National Forests Technology

How to Add Forest Service Roads to Google Earth

Forest Service roads are a tremendous asset for those interested in exploring all that our National Forests have to offer.

How can you add U.S. Forest Service roads to Google Earth? Google Earth allows users to create Image Layers based on data from WMS servers. U.S. Forest Service roads are available as a data layer on the Geospatial Data Discovery tool, which can be added as a WMS server.

Let’s get to it: in this post we’ll go over everything you need to know in order to add U.S. Forest Service roads into Google Earth.

How to Add U.S. Forest Service Roads to Google Earth

Before we get into the step-by-step instructions on how to incorporate U.S. Forest Service roads in Google Earth, I need to quickly cover the best options available to us.

A Brief Summary of Our Options

Without digging into the boring details too much, there’s not exactly an easy way to add U.S. Forest Service roads to Google Earth.

The easiest route would be to download the necessary KML file directly from the Geospatial Data Discovery tool that is provided by the Forest Service. They do offer KML files as an output for their data layers, but unfortunately the data layer we need (National Forest System Roads) is much too large to function in Google Earth, as it comes in at over 1 GB in size.

Ideally, we’d be able to filter down to our area and then download the filtered results in a KML file. The unfortunate truth is that the filtered dataset option in ArcGIS is either crazy slow, or straight-up broken (background info for the curious).

So in order to add Forest Service roads into Google Earth we’re left with a workaround that produces a somewhat unsatisfying result. It still works, but it’s a bit laggy and it is rather difficult to discern the road numbers from the created layer.

Add an Image Overlay With the WMS Server Tool

As I mentioned above, we’re unable to import the data on the Forest Service roads directly into Google Earth, but we’ll be able to employ a workaround. To do this we’ll be creating an Image Layer in Google Earth that is based on data from something called a WMS connection. To get started, copy the below URL:

Next, go over to Google Earth and select the ‘Image Overlay’ menu item from the ‘Add’ part of the top menu:

This will open up a window that looks something like this:

Your cursor should already be in the ‘Name’ field at the top. This is what we’re going to see in the Places panel on the left side of the screen, so change the Name to something like ‘Forest Service Roads’.

After you’ve done this, then click on the ‘Refresh’ tab and then click on the ‘WMS Parameters’ button on the right:

This will bring up a new window, and this is where we’ll be needing the WMS URL from before. The top part of this window has a ‘WMS Server’ area with a dropdown menu. You’ll want to click on the ‘Add…’ button highlighted in the below screenshot:

You’ll paste the URL into the ‘Enter WMS Server URL’ window with the red arrow pointing to it. Once you paste it in, click ‘OK’ and then your screen window should update to something like this:

Notice that the Transparent Layers section now has two layers listed if everything worked.

Add the Correct Layer Over to the Selected Layers Section

Now that we’ve established the connection to the WMS server for the U.S. Forest Service roads, we have to add the correct layer over to our Image Layer in Google Earth. There should be two options available:

  • National Forest System Roads closed to motorized uses
  • National Forest System Roads

As you can probably guess, we’re interested in the second layer, as the first layer will only show you roads that are currently closed. We’ll need to move to second layer over to the ‘Selected Layers’ panel on the right. To do that we’ll click on the ‘National Forest System Roads’ layer and then click the ‘Add ->’ button highlighted below:

Once you move the layer over, you can hit the ‘OK’ button for the window. At this point your screen will likely update and show you something that looks like this:

I don’t think I have to tell you that the ‘strange white box at an angle’ is not the intended result from doing all this. We’re going to have to make a few minor tweaks in order to fix this.

Tweak the Values in the Link for Increased Clarity

We’ll make a few small tweaks to the value in the ‘Link’ field at the top of the window. Admittedly, this field might look a little overwhelming to those that don’t spend a lot of time querying APIs, but it’s pretty straightforward. Here is end of the link that Google Earth generated automatically after adding in the WMS layer:

I’ve added red lines to highlight three different parts of the URL, the width, height, and image format.

First, we’re going to adjust the height and width of the image that Google Earth adds to our map. The default value is 512 pixels, as you can see in the above screenshot. We’ll want to bump that up to something like 1920 pixels. I don’t think the exact number you choose matters, you just need to ensure that the height and width are equal. You can update these values by typing the 1920 over the previous value of 512. Ensure that you don’t overwrite the equal sign and ampersand on either sides of your number.

After bumping up the pixel count on your height and width, you’ll want to change the format of the image. As you can see at the end of the URL, the default format is GIF, represented by the ‘image/gif’ part at the end. We’ll need the ‘image/’ part, but you need to change the ‘gif’ part to ‘png’ like so:

After doing all of this, your updated entry in the ‘Link’ field should look something like this:

Adjust the Settings in the Refresh Tab for the Image Overlay

With the entry in the Link field sorted, you next have a make a few tweaks back down in the ‘Refresh’ tab. We’re going to adjust two values:

  • The duration of the View-Based Refresh (default should be 4 seconds)
  • The View Bound Scale (default set to 0.75)

Make the following changes to your settings so that they look like this:

My general understanding is that this will allow the data to refresh much faster, as you won’t have to wait so long for the server to pull over new information.

As a side note, huge thanks to everyone over on StackExchange for their discussion of how to figure out this problem in Google Earth.

Zoom in and Out to Refresh the Image Layer

Now that you’ve gone through all of this work to get this connection established and working just right, it’s time to actually use this info!

You’ll want to zoom in and out to trigger Google Earth into loading the U.S. Forest Service roads onto your screen via the Image Layer we just set up. It does appear that there is a limit to how far zoomed out your screen can be in order to load the roads image.

You don’t have to be super close in zoom, but this was the farthest zoom I could pull off where the road layer was successfully added:

Note the value on the scale on the bottom part of the screenshot for reference.

As you move the screen around and adjust the zoom you’ll notice that it takes a little bit for the roads to appear.

While I’ll be the first to admit that it’s rather convenient that we can hook up this server like this, there is one major caveat for me: the labels for the Forest Service roads are unfortunately barely readable.

I’ve played around with the zoom and the other settings in order to try and improve this, but I haven’t had much luck.

Final Thoughts

Hopefully you were able to get everything working and you are now enjoying the convenience of having Google Earth automatically pull in open U.S. Forest Service roads. I’ll be the first to admit that this solution isn’t ideal, but I’m on the lookout for a better solution. I’ll update this post if I find a better method.

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By Drew Meulemans

I've long admired forests and devote much energy to learning about them and exploring. I enjoy sharing what I learn and wish to inspire others to do the same.