Portable C implementation of Moody's method (Union Jack) for surface plate calibration

This directory contains a simple program which computes the height of a surface plate, starting with angular measurements from an auto-collimator or tilt meter (clinometer).

The method makes use of eight lines of measurement: two diagonals, four perimeter lines, and two center lines. This is often called the "Union Jack" method because the lines look like those on the UK flag. The method was described by Hume in his book "Engineering Metrology" around 1950, and then was published in more detail in a paper by Moody, "How to calibrate surface plates in the plant'', which was published in "The Tool Engineer" in October 1955.

• README.txt has instructions about how to compile and run this code. These are reproduced below.

• Moody's 1955 paper contains a number of typographical errors and omissions. These are documented in a short paper which is included here, called MoodyCorrections.pdf .

To use this code follow these steps:

1. Compile the code if it has not already been done, with:
   cc -o moody moody.c -lm
   This creates an executable called moody .


2. To see how the program works, a set of files containing Moody's original data from his paper are in the subdirectory Moody_data/ . Go into that directory and then run the moody executable within that directory. On a Linux system or on a Mac terminal:
   ../moody
   See below for a description of the output.

3. To use this program for your own data:

   • Create another subdirectory and move into it. Copy the configuration file Config.txt there.

   • The included Config.txt file is set up to agree with Moody's paper (a 4-inch foot spacing). Edit the Config.txt and put in the correct foot spacing for your measurements. Config.txt has one line with either "I" or "M" (to indicate inch or metric units) followed by a blank space and then the foot spacing in inches or mm respectively. White space and lines beginning with "#" are treated as comments and ignored.

   • Create eight text files containing the measured angular deviations in arc-seconds:
     NE_SE.txt SE_SW.txt NE_NW.txt NW_SW.txt
     NW_SE.txt NE_SW.txt
     N_S.txt E_W.txt
     Here N=North, S=South, E=East and W=West. The first four files are perimeters, the next two files are diagonals, and the last two files are center lines.

   • In these text files, put one data value per line. For example:
"-12.3" means -12.3 arcseconds.
Lines beginning with "#" and blank or empty lines are treated as comments and ignored. See MoodyCorrections.pdf for information about the sign and direction conventions.

   • Run the program. On a Linux system or on a Mac terminal:
     ../moody

   • The main output (Moody's eight tables) will be printed on the terminal. Some commentary of interest is printed before the tables.

   • Two text files are created, that can be used to plot the output:
gnuplot.dat and gnuplot.cmd .

   • If gnuplot is installed on your computer, the command:
     gnuplot gnuplot.cmd
     should create a surface plot of your plate, like the one shown below (which is for Moody's example data). You may have to edit the first line of gnuplot.cmd to set the correct terminal type for your computer. If unsure, comment out the first non-comment line in gnuplot.cmd by adding a "#" character at the start of the line.