# 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](/osngd/data-structure/water/water-features/tidal-boundary.md) 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](/osngd/getting-started/downloading-with-os-select+build/getting-started-with-data-packages/getting-started-with-temporal-filtering.md). {% 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](/osngd/code-lists/code-lists-overview/changetypevalue.md) * **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](/osngd/code-lists/code-lists-overview/themevalue.md) * **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](/osngd/code-lists/code-lists-overview/tidalboundarycontinuoushighdescriptionvalue.md) * **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 --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.os.uk/osngd/data-structure/water/water-features/tidal-boundary-continuous-high.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.