On Qgis 2.18, I'm trying to write a python code that allows me to create a 1km, 2km, 3km, 4km, 5km buffer around a selected point feature. To avoid having to reproject things, I'm using the reverse haversine formula. My workflow is as follows:
- Get lat long of selected point feature.
- Use reverse haversine formula to get coordinates of new points 1km away from origin at specified angle intervals.
- Join new points to form buffer ring polygon feature.
Repeat for 2km, 3km, 4km, 5km.
from math import * from qgis.core import * from PyQt4.QtCore import * from PyQt4.QtGui import * layer = iface.activeLayer() for feat in layer.selectedFeatures(): geom = feat.geometry() start_x = geom.asPoint().x() start_y = geom.asPoint().y() start_lon = start_x * pi / 180 start_lat = start_y * pi / 180 sides = 64 radius = 6378137.0 # meters points =  distance = [1000, 2000, 3000, 4000, 5000] for i in range(len(distance)): dist = distance[i] degrees = 0 while degrees < 360: degrees = degrees + 360/sides bearing = degrees * pi / 180 end_lat = asin((sin(start_lat) * cos(dist / radius))+ (cos(start_lat) * sin(dist / radius) * cos(bearing))) end_lon = start_lon + atan2(sin(bearing) * sin(dist / radius) * cos(start_lat), cos(dist / radius) - (sin(start_lat) * sin(end_lat))) points.append(QgsPoint(end_lon * 180 / pi, end_lat * 180 / pi)) geometry = QgsGeometry.fromPolygon([points])
Two places where I'm stuck:
- When I add this script on the Qgis processing toolbox (Add script from file) and try to run it, I get an error which says "iface is not defined".
- How can I save each iteration of the distance buffer as a shp file?