[TowerTalk] HFTA Disc....

[David Gilbert]

Hi, Jim.

I did pretty much the same thing for the key azimuth points I was 
interested in.  I used Delorme's 3D-Topo Maps program (which no longer 
works on Windows 8 or 10, by the way).   I simply drew a line in the 
desired direction and manually read the elevation and distance figures 
off the terrain plot.  By doing that I was able to pick data points 
determined by the change in elevation instead of the change in 
distance.  So my text files looks more like:

0, 5000
15, 4990
35, 4980
70, 4970
85, 4960
etc (numbers above for illustration only)

instead of:

0, 5000
10, 4993
20, 4987
30, 4982
40, 4978
etc

HFTA simply draws lines between the data points, so in my opinion it 
gives more accurate rendering of the terrain profile with a relatively 
fixed increment of elevation than with a fixed increment of distance.  
It also allows 150 data points to extend out much further unless the 
terrain profile is very choppy.  In my case here in southern Arizona, 
HFTA can recognize the effect of a mountain range some 15 miles distant 
so the extra distance from the method I used was useful to me.

73,
Dave   AB7E




On 7/16/2016 4:28 PM, Jim Brown wrote:
> Gary,
>
> When I was running HFTA on my QTH in the Santa Cruz mountains, Dean 
> advised me to to out to 10-15 miles. This ignores small variations, 
> like the gullies being described.  The radial data is a plain text 
> file, and it is possible to generate your own data from topo maps. 
> When I started using HFTA, I did a few radials this way as an exercise.
>
> 73, Jim K9YC
>
> On Sat,7/16/2016 3:03 PM, StellarCAT wrote:
>> I use the 10M range data with HFTA exclusively! The 30 is far too 
>> long of a sample point. I'd prefer even smaller if available. I set 
>> up microdem at 5° increments and never have a problem getting the 
>> full data set. Works great. 
>