Download
1 / 35
350 likes | 487 Vues
National Hydrography Dataset. Bill Smith. NHD Maintenance Training. U.S. Department of the Interior U.S. Geological Survey. Types of SubBasins. 1. Headwater 2. Chain 3. Frontal 4. Isolated??. Headwater – a SubBasin where flow begins. Chain – One subbasin flows into another.
E N D
National Hydrography Dataset Bill Smith NHD Maintenance Training U.S. Department of the Interior U.S. Geological Survey
Types of SubBasins • 1. Headwater • 2. Chain • 3. Frontal • 4. Isolated??
NHD Production Process for SubBasins 1:24,000-scale NHD was created based upon SubBasins. Created from various ‘BEST AVAILABLE’ 1:24,000-scale data, including: USGS DLGs USFS CFFs Local data (if available) Because various SubBasins were created by various personnel, production issues exist between adjoining SubBasins
NHD Stewards • The NHD is a living dataset • Revision updates needed • Quality updates needed • Organizations closest to the hydrography • are most aware of ground truth • Such organizations should have • the opportunity to serve as stewards • The USGS will assist
What is Stewardship? Distributed Maintenance Typically on a State-by-State basis Suited to regional needs Identifying a Primary Steward Agency recognized by entities within state as geospatial leader Acts as single POC to USGS Coordinates maintenance activities
What is Stewardship? (cont.) • Developing a Stewardship agreement • Roles defined in Memorandum of Understanding (MOU) • Draft “Boiler plate” MOU available, Example signed MOU’s available for review
Partner: Responsibilities and Procedures The Partner agrees to: Act as the single entity Represent the interests of the user community Coordinate with others for the maintenance of sub-basins. Accept input and adjudicate, and report the decision publicly.
Partner: Responsibilities and Procedures • Be responsive • Maintain an awareness of the activities of others • Provide contact information for management and technical issues. • Provide publicly available information on status of data stewardship activities. • Provide updates in the agreed upon format.
Partner: Responsibilities and Procedures • Provide metadata • Provide the USGS with updates that meet agreed upon quality standards • Maintain quality assurance as follows: • a. Strive to ensure that the data is error free • b. Ensure that the core content is included • Utilize nationally consistent reach codes.
USGS: Responsibilities and Procedures • The USGS agrees to: • Process transactions in timely manner • Provide assistance to State Stewardship program. • Provide Maintenance tools, documentation, and training • Develop solutions to incorporate State hydrographic data • Communicate Transaction status
USGS: Responsibilities and Procedures • Provide reach code allocator • Communicate NHD structure, format, or content changes. • Provide clear guidance for updates tracking. • Provide documentation on update validation. • Provide documentation on formats for update transactions. • Provide POC for management and technical issues.
Data Ownership and Rights • All data produced, updated, and maintained in the NHD is public domain and thus is available to any interested party.
Financial Commitments • The Memorandum of Agreement (MOU) does not constitute a financial commitment on the part of either partner, but rather supports the two agencies to work cooperatively to exchange updates and continually make improvements to the NHD.
Period of Agreement • The agreement becomes effective on the last date of signature by both partners and continues until modified by mutual consent or unless terminated within 60 days written notice by either partner. The agreement will be reviewed periodically and amended or revised when required.
What are the advantages for participating in NHD stewardship? • Change management (Live Database) • Statewide seamless dataset • Allows for regional studies • Share data • Update notification • Receive National updates • Events • Applications
NHD Production Process for SubBasins 1:24,000-scale NHD was created based upon SubBasins. Created from various ‘BEST AVAILABLE’ 1:24,000-scale data, including: USGS DLGs USFS CFFs Local data (if available) Because various SubBasins were created by various personnel, production issues exist between adjoining SubBasins
Main Issues with existing NHD SubRegion data Topology Issues Measure (M-Value) Issues Network Issues
Topology Issues in the NHD A user may find NHDFlowline features that intersect. Create Flowline Topology (1D) on the NHDFlowline feature class to check for: Features that overlap Features that self overlap Features that self intersect Features that are multi-part features a feature with one ComID, but is made up with more than one part.
Topology Issues in the NHD A user may find polygon features which overlap. Create WaterArea (2D) topology on the NHDArea and NHDWaterbody feature classes to check for: NHDAreas that overlap NHDWaterbodies that overlap NHDAreas that overlap NHDWaterbodies Note: There are some legal exceptions: SwampMarsh over a LakePond
Measures (M-Value) Issues in the NHD Measures (M-Value) - Used to Linear Reference ‘Events’ to the NHD. Measures are created based on ReachCodes. Several features may exist with the same ReachCode. Once a unique ReachCode is detected, MEASURES are created, from Start to End junctions. Start junction – 0% End junction – 100% Errors include: Inconsistent or opposing flow Disconnected ReachCodes or Gaps Branched ReachCodes Multi-part feature
Network Issues in the NHD Network - The Network allows a user to navigate the NHD. Can trace upstream or downstream. Are based on junction to junction connectivity. Tables are created (NHDFlow) defining START and END. The NHDFlow table may be used to create analysis software outside of a GIS. Allow modeling/navigation to resolve real world issues. Connectivity is the main factor in a network. Errors include: Inconsistent or opposing flow Isolated Networks Missing NHDFlowline features Gaps or breaks between NHDFlowline features. ‘Uninitialized’ versus ‘WithDigitized’
