Posts about Spatial

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

Let's put that on a map!

PostGIS has so many cool features that it is possible to do full GIS analyses without ever leaving the SQL language, but... at the end of the day, you want to get those results, show that data, on the map.

The Crunchy Data geospatial team has been thinking about how to bring PostGIS to the web, and we established some basic principles:

• Use the database, as much as possible.

• The database already has a user model and security model.

• The database can already generate output formats, like MVT

Where are you? Go ahead and figure out your answer, I'll wait.

No matter what your answer, whether you said "sitting in my office chair" or "500 meters south-west of city hall" or "48.43° north by 123.36° west", you expressed your location relative to something else, whether that thing was your office layout, your city, or Greenwich

While PostGIS includes lots of algorithms and functionality we have built ourselves, it also adds geospatial smarts to PostgreSQL by linking in specialized libraries to handle particular problems:

• Proj for coordinate reference support;
• GDAL

Parallel query has been a part of PostgreSQL since 2016 with the release of version 9.6 and in theory PostGIS should have been benefiting from parallelism ever since.

In practice, the complex nature of PostGIS has meant that very few queries would parallelize under normal operating configurations -- they could only be forced to parallelize using oddball

With the availability of MVT tile format in PostGIS via ST_AsMVT(), more and more people are generating tiles directly from the database. Doing so usually involves a couple common steps:

• exposing a tiled web map API

The raster functionality in PostGIS has been part of the main extension since it was introduced. When PostGIS 3 is released, if you want raster functionality you will need to install both the core postgis extension, and also the postgis_raster extension.

CREATE EXTENSION postgis;
CREATE EXTENSION postgis_raster;

Vector tiles are the new hotness, allowing large amounts of dynamic data to be sent for rendering right on web clients and mobile devices, and making very beautiful and highly interactive maps possible.

Since the introduction of ST_AsMVT()