4

I have several buffers distributed along a whole country (therefore, the distances between them is very high). These buffers are represented in the same layer/shp.

I want to create a regular point layer (spaced between 100m) only within each buffer, but so far the only procedure I know is to create a regular point layer in all surface, and then use "clip" tool to get only the points within each buffer.

However, it seems impossible (at least with my computer) to create a regular point layer for a whole country separated by 100m, and then clip it.

Is there any other way to obtain the regular point layer only within each buffer?

3

It could be done with PyQGIS. Assuming that vector layer in next image is your buffer (it was relatively small for verification purposes):

enter image description here

I tried out next code for creating the regularly spaced point layer grid (100 m) for each feature.

layer = iface.activeLayer()

feats = [ feat for feat in layer.getFeatures()]

points = []

for feat in feats:
    extent = feat.geometry().boundingBox()
    xmin = extent.xMinimum()
    ymax = extent.yMaximum()
    xmax = extent.xMaximum()
    ymin = extent.yMinimum()

    rows = int(ymax - ymin)/100
    cols = int(xmax - xmin)/100

    x = xmin
    y = ymax

    geom_feat = feat.geometry()

    for i in range(rows+1):
        for j in range(cols+1):
            pt = QgsPoint(x,y)
            tmp_pt = QgsGeometry.fromPoint(pt)
            if tmp_pt.within(geom_feat):
                points.append(tmp_pt.asPoint())
            x +=100
        x = xmin
        y -= 100

epsg = layer.crs().postgisSrid()

#points
uri = "Point?crs=epsg:" + str(epsg) + "&field=id:integer""&index=yes"

mem_layer = QgsVectorLayer(uri,
                           'point',
                           'memory')

prov = mem_layer.dataProvider()

feats = [ QgsFeature() for i in range(len(points)) ]

for i, feat in enumerate(feats):
    feat.setAttributes([i])
    feat.setGeometry(QgsGeometry.fromPoint(points[i]))

prov.addFeatures(feats)

QgsMapLayerRegistry.instance().addMapLayer(mem_layer)

After running the above code at the Python Console of QGIS, I got:

enter image description here

It works adequately for these smalls areas.

  • Thank you very much! I have never used the Python Console, but I will try the code you provided! – Teresa Aug 30 '16 at 13:54
2

Two possible way I can think of is

1) Instead of clipping the points to the buffers, use 'select by location' and save only the selected points out as a new layer. That could be less intensive on the ol' computer.

2) Save the buffers out separately and create the points layers for each individual buffer. Then 'Vector > Data Management Tools > Merge Vector Layers' to create a single layer of points

  • 1
    That's an option, but since I also have several buffers, it will take a while. It is better than crashing QGIS though!! Thank you for your suggestions! – Teresa Aug 30 '16 at 13:54

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