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import os
import numpy as np
from shapefile import Reader
lsd = 5
UTILS_DIR = os.path.dirname(os.path.abspath(__file__))
OUTPUT_DIR = os.path.join(UTILS_DIR, '..', 'lib', 'mpl_toolkits',
'basemap', 'data')
# Folder where GSHHG shapefiles were extracted. Change if needed
GSHHS_DIR = UTILS_DIR
def quantize(data,least_significant_digit):
"""
quantize data to improve compression. data is quantized using
around(scale*data)/scale, where scale is 2**bits, and bits is determined
from the least_significant_digit. For example, if
least_significant_digit=1, bits will be 4.
This function is pure python.
"""
precision = pow(10.,-least_significant_digit)
exp = np.log10(precision)
if exp < 0:
exp = int(np.floor(exp))
else:
exp = int(np.ceil(exp))
bits = np.ceil(np.log2(pow(10.,-exp)))
scale = pow(2.,bits)
return np.around(scale*data)/scale
def interpolate_long_segments(coords, resolution):
lookup_thresh = {'c': 0.5, 'l':0.3, 'i':0.2, 'h':0.1, 'f':0.05}
thresh = lookup_thresh[resolution]
spacing = thresh / 5.0
lons, lats = coords.T
dist = np.hypot(np.diff(lons), np.diff(lats))
if np.all(dist <= thresh):
return coords
out_lon, out_lat = [], []
for i in np.arange(len(dist)):
if dist[i] <= thresh:
out_lon.append(lons[i])
out_lat.append(lats[i])
else:
x = [0, dist[i]]
new_x = np.arange(0, dist[i], spacing)
out_lon.extend(np.interp(new_x, x, lons[i:i+2]))
out_lat.extend(np.interp(new_x, x, lats[i:i+2]))
out_lon.append(lons[-1])
out_lat.append(lats[-1])
return np.column_stack([out_lon, out_lat]).astype(coords.dtype)
def get_coast_polygons(resolution):
polymeta = []; polybounds = []
for level in [1,2,3,5]:
filename = os.path.join(GSHHS_DIR, 'GSHHS_shp/', resolution,
'GSHHS_{}_L{}'.format(resolution, level))
print filename
shf = Reader(filename)
fields = shf.fields
try:
shf.shapeRecords()
except:
continue
for shprec in shf.shapeRecords():
shp = shprec.shape; rec = shprec.record
parts = shp.parts.tolist()
if parts != [0]:
print 'multipart polygon'
raise SystemExit
verts = shp.points
lons, lats = list(zip(*verts))
north = max(lats); south = min(lats)
attdict={}
for r,key in zip(rec,fields[1:]):
attdict[key[0]]=r
area = attdict['area']
id = attdict['id']
polymeta.append([level,area,south,north,len(lons),id])
b = np.empty((len(lons),2),np.float32)
b[:,0] = lons; b[:,1] = lats
if lsd is not None:
b = quantize(b,lsd)
polybounds.append(b)
# Manual fix for incorrect Antarctica polygons at full resolution
# This issue is only present in the shapefile version and may be fixed
# in future versions of GSHHS!
if resolution == 'f' and level == 5:
i = [item[-1] for item in polymeta].index('4-E')
coords = polybounds[i][2:-1, :]
coords = np.vstack([coords,
[180.0, -90.0],
[0.0, -90.0]]).astype(np.float32)
polybounds[i] = coords
polymeta[i][-2] = len(coords)
j = [item[-1] for item in polymeta].index('4-W')
coords = polybounds[j][3:, :]
np.savetxt('coordinates.txt', coords)
coords = np.vstack([coords,
[0.0, coords[-1][1]],
[0.0, -90.0],
[-180.0, -90.0],
coords[0]]).astype(np.float32)
polybounds[j] = coords
polymeta[j][-2] = len(coords)
return polybounds, polymeta
def get_wdb_boundaries(resolution,level,rivers=False):
polymeta = []; polybounds = []
if rivers:
filename = os.path.join(GSHHS_DIR, 'WDBII_shp', resolution,
'WDBII_river_{}_L{:02}'.format(resolution, level))
else:
filename = os.path.join(GSHHS_DIR, 'WDBII_shp', resolution,
'WDBII_border_{}_L{}'.format(resolution, level))
print filename
shf = Reader(filename)
fields = shf.fields
for shprec in shf.shapeRecords():
shp = shprec.shape; rec = shprec.record
parts = shp.parts.tolist()
if parts != [0]:
print 'multipart polygon'
raise SystemExit
verts = shp.points
# Detect degenerate lines that are actually points...
if len(verts) == 2 and np.allclose(verts[0], verts[1]):
print 'Skipping degenerate line...'
