OpenCPN Manual

Table Of Contents

Getting Started


Getting started using OpenCPN consists of 3 basic steps:

  1. Installing OpenCPN
  2. Installing Nautical Charts to be read by OpenCPN
  3. *(Optional) Setting up GPS to "talk" to your computer and OpenCPN
Completing these 3 steps will get you started and allow you to check out the program.  Later, after exploring the program, you may want to read through the Basic Featues and Advanced Features sections to really get a good grasp of what the program offers.  If you still have questions or would just like to get in touch with other OpenCPN users, there is also a fairly large community behind OpenCPN. You can find us in this Cruiser's forum.

Installing OpenCPN

Windows 98/ME/2000/XP/Vista/7

  • Download the installation package for Windows from
  • Run the downloaded installer.
  • If upgrading from a previous version of OpenCPN, there is no need to uninstall the previous version. Simply install the new version and it will upgrade OpenCPN, saving all your existing configuration and preferences.
  • If this is a new installation, click on the Toolbox icon Toolbox Settings and configure your GPS source, chart directories, and other settings.


32bit Ubuntu/Debian Distributions

  • Download the .deb from
  • Install the package via dpkg:
    • $ sudo dpkg -i <downloaded_file.deb> 
    • The binary will be installed to /usr/local/bin/opencpn.
  • If this is a new installation, click on the Toolbox icon Toolbox Settings and configure your GPS source, chart directories, and other settings.

Other 32 and 64bit Linux Distributions and the BSD operating systems.

  • Currently other distributions requires compiling the source. This will involve resolving various dependencies and is for folks comfortable with developing on Linux.
  • Download the source from from or directly from the CVS server. The SourceForge link for this project is
  • Interested in maintaining a package for your favorite Linux distribution? Follow the SourceForge link above.
  • This also includes the different BSD distributions. Report your experiences back to the forum.


Location of Important Files
  •  It is important to know the location of the log file and the configuration file on your computer. If you ask questions on the forum, there is a fair chance that you will be asked about the content in these files. Once you get familiar with OpenCPN, have a look at the files!
  • On Linux the "opencpn.log" is in your home directory.
    The "opencpn.conf" is in a hidden directory, called "opencpn", also in your home directory.
    For a quick way to view the files you can try these commands.
    $gedit `echo $HOME/opencpn.log`
    $gedit `echo $HOME/.opencpn/opencpn.conf`
    Of course you can swap "gedit" for your favourite editor.
  • On Windows 2000, XP and Vista and Windows 7 the two files, opencpn.log and opencpn.ini are in a location governed by the environmental variable %APPDATA%.
    From any command prompt enter: explorer %APPDATA%\opencpn. Windows Explorer will start with the correct folder open.
  • As an alternative follow these instructions:
    1 Go to Start -> Run
    2 Enter Code: %APPDATA%\opencpn
    3 Click OK!
  • On Windows 7, instead of "Run" use   "Search programs and files".
  • Note that some folders in the path %APPDATA% are hidden, so to be able to navigate to the log- and ini-file you may have to adjust your settings.

Installing Charts

To install charts OpenCPN must be pointed to a directory containing charts of a recognized format. Don't point OpenCPN to individual charts, you must specify the directory that contains the charts. Download some charts (see below) 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 accidentaly.
Open the Toolbox by clicking .  You are sent to the first tab "Settings", tick the box "Show Chart Outlines", this 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 South China Sea vector charts in the /opt/Navigation/ENC directory. When clicking the button "Add Selection" the selected chart directory appears in the box "Active Chart Directories". The screenshots are from Linux, but this process works similar 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.

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.
  • 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.
  • Be aware that it is possible to "Over-zoom" charts in OpenCPN. A warning will appear on the display. Please respect this warning. It is recommended to not zoom more than a factor 2, for safe navigation. You will find the actual zoom-factor 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.
    However, 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.
  • The option "Force Full Database Rebuild" is mainly aimed at users converting charts, in a situation where minor changes or corrections are made.
  • OpenCPN, for now, only supports the Mercator chart projection. Charts using other projections will be displayed as if the were Mercator charts. Most charts are using Mercator projection, so this limitation is not to bad.
    Other projections, such as Transverse Mercator or Gnomonic, are mainly used in larger scale 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.

