# Tidal Boundary Continuous High The alignment of the limit of tidal water at Mean High Water (or Mean High Water Springs in Scotland), formed by merging individual [Tidal Boundary](https://docs.os.uk/osngd/data-structure/water/water-features/tidal-boundary) features.
Example showing Tidal Boundary Continuous High and Tidal Boundary Continuous Low features along a section of coastline. A background map has been included for context. The example shows a section of coastline where the new Tidal Boundary Continuous High Feature Type is marked with a blue solid line and the new Tidal Boundary Continuous Low Feature Type is marked by a red solid line.

Example showing Tidal Boundary Continuous High and Tidal Boundary Continuous Low features along a section of coastline. A background map has been included for context.

## Temporal filtering 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 25 September 2025; any data temporally filtered earlier than the specified earliest date noted for the data schema version may contain data inconsistencies. {% hint style="info" %} ## What is temporal filtering? Temporal filtering allows you to order a one-off snapshot of data from the OS NGD from a current or past date. It is an optional step when you create a new data package in OS Select+Build (the OS NGD download service). More information about temporal filtering on OS NGD feature types is available from the [Getting started with temporal filtering guide](https://docs.os.uk/osngd/getting-started/downloading-with-os-select+build/getting-started-with-data-packages/getting-started-with-temporal-filtering). {% endhint %} ## Feature type attributes 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. {% hint style="info" %} ## Loading OS NGD CSV files into databases Comma-separated values (CSV) file format is universally supported for easy ingestion into all major database products. Before loading OS NGD data contained in CSV files into a database, it is necessary to create relevant tables. Data definition language (DDL) statements for PostgreSQL, SQL Server and Oracle can be accessed in our [OS NGD Resources GitHub repository](https://github.com/OrdnanceSurvey/osngd-resources/tree/main/database-resources). For instructions on loading CSV files, see the [Getting Started with CSV](https://docs.os.uk/osngd/accessing-os-ngd/downloading-with-os-select+build/getting-started-with-csv/loading-csv-files) guide. {% endhint %} ### osid 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 (GeoJSON), String (GPKG), String (CSV) * **Nullable:** false * **Max Length:** 36 * **OS NGD API – Features Filterable:** Yes * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### versiondate Date when the version was last updated. * **Data Types:** String (GeoJSON), Date (GPKG), Date (CSV) * **Nullable:** false * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### versionavailablefromdate The date this version of the feature became the latest version. * **Data Types:** String (GeoJSON), DateTime (GPKG), DateTime (CSV) * **Nullable:** false * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### versionavailabletodate The date this version of the feature was superseded by an update or ceased to exist. * **Data Types:** String (GeoJSON), DateTime (GPKG), DateTime (CSV) * **Nullable:** true * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### changetype The type of change that generated a new version of the feature. * **Data Types:** String (GeoJSON), String (GPKG), String (CSV) * **Nullable:** false * **Code List Name:** [changetypevalue](https://docs.os.uk/osngd/code-lists/code-lists-overview/changetypevalue) * **Max Length:** 50 * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### geometry Geometry for the feature. * **Data Types:** Geometry (GeoJSON), Geometry (GPKG), WKT (CSV) * **Nullable:** false * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 * **Geometry Type:** LineString ### geometry\_length\_m The measured length of the geometry in metres. * **Data Types:** Number (GeoJSON), Float (GPKG), Real (CSV) * **Nullable:** false * **Precision:** 15 * **Scale:** 3 * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### geometry\_evidencedate The date on which the latest evidence was gathered to make an update if required. For example, the date of collection by a surveyor or third party information received. * **Data Types:** String (GeoJSON), Date (GPKG), Date (CSV) * **Nullable:** true * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### geometry\_updatedate Date when the attribute was last updated. * **Data Types:** String (GeoJSON), Date (GPKG), Date (CSV) * **Nullable:** false * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### theme The OS NGD theme to which this feature belongs. * **Data Types:** String (GeoJSON), String (GPKG), String (CSV) * **Nullable:** false * **Code List Name:** [themevalue](https://docs.os.uk/osngd/code-lists/code-lists-overview/themevalue) * **Max Length:** 40 * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### description A single descriptive value intended for a quick understanding of what the feature represents. * **Data Types:** String (GeoJSON), String (GPKG), String (CSV) * **Nullable:** false * **Code List Name:** [tidalboundarycontinuoushighdescriptionvalue](https://docs.os.uk/osngd/code-lists/code-lists-overview/tidalboundarycontinuoushighdescriptionvalue) * **Max Length:** 25 * **OS NGD API – Features Filterable:** Yes * **OS Select+Build Filterable:** Yes * **Data Schema Version:** 1.0 ### description\_evidencedate The date on which the latest evidence was gathered to make an update if required. For example, the date of collection by a surveyor or third party information received. * **Data Types:** String (GeoJSON), Date (GPKG), Date (CSV) * **Nullable:** true * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### description\_updatedate Date when the attribute was last updated. * **Data Types:** String (GeoJSON), Date (GPKG), Date (CSV) * **Nullable:** false * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0 ### iscoincidentwithlow Indication that the feature is both mean high water and mean low water and also exists in the Tidal Boundary Continuous Low dataset. * **Data Types:** Boolean (GeoJSON), Integer (GPKG), String (CSV) * **Nullable:** false * **OS NGD API – Features Filterable:** No * **OS Select+Build Filterable:** No * **Data Schema Version:** 1.0