Using Google Earth for Navigation     Back to Navigation       Back to Valhalla's Mooring Page

Jump to:

(28 Jan 2011)    Original article

(Added 3 Feb 2011)  How to download my saved Google Earth Caches   ( Revised 1 Nov  11)

(Added 3 Feb 2011)  How to view Google Earth Saved Caches while offline

(Added 8 Feb 2011)  How to convert MaxSea Routes to Google Earth Routes  

(Added 9 Feb 2011)  How to convert MaxSea Tracks to Google Earth Tracks 

(Added 9 Feb 2011)  How to view saved GE Tracks in Google Earth

(Added 11 Feb 2011)  How to view saved GE Routes in Google Earth

(Added 11 Feb 2011)  How to view your GPS POSITION in GE (online or offline) 

(Added 25 Mar 2011)  How to convert MaxSea Anchorages to Google Earth Anchorages   

(Added 25 Mar 2011)  How to view saved GE Anchorages in Google Earth (offline or online)

(Added 4 April 2011)  Google did it again!

(Added 15 Jun 2011)  And look what's coming along to make all of this easier!

(Added 4 Jul 2011)     ChartAid Program 

(Added 22 Jul 2011)    ChartAid Program vs Saved GE Caches

(Added 28 Jul 2011)     And in the final analysis ... something even better!

(Added 3 Aug 2011)     Creating a KAP chart using OpenCPN and GE2KAP

(Revised 17 Aug 2011)  Creating a Google Earth cache using OpenCPN and GERoute  

(Added 12 Aug 2011)   Using OpenCPN with Google Earth Saved Caches (Offline mode) 

(Added 2 Sep 2011)     The Bottom Line 

Why and how of using Google Earth offline for navigation .....

The detail of the Earth's surface provided by Google Earth gives an opportunity to augment marine navigation with this added information while offline.

While continuous internet connectivity while sailing is beyond the bank account of most cruisers, an alternative is available to use Google Earth information.  Basically, you spend some time while connected to the internet to scan areas of interest, such as coastlines where underwater obstructions can appear in better definition than shown on nautical charts, either paper or electronic.  After scanning the area of interest online, the 'cache' (storage area) for Google Earth is captured and saved for later use.  There is no limit to the number of such saved caches (except for the hard drive capacity of the computer) as each one will normally be on the order of 130MB.  It IS possible to scan an extremely large area and approach the upper limit of disk cache size in Google Earth, 2GB.  I find it is better to break areas down into smaller chunks.  When offline, the saved caches are copied over the existing cache in Google Earth, where that area will appear in the same detail you originally copied.  The procedure is nicely described here.  If you cannot find the path described in that procedure then make sure that Windows Explorer can display hidden files and folders. In Windows Explorer go to Tools/Folder Options/View and ensure the box is check beside "Show hidden files and folders".

Now that you can display an area it is only useful for navigation if you can input your vessel position on the image and, better yet, track it.  Thanks to the efforts of Greg Heppenstall (who wrote the procedure mentioned above), a shareware program, Bungee, is available to easily do this.  In fact, he has another program Harvester that automates the scanning procedure mentioned above.  Bungee, as shareware, works for 30 days until registered ($15.00, Canadian). Harvester has limited functionality until registered at the same price.

I am now using Bungee in conjunction with an electronic charting program and Google Earth (being driven by the Bungee program)  in a split screen display such as the following:

This capability to display such near real time information from Google Earth when available cartography is limited in definition can be shown from the following.  A recently constructed marina, Punta Fuego, lies on the west coast of Luzon, Philippines.

Here's what the latest electronic navigation chart (April 2010) shows with a route coming into the marina location:

Likewise, the latest raster scan chart looks like this:

However, here's what Google Earth shows, with the same route displayed:

Got your attention?  Try it, you'll like it!                                                                     Back to the Top

(Revised 1 Nov 2011)  How to download my saved Google Earth Caches

In the following table are caches I have scanned using Google Earth version (beta). This version can be downloaded from here or from this alternate location.  I would appreciate feedback about your ability to display any or all of these caches.  Let me know here.  If you have caches to share, please contact me and we will work out how to send them to me.  Thanks.