Where to find charts.

  • To get you started quickly, here are three sample charts from Puerto Rico: one, two and three. Right click and use "Save Link As", or similar. Just clicking shows you the actual file as a text file, this is an advanced subject, to be treated later.
  • For those interested in U.S. waters, S57 vector charts are now available for free download from NOAA. Find all the charts you need, both raster (RNC) and ENC's, for your region through NOAA OCS Website at :
  • Links to a wide selection of ENC's for U.S. inland waters and other countries are available at :
  • Brazil publishes free raster charts (RNC) for their whole coast and new charts for inland water is published regularly.There is also coverage for part of Antarctica. Here is a direct link to the download page: Brazilean Charts. Don't miss the link to CARTAS DE RIOS at the bottom of this page.
  • The East Asia Hydrographic Commission is providing free offshore S57 vector charts for the South China Sea area at : .  The motivation for releasing these charts is well worth reading.

    Realizing that official and high quality small scale ENCs conforming with the established IHO standard were not available for the SCS, the EAHC MSs decided to cooperate closely and resolve the situation so that mariners could use most up-to-date chart information for voyage planning and enhancing safety of navigation, rather than resorted to some commercially developed electronic products which were either prepared in proprietary formats, or containing unofficial data with very infrequent updating.

  • Colombia and Australia publishes sample S57 single charts.
  • New Zealand publishes high quality pictures of almost all their charts. There are efforts underway to convert these charts to a format compatible with OpenCPN. This project has moved quickly since the start, in the last few month of 2009.  For the latest on this subject, check the "Chart" thread in the Forum.

Chart Formats

OpenCPN supported chart formats:

BSB / RNC / KAP Versions 1, 2 and 3.
(BSB Version 4 and later are not supported due to proprietary encryption algorithms.)

NOS/GEO Version 1 Subsequent versions are probably supported but need to be tested. However, this format is obsolete for new charts.

CM93 Version 2.
(C-map Version 3 and later are not supported.)

S57/S52 (ENC).
(S63 Encrypted ENC is not supported. This is the format for the majority of newly produced vector charts from many national hydrographic offices. S63 charts are exactly the same as S57 except the they are encrypted to keep them from being illegally distributed.)

Other formats, that with some effort, can be used.

Generally many chart pictures in gif, jpeg, png, tif and other formats can be used, when properly geo-referenced, to generate KAP file (BSB / RNC) that OpenCPN can display. For the details about this process see the chart thread in the forum.  Also, make sure to browse around the forum as there are a handfull of other interesting chart related threads.

WCI charts generated with SeaClear and MapCal can also be transformed to BSB charts and used by OpenCPN.

 Before Maptech started to produce BSB charts the HDR format was used in the late eighties to mid nineties. These charts consists of many picture tiles in pcx format, more than 100 tiles is not unusual. The tiles can be merged to one picture and then used as any other picture to make an OpenCPN compatible chart. For details on this process see the Chart Conversion Manual  and this post and the following posts in the forum.

 The HDR format is from an era when computer-memory and processing power were less powerful than today, as a consequence these charts are not of the same quality as more modern charts. Furthermore, most of these charts are not using WGS84 as reference datum. These charts should not be the first choice, but can be useful if nothing else is available.

Other not supported formats.

The Hydrographic Chart Raster Format (HCRF), used by the United Kingdom Hydrographic Offices' ARCS (Admiralty Raster Chart Service), Australian Hydrographic Services' Seafarer products and the NZMariner, New Zealands Official charts, are not supported.  This is also due to proprietary encryption algorithms and copyright issues.

Mapmedia's various chart formats are also not supported.

Setting Up GPS

Windows 98/ME/2000/XP/Vista/7

To use OpenCPN with a GPS, a GPS receiver is needed.

