Clustering (for all its faults) is the only off-the-shelf technique for seamlessly switching between these two modalities without having to change the underlying data representation. Need more detail? Zoom in. And the zoom level is adaptive so it works with any scale.

There are better aggregation techniques (summing to a hexagonal grid, heatmaps, etc) but they generally require a separate calculation (possibly server side) and then switching to the raw source for the individual point view, either manually or at some hardcoded zoom level. It's not the same experience - it feels like two separate map layers instead of one integrated clustered layer.

This is mostly a matter of what's available in the mapping libraries. You could imagine building an alternative to clustering that calculates a heatmap on the fly when zoomed out, eventually revealing points as you zoom in. But presently this is something you'd have to DIY. For now, clustering is the only thing that works right out of the box.

The heat map is a good example. What does it mean? Points per what? And I can’t bear to talk about the tyranny of Web Mercator.

Maps are so much more powerful when they mean something, and convey scientific facts or actionable evidence.

As far as I know there isn’t a permissively licensed, open source map renderer SDK that can work in a true GIS, e.g. supporting multiple projections.

I'm working on a project (using Protimaps and MapLibre, even, so this is very timely for me) where users create groups at physical locations. If 12 groups choose the local public library's schedulable meeting room as their meeting space, how would anyone click to see the list of groups that use that one room? Wouldn't I just end up with what looks like one very dark dot?

The default heatmaps for these maps are bad. Heatmaps should use filled contours so the gradations are more easily identified. (Continuous raster maps are blobby.) See the ascii glyph map in this post, https://andrewpwheeler.com/2015/06/12/favorite-maps-and-grap.... I think those should be static for various levels of zooms as well, and not recalibrated when zooming.

Another option (not shown here) is to just use polygons and aggregations, and when zoomed in can turn on that point layer (or just have it appear). Or can just make actual clusters (like DBSCAN).

I have a map I made on my website that shows these (with various interaction tooltips/hover), https://crimede-coder.com/graphs/DurhamHotspots (hotspots of crime in Durham, NC). And an explanation of the cartographic decisions and when to use the different techniques, https://www.youtube.com/watch?v=mBm6sTR08BI

There's a deeper issue which the author touches on, showing too much information on a map. This is possible independent of technology limits depending on what level of focus you wish each point to have. For many maps, showing a bunch of small points is an elegant solution, the map turns into more of a data visualization. But a bunch of points tells you very little about a particular thing. It is rich in aggregated information and poor in specific information.

If Google Maps just gave you a bunch of points instead of labels, it would be less functional. Every city would just be a large collection of points. Great, that might be interesting if you want to visualize how the locations are distributed in the region, but you are probably looking at the map because you want to find a particular thing.

Clustering is the natural choice: show the most important thing out of all the points in the area. A label is important, a big circle with a number in it is the worst out all the options discussed. My issue with Google Maps is that there is no visual indicator that there are other points there, and that seems to be largely driven by the fact that it is a marketing platform.

I'm working on a map that uses a hybrid approach. Each map has a narrow focus and is tied to a particular community/interest: concerts, bear sightings, hostels, food trucks, whatever you want. For each point of focus, there is a label and a thumbnail. Showing a bunch of these all in the same place is a bad user experience, so it ranks them and shows the most important one, and the thumbnail is replaced by a number indicating there are other points of focus in the vicinity. Users can click on the item to get a side panel that shows a listing of all the points.

There are also other points on the map that are secondary to its focus, public transportation vehicles and other location points that the user can filter. These are displayed as little dots, similar to the example that the author provides. If you zoom in far enough, they become more than just dots.

In designing the user experience, I tried to make it like a map experience that you might find in a strategy game. Each focus point is like a unit that will bring up more information in a side panel. If there is more than one unit there, show an overview of the units. It's a work in progress, but I'm happy with the result so far.

Also pour one out to google fusion tables which back in the day was the amazing way to get tons of dots onto a map.

I found that the built-in AM clustering truly sucks, so I wrote my own. It's not perfect, but delivers a much better experience than the native one.

Overall, spatial clustering is a very common strategy to understand trends. To dismiss it entirely is a bit sensational.

I’ve consistently heard complaints from customers that they don’t like it. At this point, map technology has come far enough that we could visualize thousands of points using Cesium on consumer-grade hardware so I don’t think it’s a performance issue either.

When it comes to overlapping dots, we generally solve this by displacing the dots minimally so that they’re all still in the same building or same area but visibly different locations.

I have seen some better clustering implementations, which give good sense for whats inside the cluster if you click on it.

Generally agree that the stacked individual points are a much better approach on modern hardware.

A big offender to me is https://urbantoronto.ca/map - You can zoom in pretty far and still get clusters of 2-5 points that are easily far enough apart that they could be individually seen and clicked.

https://www.realtor.ca/map is another annoying one.

The dataset he's using is like 10x smaller than the one displayed in AO.

Edit: <@gregsadetsky I have to answer you like this as HN partially censors me by limiting my comments to around 4/day>

Something's weird then (on either end).

Go to Downtown Toronto, I see about 200 places total. On your map I only see about 50.

Actually ... if you scroll down from there, on the southwest side of Lake Ontario, just north of St. Catharines, I see a big cluster of 197 elements, which does not show on your map. I think the map on AO is overcounting markers. You discovered a bug Greg, congrats!

Try to get Google Maps or Apple Maps running on a phone with more than 200 Markers/Annotations, then come back to me with that. Their performance is fucking dreadful. Google Maps released a new renderer that just OOMs if you're rendering a Polyline with 5k segments. Decimate it or face consequences.

As far as I know, MapBox is about the only one that has tolerable performance. Anyone else doing heavy work and using the gmaps SDK is figuring out tricks: overlay rendering (drawing on a canvas above the map, which requires expensive RPC calls to get visible bounds / map projection which makes performance shit if you're not careful and always lags a frame behind), intense caching of marker descriptors, careful management of markers (dropping 200 Markers from scrolling the map + adding 200? Enjoy your main thread work that freezes the map), etc, etc.

First party map tools are absolute dog shit.