                                                                              See downloading instructions below

Google Earth Caches
BRUNEI  OpenCPN Waypoints (See NOTE below)
Cache Name Location Download URL DL Size (MB) Hash Tab (CRC32)
Juradong 04° 57.485'N  114° 48.641'E Click here 21.9 8897F473
Kuala Belait 04° 35.852'N  114° 10.777'E Click here 17.2 26E7D0FE
Muara Channel 05° 04.008'N  115° 06.628'E Click here 29.1 773BABA7
GUAM  OpenCPN Waypoints
Cache Name Location Download URL DL Size (MB) Hash Tab (CRC32)
Agana Boat Basin 13° 28.786'N  144° 44.957'E Click here 54.3 FC1D41B3
Agat Marina 13° 22.134'N  144° 39.008'E Click here 25.5 11878A83
Apra Harbor 13° 27.185'N  144° 38.932'E Click here 46 DF632C24
Cetti Bay 13° 18.942'N  144° 39.312'E Click here 57.2 2EC8F9EF
Harbor of Refuge 13° 27.654'N  144° 40.933'E Click here 29.3 EDA8E101
Sumay Cove Navy Marina 13° 26.426'N  144° 39.286'E Click here 30.9 22BA016F
HONG KONG OpenCPN Waypoints
Cache Name Location Download URL DL Size (MB) Hash Tab (CRC32)
Aberdeen                          22° 14.438'N  114° 09.734'E Click here 5.3 B2E4EE86
Discovery Bay                   22° 17.552'N  114° 01.537'E Click here 4.9 88BC95FA
Hebe Haven & Approach    22° 21.868'N  114° 15.878'E Click here 10.4 6A7A4C98
Marina Club Marina             22° 21.484'N  114° 15.343'E Click here 6.6 E684FD60
MALAYSIA OpenCPN Waypoints
Cache Name Location Download URL DL Size (MB) Hash Tab (CRC32)
Admiral Marina & S   02° 28.555'N  101° 50.784'E Click here 36 FB973705
Bintulu    03° 15.632'N  113° 02.807'E Click here 18.8 7C270C4D
Port Klang Bypass   02° 58.088'N  101° 15.753'E Click here 34.8 C83357F2
Kudat    06° 53.362'N  116° 51.524'E Click here 6.1 9AE6D9EB
Labuan    05° 16.397'N  115° 14.877'E Click here 21.4 F68D5213
Miri Marina    04° 22.968'N  113° 58.163'E Click here 6.2 E11451EE
Pinang & S   05° 23.513'N  100° 15.291'E Click here 109 604574B6
Pisang Is   01° 27.305'N  103° 15.724'E Click here 15 758BDF3F
Sandakan    05° 48.391'N  118° 04.629'E Click here 12.1 3543B418
Santubong River    01° 42.740'N  110° 17.830'E Click here 30.1 91BBC88F
SantiRiver2SebanaCove   01° 23.822'N  104° 06.539'E Click here 28 0441EB8A
Sutera Harbour Marina    05° 58.110'N  116° 03.341'E Click here 3.6 7E684AA3
Tioman & Vicinity   02° 48.675'N  104° 10.437'E Click here 13.8 4DD03B7A
Telaga Harbour   06° 22.048'N  099° 41.082'E Click here 21 D72CCA0E
Water Is   02° 04.923'N  102° 20.328'E Click here 12 59D96E0D
Cache Name Location Download URL DL Size (MB) Hash Tab (CRC32)
North Helen Reef 02° 54.964'N  131° 46.509'E Click here 143.5 E17A376C
Olimarao Is. 07° 41.386'N  145° 52.014'E Click here 83 D6F808C0
