HOW IS SLOPE MEASURED?
You can calculate slope by determining the ratio of “vertical change” to the “horizontal change” between two points on the same line. Just divide the vertical change by the horizontal change (what’s called “rise over run”). From there, you can determine the slope of a line (which is expressed as a percentage). This information is useful in a number of applications, especially when grading information is critical to the completion of a project.
WHAT IS A BLUEPRINT?
A blueprint is a reproduction of a technical drawing that uses a contact print process on light-sensitive paper. The original method was invented in 1842 by Sir John Herschel, and it produced white lines on a blue background. The light-sensitive paper turns blue because of a chemical reaction, while leaving the corresponding drawing as white lines. The diazotype method was invented in the early 1940’s, and it left blue lines on a white background. That’s why this method was often referred to as “whiteprinting.” It was a simple process that didn’t need a lot of complicated parts, and equipment maintenance was inexpensive. In both methods, the drawings were produced on vellum or some other paper where light can pass through.