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Cultural features (CulturePly)

Cultural features (CulturePly)

by National Capital Planning Commission on 06/10/2002

Keywords
About: Geographic Information System, society, Planimetrics
Taking place at: Washington, DC, District of Columbia

Abstract

Miscellaneous (parks, zoos, gardens, and cemeteries). Contract NCPC 93-02. This document describes the
planimetric map production for the 350 tiles located in Washington DC and the surrounding states of MD and VA.

Purpose

This data set was created to act as a basis for public and private institutions to improve their policy and decision making; promote economic development; and enhance the quality of life for residents and businesses.

Access constraints

Contact OCTO GIS. Any data obtained outside of OCTO GIS are unauthorized copies.

Use constraints

Acknowledgment of the DC Geographic Information Systems Program (DC GIS). The District of Columbia Government makes no claims as to the completeness, accuracy or content of any data contained hereon, and makes no representation of any kind, including, but not limited to, the warranty of the accuracy or fitness for a particular use, nor are any such warranties to be implied or inferred with respect to the information or data furnished herein.

Point of contact

GIS Data Coordinator
in DC Office of the Chief Technology Officer (OCTO)

441 4th St NW, Suite 930 South
Washington DC, 20001, USA

fax: (202) 727-5660
hours: 8:30 am - 5:00 pm

Data accuracy

Accuracy
Validated by source and/or responsible agency. Attribute accuracy is tested by manual comparison of the digital orthos/aerial photography with the hard copy plots. In addition, several computer quality control programs are run on the accompanying digital data.

Logical consistency
Validated by source and/or responsible agency.



Edit/Quality Control Process in ARC/INFO

The final topological structure is created and verified using ARC/INFO's Map Librarian functionality. In general, use of a map library ensures overall compliance with defined database structures and conventions, and, for this specific project, guarantees adherence to the database structure and conventions. In addition, in-house-developed ARC/INFO routines are employed for translation of vector data from a CAD to GIS environment. These routines maintain coding of all CAD data, construct both topologically clean and topologically structured data sets, and combine or separate data into the correct user-defined output data sets. For this project, for example, all CAD data are translated to ARC/INFO coverages while eliminating topological errors such as overshoots and undershoots. EDMD GIS division verifies that all vector data produced for the project meets the Graphic Data Standards, as outlined in the modification of Task 4.



A combination of automated procedures and interactive processes are used. The following is a listing of AML Default Routines:

QC_PROC.aml
This routine will run all of the following AMLs. The &run qc_proc.aml

- The name of the map library (i.e. NCPC)

- the tile within the map library upon which the AMLs are to run

- the layer defined for the map library (i.e. roads)



General Data Set Verification

QC_DATAPROJ.aml
This routine checks correctness of all projection parameters. It verifies map projection, projection zone, datum and projection units.

QC_DATAEXT.aml
This routine checks if all data in the selected data set are within the corresponding map sheet boundaries.

QC_CORN.aml
This routine checks if corner coordinates of the selected data set coincide with corner coordinates of the corresponding map sheet.

QC_DATATOL.aml
This routine checks mapping tolerances. Mapping tolerances implicitly define accuracy and precision of vector data.



Attribute Verification

QC_FEATNODE.aml, QC_FEATPNTS.aml, QC_FEATLINE.aml, QC_FEATPOLY.aml
These routines check the field definitions of the selected data set and data type.

QC_ATTRPNTS.aml, QC_ATTRLINE.aml, QC_ATTRPOLY.aml
These routines check the attribute codes of all features in the selected data set against the range of possible attribute codes defined in the database.



Topological Consistency Verification

QC_DATAEDGE.aml
This routine checks for spatial mismatches of linear features among adjacent map sheets. It displays any mismatch.

QC_ATTREDGE.aml
This routine checks for attribute mismatches of polygon features among adjacent map sheets.

QC_DANGINT.aml
This routine displays intersections of features within a data set such as contour data. Intersections of contour features indicate errors as contours are by definition non-intersecting isometric. This routine also displays any terminal node that is not connected to any other feature.



The following is a description of the steps undertaken to inspect and verify the quality of the planimetric data.

Step 1 EDMD prepares an ARC/INFO map library using the database design as developed by Dewberry & Davis dated June 30, 1997. Using an ARC/INFO map library, any inconsistencies in the database are immediately apparent when loading or modifying the digital planimetric data.

Step 2 Compiled data are translated to the appropriate ARC/INFO coverages and inserted into the map library. The translation procedures ensure that all codes are within the range of possible domain values. Illogical coding or configuration of features such as roads within buildings is immediately flagged.

Step 3 Using the Map Librarian functionality, routines (i.e., Arc Macro Language - AML) can be automatically applied to the entire database using the Map Librarian VISIT command. Similarly, other layers are validated with the appropriate routines.