Puluwat  07° 20.631'N  149° 11.451'E Click here 59.1 4576DF08
Woleai Atoll  07° 21.000'N  143° 52.190'E Click here 137 BF963E61
Cache Name Location Download URL DL Size (MB) Hash Tab (CRC32)
Bais Bay North Negros       09° 36.410'N  123° 10.215'E Click here 10.2 3888A0C3
Bais Bay South Negros    09° 33.500'N  123° 09.420'E Click here 4.1 E58C6F13
Bolinao Luzon   16° 23.200'N  119° 54.800'E Click here 10.2 C60E6F2A
Boracay Panay  11° 58.003'N  121° 55.687'E Click here 6 A583F7F6
Calape Bay Bohol   09° 52.978'N  123° 50.885'E Click here 5.5 F93D7423
Car Car Bay Cebu   10° 04.996'N  123° 39.185'E Click here 9.8 FB26E439
Cebu Yacht Club Cebu  10° 19.800'N  123° 58.546'E Click here 10.7 9691753C
Coron  Busuanga  12° 00.094'N  120° 12.789'E Click here 32 2A6CD871
Davao  Mindanao  07° 06.044'N  125° 39.248'E Click here 11 02F06D50
El Nido  Palawan  11° 11.404'N  119° 23.273'E Click here 74 3D7F8F70
Kanin Bay Bucas Grande Island  09° 34.408'N  125° 55.814'E Click here 11.4 0791A612
Manila Yacht Club Luzon  14° 33.692'N  120° 58.965'E Click here 4.9 D6871F4D
Nagabungan Bay Luzon   18° 29.025'N  120° 33.875'E Click here 6.6 B7D9E7B3
Negros SE Coast   09° 03.433'N  123° 08.885'E Click here 36 CC4D8FDF
Palawan  11° 05.951'N  119° 27.101'E Click here 184 40C3D3A5
Panaon Strt to Liloan Leyte  10° 09.654'N  125° 07.320'E Click here 8.8 9AF14310
Port Bonbonon  Negros  09° 03.348'N  123° 07.807'E Click here 10 51EDB8F6
Port Carmen  Cebu  10° 35.090'N  124° 01.965'E Click here 19 B8ED865B
Port Isabel Leyte               10° 54.851'N  124° 25.268'E Click here 9.6 E52959AF
Port Palompon Leyte           11° 03.309'N  124° 22.542'E Click here 8.3 31EE631A
Puerto Galera (New) Mindanao  13° 30.715'N  120° 57.491'E Click here 71 1F1B79DE
Puerto Princessa (New) Palawan  09° 43.700'N  118° 43.592'E Click here 19.2 46514148
Punta Fuego  Luzon  14° 07.867'N  120° 35.370'E Click here 11 D83A97C3
San Fernando Luzon   16° 37.496'N  120° 18.000'E Click here 9.2 09545B77
Subic Bay  Luzon  14° 48.818'N  120° 15.765'E Click here 80 BDA9D017
Surigao Mindanao  09° 46.952'N  125° 30.132'E Click here 6.1 793596D3
Tagbilaren Bohol   09° 39.530'N  123° 49.576'E Click here 10.5 59CF0B8A
TAIWAN  OpenCPN Waypoints
Cache Name Location Download URL DL Size (MB) Hash Tab (CRC32)
Green Island   22° 39.602'N  121° 28.725'E Click here 4.5 381462BF
Hualien              23° 58.776'N  121° 37.809'E Click here 9.9 715CEFAB
KaoHsiung         22° 37.198'N  120° 15.383'E Click here  7.3 0F2DCBA4
Keelung           25° 09.692'N  121° 45.174'E Click here 6.4 EC69F5A5
Suao                 24° 35.762'N  121° 52.548'E Click here 6.4 C45FB23E
Taichung            24° 17.803'N  120° 29.222'E Click here 7.5 20897F97

