Geographic Information Systems: From maps to analysis

SunoikisisDC Digital Approaches to Cultural Heritage: Session 4

Date: Thursday Feb 8, 2024. 16:00-17:30 GMT.

Convenors: Justin Colson (University of London), Rebecca Seifried (University of Massachusetts Amherst)

Youtube link: https://youtu.be/vgYUjki0TwE

Slides: Combined slides (PDF)

Outline

This session introduces Geographic Information Systems (GIS) and illustrates how it can be used to explore spatial patterns in cultural heritage datasets. We begin with an overview of the basic building blocks of GIS, including raster and vector data types, spatial vs. attribute data, and coordinate reference systems. We include concrete case studies involving the use of GIS with ancient spatial data, and we show how to use QGIS – a free and open-source software – to work with geospatial data. A hands-on exercise for learners to take away and try for themselves is also described, with further reference to external tutorials.

Required readings

• Li, Y., X. Jia, Z. Liu, L. Zhao, P. Sheng, and M.J. Storozum. 2022. “The Potential Impact of Rising Sea Levels on China's Coastal Cultural Heritage: A GIS Risk Assessment." Antiquity 96(386): 406-421. Available: https://doi.org/10.15184/aqy.2022.1
• Tzvetkova, J. 2022. "Ancient Thrace: GIS and Reality." in Delev, P., Stoyanov, T. et al (eds.), Ancient Thrace: Myth and Reality. The Proceedings of The Thirteenth International Congress of Thracology. Kazanlak, September 3 – 7, 2017. Volume 2. Sofia. Pp. 355–364. Available: https://unipress.bg/image/catalog/1pdf/Ancient%20Thrace_Chast%202.pdf

Further readings

• Bonnier, A., M. Finné, and E. Weiberg. 2019. "Examining Land-Use through GIS-Based Kernel Density Estimation: A Re-Evaluation of Legacy Data from the Berbati-Limnes Survey." Journal of Field Archaeology 44(2):70-83. Available: https://doi.org/10.1080/00934690.2019.1570481
• Donaldson, C., I.N. Gregory, and J.E. Taylor. 2017. "Locating the beautiful, picturesque, sublime and majestic: spatially analysing the application of aesthetic terminology in descriptions of the English Lake District." Journal of Historical Geography 56:43-60. Available: https://www.sciencedirect.com/science/article/pii/S0305748817300178
• Field, S., C. Heitman, and H. Richards-Rissetto. 2019. “A Least Cost Analysis: Correlative Modeling of the Chaco Regional Road System.” Journal of Computer Applications in Archaeology 2(1):136-150. Available: https://doi.org/10.5334/jcaa.36
• Lysandrou, V., and A. Agapiou. 2020. “The Role of Archival Aerial Photography in Shaping Our Understanding of the Funerary Landscape of Hellenistic and Roman Cyprus." Open Archaeology 6: 417–433. Available: https://doi.org/10.1515/opar-2020-0117
• Murrieta-Flores, P., C. Donaldson, and I. Gregory. 2017. “GIS and Literary History: Advancing Digital Humanities research through the Spatial Analysis of historical travel writing and topographical literature.” Digital Humanities Quarterly 11. Available: http://www.digitalhumanities.org/dhq/vol/11/1/000283/000283.html
• Rayne, L., J. Bradbury, D. Mattingly, G. Philip, R. Bewley, and A. Wilson. 2017. "From Above and on the Ground: Geospatial Methods for Recording Endangered Archaeology in the Middle East and North Africa." Geosciences 7(4):100. Available: https://doi.org/10.3390/geosciences7040100
• Richards-Rissetto, H. 2017. "An iterative 3D GIS analysis of the role of visibility in ancient Maya landscapes: A case study from Copan, Honduras." Digital Scholarship in the Humanities 32(S2):ii195–ii212. Available: https://doi.org/10.1093/llc/fqx014
• Seifried, R.M., C.A.M. Gardner, and M. Tatum. 2023. "Mapping the Leigh Fermors' journey through the Deep Mani in 1951." Annual of the British School at Athens 118:417-440. Available: https://doi.org/10.1017/S0068245423000023
• Turchetto, J. and G. Salemi. 2017. “Hide and Seek. Roads, Lookouts and Directional Visibility Cones in Central Anatolia.” Open Archaeology 3:69-82. Available: https://doi.org/10.1515/opar-2017-0004
• Weiss, C. 2010. "Determining Function of Pompeian Sidewalk Features through GIS Analysis." In: Frischer, B., J. Webb Crawford, and D. Koller (eds.) Making History Interactive. Computer Applications and Quantitative Methods in Archaeology (CAA). Proceedings of the 37th International Conference, Williamsburg, Virginia, United States of America, March 22-26 2009. BAR International Series S2079. Archaeopress, Oxford, pp. 363-372. Available: http://proceedings.caaconference.org/files/2009/43_Weiss_CAA2009.pdf

