Displaying DEM files as images and wire frames

To begin this project, I've written two small Python/Wx programs to display the kind of digital elevation model (DEM) files we will be using as input. These two programs are:

> PlotGrid.py 
Usage: PlotGrid.py data-file [min max mode]
       data-file = text file of 2d array with optional header
                   set to 'demo' for demo mode
       min = data minimum
       max = data maximum (set both to 0 for auto-scaling, default)
       mode = 0 (b & w), 1 (color, default)

> Plot3dGrid.py
Usage: Plot3dGrid.py data-file [x-decimation y-decimation z-scale]
       data-file = text file of 2d array with optional header
                   set to 'demo' for demo mode
       x-decimation = plot every nth column of data (default 1)
       y-decimation = plot every mth row of data (default 1)
       z-scale = exaggerate z values by factor (default 1.0)

These programs also show examples of how to use Python, Numpy, and Wx. They can be copied to your computer and used with the examples shown below.

PlotGrid.py
Plot3dGrid.py

PlotGrid.py

• The window can be resized, and the plot can be dragged around (scrolled) in the window with the mouse.
• The y orientation is such that the first element in the file (at upper left of array) is plotted at the lower right of the plot. Thus, the y direction is 'up'. This can be changed in the program code by not flipping the color arrays.

Examples:

> PlotGrid.py demo

> PlotGrid.py demo 0 0 0

> PlotGrid.py ../Data/skt_center.txt -1 0 0
Header =  {'ncols': 218.0, 'cellsize': 1.0, 'nrows': 1062.0, 'xllcorner': 439842.77399168001, 'yllcorner': 4868378.0193355996, 'NODATA_value': -9999.0}
Shape =  (1062, 218)
Valid data: 1479 entries, max = 0, min= 0, mean = 0, std = 0

> PlotGrid.py ../Data/skt_dem.txt
Header =  {'ncols': 540.0, 'cellsize': 1.0, 'nrows': 1254.0, 'xllcorner': 439663.20871739998, 'yllcorner': 4868282.7153642001, 'NODATA_value': -9999.0}
Shape =  (1254, 540)
Valid data: 432607 entries, max = 276.81, min= 80.0383, mean = 151.401, std = 38.6623

Plot3dGrid.py

• The window can be resized, and the plot can be rotated in the window with the mouse (dragging) or arrow keys. The plot can be zoomed by shift-dragging toward/away from the window center, or with the +/- keys.
• The y orientation is such that the first element in the file (at upper left of array) is plotted at the lower right of the plot. Thus, the y direction is 'up'. This can be changed in the program code by not flipping the data and mask arrays.
• Attempting to plot a large array without using decimation will take a much longer time.

Examples:

> Plot3dGrid.py demo 4 4 10

> Plot3dGrid.py ../Data/skt_dem.txt 10 10 0.1
Header =  {'ncols': 540.0, 'cellsize': 1.0, 'nrows': 1254.0, 'xllcorner': 439663.20871739998, 'yllcorner': 4868282.7153642001, 'NODATA_value': -9999.0}
Shape =  (1254, 540)
Valid data: 432607 entries, max = 276.81, min= 80.0383, mean = 151.401, std = 38.6623

> Plot3dGrid.py ../Data/skt_dem.txt 5 5 0.1
Header =  {'ncols': 540.0, 'cellsize': 1.0, 'nrows': 1254.0, 'xllcorner': 439663.20871739998, 'yllcorner': 4868282.7153642001, 'NODATA_value': -9999.0}
Shape =  (1254, 540)
Valid data: 432607 entries, max = 276.81, min= 80.0383, mean = 151.401, std = 38.6623