Thursday, 23 April 2015

GoogleEarth KAP library for OpenCPN and SEAiq

Hi everyone,
For several years I have been creating and swapping GoogleEarth imagery for use in the free chartplotter OpenCPN.  The imagery is captured using GoogleEarth and GE2KAP while online and produces KAP files for use offline in OpenCPN.  Perfect as an extra aid to navigation in poorly charted areas, as described in my 2012 post here.

All the imagery I have created and which I have collected from others is intended to be shared.  I have shared on an individual basis so far.  The data is now available online.

The library is on Dropbox here.

For those who return to the library looking for new or updated information: click on the "Modified" column heading in Dropbox.  This will sort the files by modification date with most recent at the top.

First download and store somewhere safe the file "_readmefirst.txt".  Keep it for offline use.  The contents of the file are below since it provides much of what I need to explain here.  Please read on!

                               A Guide to using 
                     Zen Again's Dropbox KAP File Library
                        for use with OpenCPN and SEAiq

Origin and Further Distribution
The KAP files in this library have been generated by various cruisers 
including myself.  All who have provided files to me have indicated their 
willingness for me to distribute them further.  The only proviso we make is 
that they be further freely shared to assist other cruisers.

Intended Applications
The KAP files have been tested in OpenCPN and SEAiq using the latest versions
available at the above date.

File Naming
The ZIP files are named in the following formats:
A. <Region>_<Country>_<Locality>.zip or
B. <Australia>_<State>_<Locality>.zip

File Size
The KAP files are split into modest size ZIP files for two reasons:
1. To allow the selection of specific KAPs of interest without having to 
   download large files.
2. To allow for use in SEAiq which (since it runs on tablets) could be 
   slowed dramatically if many hundreds of KAPs are loaded.

For those with pre-existing OpenCPN chart folders such as:
  MacOSX:  /user/Shared/charts/opencpn/ge/<region> or 
  Windows: /Users/Public/charts/opencpn/ge/<region> where region is Asia, Indian etc
simply add to (or replace) the existing contents with the contents of the 
ZIP files you download here.

For those with pre-existing SEAiq chart ZIP files simply add my zip files 
nearby and use iTunes to add them to (or later delete them from) SEAiq. 

Using KAP Files
See the following blog posts:
Using GoogleEarth Imagery for Marine Navigation

Making KAP Files

GoogleEarth Imagery on iPad

GoogleEarth Imagery on Raspberry Pi

The library will be updated from time to time.  Individual files may be updated 
so check the date stamp of files you use.  New files may be added so check for 
new files in your region of interest.

If you would like me to add your images to this library just let me know.

GoogleEarth images FADE TO BLACK a few hundred metres from land!!!


Now to add some help for installing charts in OpenCPN and SEAiq.

Installing and Configuring in OpenCPN
  1. Download all the ZIP files of interest from Dropbox - usually to your downloads folder.
  2. Identify where your existing charts are located (Shown in OpenCPN in Options => Charts => Chart Files.  [I locate my KAP charts in /Users/Public/charts/opencpn/ge on Windows and /Users/Shared/charts/opencpn/ge on Mac OS X]
  3. If they don't already exist, create folders for regions (eg SEAsia, Australia, IndianOcean or similar) in the folder you intend to use for your GE imagery.
  4. Unzip (on Windows use right-mouse-button => Extract To) each of the downloaded ZIP files to the appropriate region folder.  Unzipping will create a folder for the <Locality> described in the readme file above.
  5. Check that your folder structure looks something like "charts/opencpn/ge/Australia/Abrohlos" with .kap files in the Abrohlos folders.
  6. If you wish you can add an extra layer of folders to fully mimic the file naming structure in the readme.  This depends on how you wish to use Chart Groups - read on!
  7. In OpenCPN go to Options => Charts => Chart Files.
  8. You should see a list of chart folders OpenCPN is using, often including a folder "CM93".  If you have some KAP files already loaded then there should be another folder.
  9. Click the Add Directory button, browse to the folder where your new KAP files exist, highlight the folder then click on Open.  I suggest highlighting the region folder (eg Australia, SEAsia etc), not the locality folder (unless you want a Chart Group for each locality).
  10. Tick the "Force Full Database Rebuild" switch and click OK.  OpenCPN will then scan all your chart directories building its chart index database, which may take a minute or three.
  11. When the rebuild finishes, zoom way out (using the "-" key) so you can see the regions covered by your GE imagery.  You should see small red boxes which show the location of each image.  If not go into Options => Display, turn on Show Chart Outlines, click OK and look again.
  12. To view a GE image zoom in over one of the red boxes and centre it in the screen.  At the bottom of the OpenCPN window you should see blue "tabs" appear to the left of the yellow tab which was there before.  The rightmost tab is always the real (vector) chart.  Others are image (raster) charts.  Click on the leftmost tab to open what is usually the best image for the location.
  13. Sometimes OpenCPN zooms when you change from one "tab" to another.  IMHO this is a bug.
Configuring Chart Groups in OpenCPN
  1. Go to Options => Charts => Chart Groups.  In the Chart Groups panel you will see an All Charts tab.  We are going to add more so that the number of GE images OpenCPN is dealing with can be controlled despite them all being installed.  I usually define Chart Groups for a region of the globe (SEAsia, Australia etc).
  2. To create a Chart Group click on New Group and give it a name (for example GEseasia) and click OK.  Then click on your vector charts (often CM93) folder and click Add.  Click on the relevant GE chart folder and click Add.  You may wish to create a Chart Group called CM93only with no GE folders included.
  3. When finished click OK to exit Options.
  4. In OpenCPN zoom way out (using the "-" key) so you can see the regions covered by your GE imagery.  You should see small red boxes which show the location of each image.
  5. Right mouse button, move over to Chart Groups and right into the list of groups.  All Chart Groups is probably ticked.  Click over another group and you should  see a set of red boxes disappear.  Chart Groups are a nice way to manage what images are accessible.  Once familiar with all this you can turn off Show Chart Outlines since drawing them seems to keep OpenCPN quite busy.
Installing and configuring in SEAiq
  1. Download all the ZIP files of interest from Dropbox to the computer you use to sync your iPad - usually to your downloads folder.
  2. Identify where your existing charts are located.  [I locate my KAP charts in /Users/Public/charts/opencpn/zip on Windows and /Users/Shared/charts/opencpn/zip on Mac OS X].
  3. Connect your iPad to the computer and let it sync if it wishes.  Open iTunes if it doesn't open automatically.
  4. Click on the iPad symbol at top left of iTunes, then click on Apps on the left.
  5. Scroll all the way down past the Apps list to the File Sharing list.
  6. Click on SEAiq Open in the File Sharing list on the left.
  7. On the right you now have a SEAiq Open Documents list which may be empty.  At the bottom of the list click on Add.  Browse to the folder containing the downloaded ZIP files.  Select those you wish to install in SEAiq and click Add.  You will see a progress bar at the top of iTunes.
  8. On the iPad open SEAiq and click on Charts at bottom right.  Wait for it - the response can take a few seconds if you downloaded ZIP files containing hundreds of images.
  9. When the Charts page loads you should see a row for each ZIP file, with each showing its size and number of KAP (image) files it contains.
  10. Now you see the logic behind the file naming scheme!
  11. Note that you download CM93 charts in a similar way, just select your CM93 ZIP file in iTunes and Add it to SEAiq.
  12. Click on Navigate and pan/zoom to the locality of the imagery you transferred.  You should see faint orange boxes delimiting the images.
  13. To change between vector (CM93) and raster (KAP image) charts click on the Settings tab and and move the slider on the Raster line in the Charts section, then return to Navigate.  You may need to pan slightly to have the page redraw.  Hey Presto!
  14. ZIP files can be removed from SEAiq in either iTunes or on the iPad directly in the Charts page. 
Hope the above helps you install the imagery.  Let me know if you like it and if you want more.

