Open GIScience

Sep-16 : In this lesson, we will read and debate the motivations and visions for Open GIScience.

Reading

• Rey, S. J. 2009. Show me the code: Spatial analysis and open source. Journal of Geographical Systems 11 (2):191–207. http://dx.doi.org/10.1007/s10109-009-0086-8
• Singleton, A. D., S. Spielman, and C. Brunsdon. 2016. Establishing a framework for Open Geographic Information science. International Journal of Geographical Information Science 30 (8):1507–1521. http://dx.doi.org/10.1080/13658816.2015.1137579
• Remember the course literature repository

Discussion

While you read these, consider:

• What are the meanings of free software, open source, and open science?
• How is free as in the free software movement different from free as in a cost of $0.00?
• In what way might something be open source but not free?
• As we practice Open GIScience in this class, what are the implications for:
  • Learning
  • The Honor Code
  • Evaluation & Grades
• Is there space for Open GIScience in an undergraduate liberal arts education?
• What risks/benefits do you see for use of open source GIS in:
  • science?
  • government?
  • private businesses?

Slides

Resources from the slides

• High-profile coronavirus retractions raise concerns about data oversight, Nature
• NSF Project to create a geospatial virtual data enclave and Doug Richardson’s short article about it
• Ord, J. K., and A. Getis. 1992. The Analysis of Spatial Association. Geographical analysis 24 (3):189–206. DOI:10.1111/j.1538-4632.1992.tb00261.x
• Python spatial analysis library PySAL
• Rocky Moutain Research Data Center

We can debate this in the context of this ESRI tool for managing COVID testing sites

Additional resources on open science and licensing

• Stodden, V. 2014. What computational scientists need to know about intellectual property law: A primer. In Implementing Reproducible Research, eds. V. Stodden, F. Leisch, and R. D. Peng, 325–340. Boca Raton: CRC Press.
• The Open Source Geospatial Foundation (OSGeo) take on open source
• The MIT License
• Creative Commons Licensing
• GNU’s Philosophy of Free Software and how open source misses the point
• How is OpenStreetMap having a moment concurrently with the death of an open source business model?

A ‘Show Me the Code’ Example: Distance Matrix in QGIS

The Distance Matrix algorithm documentation says nothing about how it calculates distances!

Watch a video of the issue, and/or follow the notes below.

Reading code to understand an algorithm

• Go to the QGIS GitHub repository github.com/qgis and search for distancematrix within the repository
• distance matrix algorithm source code
  • line 179: Transforms the target features into the source CRS (coordinate reference system)
  • line 182: CRS set to source CRS
  • line 183: Ellipsoid set to context ellipsoid
• distance area class source code
  • line 413: converts to meters
  • the only information passed to qgisdistancearea is the context ellipsoid and transformation, and the source crs
• The API (application programming interface) guide can also be a quick and helpful reference to QGIS variables qgis.org/api
  • there is a context.ellipsoid() and a context.distanceUnit(), but the distance matrix algorithm never uses distanceUnit.

Conclusions

• Distance Matrix appears to calculate distance in meters, no matter what.
• Target features are automatically re-projected to match the CRS of input features
• If the input layer uses a projected coordinate system, that system is used or planar distance calculation.
• If the input layer uses a geographic coordinate system, the project ellipsoid is used for ellipsoidal distance calculation.

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