1

I have made a buffer around a point using the CRS WGS84.

I made my buffer by Selecting a point and using the Buffer tool within the Processing toolbox.

I ideally wanted my buffer in meters but because I am using WGS84 and my data was originally ED50 31N, all the data is in Degrees, so I have had to estimate my diameter through trial and error to get to the correct distance.

The latitude of the center point is 58.352847, and my longitude is 0.862616.to measure the distance of my diameter I used the Measure line tool. However my buffer is circular.

If I am correct, using WGS84 should make my buffer more of an elliptical shape. therefore is my CRS not truly changed even though I have manually changed it within the Project Coordinate Reference System within Project properties and applied changes.

If however, my CRS does anyone know how to make the buffer (black circle) within the figure below into an elipical shape. The reason being as I need a 500m exclusion zone around the point however horizontally it is giving me a diameter of 500m, but vertically a diameter of 1000m. (Shown in the WGS84 Projection (I use QGIS V 3.2) enter image description here

| improve this question | |
  • Please Edit the question to provide missing information: How did you construct the buffer? At what latitude is the center point? In what projection is the map above? How did you measure the vertical and horizontal diameters? – Vince Nov 29 '18 at 13:50
  • Changing the project CRS will not change your CRS. – HeikkiVesanto Nov 29 '18 at 14:21
  • Whats the best way to change the CRS then for example, ED50 31N into WGS84 CRS Projection? – Bodhi Nov 29 '18 at 14:22
  • gis.stackexchange.com/questions/35590/… – HeikkiVesanto Nov 29 '18 at 14:33
  • @Heikkivesanto I have done that now, however Im still unclear on how to solve my buffer shape issue – Bodhi Nov 29 '18 at 14:38
1

If you want to stay in WGS84, there is helpful Shape Tools plugin.

It will add a new toolbar on your QGIS GUI. Click on the leftmost (flower-like) Create Shapes icon.

Ellipse shape (as shown below) has several options, and you will need to set:

  • Axis units = Meters
  • Semi-major axis = 500
  • Semi-minor axis = 500

You will obtain 500m-radius circle displayed as an "ellipse" (WGS84 space), like the blue one in this example.

enter image description here

| improve this answer | |
  • this is perfect, thank you, Am I right in saying that this tool could work for square shape polygons? – Bodhi Nov 29 '18 at 15:01
  • @Bodhi Interesting question...I have never tried a square, but you could try polygon option (pentagon icon - fifth from the left) and give 4 to the number of sides. – Kazuhito Nov 29 '18 at 15:07
  • I have tried it and it does, however not exactly as I would like it. I will have to play around with the dimensions. it becomes confusing as it asks for a default starting angle and default outer radius but the distance units of measure are in Kilometers. – Bodhi Nov 29 '18 at 15:11
  • @Bodhi Perhaps you want to align your square to N-S / W-E direction. Then the default starting angle would be 45 (as starting corner). As to the measurement unit, there is a pull-down menu which allows you to select km, m, nm, ... – Kazuhito Nov 29 '18 at 15:15
  • I am just trying that now, originally I put in data as a 90 degree angle. 45 seems to work a lot better. Thank you for all your help – Bodhi Nov 29 '18 at 15:22

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.