Installing Charts

The potential danger to the mariner increases with digital charts because by zooming in, he can increase the chart scale beyond what can be supported by the source data. The constant and automatic update of the vessel’s position on the chart display can give the navigator a false sense of security, causing him to rely on the accuracy of a chart when the source data from which the chart was compiled cannot support the scale of the chart displayed. Bowditch 2002 Ed p 412.

OpenCPN does not come with any pre-installed charts. It is up to the user to find and install charts. Read on, and you will find detailed information about which chart formats that OpenCPN can display, as well as pointers to all available free charts that we know of.

To install charts OpenCPN must be pointed to a directory containing recognized Chart Formats. Don't point OpenCPN to individual charts. You must specify the directory that contains the charts. Download some charts (see Chart Sources) and organize them in a fashion that suits you.  You may want to consider storing them in a directory where they will not be tampered with or moved accidentally.
Open the Toolbox by clicking .  You are sent to the first tab "Settings". Tick the box "Show Chart Outlines". That will help you visualize the loaded charts.
 


Then click the tab "Charts".



Under "Available Chart Directories" navigate to your chart-directory. Above we have found the Brazil charts in the /home/thomas/charts/charts/BSB3/Brazil directory. When clicking the button "Add Selection" the selected chart directory appears in the box "Active Chart Directories". The screen-shots are from Linux, but this process works similarly on all platforms. All that remains is to click the "Ok" button. OpenCPN will then process your selection. You can now start using your charts.
Note that in OpenCPN you must add directories (folders) containing charts, not individual charts.

Start using your charts.
You can click and drag the chart with your mouse. The scroll wheel zooms in and out. Left clicking anywhere centers the view on that position. Right clicking brings up a menu with useful actions. Exactly what the menu contains depends on the circumstances. Read the rest of the manual for a full explanation.

If you are running OpenCPN for the first time you may see a black background instead of the charts you installed.  That simply means OpenCPN is pointed at a location that is not on any of the charts you installed.  Click and drag, or use the arrow keys, to move the view-point to the  location of one of your installed charts as descirbed under "A few hints" below. The first time you start OpenCPN the view will be centred on Georgetown in South Carolina.


Starting with vector charts?
If you are new to vector charts, including CM93 v2, on OpenCPN follow this quick-start guide:

1 Go to ToolBox ->Vector Charts and copy the settings below for the Display Category.


2 Press this button in the ToolBar to toggle text display.

These are not the perfect settings, but you will see most of what you expect from a vector chart.
As soon as you have made yourself reasonably comfortable with OpenCPN and before using Vector Charts for actual navigation, make sure you understand all the settings in the ToolBox-> Vector Chart Tab by reading this page.
Loading Vector Charts
When using a vector chart for the first time OpenCPN has to process the data, and transform the information to an internal display format. This can take some time, depending on your computer. This internal SENC chart is then saved for future use. The created files are quite large, but is in a format optimized for quick loading. The SENC files are saved in the SENC directory in the same place as the opencpn.conf file -opencpn.ini on windows.
You probably do not want to build SENCs for all of your loaded S57 ENCs unless you plan to actually go there....
For an advanced approach to building SENC files look here.
Updating Vector Charts
Publishers of Vector Charts, such as NOAA and EAHC issues regular updates. OpenCPN updates the created SENCs automatically. The chart itself, the base-chart, is named "name".000 , the first update is "name".001 and so on. As a user you only have to make sure that the update files are saved in the same place as the base-chart. In the case of a new edition of the chart a new "name".000 file is issued. Just replace the old file with the new file and OpenCPN will update the SENC file.

CM93 Charts



CM93-version2 Charts are different from the S57 vector charts and has it's own data structure consisting of a number of folders and files. To load these charts in OpenCPN just add the top directory to the list of "Active Chart Directories"
The CM93 top directory contains a number of (144) subdirectories named from
"00300000" to "04501020", as well as six other files. These sub directories each cover a geographical area of 40° x 40° . The first four numbers describes the latitude and the last four, the longitude of the SW corner of the area covered.
The key to understanding the numbers is to realize that CM93's coordinate system
of the world starts at the South Pole or to be exact at lat -90° long 0° and from there
proceeds North a East with a factor of 3 for each degree of lat and long.
The tile 00300000 hence has the SW corner at lat from -90° + 0030:3 = -80° or 80°S to
and longitude  0°E , and covers the area from 80°S latitude to 40°S and from 0° longitude to 40°E.
Looking at 04501020 it brakes down to lat -90° + 0450:3 = 60° and long 1020:3 = 340° subtracting 360° results in -20° or 20°W. So we have he SW corner at 60°N and 20°W .
One more example, the tle 03900840 has the SW corner at 40°N and 80°W.

