Re: Best way to get/create polygons

Best way to get/create polygons
June 23, 2021 02:22AM
Hi Challenge Checker Folk,

I am creating my first polygon checker, and need to check within the bounds of a US city.

It looks like the GenericPolyChecker (by lillfiluren) allows us to use either polygons that we define, OR pull polygons from project-gc's database. So questions related to that:

1. If defining polygons, what is the best way to create polygons by clicking?

2. If using project GC polys, is there a catalog of those available? Are city boundaries available?

Thanks to all replies, and if there's a better place for how-to questions, let me know!
Re: Best way to get/create polygons
June 24, 2021 03:06PM
1) I know of no way by clicking.
2)Not really. No.
Re: Best way to get/create polygons
June 24, 2021 03:41PM
OK, this has been an interesting research project, but I got it all figured out. The goal was a challenge checker for this cache in Ocean City MD:

I'll summarize:

I was able to find county-level polygons here:, and saved as KML format. It was then a matter of narrowing down to the correct county. Since Ocean City is bounded by water and a state boundary, a polygon was conveniently available. I used Google Earth Pro to determine which one.

Once I had the polygon in KML, I used notepad++ and excel to get the coordinates into the right format for the script.

So I had the polygon, but the problem now was that 1. it was too detailed, with so many points that it wouldn't fit into a tag, and 2. it hugged the shore too tightly, so caches that were placed in the water (or even on the beach) were excluded.

In the end I went back to Google Earth Pro with the KML file, and edited it (yes, by clicking), then saved a broader outline with fewer vertices. Here's the final result: (I qualify, if you want an example).

A bit of effort, but what can I say, I find these things fun.
Re: Best way to get/create polygons
June 24, 2021 07:32PM
That is the process I use.

Do be careful. The polygon's need to be closed. The first and last point must be the same.
Re: Best way to get/create polygons
June 24, 2021 03:43PM
1. You can use JOSM is an extensible editor for ​OpenStreetMap (OSM) for ​Java 8+
2. There is no catalog but the polysets can be seen on the checker config
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