NOTE: (Optional for power users) This column contains the Hash Tab CRC32 value for each download.   See this link for the Hash Tab program and explanation of using it.  This is a quick way to check downloads before attempting to extract the files in case there has been a corruption during download.

Downloading ..

To download a cache of interest, click on 'Click here' in the Download URL column.  This will start the download.

The saved caches are downloaded in .zip format.  When unzipped, a folder will contain three or four files, such as shown below:

There are three cache files and, in some cases, one KMZ file.  This latter file is a placemark file for Google Earth.  The three cache files are the ones used to replace the files in Google Earth.

(Added 1 Nov 2011) For each country the link OpenCPN Waypoints will download a .gpx file with that country's name, e.g. brunei.gpx.  This file contains waypoints with the GE symbol showing where in that country there are saved GE caches.

Place the downloaded file in a convenient folder (I use 'GE Cache Locations')  To display all of these waypoints for that country  in OpenCPN, use the Route Manager/Import GPX to load the waypoints into the program.


The saved GE cache locations are now displayed.  They can be deleted from within the Route Manager by selecting 'Delete All'.

Back to the Top

How to view Google Earth saved caches while offline

To view the cached area, make sure you are offline with Google Earth.  Navigate to the folder where you have saved the caches for your areas of interest.

1.  Copy the three GE cache files to the clipboard (select/CTL-C_)     

    a.  If using Windows XP, paste the three cache files into the folder C:\Documents and Settings\$$$$$\Local Settings\Application Data\Google\GoogleEarth\  (where $$$$$ is your windows profile name).

    b.  If using Windows 7, paste them to C:\Users\$$$$$\AppData\LocalLow\Google\GoogleEarth\  (where $$$$$ is your windows profile name).

    c.  If using a Mac, paste them to /Users/$$$$$/Library/Caches/Google Earth  (where $$$$$ is your profile name)

(HINT: Once you locate the folder send a shortcut to the desktop or wherever you are saving the caches.  You can then copy the cache files and paste them to the shortcut.)

2.  Two methods to choose from to proceed:   (First return to the folder where you have saved the caches for your areas of interest.)

    a. Copy the .kmz file to the clipboard.  Navigate to where the shortcut for Google Earth is located and paste the file onto the shortcut.

    b. Right-click on the .kmz file and select ‘Open with …’.  If Google Earth isn’t listed you will be prompted to select it.  Check the box “Always use the selected program to open this kind of file”, though this may or may not work for the future. (It’s not a perfect world, thankfully)

3.  Google Earth will/should automatically start.

    a,  After several seconds, Google Earth will present a message box stating: "Google Earth could not contact the authentication server.... The application will continue to operate but will only display data available locally (in cache)....... would you like to run a diagnostic test?......"  Click on "No"

    b. A few seconds later Google Earth will present a message box stating: "We are having trouble connecting to the internet. Please check your network connections and we will try to reconnect."  Click on "OK"

4.  You should now see the area that has been previously scanned and saved, along with the placemark.  Zoom in to the lowest level of detail that was used during the scan.

And, of course, you can plot your track on the display using Bungee as described in the beginning of this page.  Honestly, though, you can connect a GPS to your computer and follow your path on the saved cache. See here. But there are several things you cannot do:  You cannot change the altitude of the display, you cannot tilt the display and you cannot save your track for future reference  ... such as coming back later or getting out of a tight spot you managed to get in ... which are several of the advantages of the Bungee program.

 No, I don't have a pecuniary interest in Bungee ... just a satisfied user.

Back to the Top

(Added 8 Feb 2011)   How to convert MaxSea Routes to Google Earth Routes

Using the GPS Utility program which can be downloaded from here.  Registration is $60.

Start the program .. select File/Open ..

If you navigate to your saved MaxSea routes and the screen is blank as below, you need to change the type of file.

Select the elevator on the line 'File of type:"                          Select "Waypoints (.wpt .upt)"


This will display the MaxSea routes you have stored.

Select the route to be converted and click on 'Open'            On the next screen click on 'OK'


After the screen has loaded, select 'Save/Export Options..'   Click on the 'Format' elevator.


Select the format line 'Google Earth (kml.kmz)"                 Navigate to where you save your Google Earth routes ..


At this point you can change the name of the saved route or elect to save it with the same name (recommended)             

      All done!  (NOTE: This same procedure can be used with other route formats!)

