README for the RDF Calculator
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Author:  Wolfgang Buescher (DL4YHF)
Date(YYYY-MM-DD):  2006-03-31 


Introduction
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The RDF Calculator was primarily written for radio-direction finding. It can be used to calculate and visualize the intersection from the beam heading of two observers to find the location of an unknown transmitter.
The positions of the two observers can be selected from a city database, or entered in the program by latitude and longitude.
Next, the beam heading of both stations towards the unknown transmitter is entered.

The program will then calculate the center coordinate of the intersection of both beams, and draw both beams (and the intersection) on a simple map (which shows cities, coastlines, borders, rivers, and optionally the topographic relief if you have the GTOPO30 data base on your system - see notes below).

Alternatively, the RDF calculator can be controlled from other programs. One such candidate is the author's Spectrum Lab, which can periodically send the antenna beam heading to the RDF calculator.



Installing the GTOPO30 database
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Please note that the "topographic view" can only be enabled if you installed the GTOPO30 database for your area !

Parts of the GTOPO30 database can be downloaded (free) from http://edc.usgs.gov/products/elevation/gtopo30/gtopo30.html .

For legal reasons (and size limitations) the GTOPO30 database is not contained in the installation package of the RDF calculator. Instead, you must download the database for your part of th world from the above link. Alternatively, you can try this anomymous FTP transfer from
ftp://edcftp.cr.usgs.gov/pub/data/gtopo30/global (not sure if this link still works; please don't ask me to send you this file via email ! ).

For western Europe, you only need to download the file w020n90.tar.gz . This is a unix-style compressed archive. You must unpack into the directory c:\gtopo30 on your local harddisk (create this directory manually). Good file managers can handle this UNIX-compressed file automatically (for example "Total Commander", formerly known as "Windows Commander"). If you have correctly done this, there must be at least the file:

c:\gtopo30\w020n90.dem (57.6 Megabytes in a single file).

All other files in the gzip'd archive are not required by the current version of the GPS preview window, but they *may* be important for other mapping applications which also use the GTOPO 30 database. So in case of doubt, don't erase those *.src, *.stx, *.sch, *.prd, *.hdr and *.dmw files.