Provide example for user of GHS Degree of Urbanisation (2023) data as alternative to UCDB (2019)

[carlhiggs]

Currently our examples use the GHS Urban Centres Database to identify urban regions, which was available when we were developing our tool in 2020. However, a newer dataset is now available for Degree of Urbanisation (2023) with an accompanying manual describing its usage to support international comparisons (2021).

I believe we should update our example and documentation to guide users to use the more recent data product, in line with these guidelines. I haven't read these in detail yet, but lodging the issue as a reminder for intent to explore implementing this.

In principle, the use of alternative urban region data sources and queries of these is possible, but it will make things easier for users if we provide direct examples of how to do this.

[carlhiggs]

So, the above Degree of Urbanisation method/data doesn't include geometries itself, but rather is designed for linkage with data from the GADM project, that collates administrative data for countries around the world. It is interesting, as it provides estimates of area and population as time series. I wonder how the time series works in the context of shifting administrative boundaries -- it would be impressive if this is captured in a complete and accurate way for the world -- I'll have to read the rest of the manual and look at the GADM data to see how that works.

[carlhiggs]

Actually, I'm not sure that the Degree of Urbanisation data can be used in the way we would want it to be used for our project.

In the below image, you can see the modelled urban centre data (blue) corresponding to Las Palmas de Gran Canaria, with the finest scale of adminstrative data from GADM loaded underneath and corresponding municipality for this city selected.

That's really just the administrative boudnary that we've otherwise used as input, and so the DEGURBA classification is a complex methodology for grading urbanisation within that administrative boundary --- but it doesn't serve the role of identifying empirically 'urban' areas, such as urban agglomerations that don't align with administrative boundaries (which is why we have been using the UCDB).

For now, I'm going to close this issue. While I think it would be interesting providing an example of how this data could be used, it is quite complicated (ie. requires downloading of multiple datasets with multiple layers and complex system of levels that isn't necessarily consistent between countries). I think our time would be better served focusing on other issues.