There are a variety of possible choices for a GPS receiver:

  • A computer, such as a Sony Vaio P has a built in GPS receiver
  • A NMEA Expander to amplify a nmea stream to multiple listeners
  • A handheld GPS receiver
  • A dedicated GPS receiver

The remainder of this section describes using OpenCPN with a dedicated GPS receiver, however, the instructions for a dedicated receiver will be similar for any serial/USB connected NMEA data stream.

A Dedicated GPS Receiver

There are several companies making dedicated GPS receivers. The Supplementary Hardware section for GPS devices lists several manufacturers.

NMEA has traditionally been implemented as a serial protocol and therefore, even if a USB connection is used, there needs to be a USB to Serial Port conversion. The specific driver for the each GPS receiver will handle this conversion.

Configuring BU-353

 It is not necessary to use the installation disk to setup the BU-353. Following the steps listed below will result in the latest driver being installed.

  1. Download the latest driver from Prolific -
  2. Unzip and install the driver
  3. Plug in the BU-353.
  4. Start -> (Right Click) My Computer -> Properties -> Hardware ->Device Manager
    or Start->Run devmgmt.msc
  5. Expand Ports
  6. Look for the “Prolific USB-to-Serial Comm Port” and note the com port number (e.g., COM4)
  7. Right click on the “Prolific USB-to-Serial Comm Port”. Choose Driver
  8. Select 4800 bits per second, 8 data bits, None parity, 1 stop bit, and None for Flow Control 
  9. Start OpenCPN
  10. Click on the ToolBox Icon Toolbox Settings
  11. Select GPS
  12. Under NMEA Data Source select the Com port noted in #6
  13. Choose OK
  14. Select Auto Follow to center the map over your GPS location


There is a small LED located on the BU-353. If the LED is off there is no power being received. Check the connection.

If the LED is solid it indicates the BU-353 is searching for a GPS signal. Try moving the GPS receiver to a clear location.

If the LED is flashing it indicates the BU-353 has a position fix and is transmitting data.

  1. Try viewing the NMEA data stream in OpenCPN. Choose ToolBox->GPS->click Show GPS/NMEA Data Stream Window
  2. Alternatively, a diagnostic program is included on the installation CD called GPSInfo.exe. Launch this program to install the diagnostic utility.

If it appears that the NMEA data stream is being received, the most likely issue is that OpenCPN is not centered over your location. Click AutoFollow to center the map at your GPS location.

Known Issues

If you change the USB port for the GPS receiver Prolific will reassign the COM port number. This will require repeating steps 4-12 above.

On some computer / GPS receiver combinations when the computer resumes from Stand By the GPS receiver will no longer transmit its NMEA data stream.

A workaround for this issue is provided by using a COM port splitter such as XPort

  1. Download XPort.
  2. Unzip it to a folder of your choice
  3. Double Click XPort.exe
  4. Set the Baud Rate to 4800
  5. Under Enable Ports add an entry for COM10
  6. Click “Find GPS”. The port returned should match the port identified in Step #6 in the Configuring BU-353 Section
  7. Select Prolific USB-to-Serial Comm Port in the check box section
  8. Return to OpenCPN
  9. Click on the ToolBox Icon Toolbox Settings
  10. Select GPS
  11. Under NMEA Data Source change the Com port to COM10


    Ubuntu/Debian Distributions

    • Install the gpsd and gpsd-clients packages
        $ sudo apt-get install gpsd gpsd-clients
    • Go to Toolbox-->GPS and select "Network GPSD" as your "NMEA Data Source"
    • On Ubuntu 9.10 and later, that is realy all you have to do. When you plug in your gps this will trigger gpsd to start.
    • If this this doesn't work for you, follow the instructions below.
    • Check first if gpsd is working:
      $ ps aux | grep gpsd
      nobody   12338  0.3  0.1   4124  1448 ?        S<s  18:31   0:00 gpsd -F /var/run/gpsd.sock
      you    12356  0.0  0.0   3036   800 pts/3    S+   18:32   0:00 grep --color=tty -d skip gpsd
      This or similar responses indicate that gpsd is running. If you only have something like the second line, is not running.
    • Determine which device your GPS is on your linux system by checking the startup.  Look for a line that says something about GPS and /dev/ttyUSB#
      • $ dmesg
        Or even better, after connecting a gps mouse, BU-353, we look for a dmesg by running this command.
        $ dmesg | grep tty
        and get this response back.
        [13616.095305] usb 2-3: pl2303 converter now attached to ttyUSB0
    • Add a script to start gpsd.  I saved mine as startgps and set thet executeable attribute.  Edit line 3 to match your device, ie /dev/ttyUSB0
      • #!/bin/sh
         sudo killall gpsd
         sudo gpsd -n -D 2 /dev/ttyUSB0
         xgps -speedunits knots -l
    • Run the script:
      • $ ./startgps
    If this is a new installation, click on the Toolbox icon Toolbox Settings and configure your GPS source, chart directories, and other settings.

