SAS Planet: How to Navigate Uncharted Reefs


Last Updated on January 18, 2023 by Amy

We absolutely love cruising remote destinations. There’s a beautiful feeling about being all alone in nature. But, just because boats have sailed the oceans since the dawn of man doesn’t mean that our charts are accurate. And here’s where SAS Planet comes in.

Why You Need to Use SAS Planet

Last year we noticed that our charts weren’t as accurate in the South Pacific as they were in the Atlantic.  Cough…  Beveridge Reef and Fiji… cough…  Fiji actually has pretty decent cell coverage so we were using our data plan to pull up Google Maps while we were out sailing.  That allowed us to supplement what we could see in our Navionics charts.  It worked well, but what about when we were in places that had a lack of cell phone coverage? For example: pretty much every other country we’d been to in the South Pacific.

Enter SAS Planet.  It allows you to download and save offline satellite imagery from Google Maps, Bing and a bunch of other sources.  We can then use these images to plot a route through reefs and bommies, all within SAS Planet, then export that route into a GPX format, which can then be imported to our Raymarine chartplotter and OpenCPN.  See, I told you it was cool!

Now on to the nitty-gritty details about how to actually use SAS Planet.

Download SAS Planet for Free

 SAS Planet is freeware, which all cruisers know and love.  But know that it also means it’s constantly under development so there may be a few quirks and I believe it’s only available for Windows at this time.  

Download SAS Planet for free.

There are a couple of other free programs I’d recommend downloading as well.  FransonGPS Gate Splitter and GPS Babel. We don’t actually need GPS Babel as a recent update of SAS Planet allows us to save routes directly to a GPX format recognized by Raymarine.  However, GPS Babel will convert to many different file types so you may still find it useful!

Hardware Needed

In truth, a computer is all you really need, but having a GPS puck will allow you to follow your track and your boat’s position in real-time.  SAS Planet isn’t a substitute for an actual navigation program or plotter but it is a really nice addition.

Setup SAS Planet

Installing SAS Planet should be pretty simple and straight forward, except for one slightly major issue.  Google Maps can’t be downloaded via the default settings.  Don’t panic, it can be fixed.  Go into the ‘Settings’ Main Menu and choose ‘Options’.

In the ‘Maps‘ tab, select ‘Satellite (Google Maps)’ and then hit ‘Settings’.

Selecting Google Maps Settings in SAS Planet
Selecting Google Maps Settings

Make sure that the Map Version is set to 718 and then hit ‘Okay’.

Map Version

See, no need to panic.

(2018 Update: Okay, there’s perhaps a slight reason to panic.  Google Maps seems to not be working again for me.  Instead, I’ve been using Bing Maps-satellite as well ArcGIS.Imagery, found under the ESRI Source.  If I can figure out how to get Google Maps working again, I’ll update once more.)

Now we need to connect SAS Planet to the GPS puck and that gets a tad bit complicated.  For some reason, SAS Planet refused to recognize that I had a GPS puck entered into a USB port. This is when we use FransonGPS Gate.  It is a program that takes a GPS input and outputs the information to several virtual USB ports (aka COMS).  SAS Planet had no problem recognizing one of those virtual COMS and you can also set up OpenCPN to use a virtual COM as well so you can get GPS data into both programs simultaneously.

GPS Gate Input

We have our GPS puck in the USB port designated as COM4.  Don’t worry if you don’t know what COM number you should use.  Try the trusty Setup Wizard or use good ol’ Mr. Google for some help on how to use your computer’s Device Manager.

Add Virtual COM Port

Once you’ve selected your input COM port, you can set up as many Virtual COM Ports as you want.  I’d suggest choosing higher numbers for these ports just to prevent any confusion within your computer.  I went with two; one dedicated for SAS Planet and one for OpenCPN.

Virtual COM Ports

Back in SAS Planet, we need to set up the program to recognize the Virtual COM Port that you just set up.  Go into the GPS Main Menu and choose ‘Options‘.  On the screen that pops up, make sure that you choose the proper COM Port, check the ‘Autodetect on connect’ and ‘Virtual’ boxes.

SAS Planet GPS SetUp

Once you have that ready, hit the ‘GPS On/Off’ button and presto changeo, SAS Planet should now be getting live GPS data! (Note: so far I’ve needed to turn on the GPS each time I use SAS Planet)

Download Satellite Imagery

Next we need to download some satellite imagery but before we get started, I’d strongly suggest that you connect to a fast and unlimited internet connection.  You can rapidly run up some large file sizes depending on the area you’re downloading and the various zooms you desire.  That being said, I know how rare that is once you’re out cruising, so I’ll try to share a few tips to manage how much data you’re using.

Selecting Your Source

SAS Planet allows you to pick the source of the satellite imagery you want to download.  This is extremely useful as one source may have some cloud cover and another may have a clearer picture.

I usually start with Google Satellite and then try Bing if I feel I need some additional detail.  Those two seem to have the most extensive imagery available.

Choosing your map in SAS Planet
Choosing Your Map

Once you’ve selected which Map you want to use, there are two ways to download the maps: the fast, automated way and the slow, manual way.

The Fast Way

If you’re trying to download large areas and have that mythical unlimited internet, the Rectangular Selection tool is the easiest to use.  If you’re looking at a specific anchorage and trying to conserve some of your crappy cellular data, I like the Polygonal Selection Tool.

Selection Tool

It allows you to choose a more detailed area for downloading.  SAS Planet downloads the satellite imagery in tiles, so the more specific you can be about the area you want, the less tiles and data you’ll need.

