Write Your Own Geospatial Utilities - Open Source Geospatial Tools: Applications in Earth Observation - page 230

the random or systematic sampling frames. We begin with the random sampling
frame:

def randomFrame(n_sample, bbox_dict, output_format):
output_ds, layer, layerDefinition =

→ createVector(output_format)

featureIndex=0
for i in range(0, int(n_sample)):
print i
x_tmp = int(random.randrange(bbox_dict['xmin'],

→ bbox_dict['xmax'], 1))

y_tmp = int(random.randrange(bbox_dict['ymin'],

→ bbox_dict['ymax'], 1))

point = ogr.Geometry(ogr.wkbPoint)
point.SetPoint(0, x_tmp, y_tmp)

feature = ogr.Feature(layerDefinition)
feature.SetGeometry(point)
feature.SetFID(featureIndex)
feature.SetField("plot_id", i)
feature.SetField("x",x_tmp)
feature.SetField("y",y_tmp)

layer.CreateFeature(feature)

featureIndex += 1

output_ds.Destroy()

We also include a function to create a systematic sampling frame.

def systematicFrame(output_format):
output_ds, layer, layerDefinition =

→ createVector(output_format)

featureIndex=0
x=0
y=0
while x < 6:
while y < 6:
print x,y
y+=1
point = ogr.Geometry(ogr.wkbPoint)
point.SetPoint(0, x, y)

feature = ogr.Feature(layerDefinition)
feature.SetGeometry(point)
feature.SetFID(featureIndex)

layer.CreateFeature(feature)
featureIndex+=1

y=0
x+=1

output_ds.Destroy()