Preparation of display maps with an electronic computer

Abstract

USAF The Joint Numerical Weather Prediction Unit has had a pressing require~ ment for preparation of results in two-dimensional contour map form° Since the unit operates essentially in real time, the displays must be ready immediately, for local use, or distribution by facsimile. Various techniques for doing this have been tried or proposed. From 1955 ~ 1959 we have repre~ sented contour fields by printing shading between alternate pairs of lines on an IBM 407-type line printer. The shading is derived by two dimensional quadratic interpolation of the variable to each point on the paper represented by a printer wheel then a decision as to whether this value is in a printable band. The resulting contour maps are able to represent very complex fields with odd shaped maxima and minima. The contour intervals need to be linear for simplicity and fringing will occur at discontinuities. Fringing can often be avoided by proper selection of values. The maps are presently copied by hand onto plastic overlays containing the background geography and copied by a diazo process. With the advent of high-speed curve plotters and digital to analogue converters an experiment was made to adapt these for complete mechanization of the map drawing process. To drive a curve plotter it is necessary