A division of HR Wallingford

Frequently asked questions

We've provided answers to some of the most commonly asked questions below. If you can't find the information you need here, please contact us for help.


Are any SeaZone data available free of charge?

Our mapping product HydroView Now: Basemap is available on a free-to-use licence. This product consists of key bathymetry feature types and a global digital terrain model (DTM). HydroView Now: Basemap is specifically designed to be visualised alongside land-focussed mapping APIs such as Google Maps, Bing Maps or OpenStreetMap. It is the ideal product for use as a contextual mapping backdrop to support marine spatial planning or situational awareness.

You can also download free data for evaluation. The evaluation data is not feature limited, enabling you to try out the data for yourself in a GIS or other software.

Can I try SeaZone data before buying?

Our sample data is available free of charge for an area around Milford Haven, South Wales, United Kingdom. The sample data includes HydroSpatial Global, HydroSpatial Base, HydroSpatial One, TruDepth Grids, TruDepth Points, Charted Points and HydroView Charts.

To download our sample data, go to http://www.seazone.com/sample-data

How can I get my data incorporated into SeaZone products?

We are always looking to expand our marine data. Please contact our sales team with details of the data you can supply.

What data is available for students?

Following an agreement made between the Higher Education Funding Council for England (HEFCE) and SeaZone Solutions, EDINA has developed a subscription service which delivers marine maps and data to Higher and Further Education institutions.

Marine Digimap is part of the Digimap Collection of on-line mapping and data delivery facilities. Users will be able to view maps through their web browser, save them for printing and download the marine and coastal data for use in geographical information systems.

Students will be able to access HydroView Charts (nautical raster maps) and HydroSpatial One (vector marine features) products. If you are unsure of what data is best for you, please download the sample data.


What acknowledgement/copyright statement must I use when printing off SeaZone data?

Acknowledgements and notices depend on which mapping product you are using and the region. If no specific region is defined, geographic data derived from any SeaZone marine data product shall include the following acknowledgement: “© SeaZone Solutions, Year, [SZ Licence Number](where available)”.

For data in specific geographic regions, please refer to Annex A of the SeaZone Data License .

Why do I need to choose between 1 user, 2 users, 5 users or more when I purchase SeaZone data?

You need a licence for the number of people who will be able to access the data, even if they will not be using it at the same time. If SeaZone data is loaded onto a single workstation, with five people able to access it, you will need a licence covering five users. This licence model is consistent with the licensing terms Seazone has with its data suppliers.


Could you please clarify the Contiguous Zone limit feature in the HydroSpatial products?

In the HydroSpatial products, certain National Limits have been given the feature type of Contiguous Zone (CONZNE – feature code: 3100 to 3103), even if they do not entirely reflect the current definition of a Contiguous Zone.

CONZNE is officially defined as “A zone contiguous to a coastal State's territorial sea, which may not extend beyond 24 nautical miles from the baselines from which the breadth of the territorial sea is measured. The coastal state may exercise certain control in this zone subject to the provisions of International Law.” (IHO Dictionary, S-32, 5th Edition, 993). However, the Renewable Energy Zone (REZ) and Marine Pollution Zone (MARPOL) zones do extend beyond the 24nm limit. These Zones can be identified using the attribute OBJNAM with attribute values of either ‘Renewable Energy Zone’ or ‘MARPOL Limit’.

In HydroSpatial, the inner limit for Renewable Energy Zone (REZ) and Marine Pollution Zone (MARPOL) is the 12nm territorial sea boundary. The Territorial Sea already includes the legislative applications for the REZ and MARPOL under the Territorial Sea legislation, which, in effect, makes these zones applicable from the Normal Baseline to their outer limit.

We intend to reclassify these two Zones, in the mean time they will stay as part of the CONZNE feature type.

HydroView Chart image looks distorted when loaded

If you find an image looks distorted then please notify SeaZone using the technical support request form. Please provide information about the coordinate systems you are working with.

HydroView Chart opens in ESRI ArcGIS but only displays a black image

You may be missing the LZW Compression Key. Go to the ESRI website at http://support.esri.com/index.cfm?fa=knowledgebase.techarticles.articleShow&d=27172 to find the instructions on how to register the Key.

I am asked for projection information when I open HydroView Charts in MapInfo

The projection for the Chart has not been updated in the MapInfo Projection file. For information on how to update the projection for the charts, please refer to text file “MapInfo Readme.txt” supplied with the HydroView Charts.

If you cannot see this file, please do contact us.

