Drainage of Loudoun County, VA (2020)

Metadata also available as

Metadata:

Identification_Information:
Citation:
Citation_Information:
Publication_Date: 20210427
Title: Drainage of Loudoun County, VA (2020)
Geospatial_Data_Presentation_Form: vector digital data
Description:
Abstract:
Drainage is a base map data layer derived by automated processes and processed for cartographic representation at 1:2400 scale. The line features represent the any visible surface drainage feature, natural or manmade, as seen from above and are mapped to National Map Accuracy Standards (NMAS). Drainage arcs must logically follow topo contours downhill and are not disconnected when traveling through culverts, under bridges or representing the centerline of double-line streams and ponds. Drain arcs will be captured according to proper orientation or direction of flow. Photogrammetrically derived drainage DOES includes known underground culvert and pipe connections with stormwater infrastructure points and other visible surface outlets. This drainage layer DOES NOT include subsurface groundwater flow, fine soil drain patterns in swales, or any other historical surface drains.
Purpose:
Drainage is used in agricultural and farm plans, stormwater management, comprehensive planning, floodplain management, and facility planning.
Supplemental_Information:
Data are stored in the corporate ArcSDE Geodatabase as a line feature class. The coordinate system is Virginia State Plane (North), Zone 4501, datum NAD83 HARN, Vertical datum, NAVD88, US Survey foot units.
OMAGI updates all base map data via photogrammetric process, using aerial imagery that is flown yearly. A different portion of the county is updated each year with the base map maintenance services contract, depending upon development patterns and update funding. The field “UPD_DATE” indicates the date a feature was last re-mapped. For a map of the most recent reviews and updates within the county, please click on https://arcg.is/0Tm9PW0
Status:
Maintenance_and_Update_Frequency: Annually
Progress: Complete
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -77.963458
East_Bounding_Coordinate: -77.313992
North_Bounding_Coordinate: 39.328361
South_Bounding_Coordinate: 38.836941
Keywords:
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword:
drains, stream, creek, channels, ditches, pond, lakes, paved ditch
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Categories
Theme_Keyword: inlandWaters
Place:
Place_Keyword_Thesaurus: none; Employee generated
Place_Keyword: Virginia, Loudoun, County
Access_Constraints: None
Use_Constraints:
These data were generated for use by Loudoun County and are available to the public. These data are intended for use at 1:2400 scale or smaller. Acknowledgement of Loudoun County would be appreciated in products derived from this data.
Point_of_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Contact_Position: Base Map Coordinator
Contact_Address:
Address_Type: mailing and physical
Address: 1 Harrison Street SE, 2nd Floor
Address: MS 65
City: Leesburg
State_or_Province: VA
Postal_Code: 20175
Contact_Voice_Telephone: (703)771-5778
Contact_Facsimile_Telephone: (703)771-5075
Contact_Electronic_Mail_Address: mapping@loudoun.gov
Hours_of_Service: 8:00-4:30 EST, M-F
Point_of_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization:
Loudoun County, VA, Office of Mapping and Geographic Information (OMAGI)
Native_Data_Set_Environment:
Microsoft Windows Server 2008 Version 6.0 (Build 6002) Service Pack 2; ESRI ArcGIS 10.0.5.4400
Data_Quality_Information:
Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: 20020408
Title: Base Map Maintenance Services Contract, QQ-00986, Phase I
Source_Scale_Denominator: 2400
Type_of_Source_Media: None
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-00986, Phase I
Source_Contribution:
Captured Western 2/3 of County generally located north of Leesburg, west of Rt. 621, Evergreen Mills Rd, and south of Braddock Rd.
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: 20040405
Title: Base Map Maintenance Services Contract, QQ-00986, Phase II
Source_Scale_Denominator: 2400
Type_of_Source_Media: None
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-00986, Phase II
Source_Contribution:
Captured Eastern 1/3 of County generally located to include Leesburg, east of Rt. 621, Evergreen Mills Rd, and north of Braddock Rd.
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: 20050303
Title: Base Map Maintenance Services Contract, QQ-00986, Phase III
Source_Scale_Denominator: 2400
Type_of_Source_Media: None
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-00986, Phase III
Source_Contribution:
Captured photogrammetric stereo models covering highest development areas in the original Phase I region and including Leesburg.
