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 QGIS Blueprints
  • Table Of Contents Toc
  • Feedback & Rating feedback
QGIS Blueprints

QGIS Blueprints

By : Mearns
4.3 (3)
close
close
QGIS Blueprints

QGIS Blueprints

4.3 (3)
By: Mearns

Overview of this book

QGIS, the world’s most popular free/open source desktop geographic information system software, enables a wide variety of use cases involving location – previously only available through expensive specialized commercial software. However, designing and executing a multi-tiered project from scratch on this complex ecosystem remains a significant challenge. This book starts with a primer on QGIS and closely related data, software, and systems. We’ll guide you through six use-case blueprints for geographic web applications. Each blueprint boils down a complex workflow into steps you can follow to reduce time lost to trial and error. By the end of this book readers should be able to build complex layered applications that visualize multiple data sets, employing different types of visualization, and give end users the ability to interact with and manipulate this data for the purpose of analysis.
Table of Contents (9 chapters)
close
close
8
Index

Creating the travel time isochron polygons

Let's say that the school in our study is located at the vertex with an ID of 1 in the newark_osm layer. To visualize the walking time from the students' homes, without releasing sensitive information about where the students actually live, we can create isochron polygons. Each polygon will cover the area that a person can walk from to a single destination within some time threshold.

Generating the travel time for each road segment

We'll use DB Manager to create and populate a column for the travel time on each segment at the walking speed; then, we will create a query layer that includes the travel time from each road segment to our school at vertex 1. Perform the following steps:

  1. Navigate to Database | DB Manager | DB Manager.
  2. Select the database to be updated.
  3. Go to Database | SQL window.
  4. Enter the following code:
    ALTER TABLE newark_osm ADD COLUMN traveltime_min float8;
    UPDATE newark_osm SET traveltime_min = length_m  / 6000.0 * 60;...
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.
QGIS Blueprints
notes
bookmark Notes and Bookmarks search Search in title playlist Add to playlist 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