Here are two screenshots from SEAiq showing Cape Vlamingh on Rottnest Island WA.  Breaks on the reefs are clearly visible.
GE image of Cape Vlamingh, Rottnest Island, WA in SEAiq
Chart (decluttered) of Cape Vlamingh, Rottnest Island, WA in SEAiq


  1. Thank you for this it is truly selfless, will pass it on and link to your blog!!!

  2. An outstanding resource. Thank you.

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  4. This comment has been removed by a blog administrator.

    1. Hi John, Thanks for your comments and for the KAP files. I have looked at the files. Only 8 appear to be GoogleEarth images. The rest are copyrighted raster charts or satellite imagery which I can't offer as part of my online library. I'll add the GE imagery in the next few days. I'll also look into the best way to provide an email address.

    2. Hi Mike, I am in the process of redoing the Panama KAP files into several areas. Here is the link to the Bocas del Toro collection, all made this morning using GE2KAP and tested on OpenCPN:
      Please email me on clueless at not easy to remember com (change the @ symbol, remove spaces, add a dot)

    3. Hi John, Thanks for that. I have downloaded the data.

  5. Hi Mike,
    thank you for your excellent instructions. They are really straight forward and easy to use. My question is that I can't find the charts on the dropbox for the east coast of Australia. There are plenty for WA but I have searched and downloaded what were possibly the correct ones but to no avail. Is this because there are no actual KAP charts (or are they copyright protected )or am I looking in completely the wrong place. (when the charts open in dropbox there is also no modified folder) Many thanks for your help. Natalie

  6. Hello Mike, I just found your website. What a great idea. Thank you so very much for sharing all these Google Earth charts, so helpful to many people. I took advantage of the Tonga Google Earth charts since we will be sailing back to Tonga this year. A lot of the charts look great, but I noticed a few charts within the Tonga collection appear to be skewed which I believe indicates that these charts are not good. The specific files I am speaking of are: Tonga-Ha'apai-Limu-large.kap, Tonga-Ha'apai-Tokulu.kap and Tonga-Ha'apai-Numuka Iki West.kap We use the GE charts as guides, and accuracy can be useful. Have you used the Tonga GE charts yourself or do you know of someone who has used these charts? I wanted to thank you and get your thoughts on the matter. Thanks so much again for all your hard work. Take care. Sandy

    1. Hi Sandy, thanks for your comment and the kind words. I have NOT checked most of the KAP files in detail - all I've done is collect or make them, then attempt to remove duplicates. That's a lot of work in itself!!! I don't know of anyone who has used the Tonga charts. KAP charts are only an aid to navigation - keep those Mk 1 Eyeballs working!

    2. Hello Mike,

      Thanks for the response. We do appreciate your help, and I completely understand how much work it takes on your blog. OMG! I hope you enjoy it, cuz that’ll make it feel a bit less like work. :-) Oh yes, we do keep the eyeballs working, I just wanted to see if you knew anyone or if you have used the charts. It’s no problem for us at all just thinking of the people who may not realize that sometimes these charts have issues. We’ll use these charts (except the skewed ones) along with our eyes this year and let you know. I may also create some additional Tonga charts too which I can send you if you like. Again thanks for everything. You really are doing a service for the cruising community. Take care and safe journeys.