[time-nuts] GPS 18 behavior

[Jim Lux]

On 7/22/13 5:48 AM, Scott McGrath wrote:
> You might want to look at what these guys have done for 40 years or so. Www.geophysical.com
>
ground penetrating radar doesn't work very well in the typical disaster 
rubble enviroment which has uneven surfaces and a lot of random 
scattering in the medium. It works great dragging it across a smooth 
field looking for buried pipes, drums of hazmat, buried bodes, etc.  It 
depends on the impulse response of the medium and target being 
relatively "clean".  GPR also doesn't typically have the ability to 
detect moving targets with displacements of 1mm (which is what 
heartbeats are).

Our scenario has an impulse response that looks like a Rayleigh 
distribution with a half power width of about 20% of the distance, and a 
very long trailing tail.

The CW radar approach we have works great through rubble and collapsed 
buildings, etc., we're just looking to improve it somewhat with coarse 
range and azimuth binning, and to synchronize data takes from multiple 
sensors dispersed around the site.  The latter is really "synchronized 
well enough to match heartbeats", so "milliseconds" is good enough.