Use Google Earth to Create Custom GPS Routes for Fishing

I created this article to share my GPS knowledge I use to safely navigate the marsh. This ability has made me successful as an inshore angler because I am able to safely venture into and out of unknown territory.

Navigate the marsh with custom GPS routes

Why use Custom GPS Routes?

Most mapping products out there are generic and may be good for freshwater lakes but are not versatile enough to be reliable in the marshes of Louisiana.

Louisiana’s Inshore Waters are Unique

For starters, the marsh is huge and very easy to get lost in.

Many areas we fish do not have cell phone coverage, so using your phone to see where you are on a map is not reliable.

Secondly, the Louisiana marsh is always changing. Land is created and lost, making previous routes unnavigable.

Yes, there are excellent mapping chips on the market, but they only work for certain name-brand GPS’s and are expensive.

What I teach here is good for virtually any GPS system and will work anywhere.

The Louisiana marsh is endless and very uniform. It is crucial to have a dependable  ability to navigate this expanse where everything looks the same.

You don’t want to get stranded!

Raining in the Marsh
You don’t want to be lost in the marsh when bad weather strikes.

Some notes before we get started

In this article I show you how to create those custom routes and waypoints using Google Earth, create a GPS file containing those items and then load the GPS file onto your GPS unit.

The GPS I’m using is a Lowrance 332C, but the method and tools used are good for any GPS.

The biggest problem we will run into is conversion issues, which will be handled on a case-by-case basis outside the scope of this article.

By “conversion issues” I mean converting from Google Earth’s Keyhole Markup Language (*.kml) to whatever format your GPS uses. In the context of this article, that is the Lowrance *.usr.

I use two programs to do this:

Google Earth and GPS Babel, can be downloaded free-of-charge.

If you find yourself needing help after reading this entire article, you can post in our GPS, Safe Routes and Navigation forum at Louisiana Fishing Reports. Chances are another angler can help you.

Download these programs at:

What is Google Earth?

Google Earth is a digital map of the entire world, represented in a small-scale, three dimensional model on your computer.

Here is a picture to show you what I am talking about. At any time you can click/tap a picture to enlarge it.

Google Earth Overview
Click to Enlarge

Google Earth uses latitude and longitude coordinates (lat/longs), but it also recognizes Military Grid Reference System and other formats.

I will use lat/longs in the format of DD° MM’ SS.SS”.

There are many tools you can use in Google Earth:

  • measure distances
  • view terrain and buildings in 3D
  • measure azimuths
  • create routes

Google Earth has features like Street View that will let you see what an area looks like from a particular location on a street in a 360° panoramic.

This is especially useful for bank fishing or learning where marina parking is without ever having been there!

Introduction to the Path Tool

When you open Google Earth, you will see a tool that looks like a ruler in the top bar of the window pane.

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Click to Enlarge

Click on it. You will see a box pop up with two tabs.

One will say “Line” and another will say “Path”.

Click to Enlarge
Click to Enlarge

The Line tab is used to measure distances. The Path tab is used to create routes.

If you look at the window pane on the left, you will see a bar titled “Places”.

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Click to Enlarge

If it is not expanded, go ahead and expand it.

When you create a route or waypoint, it will be created not only on the map, but also in this pane.

Go ahead and play with these tools in order to learn their full functionality and become comfortable with Google Earth.

Create a Route Using the Path Tool

If I wanted to create a route from Hopedale Marina to the intersection of Bayous LaLoutre and St. Malo, I would press the ruler button and select the Path tab.

For instructional purposes, the starting point is located at:

29°49′ 7.10″ N 89°36′ 42.36″ W

and ends at

29°50′ 19.21″ N 89°32′ 51.06″ W

Zooming in on Hopedale Marina, I would start my route there and trace it across the MRGO (the big canal) and down Bayou LaLoutre to my destination.

Click to Enlarge
Click to Enlarge

These three things move your screen across the map as you plot your route:

  • Press your A, W, S and D keys to scroll up, down, left and right.
  • Use the scroll symbol on the right hand side of the map.
  • Check the “Mouse Navigation” box and hold down the left mouse button to scroll around.

Use the one most comfortable for you.

Saving Your Route

Once I have completed my route, I  hit the “Save” button which will cause another box to pop up.

From this box, I can view and edit all properties of this route, to include the route’s distance under the “Measurements” tab.

For now, I will name the route “Stallion One”.

If you look at the Places window pane, you will see your route, Stallion One.

From here, you can right-click on it and hit “Save Place As”.

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Click to Enlarge

I named it “Stallion One” and, most importantly, I saved it as a Keyhole Markup Language file or .kml file and not a .kmz file.

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Click to Enlarge

This is important for conversion purposes because .kmz files usually cannot be converted to popular formats for use in a GPS.

As one last detail, I saved Stallion One.kml to the desktop, so it’s easy to find.

Why we change the file format

It is important to change the file format of your saved route.

Your GPS cannot understand the .kml file format, so it must be converted to one that can be understood and used.

Think of this process as translating instructions from one language to another, so the person speaking a different language can understand.

Different name-brand GPS units use different file formats.

Changing the File Format

Opening GPS Babel you will see two sections, an Input and Output section.

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Click to Enlarge

For the input section, I click on “File Name” and browse to the desktop, where I find the route “Stallion One” saved.

I select it.

Then for output I go to the “Format” drop down menu and select the type for my boat’s Lowrance 332C, which is the .usr file format.

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Click to Enlarge

In GPS Babel, file formats are listed in order of their manufacturer, making locating them in the drop down menu that much easier.

Next, I click on “File Name” and save the file where ever I want to save it on my computer.

I like to store them in a folder named “GPS Stuff”, so I will always have a backup after I upload the file to my GPS.

Once I have completed these steps, I hit the “Apply” button at the bottom of the application.

This changes the format of the route from a Google Earth .kml file to a Lowrance .usr file.

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Click to Enlarge

Now all I have to do is put the file onto an SD card, insert the SD card into my GPS and then follow the steps on my GPS’s manual to load the file for use.

It seems like a lot of work, but it’s really not. With enough practice, you can throw a route together in no time at all.

If your GPS does not use an SD card, then you will need the appropriate accompanying software and USB cable.