I am having difficulty reprojecting HydroView Charts

Some HydroView Chart files have an unknown Datum, which means there are no transformation parameters to translate the data to WGS84. The Geotiffs will still load into GIS software, however if being used in conjunction with user’s own data referenced to WGS84, there will be an offset between the two datasets. The value of this offset will be unknown and may amount to hundreds of metres.

Please contact SeaZone using the technical support request form for a list of HydroView Chart files affected.

Is the Mean High Water Spring (MHWS) line included in HydroSpatial One?

The Mean High Water Spring (MHWS) line is not included in HydroSpatial One. However the outer edge of the Land Area features (SZFEATURE = ‘LNDARE’ in Natural and Physical Features topic layer) is effectively the MHWS line.

It can also be found using the landward boundary of the Intertidal zone (SZFEATCODE = 4201 in Bathymetry & Elevation topic layer).

The height of MHWS relative to Chart Datum can be found in the following two features T_HMON (Tidal heights from observed readings) and T_NHMN (Tidal heights from predictions). T_HMON and T_NHMN can be found within the Climate and Oceanography topic layer. (Attribute T_MHWS).

Is the Mean Low Water Spring (MLWS) line included in HydroSpatial One?

At present the Mean Low Water Spring (MLWS) line is not included in HydroSpatial One. The nearest feature would be the Chart Datum or Lowest Astronomical Tide (LAT) line (SZFEATURE = ‘DEPCNT’ and VALDCO = 0 in Bathymetry & Elevation topic layer). MLWS line would always sit closer to shore than the LAT line as it is an average.

The height of MLWS relative to Chart Datum can be found in the following two features T_HMON (Tidal heights from observed readings) and T_NHMN (Tidal heights from predictions). T_HMON and T_NHMN can be found within the Climate and Oceanography topic layer. (Attribute T_MLWS).

What versions of ESRI software are supported?

From 1 Oct 2013 we will only provide data compatible with ESRI ArcGIS 9.2 and above. This includes symbolised MXDs, style files, and an option of shapefile, File GeoDatabase (FGDB) and Personal GeoDatabase (PGDB) files.

Why can I see a misalignment of HydroSpatial One and Ordnance Survey Mapping at the coastal interface?

If the shift across the dataset seems to be consistent, it is likely to be due to the transformation between OSGB National Grid and WGS84. Amongst the various transformation options, the OSTN02 is the most appropriate to use, however it has limited applicability offshore and may require your terrestrial data to be transformed to an appropriate offshore Coordinate Reference System (CRS) Please consult your ESRI user manual for more information on how to do transform your terrestrial data.

More information on the OSTN02 transformation can be found at:

Why can I see two identical features in HydroSpatial?

As we receive data from multiple sources, there are occasions where the feature may appear twice - once from each source. This most commonly occurs when one source is S57 and the other is a definitive source. Often the features have slightly different coordinates. To check the source of features, look at the attribute SZSOURCE.

At present we cannot remove one of the features or one of the datasets until both datasets have been deconflicted to be sure all features are present. In general if one feature has source 'S57', it is likely that the second representation is from another source e.g. 'UKHO' or 'UKDEAL'. It can then be assumed that the second source is more likely to be of use as it may have additional attributes.

Why have I received overlapping data?

If you have ordered multiple Predefined Regions and load multiple regions into the same GIS project then there will be an overlap at the boundaries. This is to ensure that if a single predefined region is ordered it contains the whole of the national limits relative to that region. For example the predefined regions of England and Scotland are split along the Eng-Sco boundary. If there were no overlaps then each region would contain only sections of the boundary and not the complete line, depending on which tile is assigned to which region.

At present the only solution to this issue is to store the data in a spatial database as data can be extracted and supplied in a more appropriate format for a database environment. We are happy to discuss this option with you, please contact us.

Why isn't the SZLABEL field always populated?

The SZLABEL field is populated with the value that is most commonly used for labelling the feature in question. If there is more than one commonly used value, then SZLABEL field is left as null. The users can then choose which attribute they require in this field.


For Depth Contours (DEPCNT) the VALDCO (Value of Depth Contour) is the most useful attribute, which is used to populate the SZLABEL field. With ADMARE (Administrative Areas) the OBJNAM (Object Name) is the most commonly used attribute for labelling and so is populated in SZLABEL field.
However in the case of Depth Areas (DEPARE) there are two important fields - DRVAL1 and DRVAL2 (Depth Range Value 1 and 2). These values denote the upper and lower bounds of the Depth Area. In this case, the SZLABEL field for DEPARE features is left as null and the user need to choose which attribute they require. We do not make any recommendation on the best label for this feature.

For further information contact SeaZone sales support

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