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: 20070305
Title: Base Map Maintenance Services Contract, QQ-00986, Phase IV
Type_of_Source_Media: None
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-00986, Phase IV
Source_Contribution:
Captured and updated photogrammetric stereo models covering highest development areas in the original Phase II region.
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: 20080303
Title: Base Map Maintenance Services Contract, QQ-01407, 2008
Source_Scale_Denominator: 2400
Type_of_Source_Media: None
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01407, 2008
Source_Contribution:
Captured and updated photogrammetric stereo models covering highest development areas in the north eastern region.
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: 20090303
Title: Base Map Maintenance Services Contract, QQ-01407, 2008
Source_Scale_Denominator: 2400
Type_of_Source_Media: None
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01407, 2008
Source_Contribution:
Captured and updated photogrammetric stereo models covering highest development areas in the western region.
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: 20130514
Title: Base Map Maintenance Services Contract, QQ-01407, 2012
Source_Scale_Denominator: 2400
Type_of_Source_Media: None
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01407, 2012
Source_Contribution:
Captured and updated photogrammetric stereo models covering highest development areas in the western region.
Process_Step:
Process_Description:
Aerial film was acquired and imaged in 2002 (Virginia Base Mapping Program (VBMP) color) and 2004 (Loudoun County annual aerial mission (black & white). The imagery was scanned at 21 microns. Ground control used to support the compilation and was collected by identifying strategic locations on the aerial photography plan and then determining the coordinates by GPS ground survey techniques.
The Aerial Triangulation was performed using softcopy workstations. Bundle adjustment was performed and Digital Elevation Models were created using and planimetric data were collected using standard photogrammetric collection techniques for breaklines and masspoints on soft copy workstations. Final deliverables in ESRI Interchange (E00) file format were placed on CD for delivery to OMAGI.
Process_Date: 20040331
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Step:
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG File imported to Microstation V8, and overlaid with the Update Parcels DGN. Identified Areas to be corrected. 3. Remap area inside parcel change layer a. If no change is detected the entities are not modified b. If new features are found they are collected as per the specifications c. If there is difference in shape or size of the planimetric, environmental or topographic features these are modified and coded as Update_Date = '2005' 4. Review remainder of model area outside the parcel change area a. If new features found they are collected as per the specifications 5. Updated Plan data in the Parcel areas have been checked for Edge matching 6. DTM was modified in the 11 major update areas 7. Contours were generated and edge matched with the legacy contour data 8. Checked contour coding at all the new buildings. 9. Checked the updated data on Ortho for completeness 10. All clean up tools have been run 11. Exported to Coverages and then to GDB. 12. Split the Area wise GDB into manageable pieces 13. Run QA/QC on each part of the Area wise GDB 14. Errors marked in the Log file have been corrected in the merged database 15. Merged the different Areas data into a single GDB i.e., Pilot, Areas 1, 2, & 4 16. Dissolved the polygons with same feature codes 17. Clipped legacy data to Phase 3 delivery boundary 18. Loaded new Phase 3 data and merged with existing Legacy data in east. 19. Loaded complete data sets (11) to enterprise SDE geodatabase
Process_Date: 20050330
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Step:
Process_Description:
Loudoun County has a goal to create an enhanced drainage arcs layer through integration of field-surveyed data, while maintaining connectivity, directionality and attribution of photogrammetrically-derived drains. Subsequently, photogrammetrically derived surface drainage was manually connected to GPS-surveyed, known stormwater infrastructure features. These connection points are the only permissable variations between orthophoto features and vector data.
