I've found a couple of other Stack Exchange questions related to this, but just like the ArcGIS online help, they were not satisfying. For instance,
Doesn't tell me how the "Inside" point is determined. While the ArcObjects may refer to centroids and label points, I have at least 4 outcomes in my situation that vary differently, wildly in some cases.
I have unidentifiable points inside zip codes, so I'm assigning each one to the centroid of that zip code. Then I will calculate straight line distances from these centroids to various locations of interest. Therefore, my choice of centroid is important. Some zip codes are also of odd shapes and may possibly be discontinuous. At least that is what I assume is generating some of the odd behaviors.
Now, I have found four different ways to identify possible centrality of these polygons.
- The polygon geometry contains a centroid information that can be directly extracted (and supposedly is used for labeling?).
- The labeling location of the polygon (which I found does not always match where the above point is located--hence, the confusion).
- Feature to point method with 'centroid' option.
- Feature to point method with 'inside' option.
Some of these or most of these may overlap. In some zip codes, they are all completely different. I would have expected 1. and 3. to be similar and maybe even 1. and 2. to be identical, depending on how labeling is set up (I'm using default).
My question is not to ask "so how are these calculated?" That's neither here nor there since their algorithms are proprietary, and there's no point in trying to figure it out. The real question is practical: how should one go about determining the appropriate centroid to use?
My conclusion is the feature to point method with the 'inside' option will be the most appropriate because it is guaranteed to reside within the polygon boundary. I also assume it will be relatively central. But the descriptions about this are nebulous. Hell, consider a crescent shaped polygon. The centroid would be outside the crescent but in the middle of the encapsulating envelope. Would an "inside" option literally just "push" it over into the crescent? We may not know the algorithm, but does the "inside" option actually identify centrality? Is it better than 1.? Maybe I'm missing something in my approach to this problem? Can the projection impact these comparisons? Is there a post-processing review of the polygons I should consider?
Note, I'm completely open to using other tools (Python, R, QGIS, etc.). Your answers and advice are appreciated.