Posts about Spatial

If constraints in general have caught your interest, our interactive learning portal has a whole section on the use of non-spatial constraints, even a video walkthrough!

In our last installment

One of the least-appreciated PostgreSQL extensions is the powerful PgRouting extension, which allows routing on dynamically generated graphs. Because it's often used for geographic routing (and is a part of Crunchy Spatial

A classic spatial query is to find the nearest neighbours of a spatial feature. Our previous post "Won’t You Be My Neighbor? Quickly Finding Who is Nearby" discussed this capability from a PostgreSQL

Constraints are used to ensure that data in the database reflects the assumptions of the data model.

• Do foreign keys match up to corresponding keys? (REFERENCES)
• Are mandatory columns filled in? (NOT NULL)
• Are unique values columns in fact unique? (UNIQUE

The GIS Stack Exchange is a great repository of interesting questions and answers about how to work with spatial data, and with PostGIS.

For example, this question

In our last blog post about pg_featureserv, we showed how it can publish spatial datasets and access them via simple web requests. In this post, we’re going to discuss how publishing PostgreSQL

In our previous posting on tile serving, we showed off how pg_tileserv can use database functions to generate tiles by querying existing tables with user parameters.

We can also use functions to build geometry on the fly without input from tables. For example, hexagons!

Hexagons are a favourite input for visualizations, because they have a nice symmetric shape and provide equal areas for summarization.

Hexagonal Grid

In my previous posting on tile serving, I demonstrated how pg_tileserv can publish spatial tables as dynamic vector tiles.

Dynamic tiles

In addition to viewing PostGIS spatial data as vector tiles using pg_tileserv, it is often necessary to access data features directly. This supports use cases such as:

• display features at a point or in an area of interest
• query features using spatial and/or attribute filters
• retrieve features for use in a web application (for tabular or map display)
• download spatial data for use in applications

Beautiful, responsive maps are best built using vector tiles, and PostgreSQL with PostGIS can produce vector tiles on-the-fly.

However, to use vector tiles in a beautiful, responsive map, you need to be able to access those tiles over the HTTP web protocol, and you need to be able to request them using a standard XYZ tiled map URL