Back to the Top

(Added 9 Feb 2011)   How to convert MaxSea Tracks to Google Earth tracks

Open the GPS Utility program (as above) then select 'Open ...'

Navigate to your saved MaxSea tracks, select a folder,

and change the 'Files of type' to MaxSea (.ptf)                        Select the track you want to convert.


On the next screen select File/Save/Export Options ...       Select Google Earth (*.kml)


At this point you can change the name of the saved track or elect to save it with the same name (recommended)

       All done!

Back to the Top

(Added 9 Feb 2011)  How to view saved GE Tracks in Google Earth (offline or online)

First determine if you want to view the track online or offline.  If online continue as below.  If offline then first load the GE caches with the area coincident with the track and close GE.

The procedure ...

Navigate to the saved GE tracks.

Copy the track to the clipboard.                                                Navigate to the Google Earth shortcut.  Paste the track onto the shortcut.


NOTE:  Alternatively, you can select "Open" or "Open with/Google Earth" as in viewing routes below.

Google Earth opens, the track is displayed and the track appears in the Temporary Places.

When finished exploring the track, close GE.  You now have the choice of discarding the track from Temporary Places or saving it to My Places.

      All done!

Back to the Top

 (Added 11 Feb 11) How to view saved GE Routes in Google Earth (offline or online)

First determine if you want to view the route online or offline.  If online continue as below.  If offline then first load the GE caches with the area coincident with the route and close GE.

The procedure ...

Navigate to the saved GE routes.

Right-click on the route and select "Open with/Google Earth"  (If you have previously associated GE with .kml files you can select 'Open")


Google Earth opens, the route is displayed and the route appears in the Temporary Places.

When finished exploring the route, close GE.  You now have the choice of discarding the route from Temporary Places or saving it to My Places.

      All done!

Back to the Top

(Added 11 Feb 11)  How to view your GPS POSITION in Google Earth (online or offline)

First determine if you want to view the track online or offline.  If online continue as below.  If offline then first load the GE caches with the area coincident with your present location.

The procedure ...

Connect a GPS to any com port on your computer.

Start Google Earth.

Select Tools/GPS.\                                                                  Select the Realtime tab, NMEA button, and check the box

                                                                                               'Automatically follow the path'


Select Start                                                                             The page should show GE reading the com port connected to the GPS.


And your position will be shown.

When you are underway, your position will follow on the display with a short, following track that maintains it's length as you move.


Unfortunately I have been unable to save this track!  Another reason to use the Bungee program!

Back to the Top

(Added 25 Mar 11)  How to Convert MaxSea Anchorages to Google Earth Anchorages

Use the GPS Utility program  It can be downloaded from here.  Select File/Open and navigate to where you have saved the MaxSea anchorage location.  In this example double-left click on  'Kudat2Sandakan.ptf''.

The anchorage locations (Waypoints) open.  Select 'File/Save/Export Options ...'

In the Format box select 'Google Earth (*kml)'                       Navigate to where you want to save the location and click on 'Save'.


You have now saved the anchorage locations in the Google Earth format.

Back to the Top

(Added 25 Mar 2011)  How to view saved GE Anchorages in Google Earth (offline or online)

First determine if you want to view the anchorages online or offline.  If online continue as below.  If offline then first load the GE caches with the area coincident with the anchorage locations and close GE.

The procedure ...

Navigate to the saved GE anchorages.  Click on the icon for the locations you want to display.

Google Earth launches and shows the anchorage locaitons.

Here's a close-up of the Sandakan harbor.

Back to the Top

(Added 4 April 2011)  Google did it again!

When Google updated the Google Earth program from version 5 to version 6 I found that the saved caches from one version would not work with the other version.

Now with version available I find the same thing regarding version ... the one I used to scan the caches above.

So my advice is to stick with the beta version.  If you have downloaded the newer version and want to revert to the beta version it can be downloaded from here or from this alternate location.

Back to the Top

(Added 15 Jun 2011)  And look what's coming along to make all of this easier!

