26 November 2013 | Pierre Jenkins, Head of InstantAtlas Support

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5 tips for creating point maps in InstantAtlas

InstantAtlas is great for showing statistics by area and there are many examples of reports containing area-based maps (called choropleth maps). But IA is just as suitable for creating point maps.

One excellent example is this report published by the Northern Ireland Statistics & Research Agency to show traffic collisions in Northern Ireland in 2012. I'm a big fan of this report and will use it to illustrate my top 5 tips for creating point maps with IA.

NISRA IA report of traffic collisions for Northern Ireland  

Tip 1: Point size & colour

Point size and colour have a major impact on how the map is perceived and should be given careful consideration. It’s best to test different sizes and colours until you settle on a combination that works for your data.

A simple rule of thumb is that the denser the distribution of your points in the map, the smaller you will need to make the symbols in order to minimise overlaps.

The data in the NISRA report are textual and IA therefore sets all points to have the same size. If data are numerical, IA will show graduated points. In both cases, the size of the points can be controlled using settings in the IA Designer.

The point size used in the NISRA report is just right; small enough that the map is meaningful despite the large density of points but not so small that the points become difficult to distinguish. There remains a degree of overlap between points but this cannot be helped as this report is for the entire country and there will inevitably be clusters where the population is concentrated. These clusters - Belfast shown below - can be exploded by zooming to them.

NISRA report zoomed to Belfast  

The red-green-blue colour scheme used by NISRA is a good decision too. For a user with normal sight, these primary hues contrast with each other and also with the background map. The result is that the data are simple to visualise, which is the ultimate goal.

Tip 2: Background mapping

Including a background is especially important for point maps; if you use a blank background the result is an abstract scattering of dots! It is usually best to use background maps that are not too busy and provide context without making it hard to see the points.

InstantAtlas supports different forms of background mapping (Google Maps, ArcGIS Online, WMS, static images). NISRA have opted for Google Maps, the main benefit being the ability to switch between Map, Satellite and Greyscale layers. Switching to the Greyscale layer makes the points stand out even more, as shown below. Note how accurately the collision locations align with the road network in Google Maps.

NISRA report with Greyscale layer  

Tip 3: Filters

The NISRA report contains roughly 600 points but effective use of the Filter button means it is very simple for the user to filter the map to a single category of interest, for example fatal collisions.

NISRA report with filter applied  

Tip 4: Labels

In IA it is possible to turn on labels for map features and this can be useful in reports where the density of points is low, such as in the map shown below.

IA report with labels turned on  

It is possible to change the label styling (font family, size, colour, etc) to make them easier to see against your background mapping. It is also possible to set scale thresholds so that the labels only show at certain zoom levels; this can be used to stop labels overlapping.

NISRA sensibly opted not to use labels in their report: there is no need to give a location name for the collisions and the high density of points in the report would have made it difficult to avoid labels overlapping.

Tip 5: Dynamic points

The NISRA report is not attempting to show collision data in real-time. But in some cases, showing dynamic point data is a necessity; tracking the spread of an epidemic would be one obvious example. When new incidents occur on a frequent basis (weekly, daily, hourly, etc) it becomes very laborious to continually update your report using IA Desktop.

This is where IA Server comes in. This server-based, database-driven solution allows live delivery of both statistical and geospatial data into a report. If you need dynamic point maps you can read more about IA Server here.

Support

I hope you have found these tips useful. If you need any help to implement them then please contact support@geowise.co.uk and we will be happy to help out.

Further examples of interactive maps produced using InstantAtlas can be found on the Northern Ireland Neighbourhood Information Service (NINIS) website.


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