Changing the centroid of a geometry object

ChrisMathers — Mon, 08 Oct 2012 13:52:49 GMT

Whats the easiest way to move one geometry to the center of another geometry? That attribute is read only. Im generating polygons and writing them out to a row in a script. Right now the first point of my geometry object is the centroid of a parcel which means the drawings intersect the correct parcel but are not centered on it. I just tried adding the difference between the parcel centroid and the geometry centroid but while that moved the new geometry it didnt move it to the centroid as
I had hoped. Below is what I tried, parcelLookup is a nested dictionary that has all of the parcel numbers with their centroids.

def addGeometry(inGeometry,parcelID,buildingNum,row):     diffX = (parcelLookup[parcelID]['x'] - arcpy.Geometry('polygon',inGeometry).centroid.X)     diffY = (parcelLookup[parcelID]['y'] - arcpy.Geometry('polygon',inGeometry).centroid.Y)     for i in range(0,inGeometry.count):         oldPoint = inGeometry.getObject(i)         newPoint = arcpy.Point(oldPoint.X + diffX, oldPoint.Y + diffY)         inGeometry.replace(i,newPoint)     row.shape = arcpy.Geometry('polygon',inGeometry)     row.PID = parcelID     row.Id = buildingNum     rows.insertRow(row)

Edit: I was subtracting the centroid of the parcel from the centroid of the geometry. Thats backwards. Subtracting the geometry from the parcel is the right order. Cursed be all typos.

Re: Changing the centroid of a geometry object

nimitz — Wed, 24 Oct 2012 17:49:59 GMT

Chris,
I'm trying to do something similar to what you're doing, BUT I just need to create a point shapefile from the centroid of a grid index I already created.
I'm trying to "copy" some of your example code in the python window, but the syntax error keeps popping up.

I guess, you did this in PYTHON IDLE environment. But, does the parcel layer need to be existing. I'm using my existing grid I created, but the syntax is messing me up.

Thanks for any help

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Changing the centroid of a geometry object

Re: Changing the centroid of a geometry object