Book Image

Python Geospatial Development - Second Edition - Second Edition

By : Erik Westra
Book Image

Python Geospatial Development - Second Edition - Second Edition

By: Erik Westra

Overview of this book

Geospatial development links your data to places on the Earth's surface. Writing geospatial programs involves tasks such as grouping data by location, storing and analyzing large amounts of spatial information, performing complex geospatial calculations, and drawing colorful interactive maps. In order to do this well, you'll need appropriate tools and techniques, as well as a thorough understanding of geospatial concepts such as map projections, datums and coordinate systems. Python Geospatial Development - Second Edition teaches you everything you need to know about writing geospatial applications using Python. No prior knowledge of geospatial concepts, tools or techniques is required. The book guides you through the process of installing and using various toolkits, obtaining geospatial data for use in your programs, and building complete and sophisticated geospatial applications in Python. Python Geospatial Development teaches you everything you need to know about writing geospatial applications using Python. No prior knowledge of geospatial concepts, tools or techniques is required. The book guides you through the process of installing and using various toolkits, obtaining geospatial data for use in your programs, and building complete and sophisticated geospatial applications in Python. This book provides an overview of the major geospatial concepts, data sources and toolkits. It teaches you how to store and access spatial data using Python, how to perform a range of spatial calculations, and how to store spatial data in a database. Because maps are such an important aspect of geospatial programming, the book teaches you how to build your own “slippy map” interface within a web application, and finishes with the detailed construction of a geospatial data editor using Geodjango. Whether you want to write quick utilities to solve spatial problems, or develop sophisticated web applications based around maps and geospatial data, this book includes everything you need to know.
Table of Contents (18 chapters)
Python Geospatial Development
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Editing features


Now that we know which feature the user wants to edit, our next task is to implement the edit feature page itself. To do this, we are going to have to create a custom form with a single input field, named geometry, that uses a map-editing widget for editing the feature's geometry.

To create this form, we're going to borrow elements from GeoDjango's built-in "admin" interface, in particular the django.contrib.gis.admin.GeoModelAdmin class. This class provides a method named get_map_widget() which returns an editing widget which we can then include in a custom-generated form.

The process of building this form is a bit involved, thanks to the fact that we have to create a new django.forms.Form subclass on-the-fly to be handle the different types of geometries which can be edited. Let's put this complexity into a new function within the shared.utils module, which we'll call get_map_form().

Edit the utils.py module and type in the following code:

def get_map_form(shapefile):
   ...