Data Processing - Vector Ops | Mastering PostGIS

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Mastering PostGIS

By : George Silva, Mikiewicz, Michal Mackiewicz , Nycz

1 (1)

Mastering PostGIS

1 (1)

By: George Silva, Mikiewicz, Michal Mackiewicz , 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.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

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

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

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

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

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

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

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

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

pgRouting

pgRouting

Installing the pgRouting extension

Importing routing data

pgRouting algorithms

Consuming pgRouting functionality in a web app

Summary

Buffering and offsetting geometries

A buffer is a very common GIS operation. PostGIS can create polygonal buffers from any geometry with configurable distance and approximation levels.

For example, a simple 1,000 meter buffer from a Point looks like the following:

SELECT ST_Buffer( 
 (SELECT wkb_geometry FROM points WHERE osm_id = '253525668'), 
 1000);

A simple buffer with default parameters

The first argument is an input geometry, and the second is the buffer distance in the units of the geometry's coordinate system.

Note

If the geometry is in a latitude-longitude coordinate system, then cast the geometry to a Geography type in order to be able to give the distance in meters.

The default buffer uses eight segments to approximate a quarter circle. If it's too coarse, more segments can be introduced at the expense of processing power:

SELECT ST_Buffer( 
 (SELECT wkb_geometry FROM points WHERE osm_id = '253525668'), 
 1000,32);

We can also do the opposite, such as when we create an octagonal buffer...

Visually different images

CONTINUE READING

83

Tech Concepts

36

Programming languages

73

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