    Other Distributions

    Bluetooth GPS Ubuntu.

    If you have a bluetooth GPS  you will need to first configure it through the standard Ubuntu Bluetooth "set up new device " proceedure.

    Once you have done that you will need to find what the address of the GPS is. To do that you run this command.

    sudo hcitool scan

    it will then start looking for the Bluetooth GPS and hopefully find your GPS. You should see something similar.

    Scanning ...
        00:1C:88:10:D3:4D    iBT-GPS

    In this case i have a IBT-GPS at address     00:1C:88:10:D3:4D   (Your GPS address will be different)

    Next we have to bind the GPS address to a "virtual" device OpenCPN understands in this case rfcomm0

    we do this with the following command.

    sudo rfcomm bind /dev/rfcomm0 00:1C:88:10:D3:4D        Note put your GPS address in this line

    It is my understanding you do not have to run these commands each time your linux is restarted as it will remeber your GPS address.

    Now all you need to do is go into OpenCPN Toolbox and select GPS

    Now in the NMEA Data Source options select from the pulldown menu


    Thats it you should now have a Bluetooth GPS Connected.

    Mac OSX

    This article is in not complete. You are welcome to assist in its construction by editing it as well. Everyone is allowed to edit after creating an account and/or logging in.
    • Add howto here

Basic Features

Let's take a look at some of OpenCPN's basic features.
Quick look at OpenCPN button toolbar and their functions
How to zoom in and out on a chart
How to scale in and out to different charts
Status bar color definitions and explanations
How to have chart follow gps or quickly center boat in chart
How to view tides and current station data  on chart
Definition of "hot keys"
How to record your track history and overlay on chart

Toolbar Buttons

From left to right:

Zoom In (Learn more)

Zoom Out (Learn more)

Scale Next Chart Down (Learn more)

Scale Next Chart Up (Learn more)

Create Route (Learn more)

Find/Follow Boat (Learn more)

Launch Toolbox

Show Vector Text Labels on Vector Chart

Show/Hide Currents On Chart

Show/Hide Tides On Chart


Import GPX File**

Export GPX File**

Toggle Track On/Off**

Grib Overlay**

Change Color Scheme

**Note: These icons can be enabled or disabled from the ToolBox

Printer 'ToolBox-Settings-Show Printing Icon' to hide or un-hide.
GPX IN, and GPX OUT 'ToolBox-Etc.-Show GPX Icons' to hide or un-hide.
Tracks 'ToolBox-Etc.-Show Track Icon' to hide or un-hide.
Grib 'ToolBox-GRIB' to hide or un-hide.

Zoom in & out

 These buttons allow you to zoom in and out on the chart currently being displayed.  


 Will zoom the chart in for more detail.

 Will zoom the chart view out for more area.


Alternatively, the + and - keys on your keyboard will zoom in and out.  If you have a mouse with a scroll wheel, it can also be used to quickly zoom in and out.

Scaling Charts

 These buttons will allow you to change the scale of chart you are using.


Will scale down/out to the next chart of less detail but greater area, if available, within the current view

 Will scale up/in to the next chart of greater detail but less area, if available, within the current view


Hint: Scaling down and up coresponds to available charts left and right on the status bar.


Status Bar

On the bottom is the Status Bar(s). Activated from 'Tool Box-Show Status Bar'.

The top line, 'Chart Selection Bar', has the following description.

