“In setting up the isometrograph, the vertical scale is positioned on a calibrated bar (fig. 5). A vertically viewed contour map of the area to be portrayed is oriented so that the direction of view is parallel to the calibrated bar. The angle of view from the horizon is adjusted by the placement of the bars that hold the pencil (fig. 5). The stylus is moved along the highest contour of the vertically viewed contour map, and at the same time the pencil is activated to draw a foreshortened contour. The isometrograph is moved on the vertical scale to the next lower contour, and the process is repeated until all of the contours have been traced. We estimate that a framework of foreshortened contours by the isometrograph is produced in half the time as one based on angular perspective.”
Would be a neat project to make a virtual one in 3D in the browser.