Why do locator maps on Wikipedia pages go blank when enlarged?

November 5, 2018 3:54 PM

Locator maps on Wikipedia pages often have red dots, such as this one for Olduvai Gorge in Tanzania. But when you click on the map to enlarge it, the red dot is no longer shown. This happens on every map of this type that I've seen on Wikipedia, including cities, mountain peaks, and other places of interest. I see this happen in both Safari and Chrome. Why?
posted by theory to Computers & Internet (6 answers total)

The short answer is, as far as I can tell, that's just not how it works. There is a location map function (template shown here) which takes an image and layers a location dot and title on top of it. That's what you see on the main page. But clicking on the image just takes you to a detail view of the underlying image, and that page doesn't have the feature that overlays a dot.

It's a bummer!
posted by wemayfreeze at 4:21 PM on November 5, 2018 [1 favorite]

It appears that what you see on the page itself is a red dot image overlaid on a base image. When you click to enlarge, only the base image is shown.

This allows the same base image to be used for many different locations in the same area, as you can see at https://commons.wikimedia.org/wiki/Special:GlobalUsage/Tanzania_relief_location_map.svg

Like wemayfreeze says, it's a bummer and you're not the first to be tripped up by it!
posted by the antecedent of that pronoun at 4:24 PM on November 5, 2018

Best answer: If I recall correctly, the locator maps are usually a MediaWiki template that lets the article editor pass in an image name along with coordinates for the red dot. So the red dot isn't in the image itself, it's the template which is generating, positioning, and overlaying the dot on the blank map image. This way a cartography nerd can work on making a single nice blank map image for the whole county/country/etc. which can be reused in many different articles.

But the image display "enlarge" mechanism doesn't know the image is inside such a template and so when you click to enlarge it just shows you the underlying blank map.

If you need an enlarged map with its marker, you may be able to cut and paste the template code into a sandbox elsewhere on Wikipedia and adjust the display size. (Though depending on how the template is written, you might also need to re-calculate the map coordinates... doing multiples will probably be easiest, so for example if you triple the map's width value you may be able to just triple each of the coordinate values.)
posted by XMLicious at 4:24 PM on November 5, 2018 [1 favorite]

Response by poster: I sort of suspected the answer was something along these lines, but it isn't clear to me why this can't also be applied to the full-size view of the base image, instead of just the thumbnail view on the main page.
posted by theory at 4:37 PM on November 5, 2018

Best answer: The short answer is that it could be, but it would take someone coding it up to work that way.

The slightly longer answer is that the media detail pages that you see when you click those images are relatively simple. You can see this in the URL for the full-size image at your first link:

http://en.wikipedia.org/wiki/Olduvai_Gorge#/media/File:Tanzania_relief_location_map.svg

It's just a simple URL, that shows only the detail view of that image. It's likely linked elsewhere without any location markers — on the wiki page for Tanzania, for instance. Adding the feature you're looking for would take non-trivial amounts of coding and, I imagine, a few hundred thousand comments of discussion between the various volunteers who work on the platform.
posted by wemayfreeze at 4:55 PM on November 5, 2018 [2 favorites]

a few hundred thousand comments of discussion between the various volunteers

Hey folks we got an optimist here!
I kid, but WP is about as nimble as an institution five times its size and ten times its age. Which is probably ok, but things move slowly, for both good reasons and bad.

I encourage you to get involved there, if you can’t tell where to start, we can probably give you some pointers.
posted by SaltySalticid at 5:06 PM on November 5, 2018 [1 favorite]