West Cork Palaeoecology

Compiling Maps from Datasets using QGIS

Maps as images can work well to illustrate patterns and processes as well as allowing the combination of different features to illustrate concepts. This can be seen in the maps on this site, in which various datasets have been used, all of which are freely available and in the public domain, except those collected specifically by me for these maps. The maps are built up in layers which can each be ‘switched’ on or off to emphasise different views. Various data conversions and assimilations were required to enable a visually satisfying set of maps, that convey the meanings intended, to be produced.

The Maps on this site have been compiled principally from data made available in the public domain. The various datasets have been imported to QGIS and the displayed properties manipulated to make them attractive and meaningfully viewable. The core software used has been QGIS and the QGIS2Web plugin without which the work involved would have been enormous.

Without question the single biggest contribution, besides the QGIS software, to creating interactive web maps, is the application QGIS2Web developed by Tom Chadwin. See the GitHub page here (opens in a new tab)

Also incorporated into most of the maps, principally for locating known sites and identifying areas, are roads and towns.

One of the principle aims in assembling these maps initially was to increase the elevation data coverage. Ordnance Survey of Ireland produce elevation data but charge quite high prices for it, presumably because of the amount of work they represent. This map uses freely available satellite elevation data, the Japanese ALOS satellite producing the most accurate freely available data. This is produced as a series of data/image files – geotiff (Geographic Tagged Image File Format); contours are created by a program that reads the elevation data on each pixel of the image and calculates where the contour should go. This does not always align with other data, such as drainage data. In addition, the accuracy of all satellite data has a limit – in the case of the JAXA ALOS this is 30 m horizontally, but subject to reflection responses of the surface vertically. River data was obtained from two sources, neither being complete. The two do not agree and some adjustment is required. There are some erroneous features in the map as a result of these minor data inconsitencies. However, once we are aware of these, they can be corrected as necessary. Both Photogrammetric and LIDAR data are available but are expensive.

Using a GIS software also allows access to the many data sets that are made available by various projects- such as BRITICE - and allows enquiries to be made of the data, and the matching and comparison of different datasets in layers. Thus the glacial features, deglaciation landforms, Quaternary sediments, Bedrock Geology when combined with topography and drainage enhance understanding of the relationships within the landscape. This can then be combined with field observation, providing very useful and informative background and enabling the relating of visible features with underlying structure.

Manipulating Data

Some polygon manipulation was required to ensure a tight fit between the GSI coastline which is precise and accurate, and the less precise EMODNET coastline. This work was made much easier by the QGIS functions that are available.

The larger scale maps of the individual sites have incorporated GPS tracking to establish small variations in land surface height. The data was obtained using two GPS receivers operating in tandem, one positioned stationary at a point of known (mapped by OSI (Ordnance Survey of Ireland)) height, the other taken across the terrain. Both were connected to HP EliteBook8470p laptops. The point data captured in this way was corrected for temporal fluctuations in the GPS signal, using comparison between the reference height of the stationary receiver with the received height of the moving receiver, and the resulting points converted to line data.

Careful checking for errors or mistakes has been undertaken, but some may exist. Please notify the website owner of any inconsistencies or problems that you feel need to be addressed.