Tuesday, July 21, 2009

Placemark Clustering: GeoCubes and Barry Hunter

I've discussed clustering placemarks before but thought a revisit was in order since coming across Barry Hunter's work which is partly based on GeoCubes.

Since Barry develops the idea (with a neat little web form in a placemark which I like) from GeoCubes (design 1) I'll just comment on this GeoCubes visualization.

The visualization shows placemarks (it doesn't matter for this discussion what they represent) collated into square cells. The number of placemarks is visualized by a colored cube and a number written on the cube.

  1. Clustering Need: You can't render thousands of placemarks on screen at any one time so they must be clustered in an easy to understand way. GeoCubes does this.
  2. Grid: In the cubes visualization shown placemarks are collated into a grid which is easily understood (other systems collate placemarks into areas where the boundaries are not known - much less comprehensible by the user)
  3. Placemarks and Visualization: When you fly into the screen the cubes dissolve to show the placemarks themselves. Thus you can find the exact location of a single placemark.
  4. It does all this automatically
  1. Figures on screen distracting: The mind processes numbers serially but color in parallel so picking out all the numbers between 500-800 in the screenshot is slow but you can almost instantly identify the 7 orange squares. This is because the mind processes colours in parallel (try it for yourself). So it would be better to have the number text revealed by a mouse rollover or click but otherwise be invisible.
  2. Seamless Cubes: The size of the cubes shows the density of placemarks as well as the color of the cubes, it would be more useful if the cubes went all the way up to the boundary of the cell as then cells with the same density would merge into one seamless, color blob. Barry tells me the geocube guys are thinking about this already.
  3. More Intervals: The number of the placemarks per cell is split into 3 intervals ( 1-100, 101-1000, 1000+). It would be better to have a color blend with more intervals as more information would be immediately apparent (see parallel processing of colour in [1]). Good blends of colors can be gained by colorbrewer which I review here.
  4. Density vs Count: As you zoom in the cells split themselves into smaller cells so that the placemark count goes down. This causes a change of color in the cells but the density of the placemarks per square km hasn't changed. I think it would be better if the cell colour illustrated placemark density as the color would remain more constant. To see what I mean compare select design #1 at geocubes and zoom in. Compare that to zooming in on this pizza resturant map (only imagine at the lowest altitude the heat map dissolves and leaves just placemarks).
If you've been watching carefully you will see that if all the changes I suggest were put in place we would end up with pretty much 'My Solution' outlined in my original post.

Barry's response to the review was positive and he's thinking of producing an experiement in line with my suggestions. I hope that it happens!

1 comment:

Rich Treves said...

This is an email from Ronny Koch from geocubes that he said I could put up. His comments are marked '>', my replies are unmarked.

Ronny Koch wrote:
> Hi Richard,
> first I have to say that we are always happy about reviews and also
> positive feedbacks about geocubes. I find that your pros and cons are
> okay but of course design issues are always a subjective assessment but
> this is totally okay.


It's true that I don't have user tests as evidence based for my comments so they are subjective but they are based on my experience of web usability, cartography and informational graphics design.

> Basically you may know that geocubes is only the provider of the
> clustering technology. We always try to develop our API so that
> everyone's wishes and ideas of what concerns the design and the
> functionality can be adapt with geocubes. Among the cons are mainly
> issues of design, which is always in the hands of the website operator
> to change such things. Our customers can find examples of integration on
> our website, that can be changed very easy and flexbile.

A good point. However, I think it is good service design to 'nudge' (a book title on a related subject) people in the right direction of good design. This would mean good design would come as a default with your service but if the customer wished they could still customize your service in any way they wished. Its similar to the criticism of PowerPoint by Edward Tufte:
He points out that it's within the power of the user to design their PowerPoint presentations well but the PowerPoint defaults and wizards push the user towards bad design. His conclusion is that Powerpoint itself is therefore at fault.

At present I don't think geocubes is nudging people towards good design.

However, that being said, I think you have developed a service that meets a definite need in the community in an accessible way. I think that your work deserves recognition. You are correct that it would be possible to produce a map meeting my criticisms from your service. In fact Barry Hunter has said he's interested in doing just that.

Interested to see the other integrations you list.