Step 4 In an interactive session, using ARC/EDIT, each map library tile, including all the associated layers, is verified by an editor. Verification consists of checking spatial and attribute data. In this session, topological inconsistencies are highlighted, for example, dangling arcs, missing label points, etc. Identification of missing features or features with incorrect shape can also easily be identified through use of the 1995 orthophotos that reside in the image catalog.

Step 5 Final quality control is performed in an ArcView session, again using the map library. Any missing features will be identified during this step.

Generally, steps 1, 4, and 5 involve interactive quality control steps, while steps 2 and 3 are based on automated quality assurance. Step 5, as a final quality control step, includes verification of vector data to hardcopy maps.

Completeness
Validated by source and/or responsible agency. The photogrammetric mapping is guaranteed to meet National Map Accuracy standards for digital mapping at a scale of 1 inch to 83.33 feet, which calls for 90% of well defined points to fall within 33.3 inches of true position horizontally. This does not apply to hidden features, which were inferred.

Horizontal positional accuracy
Validated by source and/or responsible agency. The horizontal accuracy is guaranteed to meet National Map Accuracy standards which calls for 90% of well defined points to fall within .85 meters of true position. This accuracy was verified by the completion of a fully analytical aerotriangulation adustment which resulted in an RMSE of 1 part in 10,000 which is recognized as necessary to achieve the accuracy requirement.

Vertical positional accuracy
Validated by source and/or responsible agency. The vertical accuracy of the topographic information is guaranteed to meet National Map Accuracy standards which calls for 90% of well defined points to fall within one half (.50 meters) of true position. This accuracy was verified by the completion of a fully analytical aerotriangulation adustment which resulted in an RMSE of 1 part in 9,000 which is recognized as necessary to achieve the accuracy requirement.

Lineage / Sources

  • Washington DC GIS project
    disc, Control
    EDMD1
    by EarthData International of Maryland, LLC, Unknown
  • Washington DC GIS project
    filmstrip, Aerial Photography
    EDMD2
    by Earthdata International of Maryland, LLC, Unknown
  • Washington DC GIS project
    filmstrip, Photographic Products
    EDMD3
    by Earthdata International of Maryland, LLC, Unknown
  • Washington DC GIS project
    CD-ROM, SIS data
    DD1
    by Dewberry Davis, LLC, Unknown
Lineage / Processes
Chris Barnard
in EarthData International

45 W. Watkins Mill Road Suite G
Gaithersburg MD, 20878, USA

fax: 301.963.2064
hours: Regular office hours
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.
Chris Barnard
in EarthData International

45 W. Watkins Mill Road Suite G
Gaithersburg MD, 20878, USA

fax: (301) 963-2064
hours: Regular office hours
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.
Chris Barnard
in Earthdata International

45 W. Watkins Mill Road
Gaithersburg MD, 20878,

fax: (301) 963-2064
hours: Regular office hours
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.

Distribution

Most DC GIS datasets can be downloaded from "http://dcgis.dc.gov" on the data center page. Orders can also be made by contacting OCTO GIS at "dcgis@dc.gov", especially for datasets not available for download.

Distribution liability
Acknowledgment of the DC Geographic Information Systems Program (DC GIS). The District of Columbia Government makes no claims as to the completeness, accuracy or content of any data contained hereon, and makes no representation of any kind, including, but not limited to, the warranty of the accuracy or fitness for a particular use, nor are any such warranties to be implied or inferred with respect to the information or data furnished herein.

Distributed by
GIS Data Coordinator
in DC Office of the Chief Technology Officer (OCTO)

441 4th St NW, Suite 930 South
Washington DC, 20001, USA

fax: (202) 727-5660
hours: 8:30 am - 5:00 pm

Entity

DCGIS.CulturePly

Attributes

  • Shape / ESRI
    Feature geometry.
  • OBJECTID_1
    Unique ID
  • CTP
    Coverage artifact
  • CTP_ID
    Coverage artifact
  • CTP_CODE
    Abbreviated description
  • CTP_NAME
    Name
  • Shape_Leng / ESRI
    Length of feature in internal units.
  • OBJECTID / ESRI
    Internal feature number.
  • SHAPE_LENG
  • SHAPE / ESRI
    Feature geometry.
  • DXF_LAYER
    DXF Layer
  • DESC_
    Description
  • SHAPE.AREA
  • SHAPE.LEN

Metadata

FGDC Content Standards for Digital Geospatial Metadata / FGDC-STD-001-1998 as of 12/14/2007

Provided by
GIS Data Coordinator
in DC Office of the Chief Technology Officer (OCTO)

441 4th St NW, Suite 930 South
Washington DC, 20001, USA

fax: (202) 727-5660
hours: 8:30 am - 5:00 pm