
1. Re: Polygon and point maps – coordinates of a point changed when overlaid on a polygon map
Mary Solbrig Sep 5, 2016 10:49 PM (in response to Boreak Silk)An educated guess:
The centroid as calculated by ArcMap is the actual centroid, that is, the spot where half the area is to the left of the point, half to the right, half above, half below. This is the average of the points of the polygon in a sense, but the average position of every point in the polygon, not just the vertices.The calculation in Tableau is the average location of the vertices. To really see how this is different, imagine a triangle with one of the corners slightly curved, and that the curve is defined by 100 points to make it really nice and curvy. The other to corners are sharp, so are defined by just 1 point. Taking the average position of all of the points (as is happening in Tableau) means that the curved corner will be weighted 100x more heavily than the sharp corners.
A blog post that might provide some better solutions:

2. Re: Polygon and point maps – coordinates of a point changed when overlaid on a polygon map
Boreak Silk Sep 6, 2016 3:30 PM (in response to Mary Solbrig)Hi Mary,
Thank for your response.
I was aware of the issue and used a function in the ArcMap to make sure the point is within the polygon.
And according to the XY coordinates, the point is in the polygon and when I mapped only the point layer
it is in the right position. However when I mapped both layers the point is off and I’m not sure why.
Kind regards
Boreak

3. Re: Polygon and point maps – coordinates of a point changed when overlaid on a polygon map
Mary Solbrig Sep 6, 2016 9:21 PM (in response to Boreak Silk)Do you mean the point with ID 999?
That is not what you are plotting in Tableau. Click on one of the points, select the Show Data button in the tooltip, and then select the underlying tab. This is what is being plotted: the average latitude/longitudes, that is, the average of all of the the lat/long values that make up the polygon. If you want to plot just the point location with ID 999, you will need to follow the steps here:

modified Point Polygon.twbx 249.3 KB


4. Re: Polygon and point maps – coordinates of a point changed when overlaid on a polygon map
Boreak Silk Sep 7, 2016 4:06 AM (in response to Mary Solbrig)Hi Mary,
Thanks. That is exactly what I was after.
Kind regards
Boreak