At 12:45 PM 12/23/98 -0700, k6ll@juno.com wrote:
>
>Let's see... You could take an slr camera, telephoto lens, and
>a tripod down onto the low ground and take sightings up the
>hill. Read the slant range to the focus point off the lens
>markings, and read the upward camera tilt from a carpenter's level
>and protractor. Since you want to take the readings every 50 feet,
>this should work pretty well.
>
>The vertical and horizontal distances would then resolve as:
>
>vertical distance = slant distance x sin(tilt angle)
>
>horizontal distance = slant distance x cos(tilt angle)
I'm sure Dave's method would work, but to tell the truth I also wonder how
important small imperfections in the smoothness of the foreground are at
HF. I believe that there's a formula for how smooth a reflector has to be,
as a function of frequency, and that it applies to ground reflection and
refraction as well. Seems I recall that at HF the reflector can be
"unsmooth" by +/- several tens of feet without affecting the reflected wave.
Empirically, I know that my foreground here is flat +/- 10 feet to well
beyond the Fresnel zone, and introducing a 10-foot step or "notch" into
that profile produces almost no discernible pattern effect in YTAD.
Seems to me that the largest-scale USGS topo maps contain data that are
probably more than accurate enough for HF purposes. Both the price and the
relative effort expended are a real bargain.
73, Pete N4ZR
Loud is good
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