Resources

• A Gentle Introduction to GIS
• List of DH GIS projects by John Levin
• Esri ArcGIS Blog #Cartography

Additional Tutorials (if you need more support than this video session)

• QGIS Tutorials and Tips by Ujaval Ghandi
• QGIS4Arch and QGIS 2-Minute Tutorials by AnthroYeti
• SunoikisisDC 2019 - GIS and Geovisualization for a demo and exercise using least-cost analysis
• SunoikisisDC 2021 - Geographic Information Systems for a demo and exercise using visibility analysis

Exercise

Software setup

1. Download and install the long-term release version of QGIS. Look for the link below the large green download button.

   Mac users, if you get an error message during install, see Apple’s how-to: Open a Mac app from an unidentified developer

2. Open QGIS and install the QuickMapServices plugin:
   1. From the "Plugins" menu, select "Manage and Install Plugins...".
   2. In the filter box, search for "QuickMapServices".
   3. Select QuickMapServices and click "Install Plugin".
   4. Close the plugin manager. The plugin should now be available in the menu: Web > QuickMapServices.

Exercise Option A: Georeferencing a Historical Map

1. Download W.B. Clarke’s Plan of Ancient Rome from Stanford Libraries - choose the Original JPG option and save to the folder where you’ve saved your QGIS project.

2. Raster (bitmap) images (scanned historical maps, satellite pictures etc) can be added using the Open Data Source Manager button. Try adding your image directly this way. As it has not been georeferenced already, it will appear at 0,0 on the map – not much use!

3. QGIS offers a built-in georeferencing tool called Georeferencer that is usually installed by default. (You might need to enable it via Manage Plugins.)

   1. Select the menu item Layer > Georeferencer. A new window appears with a range of options for georeferencing.
   2. There is an Add Raster Layer button on the toolbar of the new window. Use this to add your file.
   3. You will be prompted to select a Coordinate System for the raster image. You should normally select the same Coordinate System that the rest of your project is using (i.e. WGS 84 /Pseudo-Mercator EPSG:3857).
   4. You can now use the Add Point, Remove Point, and Move GCP Point options to set Ground Control Points. These buttons are shown with a kind of sideways T overlaid with an orange star (add), red X (remove) or blue arrow (move). These should be points that you can find in both your historical map and on the basemap.
      1. Click once on your historical map, and then click From map canvas to move across to your base map to find the same location and click a second time to set the point.
      2. You might find it easier to move and resize the windows so they sit side by side, or use Alt-Tab on the keyboard to move between them.
      3. Set at least four points as accurately as you can - the more the better!
   5. Use the yellow gear button to set the options for the way in which the image will be processed.
      1. For Transformation Type, select Polynominal 1 – this will allow the image to be ‘warped’ in all necessary directions.
      2. For Target CRS (Coordinate Reference System), select the same one as your project.
      3. For Output Raster, choose a new file name for the new georeferenced version of the file, in the same folder that you saved the project.
      4. Check Load in QGIS when done and click OK.
   6. Finally, click the green Play symbol to start the georeferencing process. This might take a few moments.

4. The image should now appear on your map, in the correct location, and might be slightly warped, so that the points all match their correct location.

Exercise Option B: Using Spatial Queries to Find Roman Amphitheaters

1. Download the data pack and unzip the file. This file contains modified versions of two data layers: a vector (point) layer of amphitheaters across the Roman Empire, by Sebastian Heath, and a vector (line) layer of ancient roads across the Roman Empire, by the Ancient World Mapping Center. The versions in our data pack have been projected to the ETRS89 Lambert Azimuthal Equal Area projection (EPSG 3035).

2. Use spatial queries to determine which amphitheaters were located within 500m of a (known) Roman road:

   1. Add the amphitheaters and road datasets to QGIS.
   2. Use the Buffer tool (Vector menu > Geoprocessing tools) to create 500m buffers around the amphitheater points.
   3. Launch the Select by Location tool and select from buffers, where the features intersect the roads.
   4. Launch the tool again, and now select from amphitheaters, where the features are within the selected buffers.
   5. Export the selected features by right-clicking the amphitheaters layer in the layers panel, then select Export > Save Selected Features As.