An open source computer navigation program is under development that has a feature of using Google Earth images (online or saved cache) in a companion screen showing the vessel position.

Here's an example from a beta version of the program:

This image shows the vessel's position (in this case in a berth) on both a cm93 chart and from a saved Google Earth cache of the area. Also notice  the display of AIS targets .. both moving and stationary.  Those blue segments at the bottom display raster charts at the same location with just one click.

The program, OpenCPN can be found here.  It's free and packed with features that soon will be my primary electronic navigation program.

Back to the Top

(Added 4 Jul 2011)  ChartAid Program

From the ChartAid website:


Many people have found Google Earth and Google Maps printable images helpful in supplementing their knowledge of a particular area or specific location.  The ChartAid program offers you the ability to save Google Maps printable images as Raster Charts or Photo Charts: 

ChartAid benefits boaters whose charts are inaccurate, outdated, or of poor resolution.  My wife and I are currently cruising in Mexico and find the local charts are off by one to three miles.  Having the detailed ChartAid charts has been helpful. 


The program costs $99. The raster charts work nicely with the OpenCPN Program.

Back to the Top

(Added 22 Jul 2011)  ChartAid Program vs Saved GE Caches

At the last posting I said about the ChartAid program "I think it's worth it!".  I now have some reservations about those words but with a caveat.

As I posted on 15 Jun above, the OpenCPN program is nearing completion of the stable release version 2.5 which includes the Google Earth plugin. 

Here's a similar view to the one previously posted.

With the ChartAid-produced GE/KAP image displayed you get a duplication of images and at the expense of a loss of depth information.

Is this a problem?  Yes and no.  For close-in maneuvering where you are not concerned about the depth it might be useful to see this ....

..... instead of this.

The caveat I have is for areas where I have not previously saved GE caches (remember I am talking about being offline from the internet). 

For example, if I were to find myself needing an anchorage where I did not have the foresight to save a GE cache, such as Romblon harbor, this is the coverage shown by the cm93 charts.

But having a GE/KAP image of the harbor I can now see shallow areas not readily apparent in the above.

So if you are confident that you have saved GE images for everywhere you will be going then you don't need the GE/KAP images.  But you never know, right? 

Back to the Top

(Added 28 Jul 2011)  And in the final analysis ... something even better!

Something even better!

One of the contributors to the development of the OpenCPN program is Paul Higgins.  Paul's programs (GE2KAP, GERoute and C2GPXKML) are available for download from his GDAYII website.  The programs are written in REXX programming language and use the oorexx interpreter. The latest version of oorexx can be downloaded from:  Only use the 32-bit version.  Once installed it is used by each of the programs.


This Windows program converts a Google Earth image into a .kap chart (which is what ChartAid described above does).  But it's free ... well, a donation to Paul's efforts is much appreciated!  It is integrated with the OpenCPN program for ease in finding locations you want to capture.  See the next posting for how to use it.


This Windows program allows you to use a route to determine where Google Earth searches for images that are captured in the GE cache.  As I described  in the original article you can use Google Earth to manually scan an area and later save the cache for future viewing offline.  This program does it easily by using a pre-defined route.

The input route(s) can be any of the following:
- .SRW files from SeaClear
- .GPX files created by some other navigatioon program such as OpenCPN
- .KML files such as produced by Google Eartth.
- .G7T files
You can select multiple routes on a scan and they can be of any type.

C2GPSKML  From Paul's program:

Purpose: To convert navigation routes and tracks to different formats.

This program will accept as input the following type of files:
- SeaClear route files (.SRW)
- SeaClear track files (.TRC)
- GPX route and track files produced by otheer navigation programs such as openCPN and Fugawi.
- EXECL worksheets (.xls or .xlsx) in a speccial format. A sample database is provided.
- .G7T routes or track files.

It can convert any of the above into KML, GPX, G7T, TRC, SRW formats, or update an EXCEL worhsheet.

Multiple SeaClear TRC files can be combined to create one large track file.

