HydroSpatial Technical Specification

Structure and Scale

SeaZone Hydrospatial is provided in six individual Topic Layers. Each Topic Layer is broken down into Themes, which in turn contain Feature Types.

The Bathymetry and Elevation Topic Layer is available in two scale bands:

• BE Best Available comprises data from the largest scale chart available at any given location and compiled at a nominal scale of 1:25,000
• BE Offshore Only comprises data from the largest offshore scale chart available at any given location and compiled at a nominal scale of 1:250,000

The other five Topic Layers comprise a combination of scale independent source data and best or largest scale charted data available.

A gridded (or raster) bathymetry dataset is supplied within the Bathymetry & Elevation Topic Layer engineered from best available scale chart data including spot soundings in two scale bands:

• BE Best Available includes a 1 arcsecond grid (approximately 30m cell size)
• BE Offshore Only includes a 6 arcsecond grids (approximately 180m cell size)

The reference level of the depth data approximates to Lowest Astronomical Tide (LAT). The method used to produce the grid is triangulation with linear interpolation, with breaklines and contour analysis. These grids are supplied in WGS84 Latitude/ Longitude.

Technical Standards

In creating SeaZone Hydrospatial, SeaZone has complied with internationally recognised standards where they exist. The dataset's structure is founded on the International Hydrographic Organisation's (IHO) standard for hydrographic data (IHO S-57).

However, SeaZone Hydrospatial includes many more Feature Types than is required for navigational charting. Consequently, SeaZone has extended the S-57 Feature Catalogue for SeaZone Hydrospatial to include the NATO standard for AML (Additional Military Layers). In addition, to take account of real world objects that are not included in either S-57 or AML, SeaZone has created its own extended Feature Catalogue for marine geographic information.

Please note that soundings are not included within SeaZone Hydrospatial. Gridded Bathymetry is supplied to replace these in the Bathymetry & Elevation Topic Layer. If soundings data is required for modelling purposes then please refer to SeaZone Digital Survey Bathymetry.

Coordinate Reference System

Coordinate System	Ellipsoidal
Horizontal Datum	WGS84
Vertical Datum	Chart Datum

Other datums and projections are available on request and may be subject to additional costs.

Supply Formats

SeaZone Hydrospatial is supplied with a GIS Project so that the data can be displayed fully symbolised and attributed on opening, saving project time and costs.

Software	File format	Project File
ArcGIS	Shape File (SHP)	Hydrospatial.mxd
MapInfo	MapInfo Table (TAB)	SeaZone Hydrospatial.wor
Cadcorp	Base Dataset (BDS)	SeaZone Hydrospatial.sis

Gridded Bathymetry is supplied as either ESRI Grids, ASCII grids (.asc) or MapInfo Grids (.mig). Supply will vary depending on the users GIS system. Layer files are also supplied for use in ESRI and these should be loaded rather than the raw grid files.

If you wish to load SeaZone data onto a relational database such as Oracle Spatial or ESRI ArcSDE, please contact us or state your requirement in your Quotation Request Form. If you require other non-standard formats please do contact us to discuss.