If a larger scale chart (large scale = greater detail in a smaller area) is available for the location of your mouse pointer, you will see more than one segmented bar. The segmented color bars in the Status Bar represent:

  • Blue for Raster
  • Green For ENC's
  • Brown/Yellow for CM93 charts
  • The current chart displays as a lighter shade of its color

When you hover the mouse pointer over the bar, a thumbnail of the chart will appear under the SCALE IN/OUT icons. By clicking on the appropriate bar, or using the appropriate HOT KEYS, you will switch to the chart shown in the thumbnail. This feature is especially useful if you wish to view an ENC or a Raster chart of the same area.

The bottom line starting from the left, has the position of the GPS that feeds OpenCPN (your ship or boat). SOG, COG, Cursor (position), From Ownship and TrueScale are in other boxes.

Auto Follow

  • Clicking the Auto Follow button  will center the chart directly on your vessel's current GPS location.
  • This is useful for two different situations:
  1. When you have panned the map away from your current location and want to quickly move back to your vessel.
  2. When underway, this will keep the display on the chart around your vessel, with the boat at the center of the chart.
  • Note: Panning the chart will disable this mode. Simply click  again to turn Auto Follow mode back on.

Tides and Currents


  • Tide and Current predictions are not available for all areas.
  • As with all predictions, the displayed values are calculated using mathematical models and actual tides and currents will vary.


Enable Tides and Currents Display

  • Click the toolbar button to see tide stations.
  • Select to see current stations.
  • Important: tide and currents will not be displayed unless these toolbar buttons are selected.


Displaying Tides

  • Available tide stations will show on the chart as green graphs with a "T" logo:

  • Right click the green icon  to see tidal graph:


Displaying Currents

  • Available current stations will show on the chart as orange arrows:


  • Arrow indicates current direction and strength - the bigger the arrow, the more current.
  • Right click the orange box  to see current graph:


Hot Keys

  • Arrow Keys, Moves the chart view
  • + or Ctrl + Z Zoom In
  • - or Ctrl + X Zoom Out
  • F2 Toggle Auto Follow ON/OFF
  • F3 or Ctrl + S Show / hide ENC Text
  • F4 Starts the measure tool. Escape : Stops it.
  • F5 Toggle Screen Brightness
  • F7 or Ctrl + Left-Arrow     Larger Scale Chart (Scale In)
  • F8 or Ctrl + Right-Arrow   Smaller Scale Chart (Scale Out)
  • F12 or Ctrl + O Show/Hide Chart Outlines
  • Ctrl + L-Arrow or F7 Larger Scale Chart (Scale In)      
  • Ctrl + M Drop Marker at current cursor position.
  • Ctrl + O or F12 Show/Hide Chart Outlines
  • Ctrl + Q Quits OpenCPN
  • Ctrl + R-Arrow or F8 Smaller Scale Chart (Scale Out)
  • Ctrl + S or F3 Show / hide ENC Text
  • Ctrl +space Man Over Board, sets MOB Marker at current GPS position.

Ship Track

This article is in not complete. You are welcome to assist in its construction by editing it as well. Everyone is allowed to edit after creating an account and/or logging in.

Advanced Features

Let's take a look at some of OpenCPN's advanced features.

How to overlay AIS target data from AIS reciever data stream on chart
How to import and export, waypoints, tracks, and routes in and out of OpenCPN
How to overlay GRIB file data on a chart in OpenCPN
Creating and using routes and marks
An explanation of the toolbox ( )
Viewing and customizing vector chart symbols, labels and data display


This article is in not complete. You are welcome to assist in its construction by editing it as well. Everyone is allowed to edit after creating an account and/or logging in.

Data Import/Export

  • OpenCPN can save and load waypoints and routes using the GPX transfer format.
  • This lets you save your routes and marks so you can have more than the active ones - for example to do route planning, or archive existing data.
  • GPX format is supported by a wide variety of programs.
  • The  and  buttons must be enabled in the toolbox/settings in order to use this feature:

  • You can have as many saved files as you wish, there are no limits on the number of saved files.
  • Use this for passage planning by saving multiple possible routes for a passage.
  • Save routes for historical/log purposes.


