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I am new to the QGIS platform and have been experimenting with the tool. I currently have a Basemap layer and a Shapefile layer on top of it. Now,

  1. I want to import a .csv file containing (lat, long) coordinates for a set of points (say 20) as a layer.
  2. I want to create a layer( or superimpose in the above layer), circles of a specified radius around each of these points.

How do I do these?

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    Be aware that if you want proper metric circles, you will have to convert your layer to a metric system. – bugmenot123 Aug 14 '15 at 12:20
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    You've answer from myself and Joseph that approach your problem in different ways. Were you after a style solution or a dedicated layer showing a boundary around a point (buffer)? – MikeRSpencer Aug 14 '15 at 12:50
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    If it is possible to use PostGIS then proper metric circles can be created by using geography instead of geometry. Or to cast a geometry to geography for computing the metric buffer and then back to geometry. The SQL would look like select cast (ST_Buffer(cast(ST_GeomFromText('POINT (-3 70)',4326) as geography),10000) as geometry) See also gis.stackexchange.com/questions/157848/… – user30184 Aug 14 '15 at 12:50
  • @MikeRSpencer I am really really sorry that my comments are coming in so late... Yes I was looking for a dedicated layer and not a style. – Palash Siddamsettiwar Aug 20 '15 at 7:16
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    Lack of knowledge is a problem that you can solve. Learn to use Spatialite if you want to avoid the trouble of administrating PostGIS. Here is a Spatialite query that turns lon-lat coordinates into suitable UTM zone, buffers the point with 50 km radius, and projects the result back to lon-lat SELECT ST_Transform(ST_Buffer(ST_Transform(ST_GeomFromText('POINT (-110 55)',4326),32612),50000),4326) – user30184 Aug 20 '15 at 8:22
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It sounds like you want to buffer your point layer?

  • Load your data as Joseph describes
  • Go to the menu Vector/Geoprocessing Tools/Buffer(s)
  • In the dialogue box choose your input layer (possibly only accepts shp - so you might need to save your csv as shp first)
  • then set your buffer distance and specify an output file.

Other parts of the dialogue box are optional. You can read more in the QGIS docs: http://docs.qgis.org/2.2/en/docs/gentle_gis_introduction/vector_spatial_analysis_buffers.html

  • Yes, I think you're right that the OP wants a buffer instead of a style. +1 :) – Joseph Aug 14 '15 at 12:44
  • Their intention was not helped by the style tag! Will wait to see if they clarify. – MikeRSpencer Aug 14 '15 at 12:47
  • The style tag was my doing...0_0. I will remove it and as you say, wait for the OP to clarify. – Joseph Aug 14 '15 at 12:49
  • @MikeRSpencer your buffer will most probably be in degrees, so I suggest to reproject to UTM or another projected CRS when saving to shapefile. – AndreJ Aug 14 '15 at 14:50
  • No doubt, but the OP didn't specify what units of radius they were after. – MikeRSpencer Aug 14 '15 at 15:26
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You can import your csv file with lat/lon data by going to Layer > Add Delimited Text Layer and check the 'Points coordinates' as the geometry definition:

Add delimited text layer

Once imported, you can change the style by double-clicking the layer to access its properties, go to the Style tab, select the Simple marker option and change its options such as colour, size etc. You can change the size to specified millimeters or set it accordingly to the map units:

Style options

Hope this helps!

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