4 Foot Topographic Contours of Loudoun County, VA (2023)

Metadata:

• Identification_Information
• Data_Quality_Information
• Spatial_Data_Organization_Information
• Spatial_Reference_Information
• Entity_and_Attribute_Information
• Distribution_Information
• Metadata_Reference_Information

Identification_Information:

Citation:

Citation_Information:

Publication_Date: 20240824

Title: 4 Foot Topographic Contours of Loudoun County, VA (2023)

Geospatial_Data_Presentation_Form: vector digital data

Description:

Abstract:

The 4' contour interval dataset is a result of a state Virginia Geographic Information Network (VGIN) contract that Loudoun County was able to contribute to & receive data for. The 4' contour dataset replaced the previous 5' contour dataset that was part of OMAGI's Basemap Update in 2010. 2012 was the first year of data upates to the new 4' contour datset, 2013-2020 were a continuation of the update process.Elevation contours are a base map data layer derived by automated processes and processed for cartographic representation at 1:2400 scale. The line features represent the 4' contour intervals, and 20' index contours as mapped from above and are mapped to National Map Accuracy Standards (NMAS). Contour lines are developed in accordance with the contour guidelines for 4- foot topographic maps. Every fifth contour line is an index contour. All contour lines are unbroken except where pasing through dense ground cover buildings and bridges.

Purpose:

The surface of the Earth is continuously changing at many levels; local, regional, national and global scales. Changes in terrain can have significant impacts for people, the economy, and the environment. Therefore information derived from contours can contribute in many ways.
Typically contours are used for planning land management applications such as :
Land development Site design Agricultural planning Utilities Floodplain analysis Route location Emergency response FEMA mapping Storm water management Disaster preparedness and response Water supply and quality Land transportation and safety

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 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:

Progress: Complete

Maintenance_and_Update_Frequency: Annually

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -77.983601

East_Bounding_Coordinate: -77.308375

North_Bounding_Coordinate: 39.335910

South_Bounding_Coordinate: 38.836886

Keywords:

Theme:

Theme_Keyword_Thesaurus: none: Employee generated

Theme_Keyword: Topography, Elevation, Contours, Terrain, Surface, Topo

Theme:

Theme_Keyword_Thesaurus: ISO 19115 Topic Categories

Theme_Keyword: elevation

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

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: 20130514

Title:

Digital Orthoimagery and Digital Terrain Model Production Services, VA-081223-SANB, 2009

Source_Scale_Denominator: 2400

Type_of_Source_Media: dvd

Source_Citation_Abbreviation:

Digital Orthoimagery and Digital Terrain Model Production Services, VA-081223-SANB, 2009

Source_Contribution:

Initial contract with Sanborn for creation of new countywide 4' topo contours

Process_Step:

Process_Description:

1. Existing VBMP DTM data was reviewed and updated using stereo imagery flown in April 2010. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2010 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset was loaded to enterprise SDE

Process_Date: 20100816

Process_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA OMAGI

Contact_Position: Base Map Cartographer

Source_Information:

Source_Scale_Denominator: 2400

Type_of_Source_Media: disc

Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01407, 2013

Source_Citation:

Citation_Information:

Title: Base Map Maintenance Services Contract, QQ-01407, 2013

Publication_Date: 20141218

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. Existing Loudoun DTM data was reviewed and updated using stereo imagery flown in April 2013. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2013 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset was loaded to enterprise SDE

Process_Date: 20140514

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20150803

Title: Base Map Maintenance Services Contract, QQ-01857, 2014

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.

Process_Step:

Process_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA, OMAGI

Process_Description:

1. Existing Loudoun DTM data was reviewed and updated using stereo imagery flown in April 2014. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2014 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset was loaded to enterprise SDE

Process_Date: 20150803

Process_Step:

Process_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA, OMAGI

Process_Description:

1. Existing Loudoun DTM data was reviewed and updated using stereo imagery flown in Spring 2015. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2015 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset was loaded to enterprise SDE

Process_Date: 20160825

Source_Information:

Source_Scale_Denominator: 2400

Type_of_Source_Media: None

Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01857, 2015

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. Existing Loudoun DTM data was reviewed and updated using stereo imagery flown in Spring 2016. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2016 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset was loaded to enterprise SDE

Process_Date: 20170804

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_Information:

Source_Citation:

Citation_Information:

Title: Base Map Maintenance Services Contract, QQ-01857, 2017

Publication_Date: 20181213

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. Existing Loudoun DTM data was reviewed and updated using stereo imagery flown in Spring 2017. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2017 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset 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_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA, OMAGI

Process_Description:

1. Existing Loudoun DTM data was reviewed and updated using stereo imagery flown in Spring 2018. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2018 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset was loaded to enterprise SDE

Process_Date: 20190904

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20210427

Title:

RFQ 108783, Agreement for Service for Base Map Maintenance Services, 2020

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.

