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Computer Tips and Tricks
Computer Navigation
Last Updated: 06/03/2018

  Making Charts from Google Earth Converting Maxsea Tracks and Waypoints
 to GPX for Open CPN
  Google Earth Cache How We Navigate
  Downloading the Charts we have already made

When we left the U.S. in 2007, the computer navigation systems were running in the $2,000-$5,000 range.  We just couldn't afford that, and especially not two of them (every long range cruisers needs critical equipment backups).  We also could not afford to keep buying map cartridges every time we moved a couple hundred miles--this is both a cost issue and an access issue. 

So our primary navigation system consists of the following:

1.  A Garmin GPSMap 76Cx on the helm (with maps installed).  Link to current equivalent on Amazon
2.  A laptop down below on the nav station, with a NMEA connection to the Garmin, but also a USB backup GPS if we need it
3.  A 15" 12-v (cheapo) LCD monitor on a swing out arm in the companionway.
4.  A 'presentation mouse' to manipulate the computer from the helm station. Note, there are other much cheaper-appearing options on Amazon, however, most do NOT include an actual "mouse" function.  Most only have forward and back buttons, good for slide shows, but not for mouse movement on screen.  This device also has a 60 ft range.  Here's an alternative from Keyspan with a 100 ft range.

Our original navigation laptop in 2007 was an old (purchased second-hand) Dell laptop.  It was a several thousand dollar laptop when new, but we bought it 'refurbished' for about $200.  It doesn't need to be super-fast, and it doesn't need much more than a 40-GB hard drive.  It was running Windows XP.

The first thing we did was strip almost ALL of the software off the computer.  We disabled the wifi, and took off the anti-virus and firewall, and made sure that NOTHING was being started by Windows at computer startup.  We also removed the 'user sign-in'.  So, turn this computer on, and it boots up immediately.

Then we carefully put ONLY navigation and 'underway' applications back on it:

  1. The OpenCPN navigation program

  2. GPSGate to help manage the GPS and Serial Ports for several navigation programs (optional)

  3. Airmail (properly configured for our underway communications functions

  4. WXTide32 - Worldwide Tide Program (free)

  5. GPSU - For transforming GPS waypoints and downloading to Garmin (optional)

  6. A simple photo program of your choice (see ours)

This computer NEVER connects to the internet... so it doesn't need the anti-virus applications, Windows Updates, etc.

Making Charts from Google Earth Using GE2KAP

Website URL for contact info and new versions of GE2KAP:

CruisersForum where Paul is answering questions and posting updates:

GE2KAP Facebook Group

Important:  If you like GE2KAP and use it, you should go  right now and buy Paul Higgins a beer. He has spent a lot of time on this tool, and it is VERY useful to us yachties in remote places. Just think of how much money you have previously spent on charts and chart chips, and Paypal him $20.  (Look for the Paypal link under the picture on the home page.  You can pay with credit card, don't need Paypal account).

The primary program I use here is GE2KAP. GE2KAP will interface with YOUR copy of Google Earth, and take what is currently shown on your Google Earth screen, and save it as a geo-referenced KAP file. KAP files are 'raster' files and useable on most navigation programs, including:

Maxsea (but NOT TimeZero)
Coastal Explorer
Sea Clear

The benefit of making chart files vs navigating IN Google Earth, which I have already played with, is twofold...

1. You can use the built-for-navigating programs you are already familiar with, and make routes and waypoints, etc without learning yet another new tool.

2. Once you make a chart from Google Earth, it is there, no matter what happens to your Google Earth installation or your GE cache file.

To use GE2KAP, you need to do the following:

1. Have a compatible version of Google Earth installed (see Paul's download page for details).

2. Either have your installation of Google Earth connected to the internet, or have the area you wish to make a map from (Google Earth content) cached on your computer. (see discussions on cacheing elsewhere)

3. Have the program ooRex installed on your computer.  Paul Higgins says to install the 32-bit version even if you are on a 64-bit Windows computer.

4. Have a subdirectory created to put the resulting charts (ie C:\Charts\GECharts or something.

Note: On the original instructions (if you read the sailing forum Q&A, Page 1), there are also two other requirements that are no longer needed with the latest version. (ImageMagick and libbsb)

Also, GE2KAP also works with another GoogleEarth-like program, SasPlanet.  SasPlanet offers alternative imagery, in case the GoogleEarth image is of poor quality or obscured by clouds.