This article is in not complete. You are welcome to assist in its construction by editing it as well. Everyone is allowed to edit after creating an account and/or logging in.


TODO: Tracklog?

Planning Data

Creating and Importing Great Circle Routes

GPX import can be used for many things, three sample applications follows below. First, look at this picture. Planning a trip from Cape Town to Freemantle ?

Here you have two imported routes, the Southern route is a pure Great Circle, the middle route is a Composite Great Circle, and then the normal Rhumb Line furthest to the north.
A Great Circle is the shortest distance between two point on the globe. A composite route is the same thing with the additional condition to stay below a limiting latitude, in this case 39°30'S. A rhumb line is a straight line on a Mercator chart. The Mercator projection is the standard for OpenCPN.

Let us compare the distances involved.
  • The pure great circle is 4610 nautical miles (M)
  • The great circle as plotted with 5° of longitude between the waypoints is 4627 M
  • The pure composite route, limited by latitude 39°30’ S is 4651M
  • The composite route as plotted with 3° of longitude between waypoints (for the great circles) is 4669 M.
  • The rhumb line is 4843 M.
So the advantage of a great circle is obvious. The disadvantages, in this case are many.
Colder weather, stronger winds, higher seas and perhaps even icebergs. The great circle is just one factor in the decision making when planning a route, the weather is likely to be the deciding factor in most cases.

A great circle route  is created with  the "gc" Ruby script, that is cross platform.
To create a gpx file containing a great circle you have to enter the departure points lat & long, followed by the destination points lat & long and the optionally a limiting latitude for composite sailing and the distance in long between waypoints, default is set to 5°.

Need to see some offshore weather observations?

NOAAs  NDBC site gives access to a lot of offshore observations from buoys and ships worldwide.
To easy visualize all this data the "ShipWxRep" script transform a limited set of all the available data into gpx waypoints. The format, as seen above is "wind direction, wind speed, time for observation, and air pressure". This can be helpful when evaluating the accuracy of grib files, even though the best tool in this respect probably is a calibrated digital barometer.

Plotting Miami Tropical Forecast Advisories.

If you only have access to low bandwith internet, this script is a way to quickly plott the contents of, for example an email, containing the forcast advisory. In any case, it is a good idea to have the forecast track of a tropical system available where you normally do your navigation and planning.

Download the scripts here. For some help run each script without arguments.

GRIB Weather

OpenCPN has a built in lightweight grib weather file viewer, with a limited set of features, aimed at being useful while under way. It is not possible to download grib files from within OpenCPN. Many external sources for grib files are available however,  Franks-Weather  is a good starting point.
  • To display grib files as an overlay on your normal charts you have to first activate the grib icon
  • Go to and select the GRIB tab.

  • Tick the "Show GRIB tab" box. Tick the next box as well, unless you are on old hardware. Not ticking the "High Definition Graphics" box can help to speed up the grib display, in such cases.
  • Here you see the Grib icon in the tool bar.
  • The Next step is to click the icon, which brings up the Grib Display Control. Use the upper part of this window to navigate to, and select your grib files. The grib files will then be appear in the control. See picture above.
  • Click on the ">" in front of the gribfile. The individual forecasts contained in the gribfile, is then displayed under the gribfile heading.
  • Click on one of the forecasts and it will be displayed. When you move the cursor over the grib display, the values for wind etc will be displayed for the cursor position, in the lower part of the "Grib Display Control". Here you can select what grib values to view. Note that not all gribfiles contains wave data.
  • OpenCPN will display most grib file formats, but as it is a fairly new feature, bug reports are very welcome.

What is a grib file?

  • If you are not familiar with grib weather files, make sure you understand the basics, before you start to use them. It is essential to understand the limitations of weather forecasts in the grib format. It is also worth pointing out that gribs are not reliable near tropical systems.
  • To get started with gribs and to find sources for downloads, check Franks-Weather.
  • A very good book is David Burch: Modern Marine Weather, with a thorough treatment of the subject.
  • A few files including lectures on  tropical weather and gribs are available here.
  • ZyGrib is a free and open-source software(FOSS) dedicated grib viewer.