If the input is a track, and you have created log data using SeaClear, the log data may be added to the output as waypoints

It can also convert any of the inputs to Furuno or Raymarine chartplotter format and upload it to the chartplotter via a COM port.

The final analysis

You have the choice of free or paid programs to use Google Earth as an aid to navigation.  These techniques should be part of your navigation repertoire.  They are now a part of mine.

Back to the Top

(Added 3 Aug 2011) Creating a KAP chart using OpenCPN and GE2KAP      Back to Valhalla's Mooring Page

This procedure allows you to create a KAP chart from within OpenCPN using the GE2KAP program.  To begin, in OpenCPN determine the area you want to capture.  Here's an example of Jason Bay, Peninsular Malaysia.

Display the GE window by clicking on the GE icon.


Maneuver to the view you want to capture.


Go to where you have the GE2KAP program stored and click on the GE2KAP.rex file

When the program starts and displays this screen, click on the button to select where you will store the chart.

In this case I have selected the Desktop for convenience.  Later, when I'm satisfied with the chart, it will be saved with my BSB/KAP charts.

Now return to OpenCPN and close the GE window by clicking on the icon.  (This is a 'workaround' in case you have difficulty using the 'Create Chart')

Return to the GE2KAP program and click on 'Create Chart'

When notified of successful creation click on 'View Chart'

The program will display an image of what will be in the KAP chart.

Return to OpenCPN, select the 'Toolbox/Charts' and select "Force Full Database Rebuild".  (This presumes you have included a path for charts to the folder where you have stored this chart, in this case on the desktop).

Returning to OpenCPN the newly created chart should be indicated by the red outline.

Select the chart by clicking on the blue bar at the bottom:

If you are satisfied with the chart then move it to the location of the other BSB/KAP charts you have stored.  If not, repeat the above until you are satisfied.

Back to the Top

(Revised 17 Aug 2011)  Creating a Google Earth cache using OpenCPN and GERoute      Back to Valhalla's Mooring Page

The purpose of creating and saving a Google Earth (GE) cache is to permit viewing the GE image of an area while offline, i.e. not connected to the internet.

The GERoute and OpenCPN programs work nicely together to do both the creation and later display of the GE image.  The following procedure is the one I use.  I'm sure there are other ones.  If you have a route saved that you want to use with GERoute then by all means use that one.  In this discussion I will create a new route to be used.

Begin by opening the OpenCPN program and navigate to the area you want to capture in the GE cache.  For example, I want to save the GE cache for the approach to the Royal Hong Kong Yacht Club in Hebe Haven, Hong Kong.  The HKYC is at the top of the screen shown below.

Click  'Create Route'  and use the tool to create a desired route.


Next open the Route Manager and select 'Export Route ..."


Save the route to a convenient place.  I use the Desktop.  If I want to keep it for later use I move it to another folder when done here.

Now close the OpenCPN program. 

Before GERoute is used to scan the desired area, the cache in Google Earth needs to be cleared.  There are two methods to do this.

Method 1 to clear the GE cache.  For Method 2 skip to here.

Navigate to where you have the GERoute program installed and open it.

Google Earth opens with the GE Route program in the background..  You now want to clear the GE cache.  Wait for GE to load then do the following:






Wait for GE to load then return to the GE Route program. It is minimized to the System Tray.

If using this method skip here.

Method 2 to clear the GE Cache.

Navigate to the GE cache location.  I have a shortcut from this folder for convenience.

Open the folder by double clicking on it.  Highlight the three cache files, right click on any one of them and select 'Delete'

Navigate to where you have the GERoute program installed and open it.

Using the GERoute program:  The following screen appears

First set the Delay and Options.  This will be a trial and error process until you are satisfied with the results.  The Delay is the time GE takes to load an image before moving on the the next location.  The 15 seconds shown below is for a very slow link.  A way to determine the appropriate delay is to start GE normally, zoom in to a height of about 1000 meters and watch the blue donut at the bottom right hand portion of the screen.    The time for it to completely fill in is an indication of what to set for this delay.  Too little delay and the image will be blurred.  The Options are again found from trial and error.  The ones shown seem to give an acceptable image.  Next select the 'Routes' button.  Navigate to the saved route and select it.


