Sign In Start Free Trial
Account

Add to playlist

Create a Playlist

Modal Close icon
You need to login to use this feature.
  • Book Overview & Buying Mastering PostGIS
  • Table Of Contents Toc
Mastering PostGIS

Mastering PostGIS

By : George Silva, Mikiewicz, Michal Mackiewicz , Nycz
1 (1)
close
close
Mastering PostGIS

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.
Table of Contents (10 chapters)
close
close

Outputting raster using psql


When you read through the PostGIS documentation carefully, you might find a really short section on using psql to export rasters. Basically, psql does not provide the functionality to easily output binary data, so the approach here is a bit hackish, and relies on the large object support in PostgreSQL (it is worth noting, though, that large object support is considered obsolete in the PgSQL documentation). The steps required to export a raster this way are as follows:

  • Create a large object
  • Output the raster data as bytea
  • Open the large object and write the output bytea
  • Export the large object
  • Unlink it to clean the resources

First, let's make this work in interactive psql mode. Type the following in psql, once connected to our mastering_postgis database:

select 
   loid,
   lowrite(lo_open(loid, 131072), gtiff) as bytesize
from (
   select 
      lo_create(0) as loid,
      ST_AsGDALRaster(rast, 'GTiff') as gtiff
   from (
      select
         ST_Union(rast) as rast...
Visually different images
CONTINUE READING
83
Tech Concepts
36
Programming languages
73
Tech Tools
Icon Unlimited access to the largest independent learning library in tech of over 8,000 expert-authored tech books and videos.
Icon Innovative learning tools, including AI book assistants, code context explainers, and text-to-speech.
Icon 50+ new titles added per month and exclusive early access to books as they are being written.
Mastering PostGIS
notes
bookmark Notes and Bookmarks search Search in title playlist Add to playlist download Download options font-size Font size

Change the font size

margin-width Margin width

Change margin width

day-mode Day/Sepia/Night Modes

Change background colour

Close icon Search
Country selected

Close icon Your notes and bookmarks

Confirmation

Modal Close icon
claim successful

Buy this book with your credits?

Modal Close icon
Are you sure you want to buy this book with one of your credits?
Close
YES, BUY

Submit Your Feedback

Modal Close icon
Modal Close icon
Modal Close icon