids at the completion of each line. Each of these centroids delineates the outer boundary of a polygon. In areas where a line creates a boundary for multiple features (edge of pavement, edge of parking lot, edge of parking lot-edge of building), the line segment is duplicated and assigned to all layers of the file that contain the effected features.
Step 4 The photogrammetric technician completes information for inclusion in the metadata.
Step 5 As stereo models are completed on the analytical stereoplotter, the cartographic editor copies a number of files pertaining to a block of map coverage and merges the data sets into map-sheet-oriented format. The merged data is inspected for compliance with the database design. Criteria for inspection include correct layer assignment, line color, and line style. The CAD application has incorporated quality control functions, which add temporary symbols to indicate the necessary duplication of line segments to complete polygon closure in all affected features. The editor makes any corrections or additions interactively. If necessary, lines are snapped to ensure closure.
Step 5A The cartographic editor translates the ARC/INFO coverages of the existing planimetric data that was produced as part of Task 2 and the State Department modification into a CAD readable format. The line work between the new mapping and existing mapping is tied together to ensure compliance with the contract requirements for topology.
Step 6 As coverage areas are completed; the editor informs the ARC/INFO supervisor that data is ready for conversion and final quality control. The completed vector files are copied to a designated network subdirectory. In order to avoid the possibility that incomplete or unedited data sets are mistakenly imported during production, a separate network subdirectory is used for the data at each stage in the production process. The network subdirectory structure is standardized for every project.
Step 7 Edited data sets are translated into ARC/INFO and polygon topology is created. The process used to create the final ARC/INFO coverages is described in the Attribute Accuracy Report Section.
Step 8 The cartographic technician records any pertinent dates or other information for completion of metadata.
QA/QC Plots
EDMD developed an ARC/INFO AML to generate hard copy plots of the 1995 digital orthophotos as part of Task. This routine will be modified to accommodate plotting of the planimetric and/or topographic data. The format will retain the graphic design that was developed in 1999. Design elements of the format and surround as well as the planimetric/topographic mapping will be fully compliant with the requirements stated in the contract modification. Upon completion of the initial editing and conversion of the data to ARC/INFO, EDMD will prepare a set of bond paper plots. Polygon features will be color coded for cartographic clarity and will enable NCPC quality inspectors to verify that no polygons overlap or are miscoded. A copy of the digital data that corresponds to the plots will be included to allow inspectors to review digital data content. NCPC will inspect the plots and mark any errors, omissions or mistakes on the plots. The edited plots are returned to EDMD for correction. Once the data has been corrected, EDMD will produce a total of 3 sets of inkjet mylar plots containing the planimetric data only in the approved format surround.
ARC/INFO coverage development
Extracted from Librarian using Simple option into coverage, then imported to geodatabase. Removed all voids and empty polygons from shape. The NCPC ArcInfo Librarian dataset is made up of 350 tiles. Over 29 data layers were extracted from the Librarian using the following procedures (see planimetric process.xls).
1) In order to withdraw seamless data out of Librarian an extraction polygon must be created. The extraction polygon must encompass the span of all the tiles. Extracting the index layer of the librarian and dissolving the boundaries of the 350 polygons into 1 polygon accomplished this task.
The procedures for creating the extraction polygon are as follows: ? Extract the index layer using Arcview and converting the theme into a shapefile. ? Create a field within the feature table for which the individual polygon can dissolve from by assigning a value of 1 in it for all records. ? Using the geo-processor extension option, the shapefiles' records were dissolved into 1 poly by dissolving the records with the common field. ? The polygon theme was then transformed into a polygon coverage through ArcToolbox. ? Once the extraction polygon was prepped, data layer extraction was completely done in the ArcInfo environment.
Setting the ArcInfo Environment. 1) Launch the ArcInfo Command Prompt window. 2) Set the working directory ( arc: w d:\workspace\extraction) 3) Set the precision for the environment and to all processes done in the ArcInfo Session. ( arc: Precision double double ) 4) Enter the librarian module (arc: Librarian) 5) Set the library volume (Librarian: library ncpc) 6) Set the extraction polygon coverage (Librarian: setcover index) 7) Set the layer to be extracted (Librarian : setlayer air) 8) Enter the command line to extract. (Librarian: extract OPTION # clip)
The extract command has a few options that can be set when extracting different types of layers such as polygons, lines, and points. Extract DISSOLVE is used for polygon layers only because it will extract the layer and merge the polygons where they are split by index tiles, thus removing additional polys. The ArcInfo commands involved with this option are Clip Dissolve and Build.