Process_Step:

Process_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA, OMAGI

Process_Description:

1. Existing Loudoun DTM data was reviewed and updated using stereo imagery flown in Spring 2020. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2020 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset was loaded to enterprise SDE

Process_Date: 20210427

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20211206

Title:

RFQ 108783, Agreement for Service for Base Map Maintenance Services, 2020

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 South/Central region of Loudoun County.

Process_Step:

Process_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA, OMAGI

Process_Description:

1. Existing Loudoun DTM data was reviewed and updated using stereo imagery flown in Spring 2020. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2020 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset was loaded to enterprise SDE

Process_Date: 20211206

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20230724

Title:

RFQ 108783, Agreement for Service for Base Map Maintenance Services, 2022

Source_Scale_Denominator: 2400

Type_of_Source_Media: None

Source_Citation_Abbreviation:

RFQ 108783, Agreement for Service for Base Map Maintenance Services, 2022

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_Person_Primary:

Contact_Organization: Loudoun County, VA, OMAGI

Process_Description:

1. Existing Loudoun DTM data was reviewed and updated using stereo imagery flown in Spring 2022. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2022 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset was loaded to enterprise SDE

Process_Date: 20230724

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20240824

Title:

RFQ 108783, Agreement for Service for Base Map Maintenance Services, 2023

Source_Scale_Denominator: 2400

Type_of_Source_Media: None

Source_Citation_Abbreviation:

RFQ 108783, Agreement for Service for Base Map Maintenance Services, 2023

Source_Contribution:

Captured and updated photogrammetric stereo models covering selected areas in the Northern region of Loudoun County.

Process_Step:

Process_Description:

Existing Loudoun DTM data was reviewed and updated using stereo imagery flown in Spring 2023. 2. The DTM was modified in stereo as appropriate in the areas requiring update or where changes to ground conditions had occured. 3. Contours were generated, coded and edge matched to ensure consistency across the county-wide dataset. 4. All clean up tools were run. 5. Data was exported to PGDB. 6. QA/ QC Program was run and reported errors were corrected. 7. Updated data was checked against 2023 Orthos where necessary for completeness. 8. All the delivery blocks were merged into a single PGDB. 9. Countywide complete dataset was loaded to enterprise SDE

Process_Date: 20240824

Positional_Accuracy:

Vertical_Positional_Accuracy:

Quantitative_Vertical_Positional_Accuracy_Assessment:

Vertical_Positional_Accuracy_Explanation:

Tested points have been measured at 2.3 US Survey Feet vertical at 95% confidence level.

Vertical_Positional_Accuracy_Value: RMSE (Z or Elev.) = 1.17; Tested 2.3 US Survey fee

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: 290403

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: 0.001666666666667

Ordinate_Resolution: 0.001666666666667

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.TOPO_4FT_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: TO_TELEV

Attribute_Definition: Elevation of individual contour arc in feet

Attribute_Definition_Source: Automatically generated

Attribute_Domain_Values:

Unrepresentable_Domain: 0 - 2000 feet of elevation change in Loudoun County

Attribute:

Attribute_Label: TO_SOURCE

Attribute_Definition: Source that created or edited feature class

Attribute_Definition_Source: Loudoun County

Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: See Entity and Attribute Detail Citation for Data Dictionary

Attribute:

Attribute_Label: TO_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_Domain_Values:

Unrepresentable_Domain: User generated text

Attribute:

Attribute_Label: TO_UPD_USER

Attribute_Definition:

for public distribution. Internal User ID of editor creating or modifying a feature. Intended for track and audit features internally by County.

Attribute_Definition_Source: Loudoun County

Attribute:

Attribute_Label: SHAPE

Attribute_Definition: Feature geometry.

Attribute_Definition_Source: ESRI

Attribute_Domain_Values:

Unrepresentable_Domain: Coordinates defining the features.

Attribute:

Attribute_Label: TO_TYPE

Attribute_Definition: Classification of Topo Contour

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)

Attribute_Definition: Length of Topo feature in SDE units

Overview_Description:

Entity_and_Attribute_Overview: TO_TYPE: Designation of Contour type

Entity_and_Attribute_Detail_Citation:

TO_TYPE 1 - Index - every 5th contour
TO_TYPE 2- Intermediate - all other contours at 4' intervals
TO_TYPE 3 - Index Obscured - every 5th contour that falls in an obscured or null area (dense ground cover/buildings and under bridges)
TO_TYPE 4 - Intermediate Obscured/Null - all other contours that fall in an obscured or null area (dense ground cover/buildings and under bridges)

Overview_Description:

Entity_and_Attribute_Overview: TO_SOURCE: Source that created or edited feature class

Entity_and_Attribute_Detail_Citation:

Code Description
0 Unknown 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

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

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: 20240824

Metadata_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_Electronic_Mail_Address: mapping@loudoun.gov

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 other 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.