Once you have done all this, follow these directions:

1. Start up your Google Earth program (GE) and find the location you want to make a chart of. Whatever is shown on your GE screen will go into the chart. You DO NOT have to be hooked to the internet, if you have previously been on the internet and cached (saved by displaying when connected to the internet). GE will complain that it can't find the internet. Just tell it OK, and NO you don't want it to help diagnose your network problems.

2. Make sure your display in GE has NORTH straight up. For some reason my GE wants North at about 10 degrees (probably the tilt of the earth). You can quickly orient to North straight up by double-clicking on the 'N' in the navigation controls (normally in the upper right corner of the screen).   (Newer versions of GE2KAP automatically adjust this by default before capturing the picture)

3. Clear the junk/menu overlayed on the GoogleEarth screen (using the View menu). Anything displayed on the screen will go on the chart. So you want to turn off unnecessary GE layers and the Navigation--if possible get to just the GE picture.  (You cannot get rid of the GE logo).

4. Start up GE2KAP as any normal program, from the shortcut on the desktop. If you have installed ooREX properly, it should just run. What you should see are 2 screens, one a black DOS-type screen which comes and goes, and one the user interface screen. It will say 'connecting to Google Earth'. If you have forgotten to start GE first, it will start it for you. Then you can use GE as normal to display the place you want to make a chart of.

GE2KAP Screen

5. To make your first chart you need to do 2 things:

a. Enter or browse to the chart directory where the new chart will be placed, and include the filename. This goes in the Chart/Location name field.
Ignore the stuff in the lower half of the screen for now.

ie: C:\Charts\GECharts\NeiafuHarbor.kap

I think the folder you point to must already exist

b. Click the Create Chart Button. Voila, GE2KAP shows some progess in the top window.  It is finished when it displays:

Successfully Created:
To View the output created press "View Chart"
To Calibrate another.. display the area on Google Earth.
Enter the name of the chart to create with its filespec below.
Then press the Create Chart button.

6. You can press the View Chart button, and it uses a simple KAP file viewer to display what just got created. I recommend that instead you load it into your favorite charting program and see how it looks.

Be cautious when first trying to navigate with a new chart.


More Details:

1. Check out the HELP button. It loads some nicely done HTML help which Paul has thoughtfully included in the zip file. (The button will try to load the help from a directory named Help in the same directory as GE2KAP.rex

2. The bigger screen (higher resolution) screen you have to display GE on, the more area one chart will cover at a given zoom level, AND the bigger the resulting chart file. But I have been making chartlets successfully on a 10" netbook laptop.  Each chart is about 500-700 Kb in size.

3. The overlay stuff on the expanded GE2KAP screen I haven't played with, but I think it allows you overlay another KAP file onto the GE screen, so, for example, you can create ONE CHART that has both the original chart (with depths) and the Google Earth view.  See Valhalla's Web Page for Instructions.

4. DON'T FORGET to turn off Terrain in Google Earth when using GE2KAP or the Geo-referencing may not be accurate on the chart produced.

5.  Naming conventions - it is helpful before you start out making charts of an area to come up with naming conventions.  I have ended up with over 100 charts of Fiji and ended up with a hodge-podge of naming.  Now when I create a new chart, I create it with the name:


Example:  Fiji-VitiLevu-West-VudaPointMarina.kap

This makes it easy to use Windows' 'sort on filename' to group the related groups of chart files.  You can also put spaces in the filename--neither Maxsea nor OpenCPN cares, just keep the filename from getting too long.

Fiji1.kap, Fiji2.kap, etc will make you (and/or people you share it with) very unhappy in the long run.

6.  When you are comfortable making charts, play with the Historical View function on the View menu.  Sometimes the current view (satellite photo) on Google Earth of a particular location is not the best for eyeball navigation.  Sometimes, you can go back in time, using Historical View, and find a photo that better depicts the location (the sun angle is better, fewer clouds, etc).

