The HFTA terrain file is a simple ordered list, and as you say it can be
edited with any text editor. Each line in the text file represents a
different data point ... the first number is the range, followed by a
space and then elevation.
It literally just looks like this:
0 100
10 102
20 103
30 103
47 102
50 101
55 99
57 98
etc
The only other requirement is that the file have a .pro file extension.
I found that the easiest way to do that was to take an existing sample
.pro file and just edit the heck out of it.
ALL of my terrain files were hand generated in a text editor using data
manually picked off a terrain graph from a program called DeLorme 3D
TopoMaps back when it would still run under older versions of Windows.
By doing that I could choose data points with approximately similar
difference in elevations instead of data points with the same difference
in range. If I saw any spot that looked more complicated I just used
smaller increments. Keep in mind that HFTA essentially draws straight
lines between data points so if you use constant range spacing between
points you can easily turn a rounded mound into a sharp peak, and sharp
peaks give different ray trace results than rounded ones.
I live on a long steep slope facing generally eastward, with the bottom
of the valley roughly seven miles away. There are folks who claim that
a few thousand meters or so is all the further anyone should have to
collected data points, but that's a garbage generalization. I have
another mountain range about 15 miles east of me and by editing the
terrain file to either include it or not I can see definite differences.
In case anyone wants to see what a modest tower on a steep slope can do
for (or to) your signal, check out
http://www.ab7e.com/HFTA/AB7E_HFTA.html
73,
Dave AB7E
On 1/19/2019 2:43 PM, Jim Brown wrote:
Thanks Shawn. Yes, Dean told me the same things., but he also advised
me to run a lot of simulations to find those that didn't have that
spatial aliasing. BTW -- the terrain data is a plain text file, and
can be manually edited. It's been more than 10 years since I did it,
so I don't remember format of that file, but I did generate one radial
of data by taking points off of a topo map. It might be possible to
manually edit a file to use different point spacing along different
parts of the radial.
The links to the modeling software within your older post seem to be
dead.
73, Jim K9YC
On 1/19/2019 10:17 AM, Shawn Donley wrote:
Since terrain effects have entered the discussion, here's my 2 cents
(probably less) on the subject. Like any modeling program, be careful
interpreting HFTA results. See my earlier post at:
http://lists.contesting.com/archives//html/Towertalk/2016-07/msg00350.html
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