Topi Tjukanov is doing it again: #30DayMapChallenge is returning in November 2020!
Last year I collated submissions from Twitter and made my own gallery. But the repository was large with saved map images, and it wasn't that easy for everyone to collaborate. Plus I didn't start until late November or early December. Hopefully this year - with pre-planning, a separate text-only repository and Google Sheets - we can get some good crowdsourcing going. I have created another interactive gallery, but it will also be easier for others to do their own analysis or visualisations of the submissions.
The good thing about #30DayMapChallenge being a hashtag event in that it's open to anyone to contribute however they want. The downside for meta-analysis is deciding what is a submission and how to classify them.
My general decision is to curate people following the "spirit" of the event of creating maps based on a daily theme. So if someone has made more that one map for a theme I've only included one. I someone is only tweeting historical maps, or other people's creations, or is just randomly applying the hashtag with no apparant regard to themes then I've excluded them. That's not to suggest that they're wrong, or it's not a good thing to see on Twitter - only that they don't fit within this collection.
There are some grey areas - some people have made individual submissions that don't quite fit my curatorial guidelines, but it's infeasible to check all of the thousands of maps so it's easier to keep the decision at the account level. It also seems slighly unfair to draw a distinction between creating several maps in different images and several maps in one image or animation (Topi!), but it's much simpler that way.
For comparison, Haifeng Niu took a different approach of more automation and less (no?) restrictions.
Contributions are eagerly desired. I should do a reasonable job of recording all of the tweets with the hashtag, but crowdsourcing will be needed to pick up what I miss and to ensure that the classifications are as complete as possible.
The easiest way for me is to submit a pull request on GitHub. The easiest way for you is probably to edit this Google spreadsheet that imports the TSV files from this repository. I'll get notified of changes by email and will endeavour to manually include those changes as close to once per day as I can through November.
There is quite a bit of missing metata in the 2019 data, so please feel free to make corrections/additions in the Google spreadsheet for that too.