On 3/4/12 4:46 PM, Jim Brown wrote:
> On 3/4/2012 1:01 AM, Mark Robinson wrote:
>> Sorry for the rant but I am so frustrated with this program and the lack of
>> any useful instructions on how to use it. Another half baked good idea in
>> my book..
>
> Did you study the discussion of HFTA, and of the technical concepts upon
> which it is based, in the ARRL Antenna Book? Because I did that, I
> thought it was pretty good, and I sure don't think it's "half baked!"
> As others have noted, the only thing difficult about it is dealing with
> the terrain data, which is all done by others.
>
>
The modeling part is fully baked. The terrain retrieval process is raw
and uncooked.
I was thinking, though.. The entire US, with 3arcsecond precision,
easily fits on 5 600MB CDROMs in a not very compact form (1201x1201
arrays of 16 bit signed integers). It's about 50 degrees wide by 20
degrees high, or 1000 of those (roughly 3GB uncompressed).
But it compresses really really well. I was working on a terrain
rendering program 15-20 years ago, and there are huge swaths of land
where the elevation does not vary more than a meter, so I was able to
compress the data quite well.. I don't remember how much, but I'm
thinking a factor of 3 would be easy.
So you're getting down to where ARRL could sell/include a single disk
with the terrain database at the 3 arc second (100m spacing) level and
have a decent simple interface to generate the profile files. Enter
lat/lon, push button.
Or have the data available for downloading as an .iso, or something.
(or, I guess, you could set up a intermediate site that retrieves it
from the government site and reformats it, then serves chunks in a
predictable and unchanging way).
Realistically, the terrain data doesn't actually change all that much.
It's sort of a one time capital expenditure to grab all the data, format
it somehow, and then leave it.
The problem now is that we're trying to leverage other tools to retrieve
it, and those tools are not tailored for our needs. And, of course,
there's the whole shifting sands of retrieval from the government site.
This would also only work for the US. Other countries have different
rules on the availability of terrain and mapping data, and whether you
can make it available for anyone with a computer.
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