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Trial Offer

Get your first five sessions for $1.

A session lasts twenty minutes. A session doesn't start until you click on the map to request a line-of-sight computation. (So you can work on your tower list, for example, without starting a session.)

You can use the trial sessions with any number of towers. After you've used those sessions,


If you have 100 or fewer towers, you can skip the trial offer and set up a PayPal subscription. The price is $100/month.


If you have five or fewer towers, you can use the site for free. Towers will be stored in a cookie on your machine. Use the URL

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If you have more than 100 towers or require an alternate payment arrangement, please