Volunteered Geographic Information

We all know that representation in GIS is achieved primarily in either of two ways: with objects or with fields. This classic dichotomy was discussed at length during the 1990s when it suddenly became apparent that it is important to consider how the mapped representation of geographical phenomena actually changes our experiences of these in reality, or vice-versa.

If we look at a GI science text (the top of the pile being Longley et al, 2005) we learn quite simply that objects represent discrete entities that we might encounter such as cars, wheelbarrows, buildings, fences, roads or fruit. These discrete objects are best encoded as either a point, line or area (polygon). This gives the discrete object a kind of exacting presence in the GIS environment. On the other hand, things that aren’t discrete, i.e. they exist not as a single definable thing, but as a continuous ‘everywhere’, can be lumped into the ‘field’ category, which we know as ‘raster images’. These rasters are grids of cells which cover a defined area entirely and hold a value for each cell giving a defacto continuous field. Obviously using cells means it isn’t continuous, but lets ignore that and pretend we’re happy; in the end a good resolution will fool you into thinking that a raster represents a continuous space.

Now, vectors have generally risen to dominate the discourse of how we see the world. The cutting-edge products are all vectors, OS mastermap for example, and rasters have fallen by the way side a bit, as a social researcher it is easy to look at rasters as ‘something environmental GIS’ers do’. Nonetheless it is all too easy to find impassioned reasonings for the use of raster, or field, representations in GIS – as Helen Couclelis (1992) wryly states: “People manipulate objects (but cultivate fields)”. Thus there exists a tension in how we ought to think about representing our world and thus how we actually see it.

A Grid Cell with red flares representing the position of a subject when the neuron was 'on'.

Which brings me onto the main point: it seems that scientists in UCL’s Institute of Cognitive Neuroscience has established how the brain creates internal maps of new environments. The brain uses ‘Grid Cells’. The grid cells are actually special neurons which hold a sort of ‘spatial memory’, when you encounter a space these neurons fire in a sequence that, when mapped, show up as geometrically regular, triangular grids. Regarding this, Dr Caswell Barry said:

“It is as if grid cells provide a cognitive map of space. In fact, these cells are very much like the longitude and latitude lines we’re all familiar with on normal maps, but instead of using square grid lines it seems the brain uses triangles.”

So perhaps Helen Couclelis was right, we do use fields and luckily within GIS we have implemented any number of geometric rasters, obviously a square raster is standard, but triangles are not uncommon and neither are hexagonal matrices. What is more, the triangulated irregular network (TIN) acts as a kind of go-between, part vector object and part continuous field. Therefore, your brain on GIS is actually very closely related to your brain anyway! Perhaps a more field-based view of the world is called for.

References

The original article on this discovery is here.

Couclelis H (1992) “People manipulate objects (but cultivate fields): Beyond the raster-vector debate in GIS”, in Theories and methods of Spatio-Temporal Reasoning in Geographic Space, Lecture Notes in Computer Science, 639, Springer, Berlin.

Longley P, Goodchild M, Maguire D and Rhind D (2005) Geographic Information Systems and Science 2nd Edition, Wiley, London.