For Line and Point layers, the SIMPLE option was used to extract. The topology is left unbuilt when the information is extracted. Reason being that if the tile lines segment lines and create pseudo nodes. The user-id from the ArcInfo table were used to unsplit the lines and remove the pseudo node. Once that is done, the coverage can rebuild the topology.
Data Improvements
The line data coverages had tiles with some additional pseudo nodes. The pseudo nodes were probably created as a result of different digitizing techniques (neither right nor wrong). Using the Unsplit command we were able to clean these areas up by unsplitting only lines that had the same dxf-layer value and that shared a node.
Data cleanup
The polygon coverages extracted contained void (coded 9999) areas. In Arcedit, these ambiguous features were removed with the following technique. Arc: ae (enter arcedit module)
Arcedit: ec coverage (enter the editing coverage)
Arcedit: ef poly (enter the feature to be edited)
Arcedit: select for dxf-layer = 'VOID' (querying for features in the attribute table under dxf-layer that contains attribute labeled VOID)
Arcedit: delete (delete the features found)
Arcedit: Save (save the changes)
The line coverages had the neatlines using the same method where the dxf-layer had values = 'NEATLINE'
Creating Shapefiles All data sets were converted into shapefiles and clipped to the DC Boundary for import into the geodatabase.
From the Arc: prompt window, the command ARCSHAPE was used to create the shape coverages. This required the user to specify which coverage to convert, the feature class, and naming convention of the output shapefile.
Process_Date: 19990331
Source_Produced_Citation_Abbreviation: 1999 data capture
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: EarthData International, Inc
Contact_Address:
Address_Type: mailing and physical address
Address: 200 I Street SE, 5th Floor
City: Frederick
State_or_Province: MD
Postal_Code: 21704
Country: USA
Contact_Voice_Telephone: (301)948-8550
Contact_Facsimile_Telephone: (301)963-2064
Contact_Electronic_Mail_Address: [email protected]
Hours_of_Service: 8:30 Am - 5:00 PM Mon - Fri
Process_Step:
Process_Description:
Analytical Aerotriangulation:
Source photography - Wild RC-30 camera, natural color stable base. Control - airborne GPS supplemented with photo identifiable field control. Scanning - Z/I Imaging PhotoScan flatbed metric scanner. Aerotriangulation - Photo-T. Elevation Model - Lidar, autocorrelation and manual collection and update. Radiometric Balancing - Proprietary and COTS Software (PhotoShop). Orthorectification - Z/I Ortho Pro 4.0 software package. Mosaic - Z/I Ortho Pro 4.0 software package. Processed on Windows NT/2000 systems.
The ground control and airborne GPS data was integrated into a rigid network through the completion of a fully analytical bundle aerotriangulation adjustment.
1. The original aerial film was scanned at a resolution of 21 microns. The scans were produced using Z/I Imaging PhotoScan flatbed metric scanners.
2. The raster scans were given a preliminary visual check on the scanner workstation to ensure that the raster file size is correct and to verify that the tone and contrast were acceptable. A directory tree structure for the project was established on one of the workstations. This project was then accessed by other workstations through the network. The criteria used for establishment of the directory structure and file naming conventions accessed through the network avoids confusion or errors due to inconsistencies in digital data. The project area was defined using the relevant camera information that was obtained from the USGS camera calibration report for the aerial camera and the date of photography. The raster files were rotated to the correct orientation for mensuration on the softcopy workstation. The rotation of the raster files was necessary to accommodate different flight directions from one strip to the next. The technician verified that the datum and units of measurement for the supplied control were consistent with the project requirements.
3. The photogrammetric technician performed an automatic interior orientation for the frames in the project area. The softcopy systems that were used by the technicians have the ability to set up predefined fiducial templates for the aerial camera(s) used for the project. Using the template that was predefined in the interior orientation setup, the software identified and measured the eight fiducial positions for all the frames. Upon completion, the results were reviewed against the tolerance threshold. Any problems that occurred during the automatic interior orientation would cause the software to reject the frame and identify it as a potential problem. The operator then had the option to measure the fiducials manually.
4. The operator launched the point selection routine which automatically selected pass and tie points by an autocorrelation process. The correlation tool that is part of the routine identified the same point of contrast between multiple images in the Von Gruber locations. The interpolation tool can be adjusted by the operator depending on the type of land cover in the triangulation block. Factors that influence the settings include the amount of contrast and the sharpness of features present on the photography. A preliminary adjustment was run to identify pass points that had high residuals. This process was accomplished for each flight line or partial flight line to ensure that the network has sufficient levels of accuracy. The points were visited and the cause for any inaccuracy was identified and rectified. This process also identified any gaps where the point selection routine failed to establish a point. The operator interactively set any missing points.
