Difference between two layers in PostGIS

What is polygon in PostGIS?

A polygon is a representation of an area. The outer boundary of the polygon is represented by a ring. This ring is a linestring that is both closed and simple as defined above. Holes within the polygon are also represented by rings.

How do I create a polygon in PostGIS?

Create a Polygon from a 2D LineString. SELECT ST_MakePolygon( ST_GeomFromText(‘LINESTRING(75 29,77 29,77 29, 75 29)’)); Create a Polygon from an open LineString, using ST_StartPoint and ST_AddPoint to close it.

How do I add a layer in PostGIS?

How to do it…

1. Open DB Manager from the Database menu.
2. Expand the PostGIS item to list your databases.
3. Expand the list and select the Public schema.
4. Click on the following import layer icon:
5. A dialog will pop up, providing you with import options.
6. Select the layer to import from the drop-down list.

What is the difference between polygon and Multipolygon?

A MULTIPOLYGON is a collection of Polygons. MultiPolygons are useful for gathering a group of Polygons into one geometry. For example, you may want to gather the Polygons denoting a group of properties in a particular municipality.

How do you create a polygon layer?

To create a polygon feature class, right-click the database, click New, and click Feature Class. Drag the feature class onto the map. A feature template with default settings is automatically generated for the new layer.

How do I add a shapefile to PostGIS?

This process involves the following 5 steps:

1. Step 1: create the database.
2. Step 2: create the user and grant privileges.
3. Step 3: upload the shapefile in QGIS.
4. Step 4: upload the shapefile from QGIS to PostGIS.
5. Step 5: (Optional) Access your new table.

Jul 26, 2020

What is PostGIS topology?

Quote from video: