Hydrographics
From CruisersWiki
The Cruisier's Wiki guide to finding Nautical Charts
Finding the right chart to include on a wiki page can take some research. There is no international system (yet) and so hydrographic charts of various countries can have some or all of the information.
Common hydrographic agencies are:
- NOAA (US)
- CHS (Canada)
- UKHO (UK)
- LINZ (New Zealand)
- DHN (Brazil)
- SHN (Argentina)
- AHS (Australia)
as well as many military and historic sources.
A useful tool to start with is Google Earth which will allow you to find a city or port on the world globe. From there, a neat tool called GeoGarage will allow you to find maps for most places of interest, just by zooming in on that location and looking at the numbers on the chart overlays. These are not the latest charts, but those that the various agencies are happy to release to the general public, and Notices to Seamen should still be consulted for the latest variations. Coastlines don't change much over time, but navigation aids and channel markers do. Once you have that chart number, try UKHO search engine to get the full title and scale for your webpage.
If an area isn't covered by these tools then a Google search usually reveals some useful data.
Try to list the smallest scale for the terrain being discussed, there's no point listing large scale maps at the level of a continent. Australia, for instance, is completely covered by one chart at 1:10000000 scale and six charts at 1:3500000 scale. As we drill down to view state coastlines and even further to individual ports, the maps get more detailed.
The Danish Hydrographic Office (KMS) categorizes the charts thus:
Chart Categories
- Passage/landfall Charts
- Scale: 1:2.000.000 to 1:350.000.
- These charts cover very large areas and are only to be used when navigating across open seas or oceans. These charts contain very limited amounts of nautical and hydrographical information. Close to shore, this information is sometimes omitted completely.
- Coastal Charts
- Scale: 1:350.000 to 1:75.000.
- These charts contain detailed nautical and hydrographical information, enabling safe navigation through main waterways and straits.
- Approach Charts
- Charts in the scale between 1:75.000 and 1:30.000.
- These charts contain detailed nautical and hydrographical information in order to safely approach the harbours shown in the area. In narrow straits or confined areas or in areas where a special scale chart covers the area, a simplification can have been done.
- Harbour charts & Special scale charts
- Charts produced in a scale larger than 1:30.000.
- These charts covers areas which are difficult to navigate such as narrow straits, harbours or anchorages.
Multiple sources can be listed on a wiki page if they are available. Often there is a British Admiralty chart for a region when nothing else can be found, and you can be sure that the US government has most charts as well. Both NOAA and NGA charts can be viewed online here.
Using cheap electronic charts on handheld devices is foolish, since they're based on small scale or outdated charts. If you value your yacht (and who doesn't?) always consult a proper chart with all the latest updates included. Many an otherwise competent sailor has lost his ship, crying that the rock, reef or sandbar they hit wasn't on the map. Don't let it happen to you.
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