5. The control and pass point measurement data was run through a final adjustment on the Z/I SSK PhotoT workstations. The PhotoT program created a results file with the RMSE results for all points within the block and their relation to one another. The photogrammetrist performing the adjustments used their experience to determine what course of action to take for any point falling outside specifications.
6. The bundle adjustment was run through thePhotoT software several times. The photogrammetrist increased the accuracy parameters for each subsequent iteration so, when the final adjustment was run, the RMSE for the project met the accuracy of 1 part in 10,000 of the flying height for the horizontal position (X and Y) and 1 part in 9,000 or better of the flying height in elevation (Z). The errors were expressed as a natural ratio of the flying height utilizing a one-sigma (95%) confidence level.
7. The accuracy of the final solution was verified by running the final adjustment, placing no constraints on any quality control points. The RMSE values for these points must fall within the tolerances above for the solution to be acceptable.
8. The final adjustment generates three files. The .txt file has all the results from the adjustment with the RMSE values for each point measured. The .XYZ file contains the adjusted X, Y, Z,coordinates for all the measured points and the .PHT file contains the exterior orientation parameters of each exposure station.
Process_Date: 20060630
Source_Produced_Citation_Abbreviation: Analytical Aerotriangulation
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: EarthData International, Inc
Contact_Address:
Address_Type: mailing and physical address
Address: 200 I Street SE, 5th Floor
City: Frederick
State_or_Province: MD
Postal_Code: 21704
Country: USA
Contact_Voice_Telephone: (301)948-8550
Contact_Facsimile_Telephone: (301)963-2064
Contact_Electronic_Mail_Address: [email protected]
Hours_of_Service: 8:30 Am - 5:00 PM Mon - Fri
Process_Step:
Process_Description:
Digital Elevation Model (DEM):
Both Lidar and previously produced DEM data was available to support the production process. Following an analysis of the data the previously produced DEM was selected for update and use.
The following provides a step-by-step outline of the production process.
1. The existing DEM which was comprised of both gridded mass points from 10 to 20 meters with spots, and vertices of contour lines was converted to dgn files for compilation.
2. The DEM was then merged together in MicroStation V8, and then split into 34 tiles, approximately 3077m X 3029m.
3. The compilation team updated the data with breaklines where needed, and collected 3D bridges. 3D bridges were collected to prevent smearing and warping, caused by the elevation difference between the bare earth and the elevated bridges. Proprietary MDLs for Microstation were run to create a 10 to 15 meter buffer around the bridges and to clip the surrounding ground data.
4. The dgn files were then merged into four large areas for QC purposes. The files were imported into TerraSolid/TerraModler and a tin and a color relief was generated to search for any spikes or mismatches. This check in performed to fix any problems before going to the ortho stage. Large water areas were filled with elevation points.
5. Complex lines, shapes and arcs were dropped before delivering to the ortho department. A final level listing was run to ensure all the lines were dropped and the files were clean. This listing was provided to the ortho team.
Process_Date: 20060630
Source_Produced_Citation_Abbreviation: Digital Elevation Model (DEM)
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: EarthData International, Inc
Contact_Address:
Address_Type: mailing and physical address
Address: 200 I Street SE, 5th Floor
City: Frederick
State_or_Province: MD
Postal_Code: 21704
Country: U.S.
Contact_Voice_Telephone: (301)948-8550
Contact_Facsimile_Telephone: (301)963-2064
Contact_Electronic_Mail_Address: [email protected]
Hours_of_Service: 8:30 Am - 5:00 PM Mon - Fri
Process_Step:
Process_Description:
Planimetric Data Capture:
The following planimetric layers were either updated from previous datasets or, created during the production process -
- Building Polygons (BldgPly) - Bridge and Tunnel Polygons (BrgTunPly) - Horizontal and Vertical Control Points (GeoControlPt) - Hydrography Center Lines (HydroCenterLineLn) - Metro Entrance Points (MetroEntPt) - Obscured Area Polygons (ObsAreaPly) - Railroad Lines (RailRdLn) - Road, Parking, and Driveway Polygons (RoadPly) - Sidewalk Polygons (SidewalkPly) - Under Construction Areas (UnderConstPly) - Wooded Areas (WoodPly)
The following guidelines were used for the collection of hydrography centerlines - Hydrography lines were collected in the direction of flow through the center of all visible stream course features. Hydrography centerlines were coded as hidden where streams flowed underneath features that obstructed visibility such as bridges and overpasses. Areas between visible stream courses, where the actual course could not be confidently determined based on stereo-photography, were connected using a separate connector code.
The following guidelines were used for the collection of obscured areas - Obscured area polygons were delineated in areas where features could not be confidently determined based on stereo-photography. Such instances included areas of deep shade or heavy vegetation.
