Archive for the ‘GIS’ Category

Sourcing GIS data

March 29, 2016

Where does one get GIS data for teaching purposes? This is the sort of question one might ask on Twitter. However while, like many, I have learned to overcome, or at least creatively ignore, the constraints of 140 characters, it can’t really be done for a question this broad, or with as many attendant sub-issues. That said, this post was finally edged into existence by a Twitter follow, from “Canadian GIS & Geomatics Resources” (@CanadianGIS). So many thanks to them for the unintended prod. The linked website of this account states:

I am sure that almost any geomatics professional would agree that a major part of any GIS are the data sets involved. The data can be in the form of vectors, rasters, aerial photography or statistical tabular data and most often the data component can be very costly or labor intensive.

Too true. And as the university term ends, reviewing the issue from the point of view of teaching seems apposite.

First, of course, students need to know what a shapefile actually is. A shapefile is the building block of GIS, the datasets where individual map layers live. Points, lines, polygons: Cartesian geography are what makes the world go round – or at least the digital world, if we accept the oft-quoted statistic that 80% or all online material is in some way georeferenced. I have made various efforts to establish the veracity of this statistic or otherwise, and if anyone has any leads, I would be most grateful if you would share them with me by email or, better still, in the comments section here. Surely it can’t be any less than that now, with the emergence of mobile computing and the saturation of the 4G smartphone market. Anyway…

In my postgraduate course, part of a Digital Humanities MA programme, on digital mapping, I have used the Ordnance Survey Open Data resources, Geofabrik, an on-demand batch download service for OpenStreetMap data, Web Feature Service data from Westminster City Council, and  continental coastline data from the European Environment Agency. The first two in particular are useful, as they provide different perspectives from respectively the central mapping verses open source/crowdsourced geodata angles. But in the expediency required of teaching a module, they main virtues are the fact they’re free, (fairly) reliable, free, malleable, and can be delivered straight to the student’s machine, or classroom PC (infrastructure problems aside – but that’s a different matter) – and uploaded to a package such as QGIS.  But I also use some shapefiles, specifically point files, I created myself. Students should also be encouraged to consider how (and where) the data comes from. This seems to be the most important aspect of geospatial within the Digital Humanities. This data is out there, it can be downloaded, but to understand what it actually *is*, what it actually means, you have to create it. That can mean writing Python scripts to extract toponyms, considering how place is represented in a text, or poring over Google Earth to identify latitude/longitude references for archaeological features.

This goes to the heart of what it means to create geodata, certainly in the Digital Humanities. Like the Ordnance Survey and Geofabrik, much of the geodata around us on the internet arrives pre-packaged and with all its assumptions hidden from view.  Agnieszka Leszczynski, whose excellent work on the distinction between quantitative and qualitative geography I have been re-reading as part of preparation for various forthcoming writings, calls this a ‘datalogical’ view of the world. Everything is abstracted as computable points, lines and polygons (or rasters). Such data is abstracted from the ‘infological’ view of the world, as understood by the humanities.  As Leszczynski puts is: “The conceptual errors and semantic ambiguities of representation in the infologial world propagate and assume materiality in the form of bits and bytes”[1]. It is this process of assumption that a good DH module on digital mapping must address.

In the course of this module I have also become aware of important intellectual gaps in this sort of provision. Nowhere, for example, in either the OS or Geofabrik datasets, is there information in British public Rights of Way (PROWs). I’m going to be needing this data later in the summer for my own research on the historical geography of corpse roads (more here in the future, I hope). But a bit of Googling turned up the following blog reply from OS at the time of the OS data release in April 2010:

I’ve done some more digging on ROW information. It is the IP of the Local Authorities and currently we have an agreement that allows us to to include it in OS Explorer and OS Landranger Maps. Copies of the ‘Definitive Map’ are passed to our Data Collection and Management team where any changes are put into our GIS system in a vector format. These changes get fed through to Cartographic Production who update the ROW information within our raster mapping. Digitising the changes in this way is actually something we’ve not been doing for very long so we don’t have a full coverage in vector format, but it seems the answer to your question is a bit of both! I hope that makes sense![2]

So… teaching GIS in the arcane backstreets of the (digital) spatial humanities still means seeing what is not there due to IP as well as what is.

[1] Leszczynski, Agnieszka. “Quantitative Limits to Qualitative Engagements: GIS, Its Critics, and the Philosophical Divide∗.” The Professional Geographer 61.3 (2009): 350-365.