Trajectory length calculation

distance function in migeo module of geolib package can be used to get length of LineString object. So it can be used to get the length of each trajectory in a trajectory layer.

# Open trjactory shape file
print 'Open trajectory shape file ...'
trajfn = r'D:\Temp\traj\2011_MAM\201103.shp'
trajLayer = shaperead(trajfn)

# Chek length of each trajectory
print 'Chek length of each trajectory...'
idx = 0
for tline in trajLayer.shapes():
    d = distance(tline, islonlat=True)
    t = trajLayer.cellvalue('Date', idx)
    h = trajLayer.cellvalue('Hour', idx)
    t.replace(hour=h)
    print t.strftime('%Y-%m-%d %H') + ': %.2fkm' % (d / 1000)
    idx += 1

print 'Finish...'

The output from the print code in above script:

>>> run script...
Open trajectory shape file ...
Chek length of each trajectory...
2011-03-01 00: 51.13km
2011-03-02 00: 691.60km
2011-03-03 00: 456.37km
2011-03-04 00: 1533.14km
2011-03-05 00: 1683.81km
2011-03-06 00: 944.17km
2011-03-07 00: 501.29km
2011-03-08 00: 1400.35km
2011-03-09 00: 1468.49km
2011-03-10 00: 2138.57km
2011-03-11 00: 2143.41km
2011-03-12 00: 762.63km
2011-03-13 00: 548.47km
2011-03-14 00: 629.21km
2011-03-15 00: 535.15km
2011-03-16 00: 666.08km
2011-03-17 00: 623.15km
2011-03-18 00: 1297.56km
2011-03-19 00: 966.95km
2011-03-20 00: 998.49km
2011-03-21 00: 512.22km
2011-03-22 00: 398.51km
2011-03-23 00: 1534.89km
2011-03-24 00: 843.08km
2011-03-25 00: 1403.16km
2011-03-26 00: 1956.59km
2011-03-27 00: 537.35km
2011-03-28 00: 1760.05km
2011-03-29 00: 570.91km
2011-03-30 00: 1386.61km
2011-03-31 00: 1141.01km
Finish...

distance function also suport x/y coordinate vlaues:

fn = 'D:/MyProgram/Distribution/java/MeteoInfo/MeteoInfo/sample/HYSPLIT/tdump'
f = addfile_hytraj(fn)
lons = f['lon'][:,:]
lats = f['lat'][:,:]
tn = lon.shape[0]
for i in range(tn):
    lon = lons[i,:]
    lat = lats[i,:]
    wlon = where(lon==nan)
    if not wlon is None:
        lon = lon[:wlon[0]]
        lat = lat[:wlon[0]]
    d = distance(lon, lat, islonlat=True)
    print 'Length: %.2fkm' % (d / 1000)