The following guidelines were used for data capture and change detection:
For layers tagged as update through change detection, features were removed if they no longer existed in the photography, added if new, or modified if the geometry changed (i.e. building additions). All layers carry a date of capture to delineate which features have been updated.
For change detection methodology, Earthdata thoroughly reviewed the downtown area, mapping tiles that covered the downtown core, for change detection on all of the layers. Outside the downtown area, the contractor carefully reviewed the surrounding area for change detection on all of the layers ONLY WHERE THERE WERE BUILDING OR ROAD CHANGES.
The following processes were involved in updating existing planimetric data levels -
1. Client supplied planimetric data from 1999 was received as merged ESRI shapefile layers.
2. Client supplied layers were converted into Microstation DGN format for updating in the stereo compilation environment. The conversion process involved clipping the merged layers into more manageable tile based files. Polygon feature codes were maintained and updated in the Microstation environment through the use of unique text annotation to define polygon centroid labels.
3. The Microstation linework was draped to existing DEM points to create 3D datasets that could be updated in a stereo compilation environment.
4. The Microstation tiles were updated using the 2005 stereo imagery. Any updated features were coded to reflect a change in status from existing to new.
5. The final updated tiles were checked for proper attribution and coding.
6. The tile datasets were converted into ESRI Geodatabase format for final topological and visual quality control.
7. The Geodatabase topology was checked against a rules file to detect any dangles in linework along with overlapping and intersecting features.
8. Polygon datasets were checked for adjacent areas containing the same code along with multiple code labels within the same polygon.
9. A visual check using the 2005 orthophotography was performed to look for and correct any improper attribution or missing features.
10. A final Geodatabase file was prepared based on the DC OCTO planimetric data structure.
Process_Date: 20060719
Source_Produced_Citation_Abbreviation: Planimetric Layers
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: EarthData International, Inc
Contact_Address:
Address_Type: mailing and physical address
Address: 200 I Street SE, 5th Floor
City: Frederick
State_or_Province: MD
Postal_Code: 21704
Country: U.S.
Contact_Voice_Telephone: (301)948-8550
Contact_Facsimile_Telephone: (301)963-2064
Contact_Electronic_Mail_Address: [email protected]
Hours_of_Service: 8:30 Am - 5:00 PM Mon - Fri
Process_Step:
Process_Description: Dataset copied.
Source_Used_Citation_Abbreviation:
Server=intradb.dcgis.in.dc.gov; Service=5151; User=sde; Version=SDE.DEFAULT
Process_Step:
Process_Description:
This process describes 2008 updates to planimetric data originally captured in 1999/2005. The CAPTUREYEAR field contains the data of origin for the feature. Aerial Photography
New aerial photography was collected in the Spring of 2008 to support new orthoimagery and planimetric updates. This aerial photography was composed of approximately 52 flight lines and a total of 1552 exposures. Imagery was obtained at an altitude of 8,900 ft above mean terrain (AMT). The mission was flown with one Vecxel Ultracam X camera and collected ABGPS and IMU for each exposure.
Aerial triangulation
Aerial triangulation is the simultaneous space resection of image rays projected and recorded at one source, the perspective center of the aerial camera. These image rays projected from two or more overlapping images, stereo-models, intersect at the corresponding ground location to determine the three-dimensional coordinates of each point measured. This collection of image rays is fit to known ground survey control in a simultaneous 3-dimensional least squares adjustment. After the completion of this adjustment, coordinates of the 'unknown' ground points are derived by the intersection of the adjusted image points. The purpose of aerial triangulation is to densify horizontal and vertical control from relatively few ground control points (GCPs). Since obtaining GCPs is a relatively significant expense in any mapping project, AT procedures are used to reduce the amount of field survey required by extending control to all stereo-models. This method is essentially a mathematical tool, capable of extending control to areas between ground survey points using several contiguous uncontrolled stereo-models.
SoftCopy Measurements
All photo measurements were directly observed in a digital 'softcopy' environment. Z/I Imaging, an Intergraph - Carl Zeiss joint venture, software and hardware were used to perform the photo measurements.
