Book Image

Mastering PostGIS

By : Dominik Mikiewicz, Michal Mackiewicz , Tomasz Nycz
Book Image

Mastering PostGIS

By: Dominik Mikiewicz, Michal Mackiewicz , Tomasz Nycz

Overview of this book

PostGIS is open source extension onf PostgreSQL object-relational database system that allows GIS objects to be stored and allows querying for information and location services. The aim of this book is to help you master the functionalities offered by PostGIS- from data creation, analysis and output, to ETL and live edits. The book begins with an overview of the key concepts related to spatial database systems and how it applies to Spatial RMDS. You will learn to load different formats into your Postgres instance, investigate the spatial nature of your raster data, and finally export it using built-in functionalities or 3th party tools for backup or representational purposes. Through the course of this book, you will be presented with many examples on how to interact with the database using JavaScript and Node.js. Sample web-based applications interacting with backend PostGIS will also be presented throughout the book, so you can get comfortable with the modern ways of consuming and modifying your spatial data.

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Table of Contents (9 chapters)
Free Chapter
1
Importing Spatial Data
Importing Spatial Data
Obtaining test data
Importing flat data
Importing shape files using shp2pgsql
Importing vector data using ogr2ogr
Importing data using GIS clients
Importing OpenStreetMap data
Connecting to external data sources with foreign data wrappers
Loading rasters using raster2pgsql
Importing data with pgrestore
Summary
2
Spatial Data Analysis
Spatial Data Analysis
Composing and decomposing geometries
Spatial measurement
Geometry bounding boxes
Geometry simplification
Geometry validation
Intersecting geometries
Nearest feature queries
Summary
3
Data Processing - Vector Ops
Data Processing - Vector Ops
Primer - obtaining and importing OpenStreetMap data
Merging geometries
Slicing geometries
Buffering and offsetting geometries
Reprojecting geometries
Spatial relationships
Summary
4
Data Processing - Raster Ops
Data Processing - Raster Ops
Preparing data
Processing and analysis
Analytic and statistical functions
Vector to raster conversion
Raster to vector conversion
Spatial relationship
Metadata
Summary
5
Exporting Spatial Data
Exporting Spatial Data
Exporting data using \COPY in psql
Exporting vector data using pgsql2shp
Exporting vector data using ogr2ogr
Exporting data using GIS clients
Outputting rasters using GDAL
Outputting raster using psql
Exporting data using the PostgreSQL backup functionality
Summary
6
ETL Using Node.js
ETL Using Node.js
Setting up Node.js
Handshaking with a database using Node.js PgSQL client
Retrieving and processing JSON data
Geocoding address data
Consuming WFS data
Summary
7
PostGIS – Creating Simple WebGIS Applications
PostGIS – Creating Simple WebGIS Applications
ExtJS says Hello World
Configuring GeoServer web services
Making use of PgRaster in a simple WMS GetMap handler
Consuming WMS
Enabling CORS in Jetty
Consuming WFS in ol3
Outputting and consuming GeoJSON
Outputting and consuming TopoJSON
Implementing a simple CRUD application that demonstrates vector editing via web interfaces
Summary
8
PostGIS Topology
PostGIS Topology
The conceptual model
The data
Installation
Creating an empty topology
Importing Simple Feature data into topology
Inspecting and validating a topology
Accessing the topology data
Topology editing
Topology-aware simplification
Topology output
Summary
9
pgRouting
pgRouting
Installing the pgRouting extension
Importing routing data
pgRouting algorithms
Consuming pgRouting functionality in a web app
Summary

The conceptual model

Before we start working with topology, we need to discuss the key concepts behind the PostGIS topological data model. PostGIS topology implementation is based on ISO standard 13249 - Information technology - Database languages - SQL multimedia and application packages - Part 3: Spatial. The standard name is often abbreviated as ISO SQL/MM. This standard defines two data models for topology: TopoGeometry and TopoNetwork; PostGIS implements only the former.

In this model, there are three kinds of elements/primitives used to compose geospatial features: nodes, edges, and faces.

Nodes are point features. They can exist on their own (isolated nodes) or serve as connection points for linear features (the edges). For example, this is a Czech-Polish-Slovak tripoint near Jaworzynka village, which contains a node and three edges:

An example of topological data: a node and three edges

In topology, only one node can appear for a specified coordinate pair - if there are more nodes in...

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