Routes and Marks


 Will initiate the creation of a route.  When clicked the cursor changes to a  ( ) pencil. Left click along the desired route you want to make. This will leave sequential waypoints as you click along.  If your desired route extends off the currently displayed chart, move the route cursor into the desired area.  You can zoom in and out with the mouse scroll wheel or keyboard +/- keys during route creating.  You can also right click and select 'MAX DETAIL HERE' or 'Scale Out' during route creation. When finished right click and choose end route from the context menu.

You sould now have an inactve (Blue) route.  Active routes are Red, inactivated routes are Blue.

Multiple Routes 

OpenCPN currently has no provision to hide routes, so all your routes will show on the chart all the time.

HACK: To keep the chart clear of useful but un-needed routes follow these steps:
• Create a folder called 'GPX_Routes.'
• Create your route.
• Turn on In and Out GPX icons with Tool Box-Etc-Show GPX Icons.
• 'GPX OUT' with a descriptive file name and save it in a created folder called GPX_Routes.
• Delete the route from the chart.
• You can export all your routes as one big file or export and delete a route as you create them
• When needed simply use the 'GPX IN' to open the route file.    

yachtvalhalla discovered a workaround to get rid of the way points left on the chart when a route has been imported and then deleted.

1. Right-click on any waypoint in the route and select 'Delete All waypoints'.
2. Say 'Yes' to: 'Are you sure you want to delete <ALL> waypoints?'
3. Right-click on the route line and select either 'Delete route' or 'Delete all routes'.

4. Answer in the affirmative.


You can create a mark by rightclicking anywhere in the map, and selecting "Drop Mark Here" from the menu. The mark will have a triangle icon, to change that rightclick the icon and select "Mark Properties".

You can move the mark by dragging it around.

When creating routes, openCPN will ask if it should use a nearby mark if any, when you add a routepoint.

You can delete a mark by rightclicking its icon, and selecting "Delete Mark". Deleting a mark that is part of a route, will also change the route.

Saving and Loading Routes and Marks

Toolbox (Settings)

This article is in not complete. You are welcome to assist in its construction by editing it as well. Everyone is allowed to edit after creating an account and/or logging in.

Vector Chart Display

This article is in not complete. You are welcome to assist in its construction by editing it as well. Everyone is allowed to edit after creating an account and/or logging in.

NMEA Sentences

OpenCPN Recognized NMEA Sentences:

  1. HDM - Heading, Magnetic
  2. HDG - Magnetic heading, deviation, variation
  3. HDT - Heading, True
  4. RMB - Recommended Minimum Navigation Information
    1. Status, V = Navigation receiver warning
    2. Cross Track Error - nautical miles
    3. Direction to Steer, Left or Right
    4. TO Waypoint ID
    5. FROM Waypoint ID
    6. Destination Waypoint Latitude
    7. N or S
    8. Destination Waypoint Longitude
    9. E or W
    10. Range to destination in nautical miles
    11. Bearing to destination in degrees True
    12. Destination closing velocity in knots
    13. Arrival Status, A = Arrival Circle Entered
  5. RMC -Recommended Minimum Navigation Information
    1. Time (UTC)
    2. Status, V = Navigation receiver warning
    3. Latitude
    4. N or S
    5. Longitude
    6. E or W
    7. Speed over ground, knots
    8. Track made good, degrees true
    9. Date, ddmmyy
    10. Magnetic Variation, degrees
    11. E or W
  6. WPL - Waypoint Location
    1. Latitude
    2. N or S (North or South)
    3. Longitude
    4. E or W (East or West)
    5. Waypoint Name
  7. RTE - Routes
    1. Total number of messages being transmitted
    2. Message Number
    3. Message Mode
      1. c = complete route, all waypoints
      2. w = working route, the waypoint you just left, the waypoint you're heading to, then all the rest
    4. Waypoint ID
    5. More Waypoints
  8. GLL - Geographic Position, Latitude / Longitude
    1. Latitude
    2. N or S (North or South)
    3. Longitude
    4. E or W (East or West)
    5. Time (UTC)
    6. Status A - Data Valid, V - Data Invalid
  9. VTG - Track Made Good and Ground Speed
    1. Track Degrees
    2. T = True
    3. Track Degrees
    4. M = Magnetic
    5. Speed Knots
    6. N = Knots
    7. Speed Kilometers Per Hour
    8. K = Kilometres Per Hour
  10. VDM - Automatic Information System (AIS) position reports from other vessels
    1. Time (UTC)
    2. MMSI Number
    3. Latitude
    4. Longitude
    5. Speed Knots
    6. Heading
    7. Course over ground
    8. Rate of turn
    9. Navigation status