The following Stormwater Integration Rules were applied to the compilation of drainage arcs: 1. Feature = CULVTPT, PIPEIO, and CNTRLDE are used as snapping points in drainage collection. 2.Stormwater infrastructure data provides guidance for directionality and rule of placement for location of culverts, pipes and headwalls and are snapped to coincident features within 20' radius of proximity. If no stormwater GPS point exists within 20' radius of proximity, headwall is represented as best as possible along drain network. 3. Stormwater data represents transitions from surface to sub-grade drainage. Sub-grade connections and direction can be determined using stormwater lines. 4. Snapping was done on visible surface drain arcs to CULVTPT and/or PIPEIO endpoints along network within 20' radius of proximity. 5. Sub-grade, null drains through culverts (DR_Type = 5) are collected per usual, regardless of existence of CULVERT or PIPE line. 6. If open channel (DR_Type = 9) is defined and visible along roadside ditch, it is snapped to CULVTPT culvert points and is connected with null drains (DR_Type = 5). 7. Stormwater lines are used to assist in determination of surface drainage flow direction. There is a high degree of confidence in accuracy of flow direction as these were collected in the field by surveyors. 8. Pond Null arcs (DR_Type = 4) are snapped to control devices CNTRLDE if present in wet or dry ponds. 9. All above-grade, Miscellaneous features (manholes, headwalls/culverts, paved channels) are captured as usual, per contract. Headwalls (MI_Type = 5) shall be coincident with CULVTPT points, which connect surface drain arcs (DR_Type = 2, 6, or 9) and sub-grade null arcs (DR_Type = 5)
Process_Date: 20050331
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Step:
Process_Description:
Each of the Base Map Data Layer coverages in the 27 delivery blocks comprising Phases I and II were loaded into a single Geodatabase Feature Class using ArcGIS Simple Data Loader. The entire feature class was then dissolved using ArcToolBox Dissolve, such that any adjacent features with identical values in all attributes consolidated into one feature.
Record Counts, Frequencies, Length or Area summaries and final Topology checks were performed throughout the conversion procedure to ensure that multiple coverage data input matched single feature class data output (per TYPE code). To meet satisfactory QA/QC requirements the input coverage and output feature class must have the same record total, and on a record by record basis, area, perimeter and length differential of less than +/- 0.5%
Process_Date: 20050331
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Step:
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be remapped. 3. New features were collected as per the data dictionary and the features that do not exist on 2007 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2007'. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Legacy PGDB was clipped to Phase 4 delivery boundary. 16. Updated Data was merged with the Legacy data. 17. Countywide complete dataset (11 layers) was loaded to enterprise SDE Geodatabase.
Process_Date: 20080603
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Step:
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2008 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2008'. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE
Process_Date: 20090907
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Step:
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2009 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2010'. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against 2010 Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE
Process_Date: 20101005
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Step:
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2012 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2012'. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against 2012 Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE
Process_Date: 20130514
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Step:
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2013 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2013'. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against 2013 Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE
Process_Date: 20141218
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Source_Information:
Source_Scale_Denominator: 2400
Type_of_Source_Media: None
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01407, 2013
Source_Contribution:
Captured and updated photogrammetric stereo models covering selected areas in the central region of Loudoun County.
Source_Citation:
Citation_Information:
Title: Base Map Maintenance Services Contract, QQ-01407, 2013
Publication_Date: 20141218
Source_Information:
Source_Scale_Denominator: 2400
Type_of_Source_Media: None
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01857, 2014
Source_Contribution:
Captured and updated photogrammetric stereo models covering selected areas in the central region of Loudoun County.
Source_Citation:
Citation_Information:
Publication_Date: 20150803
Title: Base Map Maintenance Services Contract, QQ-01857, 2014
Process_Step:
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2014 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2014'. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against 2014 Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE
Process_Date: 20150803
Source_Information:
Source_Contribution:
Captured and updated photogrammetric stereo models covering selected areas in the central region of Loudoun County.
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01857, 2015
Type_of_Source_Media: None
Source_Scale_Denominator: 2400
Source_Citation:
Citation_Information:
Title: Base Map Maintenance Services Contract, QQ-01857, 2015
Process_Step:
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2015 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2015'. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against 2015 Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE
Process_Date: 20160825
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Source_Information:
Source_Scale_Denominator: 2400
Type_of_Source_Media: None
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01857, 2016
Source_Contribution:
Captured and updated photogrammetric stereo models covering selected areas in the central region of Loudoun County.
