1

I am trying to map Marine protected areas. I have collected data of where all these areas are. The data is expressed as point data (seen within the top image). Within the attribute tabled I have a column heading named Area. This identifies the area of the areas situated around each point of data. The areas vary is size and shape, therefore the buffer tool, wouldn't be very useful (additionally my CRS is within degrees not meters, so would be inaccurate to do).

I need a map which looks like the bottom image, So I was wondering if there is any way to use my area data to convert the points into polygons?

enter image description here enter image description here

| improve this question | |
  • Do you have any information about the geometry, if not you can calculate an circle around the point with the same area like your value in your attribute table? – eurojam Jan 24 '19 at 15:47
  • No data on the geometry unfortunately. How would I go about calculating the circle with the same area as the values I already have? – Bodhi Jan 24 '19 at 15:49
  • 1
    Reproject your data to a CRS that uses a Cartesian coordinate system. Use the area stored in each point , and the formula for the area of a circle to get the radius. Use that radius to buffer your points. Easier still...Where are these marine protected areas? Maybe the GIS data already exists. – GBG Jan 24 '19 at 16:04
  • 2
    there are ways to convert point to area but if you don't have any information on the real area shape your only possibility is to use regular shape (ie. circle, square, exagon...) that will be meaningless in term of actual zone. – J.R Jan 24 '19 at 16:41
2

You can only convert point into polygons if you dont know what to change them into. Without any data on specific real world areas you can only symbolize it. You could also manully draw polygons based on some base maps (satelite image, georeferenced map..) if precision is not of imporance. If atrubutes from points are important you can use join or spatial join to connect them to polygons.

In your specific case its about protected areas. This should be accessible to public else noone would know what is actully protected :) Bit of researching on it led me to this site: World Database on Protected Areas . Like mentioned before, if you need attributes from your points, use spatial join.

Hope this is what you need..

| improve this answer | |
1

If you don't want to convert your layer to a polygon layer, you can either use the geometry generator for the symbols and make circles (or polygons) with the size belonging to the area field: the formular for the circle will be (with the expression builder, assuming your areafield is named area and the crs is a Cartesian coordinate system - see comment from @GBG):

make_circle($geometry, sqrt("area"/3.1415))

enter image description here

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.