I am setting up a forest inventory database that aims to store information about forest plot data from various countries. The current project is in Mozambique, others are in Laos, etc.

Each project provides their forest data in different coordinate systems. Other than that the plot data (fields) is identical (nearly), so it makes sense to store it all in one table.

I have come across the problem today where I want to view multiple project data in Mozambique. The CRS from one project is supplied in WGS84, the other UTM 36S. The geometry table has set the CRS for plots to WGS84, so when I load in QGIS I can't see the plots in UTM.

What is best practice?

  • To choose a single CRS (WGS84) for all plot data?
  • To store plot data from different countries in different tables?
  • Or depending on which record I am viewing QGIS can dynamically use the relevant projection?

I would say that the ideal situation is to store everything in one table, with the same srid. However if that is not ideal in this case, I would consider creating a view that does an st_transform on the geometry to the srid you want and then use that to view in qgis.

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If you want to be able to do queries over the entire data collection, you should definately have everything in one table. The worst thing you can do then is to store dataset for everyday use with different SRIDs in the same table, so if you have a global data set, your best choice will probably be to use WGS84 for everything. Things you can consider to do, depending on your usage pattern is: - Have a column with the original data for quality assurance. Then if you or someone else should question some of your data, you can pull out the original data set, then you should also have a column storing SRID, proj-string or some other clear definition of the original projection. - As projection is a quite CPU intensive task, you can consider having the data stored in more projections - if there should be one or more non-WGS84 projections that you use regulary. (I know this is a late answer, but some thought and experiences that came up when I came across your question when looking for something else - maybe somebody else can use it)

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