How to calculate changes in distribution in QGIS for a given polygon

Yorkshire consists of 28,272 1km squares. I would like to use QGIS to calculate how the distribution of any given species varies from one year to the next by calculating how many 1km squares are filled each year. For example, if we look at the Northern Brown Argus it is at the southern end of its range in West Yorkshire so only has a few sightings records each year.
These records are entered via a .csv file and using the Tom.Bio plugin. They are displayed at 1Km resolution as Circles. Yorkshire boundary is the Polygon.

Question : I would like to be able to compare how many 1 Km squares out of the total Yorkshire 1km squares have a 1 Km circle in them so I can do a comparison year on year to see how a species is doing with regards to distribution and therefore allowing a % distribution change to be calculated over different time periods.

Hi Martin. There are a number of ways to see how many 1 km circles are in an atlas layer generated by the tool, you can open the layer in the QGIS ‘attribute table’ tool - in the top bar of that tool it displays the number of features. Another way is to double-click the layer in the layers panel and select the ‘General information’ tab - you will see the feature count under ‘Information from provider’.


Hi Rich, Thats very helpful and very simple.
One other question can I find out how many 1km squares sit inside the Yorkshire Polygon as the number I am getting 7144, does not agree with previously used numbers and I want to check which number is right.
Thanks again


Hi Rich,
Think I have found the answer comes up using the same method you mentioned above. Wonderful.



Hi Rich,
I have a followup question. I want to be able to produce a map like that attached in QGIS which has the x and y axes labelled with the 10km grid markers. Could you let me know how to do that ?



Hi Martin. If you are working in the map view, you can use view>decorations>grid to do something like this:

In this example the settings looked like this:
(I used the font button to set font size to 10 I think).

If you are working in the composer, you can use the map grid properties of the map item to create a grid, eg:

I set the properties as shown below to achieve this.

You’d need to experiment a bit in order to find something that suits you.

Hi Rich,
Thats great found all that. Apologies my first image was not very clear I want to display the national Grid as displayed on OS as that is what our Atlas users are used to from Levana, is that possible. I guess it will be a custom coordinate system.
see example in figure.

ThanksProcessing: Nat Grid OS maps.JPG…


Hi Martin. I don’t know of a way to do that. I think it would need some custom development.

Hi Rich, Thanks for letting me know. We are going to do without it.