Polygonial Selection Tool

Once you’ve got your area selected, hit the Green Check Mark in the popup box to bring up the Download Options Menu.

Download Selection Manager

Lower numbers are the far-out zooms and the higher numbers are the closer-in zooms.  Obviously the closer in the zoom, the larger the file size needed to download.  For each box you check, SAS Planet will download that zoom for the area you have selected.  I’ve found that choosing three zooms, 10, 15 and 18 gives me a pretty good mix of overview + detail without making the download size too unreasonable.  But when I get lots of internet, you can be sure I’ll be going pretty crazy downloading lots of zoom levels!

The Slow Way

You can set up SAS Planet to download whatever you’re viewing on the screen.  If you’re really looking to limit your download sizes, this is the way to go but it takes a long time as you must scroll around at every zoom level (you can see your zoom level on the left-hand side) and wait for the tiles to download.

Screen shot of SAS Planet with satellite imagery.
Internet + Cache

Make sure you have selected ‘Internet & Cache’ as this will download the maps to your computer for offline use later.  If you want to navigate around using maps you’ve previously downloaded without using data to download more maps, select ‘Cache’.

Creating A Route Using SAS Planet

With all your satellite imagery downloaded, it’s time to work on creating a route you can use as a guide for navigation.  There is an icon in the menu bar called ‘Add a new path’.

Add a new path

You can now add waypoints and create your path.  I usually start on one of my ‘overview’ zooms before zooming in for more detail and making sure I’m not heading over a bommie.  You can adjust the waypoints so you just need to get the path close to start with.

Creating a path in SAS Planet
Creating a Path

Once you’re satisfied that you have the path set up to avoid treacherous bommies and rocks, you can save it.

Saving a Path

SAS Planet allows for different categories for your paths so I try to group them by geographic area.  Choose whatever name you want for the Path.  Once that is done, we need to go in to the ‘Placemark Manager‘ so we can export the route into a usable format by our chart plotter.

Pacemark Manager Menu

Select only the path you want and choose the drop-down box by ‘Export’.  Select ‘Export Visible Placemarks’ otherwise SAS Planet will export all tracks and waypoints to the file and that will cause issues importing it into the plotter.

Placemark Manager

Make sure you select a folder on your computer that you will be able to find later.  Our Raymarine plotter is capable of importing GPX routes and conveniently enough, that is one of the formats you can save to.  I have no idea about the types of files used by other plotters so you’ll have to do some research and find out.  If you need another format than what SAS Planet offers, that’s what GPS Babel is for.

Saving Path

Importing Route into Raymarine

Having a carefully planned out route is quite nice, but it’s way more helpful to have that information also available on our chart plotter while we’re navigating our way through the reefs.  To import into our plotter we need a microSD card.  So far I’ve just been using the ones that store our Navionics charts.

Saving to MicroSD

Put the microSD card back in the plotter and navigate to the ‘Home’ screen.  Select ‘My Data’ and scroll down to ‘Import/Export’.

Screenshot of Raymarine chartplotter while importing a route made in SAS Planet.
My Data – Import/Export

Choose ‘Retrieve Data’.

Retrieve Data

Select the route you just saved.

Choose Route

The plotter will then automatically import the route.  You can then go into your charts and marvel at how awesome it is that you now have a source that will let you find paths through reefs that you never would have found using just your chart plotter!

Imported Route
Route on SAS Planet


THIS IS VERY IMPORTANT!!!  SAS Planet is a tool and you should not rely on it with unfailing confidence.  You should always keep a lookout when navigating through difficult areas.  I don’t want to hear from anyone that they hit a reef because they were just following a route they created in SAS Planet.  Keep a lookout and use common sense!

Have fun exploring uncharted destinations!

(By the way…  A huge shoutout to Brent from Catamaran Impi for his write up on this topic.  That got me off to a good start but I hope I’ve added enough extra detail to make it worth a separate post)

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  1. Love the concept but it fails at the download-of-maps step. When I select an area around me and try to get the image tiles, all I get is “Tile not found!”, after repeated attempts with different zoom levels. Can send screen snaps, any debugging clues you can offer would be welcome.

    1. Hi Royce. Are you trying to use Google Maps? I’ve been having a few issues with them recently as well. I’d suggest trying the ARC.GIS.Imagery source. It can be found under ‘ESRI’ in the source menu. Let me know if that works and I’ll try to update this post with that info.

    1. I’ve used both methods, SASplanet is better, OpenCPN is clunky and I have an MFD. This method caches the images, no conversion required. Another useful app is Ovitalmap

  2. Hey Mate, this is incredible. Thank you for taking the time to share. Also thank you for explaining it in idiot format, which is about the only thing I understand. It helps loads. Now slow down so that we can catch up again. We about 2 000 nm behind, but a full season I guess. Shot Barry. SY Jadean

    1. Haha, reading idiot format is how I learn best so I figured it’s only fair to explain things that way too! We’re going about as slow as we can, so I’m afraid it will be you who has to speed up to catch us! Are you guys planning on going down to NZ for cyclone season this year?

  3. Oh, David -you are such fun. After googling the definition of bommie – I followed your post perfectly! Hugs and loves. Mom

    1. Hmmm… Sorry about that. Guess I thought most people who would be interested in this post would be hard-core sailors. 😉

  4. Thank you David, very easy instructions to follow thanks again for taking the time to put this info on paper. Like your Vids keep up the great work.

  5. David – I will be in complete AWE of you forever and ever!!
    Right now my landline phone isn’t working. Any suggestions to solve that??
    XXOOGrandma 🙂

    1. Well thank you! Not sure about the landline other than to say ditch it and go to using only your cellphone. 😉 Love you!

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