Topographic shielding calculator

For correcting the production rate at a site that is partially shielded from the cosmic-ray flux, either by the surrounding topography or by a reasonably extensive dipping surface surrounding the sample. This is a simple opaque-horizon calculation only -- it does not include partial shielding by nearby objects or particle leakage effects. Based on the 'skyline.m' MATLAB function.

Version 2. Revised April 2018. If you observe any unusual behavior or inconsistencies with previous calculations, contact Greg Balco,

Strike and dip of surface:

Strike (0-360 degrees):
Degrees. Follow the convention that the strike is 90 degrees less than the direction of dip, that is, if you are facing in the strike direction, the surface dips to your right. For a flat surface, enter zero in both boxes or leave them blank.
Dip (0-90 degrees):

Azimuths (0-360):
Elevations (0-90):

Azimuth - elevation input format:

Describe the horizon by entering lists of space-separated values corresponding to the azimuth (0-360 degrees) and angular elevation (0-90 degrees) of points on the horizon. If you have a full 2-pi field of view, i.e. no shielding, leave blank or enter zeros.

This procedure means that in the field you should have approximated the horizon by a series of points with straight lines between them. Note that this is not the same as approximating the horizon by the average elevation angle in a series of equally spaced quadrants, octants, etc.: the latter procedure is inappropriate because the relationship between rise angle and cosmic-ray shielding is nonlinear, and it will underestimate the actual shielding in the case of large and variable horizon angles.

For example, if the horizon around you looked as follows:

You might approximate the horizon like this:

And enter the following series of points:

0 55 115 235 310
3 0 5 0 0
This particular horizon has a shielding factor of 0.99995, that is, so small that we really didn't need to bother.

(Thanks to David Metsky at Dartmouth College for the 360-degree panorama of the view from Mt. Avalon that we've borrowed here)

Initial development of this website was supported by the National Science Foundation