continue
lons, lats = list(zip(*verts))
north = max(lats); south = min(lats)
attdict={}
for r,key in zip(rec,fields[1:]):
attdict[key[0]]=r
area = -1
poly_id = attdict['id']
b = np.empty((len(lons),2),np.float32)
b[:,0] = lons; b[:,1] = lats
if not rivers:
b = interpolate_long_segments(b, resolution)
if lsd is not None:
b = quantize(b,lsd)
polymeta.append([-1,-1,south,north,len(b),poly_id])
polybounds.append(b)
return polybounds, polymeta
# read in coastline data (only those polygons whose area > area_thresh).
for resolution in ['c','l','i','h','f']:
poly, polymeta = get_coast_polygons(resolution)
f = open(os.path.join(OUTPUT_DIR, 'gshhs_'+resolution+'.dat'), 'wb')
f2 = open(os.path.join(OUTPUT_DIR, 'gshhsmeta_'+resolution+'.dat'), 'w')
offset = 0
for p,pm in zip(poly,polymeta):
typ = pm[0]; area = pm[1]; south = pm[2]; north = pm[3]; npts = pm[4]
id = pm[5]
bstring = p.tostring()
f.write(bstring)
f2.write('%s %s %s %9.5f %9.5f %s %s %s\n' % (typ, area, npts, south,\
north, offset, len(bstring),id))
offset = offset + len(bstring)
f.close()
f2.close()
for resolution in ['c','l','i','h','f']:
poly, polymeta = get_wdb_boundaries(resolution,1)
f = open(os.path.join(OUTPUT_DIR, 'countries_'+resolution+'.dat'), 'wb')
f2 = open(os.path.join(OUTPUT_DIR, 'countriesmeta_'+resolution+'.dat'), 'w')
offset = 0
for p,pm in zip(poly,polymeta):
typ = pm[0]; area = pm[1]; south = pm[2]; north = pm[3]; npts = pm[4]
id = pm[5]
bstring = p.tostring()
f.write(bstring)
f2.write('%s %s %s %9.5f %9.5f %s %s %s\n' % (typ, area, npts, south,\
north, offset, len(bstring),id))
offset = offset + len(bstring)
f.close()
f2.close()
for resolution in ['c','l','i','h','f']:
poly, polymeta = get_wdb_boundaries(resolution,2)
f = open(os.path.join(OUTPUT_DIR, 'states_'+resolution+'.dat'), 'wb')
f2 = open(os.path.join(OUTPUT_DIR, 'statesmeta_'+resolution+'.dat'), 'w')
offset = 0
for p,pm in zip(poly,polymeta):
typ = pm[0]; area = pm[1]; south = pm[2]; north = pm[3]; npts = pm[4]
id = pm[5]
bstring = p.tostring()
f.write(bstring)
f2.write('%s %s %s %9.5f %9.5f %s %s %s\n' % (typ, area, npts, south,\
north, offset, len(bstring),id))
offset = offset + len(bstring)
f.close()
f2.close()
for resolution in ['c','l','i','h','f']:
f = open(os.path.join(OUTPUT_DIR, 'rivers_'+resolution+'.dat'), 'wb')
f2 = open(os.path.join(OUTPUT_DIR, 'riversmeta_'+resolution+'.dat'), 'w')
# Levels above 5 are intermittent rivers and irrigation canals.
# They haven't been included in the past, as far as I can tell, so I'm
# not including them here...
offset = 0
for level in range(1, 6):
poly, polymeta = get_wdb_boundaries(resolution,level,rivers=True)
for p,pm in zip(poly,polymeta):
typ = pm[0]; area = pm[1]; south = pm[2]; north = pm[3]; npts = pm[4]
id = pm[5]
bstring = p.tostring()
f.write(bstring)
f2.write('%s %s %s %9.5f %9.5f %s %s %s\n' % (typ, area, npts, south,\
north, offset, len(bstring),id))
offset = offset + len(bstring)
f.close()
f2.close()
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