I have created a point --> Figure 1

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I have then selected the Buffer tool and created a buffer around my chosen point, with a degree interval of 0.012. I have selected the End style cap as square and run in background. This has produced a buffer around my point

Figure 2

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Because I am using WGS84 CRS, I cannot use meters as the chosen map unit, instead I am using degrees and I have to guess a degree to match close to what I want. Does anyone have a solution to this specific problem?

My next problem is that after trial and error is that once created a buffer around the right dimensions they are constantly providing contradictory data.

Figure 3

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From the right side it records a distance of 705m until the center, giving a diameter of around 1400m

Figure 4

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From the left side it produces a distance to the center point of 1343m until the center and a diameter of around 2700m.

Figure 5

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indicates that from corner to corner the distance is almost exactly 3000m.

Can someone please explain to me how buffers work. because I am using the Buffer tool the way people are telling me too, yet the results from it seem so inaccurate.

  • 4
    Save your point-layer using a fitting UTM-projection, then create the buffer, then - if necessary - save back to WGS84. Problem solved. – Erik Nov 26 '18 at 15:33
  • what do you mean by 'fitting UTM-projection' what is classified by this? – Bodhi Nov 26 '18 at 15:35
  • if you mean its the CRS I want my point data to be displayed in, then I have already done that, and the error still occurs – Bodhi Nov 26 '18 at 15:35
  • 5
    What seems like a square in WGS84 actually is not a square in real life. – Erik Nov 26 '18 at 16:03
  • 1
    Note that you cannot just change the map projection--that only affects the display. You need to use the reproject tool to actually reproject your points. – Jon Nov 26 '18 at 16:08

Because WGS84 (Lat/Long) is a Geographic Coordinate Reference System (CRS) and the distance of a "degree" gets smaller as you get closer to the Poles, you will never get an accurate buffer based on a specific "measured" distance (like meters or feet).

In QGIS, you'll want to convert your layer (as shown here) to a "Projected" CRS before you buffer the features (one which preferably is "centered" as closely as possible on your geographic extent and uses the unit of measure you are interested in). When you run the buffer routine, you should end up with a perfect circle of the same distance, when viewed in that CRS.

However, if you load that "perfect circle" into a map using a Geographic CRS, the circle will look flattened out, like an oval, as shown here. This distortion is inherent in GIS and mapping, when we try to depict a sphere (earth) on a 2D-plane. As an example, try unpeeling an orange and trying to flatten it out on the table... it is impossible for the "peel" to remain un-distorted in shape or distance.

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