In order to perform measurements of digital images in softcopy, images must be processed to a panchromatic .tif format using Vexcel Ultacam Office Processing Center (OPC) Version 2.3
Photo Measurements
AT requires that a series of photographs be situated with one another in a continuous strip configuration. The orientation of any photograph that does not contain sufficient number of ground control points is determined by the orientation of the adjacent photographs. In a strip formation, each photograph aids in the exterior orientation of the adjacent photography through the pass points located in the triple overlap areas. This tri-lap area refers to the common ground area shared by two stereo-models (three consecutive photographs) along the strip. As mentioned above, a pass point is an image point that is common to two or more consecutive photographs along that strip. As the pass point is prepared and measured in a stereo-model, it can be used as control to orient the adjacent stereo-model. Thus, the point "passes" control down the strip. A pass point that is common to adjacent strips of photographs is called a tie point. Tie points hold two adjacent strips together similar to a pass point holding or tying together adjacent photos along a strip. The location of the tie and pass points are in areas which allow geometrically stability in strips and the blocks. These locations are known as the Von Gruber points.
The automatic Point measurement feature of the ZI software was used to measure the pass points in this project. This feature automatically records the image coordinates of up to 7 matched points in each Von Gruber area. All ground control points were also manually measured.
Internal software checks were performed to detect gross errors in the photo measurements.
Simultaneous Adjustment by Bundles
The surveyed control, along with the reduced image coordinates, served as input into the 'combined' block adjustment. Three-dimensional, simultaneous least squares adjustments by bundles, commonly referred to as "bundle" adjustments, were undertaken using Intergraph's PhotoT adjustment software. This particular bundle method is very sensitive to systematic errors of the photo measurements and provides the correction of constant and regular errors through self-calibration. This concept regards these types of errors to be common to all photographs or to be present in sub-sets of the photographs. This bundle block adjustment software has proven to be a very rigorous and stable platform. A series of aerial triangulation solutions were completed. The adjustment strategy was devised to provide the optimal solution for the subsequent mapping, while providing comprehensive quality control to detect errors, omissions and spurious data.
Fully Constrained Adjustment
The final adjustment, and the optimal solution to be used for mapping, included all control points as constraints. All image points were assigned standard deviations of 3 m.
Thirty (30) horizontal-vertical control points and one (1) vertical control point were used to constrain the AT solution. All existing ground control points were photo identified. The airborne GPS was weighted at 0.14 meters in all three dimensions. The results may be found in Table 2 of this report.
The sigma naught is a significant indicator of the quality of the adjustment. The sigma value derived by the adjustment is the root mean square of all photo measurement residuals for the entire block. The lower the sigma naught value, the less tension within the adjustment. Typically, a sigma naught in the range of 2 - 4 m is an indication of a high quality internal adjustment. The sigma naught value for the City of Washington block was 1.71 m.
Computation of Final Coordinates and Elevations
After the completion of the final AT solutions, the local space rectangular coordinates of the tie and pass points were transformed back into NAD83 and NAVD88 horizontal coordinates and orthometric heights. The final horizontal coordinates are Maryland (zone 1900) state plane coordinates All final values as presented in the AT report are in the following measurement units:
- Coordinate - X,Y (State Plane Maryland State Plane Coordinates in NAD83/91) in units of meters - Elevation - Z (NAVD 88 U.S. Survey feet) in units of feet
The final AT solution was found to be of a very high quality and will meet or exceed the ASPRS Class I accuracy standards for 1"=100' scale mapping with 2 foot contours.
Digital Elevation Model (DEM):
Previously produced DEM data was available to support the production process. Because no suitable DEM was available for areas outside of the Washington DC city boundary, USGS 10-Meter NED surface was processed and merged with the existing DEM data and used for rectification. Planimetric Data Capture and Edit: All planimetric features were stereocompiled using softcopy photogrammetric workstations. Planimetric features included the following layers:
- Buildings - Bridges/Tunnels - Control Points - Railroad Lines - Roads (Roads/Medians/Islands/Alleys/Paved Drives/Parking Lots/Parking Garages) - Sidewalks - Street Centerlines
Each layer contained one or more features, each of which was individually coded based on its feature type. Capture actions describe the 2008 edits which were applied to a given feature (U=update, "N"=new, E=Extended). All features were compiled in accordance with industry standards photogrammetric features. The overall process is described below:
- Source materials obtained from the City (imagery, AT, Control) - Stereo-Model boundaries are created for the entire area of interest. - Imagery, AT information and data files for a model boundary are brought into Microstation V7 - Existing DTM data from the City is brought so that it is viewable - Specific planimetric features are newly compiled in a 3D stereo-environment in compliance with the specifications detailed in the database design. A DGN file is the deliverable to the Vector department. ZI-Imaging photogrammetric workstations used for compilation - Planimetric features are exported from DGNs and converted to ESRI shapefiles according to the schema. - Polylines are cleaned and converted into polygons for closed features (structures, roads, parking lots, etc.) - The delivery database is set up and domains are created. The polygons and polylines are appended into the correct feature class in the geodatabase. - The database is QCed visually, and using a database topology reviewer. Any missing features are added and errors are corrected.
