The National Topographic Data Base (NTDB) comprises digital vector data sets that cover the entire Canadian landmass. Geomatics Canada has digitized and structured thousands of topographic maps, creating a complete and uniform product that can be highly useful in a broad range of industries. The NTDB includes features such as watercourses, urban areas, railways, roads, vegetation, and relief. The organizational unit for the NTDB is the National Topographic System (NTS), based on the North American Datum of 1983 (NAD83). Each file (data set) consists of one NTS unit at the 1:250,000 scale. The ground data is depicted through points, lines, and areas.
The contour interval for this dataset is 20 meters.
Purpose:
The NTDB provides a base of properly structured vector data (segmentation, mathematical closure, connection and sharing between entities) designed and suited for geographic information system (GIS) applications. It also can be used for preparing thematic maps.
Supplemental Information:
As of February 2008, this product is no longer subject to discrepancies treatment process.
The data are free from any spatial inconsistencies such as overshoots, undershoots, and area misclosures. To obtain this result, two relations are defined: connection and sharing.
Completeness Report:
Generally speaking, data sets covering maps that exceed the theoretical NTS limits at the 1:250,000 scale are separated and placed into their own data set. The international boundary automatically becomes the data set limit. The NTDB contains only data that lies within Canadian borders, even when the boundary coincides with the centre of a river. Data from maps with border breaks along the international boundary, those from a new territory resulting from a change in the reference surface, and a few special cases can deviate from regular NTS limits and be included in a special territory with irregular limits.
Positional Accuracy:
Horizontal Positional Accuracy:
Horizontal Positional Accuracy Report:
The accuracy of geometric representation data is given by the difference between the position of the geometric representation associated with an entity and the real ground position of the corresponding topographic feature, as measured with respect to the geodetic network. The NTDB dataset horizontal positional accuracy assessment can vary from one occurrence of an entity to the next. The maximum horizontal accuracy value extracted from all sources in the dataset is provided when available.
The altimetric accuracy of the source material is provided when available. It is expressed as the Linear Map Accuracy Standard (LMAS), obtained according to the equation below: Linear Map Accuracy Standard: LMAS = 1.6449 σ z σ z = standard deviation of the elevation.
The maximum accuracy values extracted from all sources in the dataset is provided when available.
FGDC Content Standard for Digital Geospatial Metadata
Metadata Standard Version:
FGDC-STD-001-1998
Metadata Use Constraints:
Only the English XML metadata file is valid according to the XML (W3C) schema as defined by the Federal Geographic Data Committee (FGDC) (http://www.fgdc.gov). The French version of the XML metadata file does not respect the domain of values, which is only available in English in certain fields, and exists solely for the presentation of information.
Users must ensure that they use the FGDC XML schema with the English version of the XML metadata to validate the metadata.