[FEATURE REQUEST] Link ADM2 boundaries to ADM1 entities in geojson properties

[brettonw]

Is your feature request related to a problem you run into when using geoBoundaries? Please describe.
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When I load ADM1, ADM2, or smaller boundaries, the properties object contains a shapeGroup identifier that can be used to link to the ADM0 data, but nothing that specifies how the ADM2 and ADM1 data are related.

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I would like an additional property that specifies the immediate superior jurisdiction boundary. For instance, If I have Harris county from the ADM2 boudnaries, I would like to know that the corresponding ADM1 boundary is Texas.

When the properties: { "ShapeType": "ADM2" }, then you could add `properties: { "ADM1": "..." }, similarly repeated for ADM3 (specify the ADM2), and etc. Or you could use the word "parent" or some such nomenclature, for a more consistent structure.

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I've tried generating random sample points within the ADM2 polygons and testing the ADM1 polygons for containment, but this is not a perfect solution and is rather brute force.

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[brettonw]

USA-ADM2-mappings.json
MEX-ADM2-mappings.json

Using the point location method I mentioned above (imperfect, I know), I captured these outputs. I am unsure of their accuracy. For Mexico, I was not successful at locating the ADM1 correspondence for these ADM2 names using the point location method:

Ensenada
La Paz
Los Cabos
Othón P. Blanco
Mazatlán
Veracruz
Celestún

I can manually look these up in Google, but it would be really great if the correspondence was already present.

I did this just for illustrative purposes. The list of ADM2 boundaries inside an ADM1 boundary might not be unique...