area_field = ogr.FieldDefn('area', ogr.OFTReal) #A
area_field.SetWidth(30) #A
area_field.SetPrecision(4)
location_field = ogr.FieldDefn('location', ogr.OFTString) #A
poly_lyr.CreateFields([id_field, area_field, location_field])
poly_row = ogr.Feature(poly_lyr.GetLayerDefn())
land_lyr = ds.GetLayerByName('land_lambert') #A
land_row = next(land_lyr) #A
land_poly = land_row.geometry().Buffer(100000) #A
for tag_id in ch7funcs.get_unique(ds, 'albatross_lambert', 'tag_id'):
print('Processing ' + tag_id)
pt_lyr.SetAttributeFilter("tag_id = '{}'".format(tag_id))
pt_locations = ogr.Geometry(ogr.wkbMultiPoint)
last_location = None
for pt_row in pt_lyr:
pt = pt_row.geometry().Clone()
if not land_poly.Contains(pt): #B
continue #B
if pt.GetX() < -2800000: #C
location = 'island' #C
else: #C
location = 'mainland' #C
if location != last_location: #D
if pt_locations.GetGeometryCount() > 2:
homerange = pt_locations.ConvexHull()
# Calculate distance between adjacent points.
from osgeo import ogr
import ch7funcs
# Open the layer and add a distance field.
ds = ogr.Open(r'D:\osgeopy-2001\Galapagos', True)
lyr = ds.GetLayerByName('albatross_lambert')
lyr.CreateField(ogr.FieldDefn('distance', ogr.OFTReal))
# Get the unique tags. Notice this uses the ch7funcs module but the text
# assumes the function is in the same script.
tag_ids = ch7funcs.get_unique(ds, 'albatross_lambert', 'tag_id')
# Loop through the IDs.
for tag_id in tag_ids:
print('Processing ' + tag_id)
# Limit the GPS points to the ones with the current tag ID.
lyr.SetAttributeFilter("tag_id ='{}'".format(tag_id))
# Get the point and timestamp for the first location.
row = next(lyr)
previous_pt = row.geometry().Clone()
previous_time = row.GetField('timestamp')
# Loop the rest of the locations for the current tag.
for row in lyr:
current_time = row.GetField('timestamp')
if current_time < previous_time:
raise Exception('Timestamps out of order')