Each of these sub-directories in turn contains directories with the individual charts. Ordered in scale from smallest to largest they are Z,A,B,C,D,E,F and G. Where Z contains  overview charts and G contains harbor plans. Note that, generally, not all of these are present in each subdirectory.

Z covers 40° x 40° deg area and OpenCPN typically uses 1:3.000.000 scale
A covers 20° x 20° deg area and OpenCPN typically uses 1:1.000.000 scale
B covers 10° x 10° deg area and OpenCPN typically uses 1:200.000 scale
down to
..
G covers 20' x 20' and OpenCPN typically uses 1:3500 scale.
The individual chart tiles in these directories have the same logic in the naming scheme as described above.



A few hints.

• If all is just black, with maybe some blue lines, you are viewing the background world vector shoreline chart. You must move to the geographical position of the charts you just loaded. As you come close you will see the outlines of your loaded charts, in red for raster charts and in green for S57 vector charts. Click in the rectangle created by the outlines, to activate, and view the chart.
• If you ticked the "Show Chart Outlines" box under the "Settings" tab the loaded charts will be outlined in red for raster and green for vector charts. In CM93 the charts will be outlined in purple. The smallest scale charts in CM93, the Z scale and A scale charts, will not be outlined. Neither will all available charts be visible as outlines at the same time. The reason for this is computing speed and clarity. Generally the next level or two of larger scale charts are shown. When large scale plans are available directly from A scale charts, with no intermediate charts, the outline of the larger scale charts will be visible from a zoom level between 1.5 and 2.0. Generally in areas where only A or Z scale charts are available, expect potentially dangerous omissions. Warning, do not use CM93 small scale charts alone for navigation without referring to other sources.
• Be aware that it is possible to "Over-zoom" charts in OpenCPN. A warning will appear on the display. Please respect that warning. It is recommended to not zoom more than a factor 2, for safe navigation. The actual zoom-factor appears in the lower right-hand corner of the display.
• It is safe and reasonably efficient to put all your charts except the CM93 database in one large directory, and set that directory in Toolbox->Charts. The CM93 database contains its own file and directory structure. The top-level directory only, of this database should be loaded, as described above, into OpenCPN.
  If you do a lot of chart downloads, updates, etc., then it will be faster to break the charts folder into smaller groups, and specify them individually in the Toolbox->Charts dialog. Consider using Chart Groups as well.
• "Scan Charts and Update Database " Use this option if you have made any changes to the contents of your chart directories, as for example after downloading new charts from NOAA, etc. It need not be checked if directories are added or subtracted, as the entire database will be scanned and updated automatically in this case.
• "Force Full Database Rebuild" is mainly aimed at users converting or correcting existing charts, in a situation where changes are made to the geo-referencing, outline of the chart, or other attributes in the kap file header section.
• OpenCPN,  supports  Mercator Charts, Transverse Mercator Charts, Universal Transverse Mercator (UTM) Charts and Polyconical Charts (used in parts of US and Canada). Charts using other projections will be displayed as if they were Mercator charts, but they will not be used for quilting.  Most charts are using one of the "Mercator" projections, so this limitation is not too bad.
  Other projections, such as Gnomonic, are mainly used in older, larger scale BA charts, for smaller areas, for example harbor plans, in scales larger than 1:50,000.
  The errors introduced in OpenCPN by treating these charts as Mercator are generally small, but be aware of this limitation.

A Linux/Unix Note
These operating systems have a problem handling chart names containing spaces and non ASCII characters. A typical example is Swedish chart names. To sort this out use the utility program "detox". Detox changes the file names so space becomes "_"; "(" and ")" become "-"; and "å","ä" and "ö" become "a","a" and "o", etc.

To see what "detox" suggests to do, try a dry run first, like this:
detox -n File_with_swedish_charts > outfile