As a newbie on QGIS, I would like to find out if the way I put a species frequency map together could be improved upon.

I had to map the presence or absence of 7 plant species surveyed in 30 2m x 2m quadrats. This data was saved in separate csv files for each species. I then table joined a single csv file to a single vector layer consisting of a 2m grid polygon. The unique ID for the table join involved zooming in on the 2m grid to identify where the survey quadrat had been placed and noting down the polygon identifier number using the identify feature tool. This number was then input as an extra field in the plant species spreadsheet before saving as a csv file.

The final product consists of an background Ordnance Survey 50k Raster map, 7 x 2m grid polygon vector layers each joined to one of 7 x csv files.

Although this has achieved the desired product, I am convinced there must be a slicker way of reaching the same end result, particularly in reducing the number of polygon layers used. Can anyone make any suggestions? Thank you

  • So you want one polygon layer which contains information for all 7 plant species? – underdark Jul 9 '13 at 21:13
  • I have been able to make polygon layer containing the information for all 7 species. What I would like to do is to have separate layers for each species that link to ONE polygon layer. I could then select or de-select whichever species I choose to view. Unfortunately, I havent been able to do this without creating 7 polygon layers. – Ben Wells Jul 10 '13 at 9:27

Given the currently available functionality, I think you will have the easiest time working and sharing your data with others if you have seven polygon files. Since the polygons are quite simple and few, it shouldn't be a problem of storage space.

Alternatively, you can have one polygon file but load it 7 times into the project. Always join it with only one CSV. Saves disk space and you can enable/disable species as you want.

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