NCSU GeoForAll Lab

You can easily sculpt a model with polymer enriched sand using Tangible Landscape. Project a digital elevation model and the derived contours onto the table. Use this as a guide for sculpting. You can also use Tangible Landscape to compute the difference between the scanned model that you have sculpted and the original digital elevation model. Project the color coded difference (i.e. cut/fill) for a real-time guide of where to add or remove sand. You can also vertically rescale and translate the scanned raster to match the original DEM using the module r.regression.line.

import grass.script as gscript

def run_difference(real_elev, scanned_elev, env, **kwargs):
	regression_params = gscript.parse_command('r.regression.line',
		flags='g',
		mapx=scanned_elev,
		mapy=real_elev,
		env=env)
	gscript.mapcalc('{regression} = {a} + {b} * {before}'.format(
		a=regression_params['a'],
		b=regression_params['b']
		before=scanned_elev,
		regression='regression'),
		env=env)
	gscript.mapcalc('{difference} = {regression} - {after}'.format(
		regression='regression',
		after=real_elev,
		difference='diff'),
		env=env)
	gscript.write_command('r.colors',
		map='diff',
		rules='-',
		stdin="-100 black\n-20 red\n0 white\n20 blue\n100 black",
		env=env)