Boundary High Water Mark
Last updated
Was this helpful?
Last updated
Was this helpful?
In the OS NGD Boundaries Collection, the mean high water (springs) mark is shown to the normal tidal limit (NTL). Areas of salt marsh, mudflats and so on often have extremely complicated tide lines. For ease of digitising and to reduce data volumes, mean high water may be generalised in these areas (not Scotland). The mean high water (springs) mark is represented in the OS NGD Boundaries Collection by a polyline feature. The mean high water (springs) mark is subject to continuous change, but the captured alignment of a tide line is a snapshot on one day. It is not practical to revise tide lines frequently.
The earliest date on which you can request a one-off snapshot of a date in the past for data in this feature type is 29 September 2022.
Any data temporally filtered earlier than the specified earliest date noted above for the data schema version may contain data inconsistencies.
The following sub-sections provide details about the attributes included with this feature type, their data types in the different output formats, and other important metadata about them.
Primary identifier for the feature. The OSID is a Globally Unique Identifier (GUID) and requires no centralised authority to ensure uniqueness. Note that the same OSID can occur in more than one feature type when a single feature is represented multiple times in the OS NGD.
Data Types: String (GPKG), String (CSV)
Nullable: false
Max Length: 36
OS Select+Build Filterable: No
Data Schema Version: 1.0
Date when the version was last updated.
Data Types: Date (GPKG), Date (CSV)
Nullable: false
OS Select+Build Filterable: No
Data Schema Version: 1.0
The date this version of the feature became the latest version.
Data Types: DateTime (GPKG), DateTime (CSV)
Nullable: false
OS Select+Build Filterable: No
Data Schema Version: 1.0
The date this version of the feature was superseded by an update or ceased to exist.
Data Types: DateTime (GPKG), DateTime (CSV)
Nullable: true
OS Select+Build Filterable: No
Data Schema Version: 1.0
The type of change that generated a new version of the feature.
Data Types: String (GPKG), String (CSV)
Nullable: false
Code List Name: changetypevalue
Max Length: 50
OS Select+Build Filterable: No
Data Schema Version: 1.0
Geometry for the feature.
Data Types: Geometry (GPKG), WKT (CSV)
Nullable: false
OS Select+Build Filterable: No
Data Schema Version: 1.0
Geometry Type: LineString
The measured length of the geometry in metres.
Data Types: Float (GPKG), Real (CSV)
Nullable: false
Precision: 18
Scale: 6
OS Select+Build Filterable: No
Data Schema Version: 1.0
The OS NGD theme to which this feature belongs.
Data Types: String (GPKG), String (CSV)
Nullable: false
Code List Name: themevalue
Max Length: 40
OS Select+Build Filterable: No
Data Schema Version: 1.0
A single descriptive value intended for a quick understanding of what the feature represents.
Data Types: String (GPKG), String (CSV)
Nullable: false
Code List Name: boundaryhighwatermarkdescriptionvalue
Max Length: 50
OS Select+Build Filterable: Yes
Data Schema Version: 1.0
A single description value for boundary type.
Data Types: String (GPKG), String (CSV)
Nullable: false
Code List Name: boundarytypevalue
Max Length: 50
OS Select+Build Filterable: Yes
Data Schema Version: 1.0