NHN Completeness Levels

pyramideNHN Completeness Levels realize the NHN Implementation Strategy which aims for a progressive creation of the National Hydro Network (NHN) in Canada. In the short term, its goal is to obtain a national coverage of basic NHN data, followed by an evolution through completeness levels and gradual updating of the product. The NHN creation through completeness levels aims at:

  • Simplifying the data creation processes;
  • Getting maximum benefit from automatic processes;
  • Facilitating the use of provincial/territorial data and capabilities;
  • Providing users with useful intermediate products while building the NHN.

Four completeness levels, from CL1 to CL4, define the content of the NHN product. The first level, Completeness Level 1, presents a version of the NHN product generated exclusively from an automated process. It targets a quick coverage of the country with minimal NHN data content. The last level, Completeness Level 4, presents a full NHN data content. Each completeness level meets the NHN product standards and specifications.

Tabular documents describing in detail the NHN completeness levels are also available and directly accessible through the following links:

  • NHN Completeness Levels Main Characteristics, 2008-03-15 [pdf 61 KB]
  • Detailed View of NHN Completeness Levels, 2008-03-15 [pdf 68 KB]

Finally, NHN data at various completeness levels can be subject to some particularities, deviations or differences compared to NHN standards and specifications. For more information on this matter, please refer to the Differences in NHN Data section.

National Hydro Network - Completeness Level 1 (NHN-CL1) - NETWORK

"Network Linear Flow Construction"

The first completeness level is defined by the NHN's automatic construction using National Topographic Data Base (NTDB) data from Natural Resources Canada. These data will gradually be replaced by current federal, provincial or territorial data in a subsequent completeness level.

The objective set out at this level is to produce the NHN using a fully automated process and make it available to the public within a one-year period (2008). At this level, some concepts are partially implemented. For example, Network Linear Flows are created for the entire NHN Work Unit, but their continuity is not assured between the source data's cartographic map sheets or tiles. The hydrographic network directionality (flow direction) is only partially built-in, especially in flat areas. Toponymy (geographical names) is mainly supported by a point type geometry and not necessarily linked to features via toponymic attributes. A fraction of the named NHN features will bear toponymic information in attribute. Subsequent completeness levels will enable the completion of features and concepts not dealt with at this level.

NHN-CL1 data may show particularities, deviations or differences as opposed to the National Hydro Network standards and specifications. For more information, refer to the Differences in NHN Data section.

National Hydro Network - Completeness Level 2 (NHN-CL2) - WATERBODY DEFINITION

"Waterbody Definition by Adding Delimiters"

The second completeness level defines waterbody areas. The main objective consists at delimiting the various types of Waterbodies by adding Delimiters, for example between lakes and area type watercourses. Network Linear Flows created at the previous level (NHN-CL1) are segmented by the newly added Delimiters. The updating process that usually follows the NHN-CL2 should minimally affect Network Linear Flows or network segments within waterbody areas. Completeness Level 2 stabilizes the hydrographic network since the majority of Network Linear Elements are present.

NHN-CL2 data may show particularities, deviations or differences as opposed to the National Hydro Network standards and specifications. For more information, refer to the Differences in NHN Data section.

National Hydro Network - Completeness Level 3 (NHN-CL3) - DATA CONTINUITY

"Hydrographic Network Structuring by NHN Work Unit"

The third completeness level aims at completing the hydrographic network structuring within a drainage area or NHN Work Unit.

Three main factors must be assured within a NHN Work Unit in order to comply with the NHN-CL3, namely:

  • Assure the linear network global continuity (Network Linear Flow geometric continuity);
  • Validate/Correct the flow direction of network linear segments (Network Linear Flow directionality);
  • Assure geometric continuity of toponymy (geographical names) provided as feature attributes

Even though it is preferable to update an NHN Work Unit before completing the NHN-CL3, this level can nevertheless be reached without data being updated. The NHN-CL3 ensures that all features required for network analysis are completed and validated.

NHN-CL3 data may show particularities, deviations or differences as opposed to the National Hydro Network standards and specifications. For more information, refer to the Differences in NHN Data section.

National Hydro Network - Completeness Level 4 (NHN-CL4) - TOPONYMY UPGRADE

"Toponymy Geometric Completion and Update"

The last toponymy (geographical names) update in the National Topographic Data Base (NTDB) dates back to 1995. Completeness Level 4 (NHN-CL4) is intended for the completion of toponymy in NHN data. This operation consists in modifying the geometry of toponyms not yet associated with NHN features and updating toponymic information using an official geographical names database. Official geographical names databases are from a province/territory or lacking these, the Canadian Geographical Names Data Base (CGNDB) 1997. This last step in building the NHN provides a full NHN content that meets the National Hydro Network Standard adopted by the CCOG in August 2004.

NHN-CL4 data may show particularities, deviations or differences as opposed to the National Hydro Network standards and specifications. For more information, refer to the Differences in NHN Data section.