Activity 1

Original

Reconstruction

Overlay

This is the final product of the reconstruction of an old plot scanned from the paper: "Contributions to the Chemistry of Thallium I" by L. F. Hawley, compiled in The Journal of the American Chemical Society Volume XXIX, accepted in Jan. 11, 1907.

The reconstruction was done by first obtaining a ratio of the number pixels to the physical variables in the plot - cc KMnO4 for the x-axis and grams Tl per one cc KMnO4 (Thallium factor) for the y-axis. The pixel coordinate corresponding to the grid lines were taken. The increments of the grid lines for x-axis is 5 cc, while 0.00001 Thallium factor for the y-axis. The ratio was obtained by taking the average of the difference between pixel coordinates of successive grid lines for the corresponding axis. The obtained value for the x and y axes will be used as a factor for obtaining a relation of the pixel coordinates to the physical variables on the plot.
This method assumes that the x and y axes aligns with the horizontal and vertical, i.e., the y(x) value of the pixel coordinates along the x-axis (y-axis) does not change. If this was not attained upon scanning of the plot, the image can be rotated so that the mentioned criterion is satisfied. This can be done using image rotating softwares, such as one function in MATLAB (imrotate('image file', 'angle in degrees')).
After obtaining the ratios, points were sampled from the plot and the corresponding pixel coordinates were noted. An increment of 10 pixels along the x was done for sampling points on the curve to ensure that the shape obtained would be accurate. The pixel coordinate of the origin of the plot was also recorded.
An adjustment should be made by having an offset based on the pixel coordinate of the origin. The x-coordinate should be added to the x pixel coordinates while the y-coordinate should be subtracted since the y-pixel coordinates increases downward along an image. From the obtained parameters, the physical values on the plot were obtained by multiplying the increment of the grid lines of the axis to the corresponding pixel coordinate and then dividing this by the ratio for the axis. Another adjustment was also made since the origin of plot did not start at (0, 0). The initial values were simply added to the values obtained after applying the ratio.
The obtained physical values were plotted in Excel, adding major grid lines and adjusting the parameters of the plot (min and max values of the axis). The original plot was filled in as a background of the plot to have a better visual evaluation of the resulting reconstruction. The plot was simply adjusted to fit the features of the plot on the image.
From the image posted, the reconstruction fits the original plot accurately, and for that, I feel that I can evaluate my grade for this activity as 10. There still are limitations in the reconstruction, mainly due to inconsistent judgment upon sampling points concerning the exact pixel coordinates that would be taken because of the thick lines (or points), and also the imprecise pixel differences that correspond to the physical variable increments. Averaging can limit, but not eliminate, this error.
I would like to acknowledge Winsome Chloe M. Rara, for her help in doing this activity, Mark Jayson Villangca and Jica Monsanto for their insights in the blog layout, and also for the guidance of our professors, Dr. Maricor Soriano and Dr. Gay Jane Perez.