Source_Citation:
Citation_Information:
Title: Base Map Maintenance Services Contract, QQ-01857, 2016
Process_Step:
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2016 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2016. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against 2016 othos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE
Process_Date: 20170804
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: 20181213
Title: Base Map Maintenance Services Contract, QQ-01857, 2017
Source_Scale_Denominator: 2400
Type_of_Source_Media: none
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01857, 2017
Source_Contribution:
Captured and updated photogrammetric stereo models covering selected areas in the central region of Loudoun County.
Process_Step:
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2017 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2016. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against 2017 Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE
Process_Date: 20181213
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: 20190904
Title: Contract # - QQ-01857, 2018
Source_Scale_Denominator: 2400
Type_of_Source_Media: none
Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01857, 2018
Source_Contribution:
Captured and updated photogrammetric stereo models covering selected areas in the northern region of Loudoun County.
Process_Step:
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2018 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2018. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against 2018 Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE
Process_Date: 20190904
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Source_Information:
Source_Scale_Denominator: 2400
Type_of_Source_Media: none
Source_Citation_Abbreviation:
RFQ 108783, Agreement for Service for Base Map Maintenance Services, 2020
Source_Contribution:
Captured and updated photogrammetric stereo models covering selected areas in the Southeast region of Loudoun County.
Source_Citation:
Citation_Information:
Publication_Date: 20210427
Title:
RFQ 108783, Agreement for Service for Base Map Maintenance Services, 2020
Process_Step:
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Process_Description:
1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2020 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2020. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against 2020 Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE
Process_Date: 20210427
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Vector
Point_and_Vector_Object_Information:
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type: String
Point_and_Vector_Object_Count: 109051
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Map_Projection:
Map_Projection_Name: Lambert Conformal Conic
Lambert_Conformal_Conic:
Standard_Parallel: 38.03333333333333
Standard_Parallel: 39.2
Longitude_of_Central_Meridian: -78.5
Latitude_of_Projection_Origin: 37.66666666666666
False_Easting: 11482916.66666666
False_Northing: 6561666.666666666
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: coordinate pair
Coordinate_Representation:
Abscissa_Resolution: 0.00020833333333333297
Ordinate_Resolution: 0.00020833333333333297
Geodetic_Model:
Horizontal_Datum_Name: D North American 1983 HARN
Ellipsoid_Name: GRS 1980
Semi-major_Axis: 6378137.0
Denominator_of_Flattening_Ratio: 298.257222101
Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: GISDBB.GISBROW.DRAINS_LINE
Entity_Type_Definition: line feature class
Entity_Type_Definition_Source: ESRI
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: DR_CLASS
Attribute_Definition: Flow Characterization of Drainage Feature
Attribute_Definition_Source: Loudoun County
Attribute_Domain_Values:
Unrepresentable_Domain: See Entity and Attribute Detail Citation for Data Dictionary
Attribute:
Attribute_Label: DR_SOURCE
Attribute_Definition: Source that created or edited feature class
Attribute_Definition_Source: Loudoun County
Attribute_Domain_Values:
Unrepresentable_Domain: See Entity and Attribute Detail Citation for Data Dictionary
Attribute:
Attribute_Label: DR_UPD_DATE
Attribute_Definition:
The date a feature was last re-mapped, although it may have been reviewed for changes more recently.
Attribute_Definition_Source: Loudoun County
Attribute:
Attribute_Label: DR_UPD_USER
Attribute_Definition:
Not for public distribution. Internal User ID of editor creating or modifying a feature. Intended to track and audit features internally by County.
Attribute_Definition_Source: Loudoun County
Attribute:
Attribute_Label: DR_TYPE
Attribute_Definition: Classification of Drain Type
Attribute_Definition_Source: Loudoun County
Attribute_Domain_Values:
Unrepresentable_Domain: See Entity and Attribute Detail Citation for Data Dictionary
Attribute:
Attribute_Label: DB2GSE.SdeLength(SHAPE)
Overview_Description:
Entity_and_Attribute_Overview:
DR_TYPE: Classification of Drain Type code description ---- ------------------ 1 Null centerline through Double line stream 2 Single-Line stream network 3 Soil drain 4 Null centerline through pond or lake 5 Null centerline through bridge or culvert 6 Null centerline over paved channel 7 Null Connecting Arcs 8 Discontinuous drain 9 Centerline of open (unpaved) channel or ditch 10 Null centerline through Potomac River
Entity_and_Attribute_Detail_Citation:
Feature Depiction Descriptions based on USACE publication, EM 1110-1-1000, July 31, 2002 and further developed according to Loudoun County Data Dictionary.
