Whenever possible, I do route planning with Google Earth. Google Earth’s 3D imagery allows me to fine-tune a route and identify features I might otherwise miss in two dimensions.
But Google Earth is losing the resolution battle with the other imagery powerhouse, ESRI. I’m willing to trade resolution for 3D exploration in many applications, but not all. I want higher resolution imagery for identifying rapids on remote rivers. Here is an example of the difference in resolution, from unusable in Google Earth to unbelievable in ESRI Worldview.
The good news is, there are several ways to work with the ESRI imagery, including pulling it into Google Earth!
If you are unfamiliar with CalTopo, here is a basic introduction. ESRI Worldview is not available in CalTopo by default; you have to load it manually.
- Go to http://caltopo.com/.
2. Select Add New Layer from the menu on the left side of the page and choose Custom Source.
3. In the Custom Source dialog box, provide a name for the layer and paste the url below in the URL Template field. I’ve increased the Max Zoom from the default 16 to 20. Zoom levels above 16 aren’t always available, but if they are, I want them.
If you have a CalTopo account ($20/year), click the Save To Account link so that you don’t have to repeat this process. Saved layers can be found in the layer menu in the upper right, at the bottom of the list of options, under Your Layers.
Now I can add waypoints at each rapid and identify which side of the river might be easier to portage. At the end of my work in CalTopo, I save the waypoints and portage line segments to be imported into Google Earth and combined with the rest of my existing route work. But you could certainly do all of your route planning within CalTopo.
You can pull ESRI Worldview imagery directly into Google Earth two ways.
The free option is to pull the kmz directly from arcGIS: https://services.arcgisonline.com/arcgis/rest/services/World_Imagery/MapServer/kml/mapImage.kmz (direct download). This source is a bit sluggish and does not go to as high a zoom level as what we can get from CalTopo. It also doesn’t seem to work on Linux computers.
The second option is to pull the layer via CalTopo’s servers. You need a CalTopo account, the basic subscription level costs $20/year.
Sign in (upper left) and click on your account name (email address) in the upper left corner. Select the Your Account tab under the View Account window. Click on the KML hyperlink toward the bottom of the window to download the superoverlay.kml file.
Open superoverlay.kml in Google Earth. Select Your Layers from the bottom of the list, and move the folder with your ESRI Worldview layer out of the Temporary Places folder so that you don’t have to repeat this process after restarting Google Earth.
Note that you might want to save other layers as well; I used the USGS 7.5′ layer for my topo map work in Google Earth.
ESRI Worldview is available at the premium subscription level of GaiaGPS. Select the Layers & Overlays icon from the buttons on the left, then Add Map Layers at the bottom, Satellite Imagery –> World Imagery.
If you don’t have the premium subscription level, you can manually load the ESRI layer. Follow the directions in the Custom Load Google Earth Imagery section of my Gaia tutorial, but use the ESRI URL instead of the Google Earth URL.
My routes are all going to end up in GaiaGPS anyway (so that I can load them onto my phone for the trip), so why not use the Gaia website in the first place? The reason is that Gaia’s web application tile servers are prohibitively slow. GaiaGPS is absolutely the easiest way to work with the ESRI basemap. I just get impatient. The hassle of loading ESRI into CalTopo pays for itself after 10 minutes of mapping.
There are a few easy ways to view the ESRI layer without the ability to add waypoints or routes. These are my go-to in the exploration phase of trip planning.
The direct from ESRI option allows you to determine the date that the imagery was collected. In this case, the river imagery was collected August 31st, 2015. The timestamp is very helpful for anticipating water levels at other summer months.