When I first heard about an attempt to create a map of the world usable by everyone, I probably thought something like "uh, this is not going to work ever". But somehow I was intrigued anyway and kept following it a little. And yes it was a daunting task, but the founders of openstreetmap just started.
In a talk the speaker made a point that this project was successful only because they chose
as the data model. There is no elevation in the data of any point. That decision reduced complexity to a large extent. And so they "just started". A lot of people contributed to the dataset, but also to hosting, software, tools and amazing new uses of geo-data.
A gallery of nice examples
A side by side view of maps from openstreetmap, google, and others in different styles
Wnen I moved to the place I'm living now in 2007 the osm map around here was still quite sparse. So I went ahead on bicycle with my trusty gps logger and a notebook and a camera. For about four years I regularly added points to terrain uncharted. I got to know the area quite well. And I got an impression what it takes for each and everyone contributing to this giant database of tagged geo-data.
I do use openstreetmap.org data. It can be downloaded and used while being offline. No need for a data connection (via phone or wireless) while being on tour. This in itself I consider very impressive. Of course my device has to render the map. But that is actually an advantage. I can change what data I want to see and how it is presented on the fly. With online services you have to content with the map tiles you are served.
https://archive.fosdem.org/2016/schedule/event/keynote_crisis_response_through_open_mapping/
This talk was impressive. It illustrated how determination of a group, free software, volunteers around the world and a set of available tools makes a difference for many people on the planet. Highly recommended.