1

Following this istructions on how to draw a circle I can make buffer layer on each point I need.

I am not able to draw perfects circle because the buffer will be elliptic?

The CSR is EPSG:4326 - WGS 84

And I am also not able to set unit misure in meters as I need (300 meters)

Where is my error? I use QGIS 1.8 on windowx 7

PolyGeo
  • 65,136
  • 29
  • 109
  • 338
Ale
  • 1,313
  • 4
  • 26
  • 48
  • How large are your buffers? Maybe you run into distortion because of the projection you are using. – til_b Oct 20 '14 at 07:16
  • The set radius I need is 300 meters. The difference between tho axes is a lot (the ratio is 4:3) – Ale Oct 20 '14 at 07:17
  • Whats the projection/crs you use? – til_b Oct 20 '14 at 07:19
  • I cannot reproduce this using QGis 2.4 on Windows and a UTM 32N projection (EPSG:4647). – til_b Oct 20 '14 at 07:24
  • The projection is WGS84 and the location I need to work is Italy – Ale Oct 20 '14 at 07:54
  • 1
    In WGS84 the east-west distances and south-north distances look the same only at the equator. The closer to the poles you are the more flattened the circle will look. – user30184 Oct 20 '14 at 08:24
  • I use geoprocessing/buffer option to create the new layer. If I use measure option I find around 310 meters as orizontal lenght (latitude) and around 420 meters as vertical one (longitude) – Ale Oct 20 '14 at 09:15

2 Answers2

4

You have to use a projected CRS like UTM (for your part of the world) to get real circles and meters as units.

Please do not use Google/Web Mercator, it does not use real meters as units (only at the equator).

AndreJ
  • 76,698
  • 5
  • 86
  • 162
1
  1. Choose a suitable UTM grid for your area (see https://de.wikipedia.org/wiki/UTM-Koordinatensystem#mediaviewer/File:LA2-Europe-UTM-zones.png ), probably 32 or 33 (north).
  2. Save your layer in the chosen UTM coordinate system.
  3. Use the buffer tool on the new UTM layer.
til_b
  • 5,074
  • 1
  • 19
  • 36