QGIS’ expression evaluation cannot directly deal with hstore strings. Treat differently means that rules need to be specified according to layer properties. We’d like to treat buildings differently. We can modify this rule by clicking on the icon marked with a purple square in the image above. The current rendering appears as a rule with no filters. From the context menu of the multipolygon layer select Properties and on that form move to the Symbology tab.įirst change the type of the symbol from “Single symbol” to “Rule based” using the combobox at the top of the form. Let us render them differently in order to get a feeling how to identify different objects. Initially they are rendered in the same way which means that islands cover everything else. In this example polygons are mostly islands, forest and buildings. This kind of storage is called “hstore” in a PostgreSQL database and is the standard for OSM data. We can see that all the key-value-pairs for the tags of the various objects are organized in a specially formatted text string in the field ‘other_tags’. You can inspect the data of a vector layer using ‘Open Attribute table’ from the context menu of a layer, in this case the multipolygon layer. But as OSM data imported by one of the methods described above have their tags encoded in a special way here is an example how to deal with them (for the curious, the example is pitcairn-islands-latest from Geofabrik’s download page for Australia and Oceania). We cannot give you even a rough overview over what you can do with QGIS and there are many excellent tutorials and books which will guide you step-by-step towards mastering the software. You can choose to re-import the exported layer by checking the box at the bottom (activated by default). The other options on the dialogue vary depending on the format you selected. You can select from a wide range of formats including Shapefile, GeoJSON, PostgreSQL dump, SQLite. To export a layer activate its context menu and select Export -> Save Features as…
0 Comments
Leave a Reply. |