Projected coordinate system for Sierra Leone

Question

I am using geographic datasets of households (clusters) and mines in Ghana,Sierra Leone, and Liberia (I am analyzing each country separately). I am trying to calculate the distance between each clusters and the nearest mine using QGIS 3.22.7. The locations are measured in latitudes and longitudes, so the layers are in WGS 84 EPSG 4326.

I have learned that it is best to reproject the layers in Projected Coordinate reference System first before calculating distances and buffers to avoid errors. For the sake of consistency and uniformity, it appears that WGS 84 UTM would be the best projection for all 3 countries. However, I could not find any projected CRS that covers the entire country of Sierra Leone; for instance, UTM 29N only covers the eastern part of Sierra Leone.

Which projected CRS would be best for Sierra Leone in terms of coverage and for minimizing errors when calculating distances and buffers?

Answer 1

To me the key fact here is that you are doing your analysis at a country level, not across the 3 countries. You are correct that a projected reference system will be best for meaningful distances. So with that said why not use national grids?

A good resource is spatialreference.org, simply type in the nation and review what is best for each country:

• Ghana - EPSG:2136: Accra / Ghana National Grid

Both Liberia and Sierra Leone don't appear to have a national grid or the UTM covers a portion of the nation. In that case you might want to explore using the Cylindrical Equal Area. ESRI have a great story map listing the many projections and what they are best for.