Creating geographic point on the map canvas using PyQGIS

Question

I have the coordinates of a geographical point in WGS84 and I want to show it on the map on a separate layer (so that it does not belong to the map layer).

Then I would like to give it a dot symbol of my choice.

How do I achieve this in QGIS with Python?

Answer 1

You can use the QgsVertexMarker and QgsRubberBand classes to show points on the map canvas as temporary markers which are not part of a layer. Here are are a couple of short examples to get you started.

Vertex Marker:

canvas = iface.mapCanvas()
lon = 131.2
lat = -12.5
pnt = QgsPointXY(lon, lat)
m = QgsVertexMarker(canvas)
m.setCenter(pnt)
m.setColor(QColor('Black'))
m.setIconType(QgsVertexMarker.ICON_CIRCLE)
m.setIconSize(12)
m.setPenWidth(1)
m.setFillColor(QColor(0, 200, 0))
#run line below to remove:
#canvas.scene().removeItem(m)

Rubber Band:

canvas = iface.mapCanvas()
lon = 131.2
lat = -12.5
pnt = QgsPointXY(lon, lat)
geom = QgsGeometry().fromPointXY(pnt)
rb = QgsRubberBand(canvas, QgsWkbTypes.PointGeometry)
rb.setColor(QColor('Blue'))
rb.setIcon(QgsRubberBand.ICON_CIRCLE)
rb.setIconSize(10)
rb.setToGeometry(geom)
rb.show()
#run line below to remove:
#rb.reset()

See the following links:

• https://docs.qgis.org/testing/en/docs/pyqgis_developer_cookbook/canvas.html#rubber-bands-and-vertex-markers

• https://qgis.org/api/classQgsVertexMarker.html

• https://qgis.org/api/classQgsRubberBand.html

I haven't tested it, but since QGIS 3.10 you should be able to use an SVG icon with a rubber band:

• https://qgis.org/api/classQgsRubberBand.html#a4b45f866c927ca488bdb9eddda678830

• Bruno Vermeulen: Thanks that helped a lot. I got stuck in docs.qgis.org/testing/en/docs/pyqgis_developer_cookbook/…, with an error that QGis.Polygon is not defined ...

Answer 2

The following script adds a memorylayer with one point at lat/lon 20/20:

layer = QgsVectorLayer('Point?crs=epsg:4326', 'MyPoint' ,'memory')
pr = layer.dataProvider()
pt = QgsFeature()
point1 = QgsPointXY(20,20)
pt.setGeometry(QgsGeometry.fromPointXY(point1))
pr.addFeatures([pt])
layer.updateExtents()
QgsProject.instance().addMapLayer(layer)

you can set the symbol then with the normal QGIS stuff (F7->layer styling)