# GRASS GIS 7.0.0 Windows

# Name: eliminate_water_surface_features.py

# Description: A Python script for launch in GRASS 7.0.0 to eliminate water features less than 0.36

# Iterates through a folder location passed via sys.argv based on given keywords

# Unity id: ljsox

# NCSU GIS582 Spring 2015

# Date: April 15, 2015

# Reference: E. Hardin et al., GIS-based Analysis of Coastal Lidar Time-Series, Springer Briefs in Computer Science, DOI 10.1007/978-1-4939-1835-5__3

import os, sys, subprocess

from grass.script import list_strings, mapcalc

from grass.script.core import run_command

import grass.script as gscript

from grass.script import vector as grass

# take directory from command line input and change path

path = sys.argv[1]

if len(sys.argv) <1:

print "You should provide the directory path as a parameter"

sys.exit(1)

# now change the path

os.chdir( path )

# print message

gscript.message('Hello GRASS user!')

# *** use GRASS list_strings to find specified rasters using a regular expression, change as file names change

rasters = list_strings(type='raster', pattern='^elev_r_.*_2mrst_t1500$', flag='r')

for raster in rasters:

short = raster.split('@')[0]

# print message

gscript.message('We are now using map calculator to eliminate water features.')

#expression using mapcalc to save only elevations above .36 and rename with '_higher_036'

mapcalc("{short}_higher_036 = if({rast} > 0.36, 1, null())".format(rast=raster, short=short), overwrite=True)

newmap = short + '_higher_036'

# create a vector for a report

run_command('r.to.vect', input=newmap, output=newmap, type='area', overwrite=True)

# Find the unique category of the largest area

# run_command('v.report', map=newmap, option='area') #< remove comment to see on screen report

mask = short + '_mask'

masked = short + '_masked'

# Extract the features and covert back to a raster then use mapcalc to multiply by float and create new map name

run_command('v.extract', input=newmap, output=mask, cats='1', overwrite=True)

run_command('v.to.rast', input=mask, output=mask, use='val', value='1' , overwrite=True)

# use the mask to finally eliminate the cells below .36, create a new map named map_masked

# the new file name has _masked added to the end

mapcalc("{short}_masked = ({short} * float({rast}))".format(rast=mask, short=short), overwrite=True)

# print message and file names

gscript.message('The new files created are:')

newmap=newmap.split('@')[0]

mask=mask.split('@')[0]

print newmap

print mask

print masked

# print message

gscript.message('All processing is now completed. The new maps have _masked added to the file names.')