QGIS – Calculating Bounding Box Coordinates of a Selected Polygon

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I just manually (and somewhat inaccurately I'm sure) retrieved the bounding box coordinates for a county polygon, which is a selection from a larger layer of county shapes. I'd like to be able to use a QGIS plugin or other function to calculate this quickly and not-by-hand. This is almost certainly possible but I couldn't find anything with a Google search

Best Answer

The following little Python function will output the bounding box coordinates of the currently active feature:

def printBB():
    feature = iface.activeLayer().selectedFeatures()[0]
    print feature.geometry().boundingBox().toString()

To define the function, open the Python console from the Plugins menu, copy and paste the three lines into the console, and press enter. Then you can call the function by typing printBB() and pressing enter while the desired feature is selected.

Edit: For newer Python versions (Python 3.x) use this (print() with brackets):

def printBB():
    feature = iface.activeLayer().selectedFeatures()[0]
    print(feature.geometry().boundingBox().toString())

Related Solutions

[GIS] Visualizing bounding box as polygon

Yes, it's the QuickWKT plugin (WKT = "Well-Known Text"). The bounding box would be treated as a polygon, and WKT would look like:

'POLYGON(x1 y1, x1 y2, x2 y2, x2 y1, x1 y1)'

Note that any polygon shape is possible, but coordinates following this model will generate a rectangle, which is what you want for a bounding box. You can't get away specifying only two corners, as you have in the question, you have to specify all four corners, and the first and last coordinates have to be the same. That's how WKT indicates that the polygon is closed.

A screenshot with the WKT for your first example:

QuickWKT with Well-Known Text for a rectangle in WGS84.

[GIS] Getting bounding box of a selected region through PyQGIS

this is simpel in pyqgis:

layer = iface.activeLayer() # is the currently selected layer
box = layer.boundingBoxOfSelected() # creates a bounding box
iface.mapCanvas().setExtent(box) # zooms to this bounding box

you could also scale the box variable with

box.scale(2,box.center()[0], box.center()[1])

where "2" is the scale factor.

Tested with QGIS 2.18. For further research have a look athe pyqgis api of boundingBoxOfSelected

Best Answer

Related Solutions

[GIS] Visualizing bounding box as polygon

[GIS] Getting bounding box of a selected region through PyQGIS

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