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Aligning Raster and vector layer using PyQGIS when they do not match?
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Relatively new to GIS. I've created a vector layer of points based on row/col position of high population density pixels in a raster layer. The layers do not align even though they have the same CRS, presumably because they do not have the same extent.
Is it possible to edit the extent of the raster to match that of the vector layer or when creating the new vector layer can I define extent based on my raster layer?
raster coordinate-system pyqgis vector
edited 13 mins ago
PolyGeo♦
53.9k1782246
asked Apr 13 '17 at 20:22
SimonSimon
343
add a comment |
Relatively new to GIS. I've created a vector layer of points based on row/col position of high population density pixels in a raster layer. The layers do not align even though they have the same CRS, presumably because they do not have the same extent.
Is it possible to edit the extent of the raster to match that of the vector layer or when creating the new vector layer can I define extent based on my raster layer?
raster coordinate-system pyqgis vector
edited 13 mins ago
PolyGeo♦
53.9k1782246
asked Apr 13 '17 at 20:22
SimonSimon
343
If my answer solved your issue you should mark it as accepted.
– xunilk
Apr 28 '17 at 21:17
add a comment |
Relatively new to GIS. I've created a vector layer of points based on row/col position of high population density pixels in a raster layer. The layers do not align even though they have the same CRS, presumably because they do not have the same extent.
Is it possible to edit the extent of the raster to match that of the vector layer or when creating the new vector layer can I define extent based on my raster layer?
raster coordinate-system pyqgis vector
edited 13 mins ago
PolyGeo♦
53.9k1782246
asked Apr 13 '17 at 20:22
SimonSimon
343
Relatively new to GIS. I've created a vector layer of points based on row/col position of high population density pixels in a raster layer. The layers do not align even though they have the same CRS, presumably because they do not have the same extent.
Is it possible to edit the extent of the raster to match that of the vector layer or when creating the new vector layer can I define extent based on my raster layer?
raster coordinate-system pyqgis vector
raster coordinate-system pyqgis vector
edited 13 mins ago
PolyGeo♦
53.9k1782246
asked Apr 13 '17 at 20:22
SimonSimon
343
edited 13 mins ago
PolyGeo♦
53.9k1782246
asked Apr 13 '17 at 20:22
SimonSimon
343
edited 13 mins ago
PolyGeo♦
53.9k1782246
edited 13 mins ago
PolyGeo♦
53.9k1782246
edited 13 mins ago
PolyGeo♦
53.9k1782246
53.9k1782246
asked Apr 13 '17 at 20:22
SimonSimon
343
asked Apr 13 '17 at 20:22
SimonSimon
343
asked Apr 13 '17 at 20:22
SimonSimon
343
343
If my answer solved your issue you should mark it as accepted.
– xunilk
Apr 28 '17 at 21:17
add a comment |
If my answer solved your issue you should mark it as accepted.
– xunilk
Apr 28 '17 at 21:17
If my answer solved your issue you should mark it as accepted.
– xunilk
Apr 28 '17 at 21:17
If my answer solved your issue you should mark it as accepted.
– xunilk
Apr 28 '17 at 21:17
add a comment |
1 Answer
1
active
oldest
votes
To do that you need to get simultaneously x,y coordinates of each point by using some raster parameters (as xmin, ymax, and x, y resolution). Next code uses these parameters for obtaining a point memory layer where each point is situated at the middle of each raster cell.
layer = iface.activeLayer()
provider = layer.dataProvider()
extent = layer.extent()
xmin,ymin,xmax,ymax = extent.toRectF().getCoords()
rows = layer.height()
cols = layer.width()
xSize = layer.rasterUnitsPerPixelX()
ySize = layer.rasterUnitsPerPixelY()
block = provider.block(1, extent, cols, rows)
xinit = xmin + xSize/2
yinit = ymax - ySize/2
x = xinit
y = yinit
points = []
values = []
for i in range(rows):
for j in range(cols):
value = block.value(i,j)
if value > 150 and value < 255:
points.append(QgsPoint(x,y))
values.append(value)
x += xSize
y -= ySize
x = xinit
epsg = layer.crs().postgisSrid()
uri = "Point?crs=epsg:" + str(epsg) + "&field=id:integer&field=value: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, values[i]])
feat.setGeometry(QgsGeometry.fromPoint(points[i]))
prov.addFeatures(feats)
QgsMapLayerRegistry.instance().addMapLayer(mem_layer)
I used this population raster; where the criterion to get points was they represent values greater than 150 (254 = 10,000 persons/km2 and 255 = No data). After running the code at Python Console of QGIS I got:
Points over raster match as expected.
answered Apr 14 '17 at 11:52
xunilkxunilk
14.9k31942
add a comment |
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1 Answer
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active
oldest
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1 Answer
1
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oldest
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active
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To do that you need to get simultaneously x,y coordinates of each point by using some raster parameters (as xmin, ymax, and x, y resolution). Next code uses these parameters for obtaining a point memory layer where each point is situated at the middle of each raster cell.
layer = iface.activeLayer()
provider = layer.dataProvider()
extent = layer.extent()
xmin,ymin,xmax,ymax = extent.toRectF().getCoords()
rows = layer.height()
cols = layer.width()
xSize = layer.rasterUnitsPerPixelX()
ySize = layer.rasterUnitsPerPixelY()
block = provider.block(1, extent, cols, rows)
xinit = xmin + xSize/2
yinit = ymax - ySize/2
x = xinit
y = yinit
points = []
values = []
for i in range(rows):
for j in range(cols):
value = block.value(i,j)
if value > 150 and value < 255:
points.append(QgsPoint(x,y))
values.append(value)
x += xSize
y -= ySize
x = xinit
epsg = layer.crs().postgisSrid()
uri = "Point?crs=epsg:" + str(epsg) + "&field=id:integer&field=value: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, values[i]])
feat.setGeometry(QgsGeometry.fromPoint(points[i]))
prov.addFeatures(feats)
QgsMapLayerRegistry.instance().addMapLayer(mem_layer)
I used this population raster; where the criterion to get points was they represent values greater than 150 (254 = 10,000 persons/km2 and 255 = No data). After running the code at Python Console of QGIS I got:
Points over raster match as expected.