Data was delivered to the City based on the City being subdivided into 4 discrete production areas. Planimetric data was extensively QC'd by the City and returned to Sanborn for corrections. Corrections were made and comments were added into a correction file for each item addressed. The data then underwent a second City review prior to distribution.
As a final step in the process data was appended based on the delivery areas into a seamless citywide dataset. Edgematching (graphic and attribute) and final data cleanup was performed as part of this process.
Source_Used_Citation_Abbreviation: C:\temp\BldgPly.xml
Process_Date: 20090612
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: OCTO
Process_Step:
Process_Description:
There were issues with the new building capture that DC GIS fixed. In most cases, staff removed extra vertices. In some cases, linework was straightened to reflect right angles for buildings. In a small set of poorly captured buildings, staff redigitizied the buildings from the orthos. This is the methodology for the building poly edits:
1) All building polygons that listed a CAPTUREACTION with the attribute of A (Add) or U (Update) were selected for review (approximately 5,900 polygons).
2) Polygons that listed a CAPTUREACTION with the attribute of E (Existing) was reviewed only if those polygons were impacted by polygons listed as an A or U.
3) Polygons that did not reflect the proper angle of the building represented were corrected (using right angles).
4) Polygons that did not reflect the proper area of the building represented were corrected.
5) Buildings that had excessive use of vertices were generalized.
6) Merged polygons where the polygons would clearly represent one structure.
7) Changed the CAPTUREACTION attribute from A or U to an E when the structure was clearly existing in 2005 and unchanged.
8) Changed the CAPTUREACTION from A to U when the structure had an addition added.
9) Changed the CAPTUREACTION from U to A when the structure was clearly demolished and rebuilt.
10) Updated the CAPTUREYEAR so all polygons with the CAPTUREACTION attribute of A or U listed the date 5/30/2008.
11) Updated the CAPTUREYEAR so all polygons with the CAPTUREACTION attribute of A or U which were changed to E listed the date 4/4/2005.
12) Removed polygons that were clearly not structures.
Source_Used_Citation_Abbreviation: C:\temp\DCGIS.xml
Process_Date: 20090630
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: OCTO
Process_Step:
Process_Description:
2010 Process Description
Introduction: This process description describes the 2010 processes used to update and/or create selective planimetric mapping data originally captured in 1999/2005/2008 by the District of Columbia from spring, leaf off, 2010 digital aerial photography flown on April 2 and 3, 2010. The development of 2010 planimetric data at a design scale of 1:1200 meeting an ASPRS Class 1 horizontal accuracy of 1 foot RMSExy is a component of an overall project commissioned by the District of Columbia to conduct a comprehensive photogrammetric mapping and GIS update. The Team of KCI Technologies and Photo Science provided comprehensive project management, map production and QC services to the District. The project area for the 2010 project covers the entire District of Columbia and immediate surrounding area equaling approximately 80 square miles. The multispectral digital aerial imagery was used to stereoscopically update/create planimetric map data and create natural color digital orthophotography with 16cm pixel resolution. All DC GIS data is stored and exported in Maryland State Plane coordinates NAD 83 meters
Imagery Acquisition: New digital aerial imagery was obtained by Photo Science using a large format Z/I Digital Mapping Camera system (DMC) equipped with Airborne GPS/IMU covering the Washington DC and immediate surrounding area. A total of 35 flight lines with 1567 frames were collected in the spring of 2010 in multi-spectral (RGB and NIR) 16 bits per band format. The imagery was acquired with a 4.7244" (120 m/m) focal length at an altitude above mean terrain of 5,000' to yield a raw pixel resolution of 0.5' suitable for photogrammetric mapping and orthophoto production. The imagery was collected during leaf off conditions in the spring of 2010 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. In the downtown areas (Area 1), additional perpendicular flight lines were planned to provide additional imagery to minimize building lean in the orthophotos. Because of airspace restrictions in the DC area (particularly in the area of the White House and Capitol Building areas), some lines did not adhere strictly to plan. 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. Only the RGB bands were used in the Orthorectification process, all four band exist in the raw georeferenced deliverables. AGPS/IMU mission data is processed together with continuously collected ground-based CORS GPS base station data in forward and reverse directions. This precisely determines the aerial camera's position and orientation in the terrain (project) coordinate system and allows for correct orientation of the imagery.
Ground Control Surveys: As Part of the 2010 Orthophoto and Planimetric Update Project, KCI Technologies Survey Crews established 115 new photo identifiable control points throughout the District and surrounding vicinity to support the aerotriangulation process. Additionally, 31 existing control points from previous DC mapping cycles were used in the aerotriangulation process. See KCI Technologies 2010 Control Report for Survey for more details. Horizontal survey projection and datum utilized was Maryland State Plane Coordinate System, North American Datum of 1983 (NSRS 2007). The vertical datum was the North American Vertical Datum of 1988 (NAVD 1988). Unit of measurement was expressed in both feet and meters.
