How are Imray charts different from official charts?
We forge close ties with the UKHO and other hydrographic offices worldwide, and licence data from them. We tailor the official hydrographic office data – which is primarily aimed at commercial shipping - to make it more useful for small craft.
There’s a common misunderstanding that Imray charts are simply the same information as official charts but re-packaged or recoloured.
But, we add verified small craft information to our charts and present all of the data at more appropriate scales for the small craft navigator. There’s an emphasis on coastal and harbour detail.
This customised combination of official data and small craft information is what makes Imray charts so useful.
Imray chart or official chart?
Compare a plan from an Imray chart (left) with an official chart (right). The Imray chart shows a small craft anchorage outside the breakwater, lit beacons marking harbour approach (rather than (buoyed), depths within harbour (rather than Unsurveyed), harbour facilities for small craft, contact details and a note explaining visiting yacht guidelines, availability of fuel and location. The Imray plan is larger scale (more detailed) and additional Imray information comes from a range of sources, including research by authors for pilot books
1. Devising the chart scheme
Here is an example of an area in production – the Bristol Channel with some of the Imray product limits shown. The first stage in the production of our charts is to devise a scheme - the area that the chart or chart pack will cover. This is based on logical sailing areas at useful scales. For example, the passage from a headland to a harbour; an overview of an island; an approach to a river or estuary. This example shows the Bristol Channel against a generic map backdrop. The Imray chart extents are selected in red.
2. Visualising the charts
This shows how the actual charts will look once the scheme above has been realised.
3. Importing the raw source data
We license the official Electronic Navigational Chart (ENC) data from the hydrographic offices and import it into our database in an International Hydrographic Organisation standard format, S-57. Like all chart producers, we receive new deliveries of data on a quarterly basis. This shows the raw ENC data for the Bristol Channel. This forms the basis for both electronic and paper charts, but requires interpretation and editing to make it useful. A lot of data is shown on screen, at many different scales.
4. Transforming the data
Using automated techniques, the data is imported, transformed and symbolised to Imray specifications. Data contained within the ENCs that is not relevant for small craft is removed (e.g. pilot boarding stations, deep water dangers, etc.) to retain clarity and make space for additional detail added later (eg. small craft facilities from pilot guides). We use familiar International Hydrographic Organisation standard symbols where available. Additional small craft symbols are created if necessary.
5. Trimming the data
Data is trimmed to the boundaries of the chart limits required.
6. Adding soundings (depth data)
Depth information in the form of individual depths (soundings) are added from the ENC sources.The depths are simply filtered to match the scale of the output paper chart, data comes directly from the ENC. It starts to look much more like an Imray chart now.
7. Adding Imray data
Additional data is added to the ENC source material. Sources are always meticulously verified, and include Imray pilot books, local experts, local port authorities and marinas, satellite imagery, etc. All of the data is traceable and its source recorded. This ensures that the charts are perfect for small craft and leisure customers.
8. Final updates
Because the source data is only supplied by the hydrographic offices on a quarterly basis, final checks of Notices to Mariners, Imray chart correction notices, lights, etc. are made prior to publication to ensure the latest updates are included.
9. The final chart is compiled
The final result is the Imray chart. The data is compiled, verified (manual quality control checks and automated quality control delivered through software tools), validated (compared to pilot volumes and local expert knowledge to ensure that it is correct for our customers, and is consistent across Imray product, and visually checked as a final paper product, outside of the software environment, to ensure quality. Then, it's published as a paper chart, or as a raster Imray Digital Chart.
10. Printing and packaging
Paper chart files are then sent to our Print Room or to Print on Demand agents for printing and packaging. We print on bespoke water resistant paper using a HP PageWide large format printing press. Charts are then folded and inserted into sturdy recycled PVC wallets, or available flat on request.