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Big-picture exploration

I use Google Earth and photo resources to identify places I want to visit.

Google Earth

Google Earth has several faces… a phone app, Web, timelapse site, and Pro. You can view routes in Web, but only Pro (the desktop version) allows you to create routes.

Photos

I really value the photos layer in GE Pro. Unfortunately, Google has killed Panoramio (the source of the photos) and it isn’t clear if the photo layer will continue to be available in Google Earth. Many Panoramio users have moved to mapsights.com. Google Maps has photos too, but I can’t figure out how to display photo locations on the map, other than scrolling over the individual photos, which annoys me.

Route Planning with Google Earth

Download a Topographic Layer

Google Earth’s satellite imagery is even more useful when paired with a topographic layer.

• The best source for topographic layers is CalTopo. See the section at the bottom of this page for more info on CalTopo. For a $20 annual fee you have access to the “superoverlay.kml” which includes USGS 7.5′ topo coverage, as well as shaded relief, slope angle, and other satellite imagery. Be sure to drag the superoverlay layers from Temporary Places to My Places, otherwise they won’t be saved. Trying to work with several overlays will seriously limit render time.
• Earth Point is a free source for a topo overlay. The topo is from Delorme, so familiar to Gazetteer users, and not as detailed as the USGS 7.5′ topo.

Historical Imagery

View → Historical Imagery
Google Earth displays the highest resolution imagery (usually the most recent) but stores older imagery. By looking at different seasons, the older imagery helps assess snow cover, crevasse fields, and other season variability.

Sun Imagery

View → Sun
This might just be eye-candy, but if you want to see when the sun finally hits the slope you want to ski, you can use the sun time slider.

Drawing Routes

• Hover over the tools at the top of the page for ‘Add Path.’
• Resist the urge to draw a path by holding down the mouse button. Drawing a path this way creates a ton of points, which is too cumbersome to edit later, and makes an unnecessarily large file.
• Draw routes by clicking along the intended route. You can come back later to refine the route.
• A common pain point is for people trying to edit routes. The routes are directional, meaning that you might have to move an endpoint and add new points in front of it. In other words, if you draw a route from north to south, you will always have to add points from north to south. Click on the northern point to select it, and draw points to the south of it. Play.

Elevation Profiles

• Right-click → show elevation profile
• Use an online calculator to convert slope percent to angle

Creating/sharing a Route

Routes and points can be saved to kml or kmz files and emailed to trip members for review, edits, etc.
Identify bail-outs, cruxes, for discussion

Other Resources

CalTopo

Caltopo is the best 2D tool for route planning. CalTopo was started by a California SAR member who wanted to provide useful information to his SAR team, and new features are constantly being added. It is a one-man show, funded by the very reasonable $20/year basic subscription (but planning and printing can be done for free). Tiles load quickly, baselayers include topo, satellite, shaded relief and more. Overlays include slope shading and weather stations. Right-click for elevation profiles and View from Here eye candy. You can export baselayers (like shaded relief to Google Earth), and import/export routes to/from Google Earth. We aren’t done yet! Export to print and use the easy controls to adjust the area to be printed. Export as a Geospatial PDF and you can view it on your phone with an app like Avenza Maps. CalTopo is a powerhouse!

For me, the greatest value from CalTopo is Google Earth integration and the superoverlay.kml, which serves USGS topos, shaded-relief imagery, slope shading (and a slew of layers that don’t extend to Alaska) to Google Earth. You need at least a basic subscription to access the superoverlay ($20/year). Then, once signed in to your CalTopo account, click on your account name (your email address in upper left) → Your Account → KML (hyperlink at bottom).

Bing Aerial

Bing (MSN search engine) has its own aerial imagery service, and when Google Earth’s resolution is bad, Bing’s is sometimes better.

Most Recent Satellite Imagery

I use these resources to get a sense for snow cover and vegetation.

NASA Worldview is my go-to for 2x daily imagery, but the resolution isn’t great. Choose the Arctic projection (globe icon, upper right) for Alaska, and rotate the image to bring north to top. The time control is at the bottom of the screen.

Zoom Earth features a stack of MODIS satellite images over Bing basemaps (zooming in automatically switches from MODIS to Bing). Tiles load quickly, a really nice feature when you are searching for cloud-free images.

Sentinel Hub is a European service featuring less frequent but higher resolution satellite imagery. The “Show acquisition dates” option in the “Effects” tab is great, as is the calendar filter. Click the satellite icon in the upper right to change satellite source.

Sentinel EO Browser is the best source for highest resolution imagery, specifically the Sentinel 2 L2A layer. Start by searching Sentinel 2, L2A, then click on the results to select a layer with minimal cloud cover percent.

Arctic DEM

• 0.5 m resolution, but only partial coverage of Alaska
• Frustrating ESRI portal access
• no easy way to get onto Google Earth or Gaia

Advanced access, from Sal Candela, Ohio State University:

• Download the shape file with all of the strip/mosaic data (http://pgc.umn.edu/system/files/ArcticDEM_Tile_Index_Rel3.zip http://pgc.umn.edu/system/files/ArcticDEM_Strip_Index_1.zip ).
• Use Arc or Qgis (free) to find the filenames that fall under the area you are interested in.
• Use either FTP (ftp://ftp.data.pgc.umn.edu/elev/dem/setsm/ArcticDEM/ ) or web access (http://data.pgc.umn.edu/elev/dem/setsm/ArcticDEM/) to grab the files directly (without using the ESRI interface).

Topo resources

I think these don’t do anything that Caltopo doesn’t do (better), but here are some other topo map resources:

Hillmap: side-by-side topo/sat, useful overlays such as slope percent
USGS: Download Topo quads
Topozone: Topo map reference

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