Aerotriangulation: ImageStation Automatic Triangulation (ISAT) software was utilized by Photo Science to provide the results needed for the planimetric and orthophoto production process. A digital image of the aerial photography was utilized to compare and measure the coordinates of selected pass points, (min. 9 per image) with the exception of end images, which have a minimum of 6 per image. Pass points were either dark spots on the ground, corner intersections of sidewalks, rocks, or road lines to name a few. These pass points and any ground based photo control points were measured using the calibration statistics to adjust measurements for the specific camera characteristics. Computer routines (relative and absolute) provide analysis of all pass points, tie points, ABGPS and photo control points. Aerotriangulation constructs a detailed model of the position of each pass point and provides residuals (and blunders) at all photo control locations.
The end result is not only the referenced image, but also a coordinate listing of all of the points and corresponding residuals. Once all strips have been checked for completeness, the strips are assembled into a block where a second degree block adjustment is run along with the full least squares bundle adjustment. Once the last set of blunders and adjustments are complete, a final block bundle adjustment in ISAT is run to produce the final solution using a rigorous simultaneous least squares bundle adjustment. The bundle adjustment was then run with minimal ground control to test the photogrammetric measurements for consistency. Next, the full ground control data set, including the ABGPS data, was added to the adjustment. The horizontal control was then tightened and the effect on the vertical control and the photogrammetric residuals were inspected. Once all strips have been checked for completeness, the strips were assembled into a block where a second degree block adjustment was run along with the full least squares bundle adjustment. Once the last set of bundles and adjustments were complete, a final block bundle adjustment in ISAT was run to produce the final solution to meet project accuracy requirements. See Aerotriangulation Report dated June 4, 2010 produced by Photo Science for more details on the procedures. DEM Processing:
The 2008 Digital Elevation Model (DEM), consisting of mass points and break lines covering District Boundaries, was utilized by Photo Science in the 2010 planimetric and orthophoto production process. This DEM was developed by the Sanborn Mapping Company for the 2008 mapping update project and was utilized to generate the City's 2008, 2 foot topographic contour data layer. Because no suitable DEM was available for areas outside of the Washington DC city boundary, USGS 10-Meter NED surface was processed and merged with the existing DEM data. Then it was used to support stereo model viewing of existing planimetric features and to support ortho rectification.
Planimetric Data Capture, Finishing and QC: The city supplied a 2008 planimetric geodatabase, which was updated and/or added by Photo Science using the 2010 aerial imagery via direct stereo compilation methods (using BAE Socet Set version 5.5 softcopy photogrammetric workstations running the Feature Extraction module). Refer to "Geodatabase Design and Data Update Methodology" document dated September 1, 2010 version 2 published by KCI Technologies and Photo Science for specifications that detail the characteristics and behaviors for each planimetric entity that has been updated/created in the final planimetrics2010 geodatabase.
Planimetric feature classes updated (or added) include: Buildings, Bridges/Tunnels, Geodetic Ground Control Points, Curb Grates, Obscured Areas, Rail Roads, Recreational Courts, Roads, Sidewalks, Stairs, Street Centerlines, Swimming Pools, Wheelchair Ramps, and Vegetation. Each feature class contained one or more features, each of which was individually coded based on its feature type. The CAPTUREYEAR field contains the data of origin for the feature. CAPTUREACTION field describes the 2010 edits which were applied to a given feature. Codes included: A - Add (feature is new), D - Delete (feature no longer exists), E - Existing (feature is left untouched), and U - Update (feature changes shape due to renovations). All features were compiled in accordance with industry standards.
The overall process is described below: The city was divided up into 4 production/delivery areas- Source materials are ingested and processed (imagery, AT, Control, DEM and 2008 planimetric geodatabase) for each delivery/production area - a shape file for each feature type is exported from the geodatabase. - Stereo-Model boundaries are created for the entire area of interest. - Imagery, AT information and shape files data files for a model boundary are brought into Socet Set - Existing DTM data from the City is brought so that it is viewable - Specific planimetric features are edited or newly compiled in a 3D stereo-environment using the Feature Extraction module of Socet Set in compliance with the specifications detailed in the database design. - A shape file of each feature type is exported from Socet Set for GIS editing, finishing, geodatabase development, and QC using ArcGIS version 9.3.1 Service Pack 1 (build 3500). The delivery database is set up and domains are created. The polygons and polylines are appended into the correct feature class in the geodatabase.
