After deciding what we were doing to launch weather balloons, our next question was: Where?

Since we are based in San Francisco, we knew we would need to travel outside the city for safe air space.

An ideal space is:
  • Safe: The launch and recovery sites need to be clear, open, sparsely populated, and away from restricted airspace. Though our balloons are exempt from the FAA regulations due to their low weight, we still aim to meet the requirements when looking for a good launch spot.
  • Accessible: The launch and recovery sites need to have access roads. So preferably not in mountains, bodies of waters, or wilderness areas.
  • Connected: Without cellular reception, the payload will not be able to phone home and tell us where it is. We aim to recover every payload we send out, so they need to have solid communication channels.
  • Close: We need to be able to drive to the location and back to San Francisco in a day.
  • Predictable: Clear skies, no rain, regular wind patterns.

In order to find such a spot, we used a variety of resources:
  • Friends who had done this before, who suggested suitable areas.
  • Google Maps to check the locations of roads, cities, mountains, and bodies of water.
  • SkyVector to look at restricted airspace.
  • HabHub to get wind predictions for various launch spots.
  • AT&T coverage map to determine cellular reception.

We discovered that the Central Valley was a perfect launch location! Not only is it ~2-3 hour drive from San Francisco, but it also has large areas that are sparsely populated yet crisscrossed with access roads, mild weather with predictable NW->SE winds, and solid cell coverage.

Central Valley.png
The Central Valley of California
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SkyVector Map of the Central Valley

Typical Central Valley Flight Path

AT&T Wireless Coverage in the Central Valley

A major component of selecting a launch site is determining the landing site. The habhub.org predictions aren’t perfect, but they are impressively close. We want to avoid landing on highways, in cities, in bodies of water, or in the mountains.

So we look for launch sites that result in landing areas like this:


When the wind predictions show undesirable flight paths (like the ones below), we delay the launch or pick a different launch site.

Avoid landing in mountains, where it is hard to access the landing site.

Avoid flying over metro areas and airports.

Here are flight predictions from two of our launches to show good launch and landing areas:

Launch 2, abnormal winds for the Central Valley
Launch 4, more typical winds

The Central Valley is mostly devoted to farming, so we end up landing in various fields.

We also got to experience the California drought up close and personal. You can read more about that in the Where's the Water? blogpost.

To see more pictures of our launch and landing locations, check out our Picasa albums.

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