answered Apr 14 '17 at 11:52
xunilkxunilk
14.9k31942
add a comment |
To do that you need to get simultaneously x,y coordinates of each point by using some raster parameters (as xmin, ymax, and x, y resolution). Next code uses these parameters for obtaining a point memory layer where each point is situated at the middle of each raster cell.
layer = iface.activeLayer()
provider = layer.dataProvider()
extent = layer.extent()
xmin,ymin,xmax,ymax = extent.toRectF().getCoords()
rows = layer.height()
cols = layer.width()
xSize = layer.rasterUnitsPerPixelX()
ySize = layer.rasterUnitsPerPixelY()
block = provider.block(1, extent, cols, rows)
xinit = xmin + xSize/2
yinit = ymax - ySize/2
x = xinit
y = yinit
points = []
values = []
for i in range(rows):
for j in range(cols):
value = block.value(i,j)
if value > 150 and value < 255:
points.append(QgsPoint(x,y))
values.append(value)
x += xSize
y -= ySize
x = xinit
epsg = layer.crs().postgisSrid()
uri = "Point?crs=epsg:" + str(epsg) + "&field=id:integer&field=value: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, values[i]])
feat.setGeometry(QgsGeometry.fromPoint(points[i]))
prov.addFeatures(feats)
QgsMapLayerRegistry.instance().addMapLayer(mem_layer)
I used this population raster; where the criterion to get points was they represent values greater than 150 (254 = 10,000 persons/km2 and 255 = No data). After running the code at Python Console of QGIS I got:
Points over raster match as expected.
answered Apr 14 '17 at 11:52
xunilkxunilk
14.9k31942
add a comment |
To do that you need to get simultaneously x,y coordinates of each point by using some raster parameters (as xmin, ymax, and x, y resolution). Next code uses these parameters for obtaining a point memory layer where each point is situated at the middle of each raster cell.
layer = iface.activeLayer()
provider = layer.dataProvider()
extent = layer.extent()
xmin,ymin,xmax,ymax = extent.toRectF().getCoords()
rows = layer.height()
cols = layer.width()
xSize = layer.rasterUnitsPerPixelX()
ySize = layer.rasterUnitsPerPixelY()
block = provider.block(1, extent, cols, rows)
xinit = xmin + xSize/2
yinit = ymax - ySize/2
x = xinit
y = yinit
points = []
values = []
for i in range(rows):
for j in range(cols):
value = block.value(i,j)
if value > 150 and value < 255:
points.append(QgsPoint(x,y))
values.append(value)
x += xSize
y -= ySize
x = xinit
epsg = layer.crs().postgisSrid()
uri = "Point?crs=epsg:" + str(epsg) + "&field=id:integer&field=value: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, values[i]])
feat.setGeometry(QgsGeometry.fromPoint(points[i]))
prov.addFeatures(feats)
QgsMapLayerRegistry.instance().addMapLayer(mem_layer)
I used this population raster; where the criterion to get points was they represent values greater than 150 (254 = 10,000 persons/km2 and 255 = No data). After running the code at Python Console of QGIS I got:
Points over raster match as expected.
answered Apr 14 '17 at 11:52
xunilkxunilk
14.9k31942
To do that you need to get simultaneously x,y coordinates of each point by using some raster parameters (as xmin, ymax, and x, y resolution). Next code uses these parameters for obtaining a point memory layer where each point is situated at the middle of each raster cell.
layer = iface.activeLayer()
provider = layer.dataProvider()
extent = layer.extent()
xmin,ymin,xmax,ymax = extent.toRectF().getCoords()
rows = layer.height()
cols = layer.width()
xSize = layer.rasterUnitsPerPixelX()
ySize = layer.rasterUnitsPerPixelY()
block = provider.block(1, extent, cols, rows)
xinit = xmin + xSize/2
yinit = ymax - ySize/2
x = xinit
y = yinit
points = []
values = []
for i in range(rows):
for j in range(cols):
value = block.value(i,j)
if value > 150 and value < 255:
points.append(QgsPoint(x,y))
values.append(value)
x += xSize
y -= ySize
x = xinit
epsg = layer.crs().postgisSrid()
uri = "Point?crs=epsg:" + str(epsg) + "&field=id:integer&field=value: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, values[i]])
feat.setGeometry(QgsGeometry.fromPoint(points[i]))
prov.addFeatures(feats)
QgsMapLayerRegistry.instance().addMapLayer(mem_layer)
I used this population raster; where the criterion to get points was they represent values greater than 150 (254 = 10,000 persons/km2 and 255 = No data). After running the code at Python Console of QGIS I got:
Points over raster match as expected.
answered Apr 14 '17 at 11:52
xunilkxunilk
14.9k31942
answered Apr 14 '17 at 11:52
xunilkxunilk
14.9k31942
answered Apr 14 '17 at 11:52
xunilkxunilk
14.9k31942
answered Apr 14 '17 at 11:52
xunilkxunilk
14.9k31942
14.9k31942
add a comment |
add a comment |
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If my answer solved your issue you should mark it as accepted.
– xunilk
Apr 28 '17 at 21:17