Google Earth Tips for Sailors

Map showing Tuamotus and Niku HivaA big part of the experience of sailing around the world is meeting up with other sailors doing similar routes. We have had numerous opportunities to meet up with the crews of boats we have met along the way. As the world’s biggest fan of Google Earth (I’ve been publishing the most popular Google Earth Blog since 2005 with 6 million readers per year), I have been making sure to share tips with sailors on the best ways to use Google Earth. Many of these tips apply equally to many other forms of travel. One thing is apparent, few people realize some of the less-known, but best features of Google Earth for travel. Make sure you update to the latest version of Google Earth (download here).

Here are some tips on Google Earth that every sailor (and many other travelers) should know:

  1. Google Earth can be used without an Internet connection – While sailing I actually use Google Earth more without an Internet connection than with a connection. Many people aren’t aware that Google caches the last 2 GBytes (if your cache is set to the maximum) of imagery/layers you last loaded. What I do is (while I’ve got an Internet connection before leaving on a passage) visit the places in Google Earth I’m about to travel to (in particular the anchorages) and make sure to load the imagery of those places most important to me. It’s important not to load too large an area or the cache will start forgetting the older stuff, turn off unnecessary layers before you load the images as well. Zoom down only on the most important parts – like the possible anchorages you plan to use, and the places you plan to visit on land. Once on a passage (with no easy way to be on the Internet) you can still load Google Earth and view those last places loaded. You can view what the approach to an anchorage is like, and the places you plan to visit while reading other guide materials or charts. Read more about using Google Earth off the Internet.
  2. Historical Imagery – Since Google Earth Version 5.0, Google has included a feature called historical imagery. If you look at the top of the GE window, you will see a little “clock icon”. Click on this and a “time slider” appears. Depending on your current view, you will see 1 or more “tick marks” appear on the slider. The tick marks represent available imagery on a certain date. Google has archived imagery around the world for multiple dates in the past. You can often see much better imagery for many anchorages around the world. For example, in Pago Pago the current default imagery is very dark and has some clouds. Using historical imagery, there is a much clearer more recent photo of American Samoa taken on the day after the Tsunami hit (September 29, 2009).
  3. The Ruler – I frequently make use of the Google Earth ruler to measure distances between places we are going, or the places we have already traveled. You can change the units (I frequently use the “nautical miles” units). Also, you can trace out paths, not just single measurements (look for the tabs at the top of the window that pops up to find the “Paths” tab). This is very handy for measuring routes. As a sailor, I often use this feature to check distances on passages, determine the best places to anchor, estimate dinghy runs, and distances we’ll have to walk to grocery stores and customs offices. I also use it to measure the size of vessels I see in the imagery.
  4. GPS Tracks – if you have a GPS, you can take your saved GPS tracks and use many free programs to convert your track to GPX. Some GPS programs will even output your GPS tracks directly to Google Earth’s KML. But, Google Earth will read GPX files as well. Simply open your KML or GPX file of your track. The new Google Earth 5.2 presents you with a new option to save your file as a “track”. This lets you play back the track with some new features like the time slider. I also recommend a free online program called “GPSVisualizer” to generate highly customized GPS tracks for use with Google Earth.

    Below is the GPS track of Tahina’s passage to Bora Bora from Moorea:


    View Passage to BoraBora in a larger map

  5. GPS in Real-time – Google Earth can connect directly to many GPSes. Look for the option under “Tools->GPS”. If you have a Garmin with a USB connection, it is very simple. You can also use the NMEA option to connect. Read more about that in the Google Earth user guide. Once you have your GPS connected, Google Earth can show your position in real-time. It makes Google Earth into something like a 3D “chart plotter”. Google Earth is not to be used for primary navigation. The data is not intended for that, so it is not guaranteed to be accurate enough to sail by. However, using it as an additional reference has proven to be very effective. The imagery is often (but, not always) good enough to see major underwater obstructions (such as coral heads, rocks, and even sunken ships). It has also been handy for seeing the best route through passes. In fact, I have often found GE imagery is more accurately placed than my electronic charts. You need to remember some of the imagery can be several years old though. The imagery is definitely not real-time (read about Google Earth imagery).
  6. Many other uses – I also share our position reports, GPS tracks, and photography using Google Earth. You can share your photos for free with Google’s Panoramio – which lets you map the positions of each photo when you upload them (or you can do the geotagging with another program). The photos will later appear on Google Earth and Google Maps for everyone to see as icons when the Panoramio/Photos layer is turned on. I also take 360 Panoramas and upload them to 360cities.net, which are also viewable on Google Earth, or you can put them on your web site (see example). Most importantly, I often use Google Earth while on the Internet to do research on the places we are going to find information and pictures about popular places to visit. Turning on the Photos layer is a fast way to find popular places (more photos in the most interesting spots). I also showed a bunch of sailors how to use Google Earth to see the best place to watch the solar eclipse that occurred over the central Pacific waters on July 11th.

These are just a few of the many ways I use Google Earth while sailing/traveling. They are all free, and easily available to anyone. All you have to know is that they exist, and how to use them. If you like this post, you might also like my post on using other Google products for sailing.

Here are a few posts showing how Tahina Expedition is using Google Earth:

  1. Kite Aerial Photography of BBQ Island in Google Earth
  2. Aruba Jeep Tour in Google Earth
  3. Our map of San Blas using GPS
  4. About Tahina’s Circumnavigation Route
  5. 3D Tour of Tahina (requires Google Earth plugin in your browser)
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