wget ftp://topex.ucsd.edu/pub/srtm30_plus/topo30/topo30.grd

wget ftp://topex.ucsd.edu/pub/srtm30_plus/topo30/COPYRIGHT.txt

cat COPYRIGHT.txt

ls -l

!grdinfo topo30.grd

import gdal

src = gdal.Open('topo30.grd')

topo30 = src.GetRasterBand(1).ReadAsArray()

less0 = (topo30 < 0).sum(); print less0, 'cells'

topo30.size

print '%0.2f%% of the grid is below 0' % (100. * float(less0) / topo30.size)

'%.1f %% of the grid below 0 is below 20 fathoms' % (100. * float((topo30 < -36.576).sum()) / less0)

'%.1f %% of the grid below 0 is below 100 fathoms' % (100. * float((topo30 < -182.88).sum()) / less0)

data = numpy.hstack(topo30)

data.shape

pylab.hist(data, bins=100, histtype='stepfilled')

# Now give the cumulative distribution function (CDF)
n, bins, patches = pylab.hist(data, 200, histtype='step', cumulative=True)