The program starts scanning.                                                       And notifies when the scan is completed.  The GE cache now has the image.


Navigate to the GE cache location.  I have a shortcut from this folder for convenience. The path for Windows XP is as shown.  A different one is used for W7.

Open the folder, select the three files it contains and copy to the clipboard.


Navigate to where you save the caches, create the necessary folders and paste the three cache files into that folder.

Go offline by whatever means you have.

If GE has not been disturbed at this point the files are still in the GE cache.

Now launch the OpenCPN program and select the GE icon.


Since you are offline a series of screens will appear.  Select as shown.

And the result.  Notice that the path through the crowded anchorage isn't as straight as indicated on the chart!

If you want to download the cache described above Click here

Back to the Top

(Added 12 Aug 2011)  Using OpenCPN with Google Earth Saved Caches (Offline mode)

From the above discussions (as disjointed as they may be and for that I apologize) which were an evolution in my investigations into using the Google Earth (GE)  resource for navigation, it's now time to put it all together as a guide to using the saved GE caches  with the OpenCPN program.

I will assume you have a library of caches, ones you have created or downloaded from me, somewhere on your hard drive.  See above for downloading the caches.  Here's where mine are located:

I will also assume that you have loaded the Google Earth plugin into the OpenCPN program.  If so, you will have a GE icon on the toolbar.

If these assumptions are not correct, please review the above discussions to get to this stage.

With the GPS active and the OpenCPN program running you must ensure the GE cache has been loaded for your location.  For example,

The boat is entering Subic Bay, Luzon, Philippines.

If not done previously the GE cache for this location must be loaded.  Navigate to the Saved GE Caches and open the Subic Bay folder. (left click)

Select (highlight) the three cache files.    Right click and select 'Copy'.


Navigate to the shortcut to the Google Earth Caches and right-click on it.        Select 'Paste'..


Confirm the file replacement by selecting 'Yes to All'

Go back to the OpenCPN program and click on the Google Earth iconIf not checked, check the box 'Connected to chart viewport'.

Adjust the size of the GE window as desired.  Voila!

and more along the way.

Back to the Top

(Added 2 Sep 2011) The Bottom Line

Now, after spending several months evaluating the use of Google Earth (GE) to complement other navigation programs I've come to some conclusions.

1.  GE has a definite role to play.

2.  Taking advantage of GE while online to create charts or to save GE caches is worth the time and effort in areas that are poorly or inaccurately charted..

3.  Although the OpenCPN program has a plugin for GE it is not reliable enough in maintaining connectivity nor in maneuvering the GE display to give a view of the boat's position in both the GE display and on the companion chart.  The scale of both the GE display and the chart are linked together preventing a 'big picture' and 'little picture' view at the same time.

4.  The Bungee program provides excellent flexibility and reliability.  Separate control of viewing altitude, tilt and 'north up/course up' modes is handy.  It can be used in conjunction with any other navigation program in a dual-screen display (Windows operating system).  It can maintain a track in addition to any track being maintained on other programs.

5.  Creation of GE caches can best be done through a combination of the OpenCPN program (to establish a route) and the GE2Route program to create the GE cache.  A large area can be scanned for each saved caches.

6.  Creating GE/KAP charts is an alternative to viewing stored GE cache files.  The files are relatively small but so is the size of the chart if a lot of detail is desired, requiring multiple charts for an area.  The main disadvantage I find is that it is necessary to switch between this chart and other charts that show navigation information such as depth, obstructions, marks, etc.  This entails keyboard action which may not be convenient while maneuvering the boat.

7.  The creation of GE/KAP charts can best be done using the GE2KAP program in conjunction with the OpenCPN program.  Alternatively, the ChartAid program does an acceptable job but is a bit expensive.

8.  If you have the time and storage capacity (and who doesn't these days?) having both stored GE caches and GE/KAP charts is a bonus.