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      Could they maybe use more easily distinguished colors? The gradient of blue/purple doesn’t really help with identifying the scale differences in my opinion. I keep having to go back and forth between the map and the gradient chart.

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        Yeah - interesting comparison. I prefer the selection of blue-to-white gradient to red in the new scheme as well.

        The placement and edges of the circles in the previous were also deceptive. They suggested a subset of a country as primarily affected (for instance the U.S. MidWest). Heatmaps are easier to interpret accurately at a glance.

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          Yeah - interesting comparison. I prefer the selection of blue-to-white gradient to red in the new scheme as well.

          The red version was generally meh anyways, the pure red is not very accessible.

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        This makes a good point, although it depends on the data. Circles work better if there are accurate positions for each measurement, and they can convey extra data using stroke and fill variations.

        That’s what I did in the Nigerian Oil Spill Monitor, where each circle is one spill, with the size being one pixel per barrel. The colour of the circle indicates the kind of event (operating company is responsible, third party is, location not visited so not determined, spill has been cleaned-up), and the stroke style is solid when the spill amount has been estimated/measured, and dashed if not, in which case the circle has a fixed size, big enough to see clearly. Also, for small spills, the circles have a minimum size so that each individual spill can be seen and selected on the map.

        The circles have an opaque border but translucent area, so the colour becomes more intense the more circles are stacked on a point, which makes a rough approximation to a heat map.

        All that is difficult to do with a heat map, although the choropleth variant (where a whole geographic area is coloured according to the value to display) can have style variants just like the circles, but only for traits common to all the aggregate of values in the whole area.

        The circles displayed in the OSM, since most spills have accurate GPS coordinates, show things like the spills forming lines along the pipelines, often more dense in the older ones that are degrading.

        The Gas Flare Tracker is more concerned with aggregate quantities per area, and there I used heat maps / choropleths. Even in the OSM, if you go to “Data summary” (top-right corner) and select a geographic area in “Summarise the oil spill data by:” like LGA (~province) or State, you get a choropleth because that’s a better display for those aggregates. So I agree that circle maps are over-used.

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          Logarithmic scale circles have been used in these bubble maps because a few points are much larger than the others. Absolute scale circles are more accurate in showing the current situation. Of course maybe the goal is to encourage early action and accuracy per se is not the goal.

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            Log scale can be used with heat maps.

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            Heatmaps may be harder to read for some people with colorblindness than bubblemaps, but yeah I agree with the general premise for sure.

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              Good point !

              An alternative is to go from tinted-white to tinted-black, which avoids the problem.