Edit OpenStreetMap
Edit OpenStreetMap like a pro contributor!
JOSM
Marco Fioretti shows how to get started with a multi-platform, fully fledged but friendly OpenStreetMap editor.
Credit: https://josm.openstreetmap.de
Part Two!
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OUR EXPERT
Marco Fioretti is a long-time open source trainer and writer, and an aspiring polymath, writing about all things digital at https:// mfioretti.com and https: mfioretti. substack.com.
We’re going to delve into how to contribute to the wonderful OpenStreetMap (OSM) project W with a fully fledged OSM editor. There are many such programs, but we’re looking at the popular JOSM (https://josm.openstreetmap.de), because it can handle pretty much everything you may want to do for OSM and it runs well on every Linux desktop.
You may wonder why you’d bother with another editor when iD, the one we presented last month, is so easy to use and can edit all the data structures of OSM. The simple answer is that iD is great for learning the ways of OSM, but there are at least three big reasons to graduate from iD to JOSM as soon as possible.
Firstly, yes, it’s true that describing everything JOSM can do and all its settings would fill 20 pages, not four. This is why this tutorial describes just the architecture, main features and best practices of JOSM. However, JOSM is just feature-rich rather than difficult to use, and lets you map much more efficiently than iD long before you’ve mastered all its capabilities. This is partly due to both its many keyboard shortcuts, which greatly speed up editing, and its functions that automate tasks such as drawing parallel lines, placing nodes in lines or circles, or joining overlapping areas.
NEVER TAG FOR THE RENDERER
Last issue, we explained that OSM is not a map but a mapping database, a repository of raw data usable to build every possible kind of map. We also said that any OSM-based map is a drawing made using that database by separate programs, called renderers, that in general have different drawing styles, constraints, goals and so on. Forgetting those two facts can make you make the mistake of tagging for the renderer, which is the mapping equivalent of building websites best viewed with one and only one browser, or changing font sizes manually instead of using paragraph styles in LibreOffice. Tagging for the renderer is what happens when an editor adds badly formatted tags or changes the data in any other way not because it is needed, but because it makes the map look better – as long as it’s rendered by the one renderer that specific editor likes best. The simplest example of tagging for the renderer is adding spaces to place names, such as writing ‘L o n d o n’ instead of ‘London’ to make that text fill just the right space on the map. Tagging for the renderer practically guarantees that your edits will look pretty good in one renderer and worse in all the others.
Secondly, JOSM helps you not waste your time by validating your edits before letting you adding them to the OSM database. Last but not least, with JOSM you only really need internet connectivity at the beginning and end of every mapping session.