Great circle bearing map-generation software has not been made =
available to date because it is not easy! I learned a bit about it when =
I was working with the author of GeoClock.
Geoclock's database, for example, is derived off US Navy and CIA map =
databases (sanitized for sale to the public). Coordinates are provided =
for something like every 10m of coastline, borders, etc. for all =
landmasses (islands, etc).
Great circle charts need this level of detail (especially if they are =
physically large) because physical elements located at the antipodes =
(the outer edge) of the map are blown up hugely. If one does not have =
this detail, the projection gets very jagged.
The next problem is that the databases provided are not "clean". (A =
similar problem exists for the USA database provided by the Census =
Dept.) There are many typos and other errors in the database. It takes =
thousands of labor hours to research and correct errors.
Lastly, the clean database is huge. While hugeness is less of a =
problem these days with CD drives, this is not something than one loads =
on a hard drive in a spare corner.
Bottom line: the value of the database, when kept current and =
"clean", and the storage requirements make it uneconomical to sell to =
hams for generating their own great circle charts.
Geoclock will provide you a custom great circle chart (for projection =
on your PC) for any location for $30 per chart (the last time I =
checked). I don't know how you value your free time, but $30 seems =
reasonable to me compared to the cash outlay for multi-gigibits of hard =
drives plus valuable software. I can buy a lot of special Geoclock =
charts for different locations before it makes any sense to think about =
rolling my own...
Geoclock is available on the Web as shareware (no great circle =
charts). Use your favorite search engine. You can order over the =
phone, through the Geoclock BBS, or via e-mail.
-- Eric K3NA
scace@msn.com
----------
From: owner-towertalk@akorn.net on behalf of Bill Cotter
Sent: 1996 December 17 Tuesday 13:37 PM
To: towertalk@contesting.com
Subject: Great Circle Bearing map software
Hey gang,
I am in the process of locating/installing a 40m 4sqr and am looking for
software for creating a Great Circle Bearing map of planet earth =
centered on
my QTH lat/long. Over the years there have been many ads for services to
print one such custom map for an individual, but I have been unable to
locate a source for the software. I have found many programs to create =
the
bearing tables (ie: country, heading, distance, etc.), but none to =
create
the map. Has anyone seen such shareware, freeware, buyware, anyware?
Thanks,
Bill, N4ALG
__________________________________________________________
| |=20
| Bill Cotter, N4ALG e-mail: bcotter@pop.uky.edu |
| 173 Carolyn Lane Home: (606) 887-5563,2402 |
| Nicholasville, KY 40536-9340 Work: (606) 323-6474 |
|__________________________________________________________|
=20
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