The database under goes visual QC and automated validation checks using PLTS - Reviewer - Product Version 93.01.01 Build Number 485. - a new 2010 Planimetric geodatabase for each delivery area was delivered to both KCI Technologies and the District for extensive independent QC. Refer to "Quality Control Plan" document dated August 6, 2010 published by KCI Technologies detailing the agreed upon methodology and quality control procedures between the District of Columbia Office of the Chief Technology Officer (DC OCTO), Photo Science, and KCI Technologies (KCI) for acceptance of deliverables produced under the 2010 Mapping Update Program in the District of Columbia. -Any missing features were added and errors were identified and submitted to Photo Science for correction. - A revised geodatabase reflecting any corrections was resubmitted by Photo Science and validated by KCI and the District. A final city wide, appended, seamless, 2010 planimetric geodatabase of all four delivery areas was delivered to KCI Technologies and the District for final QC and acceptance prior to distribution.
Process_Date: 20110321
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: OCTO
Process_Step:
Process_Description: Metadata imported.
Source_Used_Citation_Abbreviation: C:\temp\BldgPly.xml
Process_Date: 20110321
Process_Time: 15035000
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Vector
Point_and_Vector_Object_Information:
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: coordinate pair
Coordinate_Representation:
Abscissa_Resolution: 0.000063
Ordinate_Resolution: 0.000063
Planar_Distance_Units: meters
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257222
Vertical_Coordinate_System_Definition:
Altitude_System_Definition:
Altitude_Datum_Name: North American Vertical Datum of 1988
Altitude_Resolution: 1.000000
Altitude_Distance_Units: Meters
Altitude_Encoding_Method:
Explicit elevation coordinate included with horizontal coordinates
Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: DCGIS.BldgPly
Attribute:
Attribute_Label: OBJECTID
Attribute_Definition: Internal feature number.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label: SHAPE
Attribute_Definition: Feature geometry.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain: Coordinates defining the features.
Attribute:
Attribute_Label: GIS_ID
Attribute_Definition: OCTO GIS sequential identifier
Attribute:
Attribute_Label: FEATURECODE
Attribute_Definition: Building Feature Code
Attribute:
Attribute_Label: DESCRIPTION
Attribute_Definition: Building Description
Attribute:
Attribute_Label: CAPTUREYEAR
Attribute_Definition: Building Capture Date
Attribute:
Attribute_Label: CAPTUREACTION
Attribute_Definition: Type of edit performed on the feature
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: A
Enumerated_Domain_Value_Definition: Add
Enumerated_Domain_Value_Definition_Source: This is a new building.
Enumerated_Domain:
Enumerated_Domain_Value: E
Enumerated_Domain_Value_Definition: Existing
Enumerated_Domain_Value_Definition_Source:
Building was not updated in this project because no changes occurred on the structure.
Enumerated_Domain:
Enumerated_Domain_Value: U
Enumerated_Domain_Value_Definition: Update
Enumerated_Domain_Value_Definition_Source:
The building shape was updated due to an addition or change in the structure's shape.
Attribute:
Attribute_Label: SHAPE.AREA
Attribute:
Attribute_Label: SHAPE.LEN
Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: D.C. Office of the Chief Technology
Contact_Person: GIS Data Coordinator
Contact_Address:
Address_Type: mailing and physical address
Address: 200 I Street SE, 5th Floor
City: Washington
State_or_Province: D.C.
Postal_Code: 20001
Country: USA
Contact_Facsimile_Telephone: (202)727-5660
Contact_Electronic_Mail_Address: [email protected]
Hours_of_Service: 8:30 am - 5:00 pm
Resource_Description: Downloadable Data
Distribution_Liability:
For data terms and conditions, go to <http://dc.gov/page/terms-and-conditions-use-district-data>
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: TIFF
File_Decompression_Technique: No compression applied
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name: <http://dcgis.dc.gov>
Fees: Call for information.
Ordering_Instructions: All data is available at <http://opendata.dc.gov>
Metadata_Reference_Information:
Metadata_Date: 20110321
Metadata_Review_Date: 08/03/06
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: D.C. Office of the Chief Technology
Contact_Person: GIS Data Coordinator
Contact_Address:
Address_Type: mailing and physical address
Address: 200 I Street SE, 5th Floor
City: Washington
State_or_Province: D.C.
Postal_Code: 20001
Country: USA
Contact_Facsimile_Telephone: (202)727-5660
Contact_Electronic_Mail_Address: [email protected]
Hours_of_Service: 8:30 am - 5:00 pm
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Time_Convention: local time
Generated by mp version 2.9.12 on Thu Jun 25 15:08:08 2015