[GIS] Performing Raster Interpolation using QGIS

interpolationqgis-2qgis-plugins

I am trying to use the Rasterinterpolation plugin to pick up elevations from a Raster DEM for a series of vector points.

Once loaded, the Plugin is accessible through Plugins Menu/ Raster Interpolation and seems set up to do exactly what I need. However it will not let me select the correct Band of the Raster Layer. The plugin sees the layer as only having Band 0, whereas the Raster only has Band 1, and as a result does not populate the 'height' field in the Vector layer.

SciPy and NumPy are both loaded

I have tried the same plugin with a multiband Raster layer and it still only indicates that the Raster has a single band, Band 0.

I am using QGIS 2.0.

Best Answer

If you want to populate the table of the points shapefile with the values in the Raster (the height, in this case), maybe you should try another plugin like Point Sampling tool

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[GIS] Displaying numbers of single band raster layer in QGIS without additional vector layer

this would be a great feature.

In my dreams, I could also double-click on a raster cell and set its value...

SAGA GIS can render cells like this. These instructions are for SAGA GIS 2.2.6 . There have been a few menu changes in recent versions of SAGA, but this is also possible in older versions.

Import your raster using Geoprocessing > File > Grid > Import > Import Raster
In properties, check "Show cell values" then "Apply"
Zoom right in

This screenshot shows the result...

[GIS] Select and use raster layer from python

Hopefully the following will help get you started, I've added comments to try and explain how it works.

Essentially, you can use a QgsMapLayerComboBox to filter out all layers loaded in QGIS and only have it list the multiband rasters. You can then define a function which will read the selected layer and populate the combo boxes for the bands (note that I only added the standard red, green and blue bands):

def raster_bands(self):
    # Read current item in raster layer combobox
    rlayer = self.dockwidget.mMapLayerComboBox.currentText()
    # Match name of current item with layer in table of contents
    selected_rlayer = QgsMapLayerRegistry.instance().mapLayersByName(rlayer)[0]
    # Clear band combo boxes
    self.dockwidget.red_comboBox.clear()
    self.dockwidget.green_comboBox.clear()
    self.dockwidget.blue_comboBox.clear()
    # Add band numbers to associated combo boxes
    self.dockwidget.red_comboBox.addItem(str(selected_rlayer.renderer().redBand()))
    self.dockwidget.green_comboBox.addItem(str(selected_rlayer.renderer().greenBand()))
    self.dockwidget.blue_comboBox.addItem(str(selected_rlayer.renderer().blueBand()))

# Set first filter for QgsMapLayerComboBox to only populate with raster layers
self.dockwidget.mMapLayerComboBox.setFilters(QgsMapLayerProxyModel.RasterLayer)
# Create an empty list
rlayer_list = []
# Loop through all loaded layers in table of contents
for layer in QgsMapLayerRegistry.instance().mapLayers().values():
    # If layer is a raster and it is not a multiband type
    if layer.type() == 1 and layer.renderer().type() != "multibandcolor":
        # Add to list
        rlayer_list.append(layer)
# Set second filter to only populate with multiband rasters
self.dockwidget.mMapLayerComboBox.setExceptedLayerList(rlayer_list)

# Run function on startup
raster_bands(self)
# When raster selection is changed, update combo boxes
self.dockwidget.mMapLayerComboBox.currentIndexChanged.connect(raster_bands)

Result:

Best Answer

Related Solutions

[GIS] Displaying numbers of single band raster layer in QGIS without additional vector layer

[GIS] Select and use raster layer from python

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