The feature being rendered is S57 Text relating to 'M_QUAL'.

This is a meta-object describing the quality of data shown. The Attribute of interest is CATZOC, or "Category of Zone of Confidence". The value on most US ENC's is "6", or "un-assessed". Thus, the 'U'.

You can turn this symbol off in OpenCPN by de-selecting the box next to M_QUAL in 'Tool Box' / 'Vector Charts' tab 'Mariners Standard' selection list box.

To learn the acronyms used in this application search the S57 'Object and Attribute' catalog at:

Yes. I had originally created and maintained all my routes and waypoints in SeaClear, exported them, loaded them into GPSUtility (for Windows) and saved them as text files.

To import into OpenCPN  I opened all my text files (routes and waypoints) with GPSUtility, saved that out as one big gpx file, and loaded it into OpenCPN. Works like a champ.

I've edited them and saved them back out as GPX files with no trouble.

Individual routes can be edited and saved in appropriately named GPX files.

Chances are the chart file is corrupted. Note the name and number of the suspect chart and replace it with a fresh download.

NOTE: A list of the charts with their names and file names can be found in the README.TEXT that accompanies the charts downloaded from NOOA.

Some unzip utilities for Linux are problematic when opening ECN's. If there are many corrupt charts in your download, try using a different unzip utility.

Raster charts display bearings and headings as straight, measurable lines on the chart. Similarly, Vector ENC's are rendered as Mercator projections in OpenCPN and most other ECS's for the same reason.

For typical coastal navigation, errors which occur using rhumb line instead of great circle calculations are small for the distances usually covered by one chart.

Mercator Charts and Mercator navigation is the standard for most navigational purposes. Other terms used instead of "Mercator Sailing" is "Loxodrome Sailing" or "Rhumb Line Sailing".

OpenCPN uses Mercator Sailing and cannot directly display Great Circles, but through GPX route import , Great Circle Routes can be used as explained on this page in the wiki.

This article is in not complete. You are welcome to assist in its construction by editing it as well. Everyone is allowed to edit after creating and account and/or logging in.

License and Authors


OpenCPN is licensed under the GNU General Public License (GPL)
David S Register
OpenCPN Lead Developer
Mark A Sikes
OpenCPN CoDeveloper
Thomas Haller
GPX Import/Export Implementation
Will Kamp
Toolbar Icon design
Richard Smith
OpenCPN CoDeveloper, MacOSX
David Herring
OpenCPN CoDeveloper, MacOSX
Philip Lange
OpenCPN Documentation
Ron Kuris
wxWidgets Support
Julian Smart, Robert Roebling et al
wxWidgets Authors
Sylvain Duclos
S52 Presentation Library code
Manish P. Pagey
Serial Port Library
David Flater
XTIDE tide and current code
Frank Warmerdam
GDAL Class Library
Mike Higgins
BSB Chart Format Detail
Samuel R. Blackburn
NMEA0183 Class Library
Atul Narkhede
Polygon Graphics utilities
Jan C. Depner
WVS Chart Library
Stuart Cunningham, et al
BSB Chart Georeferencing Algorithms
John F. Waers
UTM Conversion Algorithms
Carsten Tschach
UTM Conversion Algorithms
Ed Williams
Great Circle Formulary
Philippe Bekaert
CIE->RGB Color Conversion Matrix
Robert Lipe
Garmin USB GPS Interface