Postscript routines for display of watershed data

Abstract

Frenkel(l988) quoted Richard Weinberg: “Computmg, . . , without visualization, is like assembling a jigsaw puzzle in the dark.” Visualization is critical for scientific data, especially in presenting numerous grid-based data for spatial analyses. Without visualizing analysis output, a researcher has difficulty in describing the results. However, presenting such data on an A4 or letter size sheet with a general Postscript (PS) (Adobe, 1990) the laser printer is not economically attainable. Some commercial geographic information systems (GIS), although providing such a capability, generally require tedious preprocessing of data or are expensive to obtain. A GIS may pose limitations such as lack of flexibility in satisfying the researcher’s requirements, limitation of the number of grids, and file incompatibility between various printers. Color output from a GIS, although impressive, is expensive to produce on a color printer and to publish in a report, document, or journal. A researcher generally presents his/her results in black-and-white type on a sheet of paper of standard size. Finding a tool to present data easily such as both drainage directions and gray values expressing elevation for a watershed with more than 2000 grids on A4 or letter sized sheet of paper from a laser printer can be a difficult task. Therefore, in this work, PS routines are developed to present a data set with numerous grids. Developing the PS routines stems from the author’s previous attempt to prepare numerous gridbased watershed data for a research report (Kao, 1992) and a paper submitted to a journal. Although several GIS such as IDRISI (Eastman, 1992), PC ERDAS (ERDAS, 1991), GRASS (USACERL, 1993), and PC ARC/INFO (ESRI, 1990) were available to the author during preparation of the manuscripts, none could be used easily to produce the grid data set shown in Figure 1 on a generally accessible PS laser printer in a batch fashion without undertaking tedious data preprocessing for each grid data set. The flexibility provided by the PS routines enables use of some UNIX shell scripts such as PERL (Wall and Schwartz, 1992) to produce inexpensive hard copies automatically for grid-based watershed related results.