geometry-conversionpointpolyline-creationqgisrotate
I want to create a straight line that starts from the point with the given length. And also it rotates around the point.
I have a point data of cctvs:
And I want to create a line with the given length of 50 meters on each point that rotates at 5 degrees.
To help understand the result would be like this picture for each point.
With the solution given in How to create points based on the distance and bearing from a survey point? and memory layers.
Part of a my class to create memory layers from the Python console (How to create points in a specified distance along the line in QGIS？):
class Crea_layer(object):
def __init__(self,name,type):
self.type=type
self.name = name
self.layer = QgsVectorLayer(self.type, self.name , "memory")
self.pr =self.layer.dataProvider()
def create_point(self,geometry):
# add point to the layer
self.seg = QgsFeature()
self.seg.setGeometry(QgsGeometry.fromPoint(geometry))
self.pr.addFeatures([self.seg])
self.layer.updateExtents()
def create_line(self, point1,point2):
self.seg = QgsFeature()
self.seg.setGeometry(QgsGeometry.fromPolyline([point1,point2]))
self.pr.addFeatures( [self.seg] )
self.layer.updateExtents()
@property
def show_layer(self):
QgsMapLayerRegistry.instance().addMapLayers([self.layer])
processing:
# direction cosines function
import math
def cosdir_azim(azim):
az = math.radians(azim)
cosa = math.sin(az)
cosb = math.cos(az)
return cosa,cosb
original_point = QgsPoint(50,50)
azimuth = 120
length = 50
cosa, cosb = cosdir_azim(azimuth)
end_point = QgsPoint(original_point.x()+(length*cosa), original_point.y()+(length*cosb))
# create the points layer
pt = Crea_layer("pt_120_50", "Point")
pt.create_point(original_point)
pt.create_point(end_point)
pt.show_layer
Result:
Create the line layer joining the points:
li = Crea_layer("l_120_50", "LineString")
li.create_line(original_point,end_point)
li.show_layer
Result:
There is "Vector geometry > Geometry by Expression" tool in Processing Toolbox. You should use in a projected coordinate system.
Select "Polygon" as "Output geometry type" option.
Click "Expression" button (highlighted blue square)
And paste the following expression
make_rectangle_3points(
make_point($x, $y),
make_point($x, $y + 1.5),
make_point($x - 1.5, $y + 1.5)
)
Result:
Best Answer
You can use Geometry by expression.
This will create a point projected from the center point in the directions 0, 5, 10, 15, ..., 355
at 50 m distance, then draw a line from the center point and the projected point:
It will be a multiline, you can explode it to singlepart lines with Multipart to singleparts