Centerline through double line stream [Type = 1] Null centerline of a double-line stream polygon in Water Bodies. ---------------------------------------------------------------- Single-line Creek /Stream [Type = 2] Nonnavigable stream. Digitize center lines of streams narrower than 15 ft. Streams wider than 15' are captured as double-line stream polygons in Water Bodies. ---------------------------------------------------------------- #Soil Drain [Type = 3] Captured/Coded by County as an intermittent, upland drainage swale, generally without a visible scour channel. ---------------------------------------------------------------- Centerline through pond or lake [Type = 4] Non-tangible or null arc that is created in the central location of standing water to show continuity amongst incoming and outgoing streams. ---------------------------------------------------------------- Centerline through bridge or Culvert [Type = 5] Connect with straight line (null arc) from the last visible point. Nodes shall be placed at headwalls or culverts where visible, not clipped to road casing boundary. In all cases where a surface drainage features goes underground, use this code regardless of culvert or headwall presence. ---------------------------------------------------------------- Centerline across Paved Ditch [Type = 6] Digitize null centerline of paved ditch. Cap ends or join cleanly with headwalls, if present. Paved channels will be more heavily associated with stormwater drains and water impoundments. ---------------------------------------------------------------- Null Connectors [Type = 7] Null arcs designed to maintain connectivity and directionality of flow by connecting single line streams to double line stream centerlines or one double line stream centerline to another. ---------------------------------------------------------------- Discontinuous Drain [Type = 8] Drain that is not a continuous above ground feature or fails to connect to further downstream features. ---------------------------------------------------------------- Centerline of open (unpaved) channels or ditches [Type = 9] Unpaved, manmade drainage features normally adjacent to roadways. Digitize centerline of any trough greater than 200 feet in length. ---------------------------------------------------------------- Centerline through Potomac River [Type = 10] Null CL through Potomac River.
Overview_Description:
Entity_and_Attribute_Overview:
DR_CLASS: Flow characterization of drainage feature (as yet unmaintained by County)
Entity_and_Attribute_Detail_Citation:
Code Description ---- ------------------ A Alluvial F Unknown I Intermittent N Type not evaluated P Perennial
Overview_Description:
Entity_and_Attribute_Overview: DR_SOURCE: Source that created or edited feature class
Entity_and_Attribute_Detail_Citation:
Code Description ---- ------------------ 1 Legacy (pre 2002) 2 County 3 Contract
Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Contact_Position: Public Information Counter
Distribution_Liability:
Chapter 54.1-402 of the Code of Virginia.
"Any determination of topography or contours, or any depiction of physical improvements, property lines or boundaries is for general information only and shall not be used for the design, modification, or construction of improvements to real property or for flood plain determination."
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: GDB
Format_Specification: ESRI Geodatabase Feature Class
Digital_Transfer_Option:
Offline_Option:
Offline_Media: dvd
Fees:
Loudoun County distributes spatial data in ArcGIS database or shapefile or DXF format. Selected aerial imagery is also available.
Ordering_Instructions:
Visit our website at: <http://www.loudoun.gov/omagi> and click on "Maps and Data."  Hardcopy maps may also be available. Please contact the Mapping Office Public Information Counter for more information regarding all data requests.
Metadata_Reference_Information:
Metadata_Date: 20210427
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Loudoun County, VA, OMAGI
Contact_Position: Base Map Coordinator
Metadata_Standard_Name: FGDC Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Time_Convention: local time
Metadata_Use_Constraints:
This metadata reflects the source Geodatabase format and specific elements may not apply if your data is exported to SHP, DXF, or .e00 products. User must be aware that changes to data schema occur during data export that may not be reflected in this metadata, which represents Loudoun County's corporate geodatabase. Acknowledgement of Loudoun County would be appreciated in the use of this metadata.
Generated by mp version 2.9.12 on Fri Aug 06 14:05:13 2021