Giving Back to FLOSS

Today, I had the opportunity to give back a little to FLOSS. I downloaded and installed the GNU Exterior Ballistics Calculator (gebc) to use with my hunting and target shooting. It took a bit of fiddling to install in Debian GNU/Linux because a file had a different name (case of letters). I was getting “file not found” during the build for fl_draw.h. On Debian GNU/Linux that file is fl_draw.H for some reason. Using
apt-file search fl_draw.h
libfltk1.3-compat-headers: /usr/include/FL/fl_draw.h

I found that I needed to install libfltk1.3-compat-headers (“This package provides header symlinks with .h rather than .H extensions for compatibility with some older code that relies on the lowercase-h names.“) as well as libfltk1.3-dev and libhpdf-dev in order to build gebc.

The build procedure is typical. One downloads the source in tar.gz format, unpacks with tar xzf filename and cd gebc-1.07 to enter the directory. Then ./configure lists dependencies needed as error messages. In Debian GNU/Linux the header files are usually included in libxyz-dev packages. Once the configure script creates the Makefile, run make and, as root, run make install. Then gebc starts the programme for any user.

The programme ran pretty well except for some crashes when storing to “memories”. Skipping that, I tried to run some data. The input windows included a field for “drag coefficient“. I usually use ballistic coefficients published by manufacturers of bullets but try as I might I could not enter drag coefficients and get reasonable results (Cd=k/BC). By examining the source code, I can see that the input field for drag coefficient should actually be labelled “ballistic coefficient”. Entering ballistic coefficients gives good results. I changed that string in two places, InputWindow.cpp and RangeWindow.cpp so the inputs and outputs are presented correctly. I tried to contact the authour, Derek R. Yates, but could not find any e-mail address. I could not leave a message on SourceForge. No “submit” button. By posting this perhaps Google will help others.


Beautiful, isn’t it? That’s for Hornady 180 grain RN bullets at 2600 ft/s under current atmospheric conditions. There are options to export results as PDF, spreadsheet, etc. Bullet makers from whom I usually buy include:

If you want the modified source code, download gebc-1.07a.tgz. Licence is GPLv3.

sha1sum gebc-1.07a.tgz
e79cf6bf542e9f83ba5443addbed3a80fc00c587 gebc-1.07a.tgz
md5sum gebc-1.07a.tgz
8be0613391817b0c18f1aa00cc8edabb gebc-1.07a.tgz

Happy shooting!

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2 Responses to Giving Back to FLOSS

  1. My family has a long history with firearms because my Canadian ancestors were farmers who supplemented their food supplies with game and fish. My father and uncle were both soldiers in the Second World War and had a big influence on my life. I have been exposed to hunting/shooting since about the age of six or seven. My own children have also fired rifles but only one is keen. Firearms have many good uses but unfortunately they evolved for evil purposes largely. My favourite rifle is a Mauser 98 of which many millions were produced and used in two world wars by Germany and other countries. They are simple, reliable and early in WW II were well made. They are very reliable hunting firearms. Last day of the deer hunt is tomorrow.

  2. Kozmcrae says:

    My father in-law was a marksman (damn good too). He was also a metallurgist for Savage Arms at one point in his long career as a gun smith. He was old school but he would have had no problem understanding the output of that program. I wasn’t interested in guns that much but he tolerated me because I could hold my own with him when it came to history. It was a subject we both loved to talk about.

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