Downloading the Charts we have Already Made

More charts available here:

Valhalla's SE Asia Charts

Zen Again's Charts


If you like GE2KAP and use it, you should go online and buy Paul Higgins, the GE2KAP developer, a beer. He has spent a lot of time on this tool, and it is VERY useful to us yachties. Just think of how much money you have previously spent on charts and chart chips, and Paypal him $20

Loading Raster Charts into Maxsea v10.3.2.1

1. File / Open (not Open Chart)
2. Browse to the directory (ie C:\Charts\GECharts)
3. Select any file (a new one you haven't previously loaded)) and click OK.

It should load ALL the charts.

To show the Raster chart window, use the menu item Window to switch back and forth between the Raster Chart and the CMap (vector) chart. All your routes and waypoints will be there! Unfortunately I haven't found a way to get the Raster and the CMap chart to track together, but you can always use the 'center on my boat' button to center up both screens so you can compare views.

So far, in Tonga, Fiji, the Marshall Islands, and Micronesia, the GE Charts have been a godsend... spot on in Niuatoputapu and Vavau, where the CMap charts are running us over land.

Loading Raster Charts into OpenCPN

1.  In the OpenCPN program, click the Wrench Icon, and click the Charts Tab

2. In the upper part of the window, browse to where you have the Charts, and select one of the folders. You should see the full folder path in the box just below, something like this:

C:\Charts\GoogleEarth Charts\GoogleEarth-Fiji\

3. Click on the Add Selection button, and the folder will be added to the 'Active Chart Directories' box below. Do this for whatever charts you will plan to use in the near future.  Note that if you have chart sets stored in subdirectories, OpenCPN (unlike Maxsea) will traverse the directory tree and load up all the charts in the tree.

4. Click OK, and Open CPN will rebuild its list with your new charts included.

5. If you have 'chart quilting' turned on in OpenCPN, Play with the light blue bars at the bottom of the screen to see which level of chart you can choose.

6.  If you have C-MAP CM93 charts loaded in OpenCPN also, you switch back and forth between CM93 view and Raster chart view by clicking between the blue-colored buttons and yellow/brown colored buttons at the bottom of the screen.

See our full "Getting the Most out of OpenCPN" presentation on our Presentations Page

GoogleEarth Cache

GoogleEarth has a built-in 2GB 'cache'.  What this means is that it will save up to 2GB worth of images to your computer drive, which are accessible in GoogleEarth offline, without being attached to the internet.  When you reach ~2GB, then GoogleEarth automatically 'manages' the space for you--removing older and/or seldom-visited images to make space for new images.  2GB is actually a lot of GoogleEarth images, but you can't guarantee that an image that was accessible offline yesterday will still be accessible offline tomorrow.

I use a 'Google Earth Cache Management' program called "Cache for GoogleEarth" downloadable here.  It mostly works for the intended purpose (but is a little quirky).  I have had no problems restoring a saved cache if I am connected to the internet, but something in GE seems to go wrong if I try to restore a saved cache while offline.  Even with this quirk, this program saves lots of download time on slow networks if you have the time to pre-download caches on faster networks.  (ie pre-download the South Pacific Islands when in the U.S., in manageable chunks, then restore them as needed while actually cruising the South Pacific.

You can also manually manage your cache files, and there are likely some donation-ware versions of GE Cache managers.  Like this one.

I have not played with phiggins's GERoute, which is new, but it is a way to force Google Earth to cache the files you will need for a particular route. Once you have GE2KAP working, it might be worth playing with GERoute.

Converting from Maxsea PTF files to GPX Files for OpenCPN

Quick Notes:

Do the conversion in GPSU
Do NOT save the PTF file!!
Open the resulting GPX file in Wordpad or other text editor

Search and replace the following:

<sym>265</sym> to <sym>anchorage</sym> (anchor)

<sym>120</sym> to <sym>diamond</sym> (blue diamond)
or <sym>xmred</sym> (red x)
or <sym>triangle</sym> (black triangle)
or <sym>scuba</sym> (Scuba Flag)

If left untouched, the 120 will translate to a black circle.

For tracks
You need to search and replace:
<trkseg> with <trk><trkseg>
</trkseg> with </trkseg></trk>

Useful Links:

s/v Valhalla's web page on Google Earth and Navigation

This page evolved over a period of time, his final solution ended up being OpenCPN and GE2KAP.