Book Image

Learning Geospatial Analysis with Python

By : Joel Lawhead
Book Image

Learning Geospatial Analysis with Python

By: Joel Lawhead

Overview of this book

Geospatial Analysis is used in almost every field you can think of from medicine, to defense, to farming. This book will guide you gently into this exciting and complex field. It walks you through the building blocks of geospatial analysis and how to apply them to influence decision making using the latest Python software. Learning Geospatial Analysis with Python, 2nd Edition uses the expressive and powerful Python 3 programming language to guide you through geographic information systems, remote sensing, topography, and more, while providing a framework for you to approach geospatial analysis effectively, but on your own terms. We start by giving you a little background on the field, and a survey of the techniques and technology used. We then split the field into its component specialty areas: GIS, remote sensing, elevation data, advanced modeling, and real-time data. This book will teach you everything you need to know about, Geospatial Analysis from using a particular software package or API to using generic algorithms that can be applied. This book focuses on pure Python whenever possible to minimize compiling platform-dependent binaries, so that you don’t become bogged down in just getting ready to do analysis. This book will round out your technical library through handy recipes that will give you a good understanding of a field that supplements many a modern day human endeavors.
Table of Contents (17 chapters)
Learning Geospatial Analysis with Python Second Edition
About the Author
About the Reviewers

Calculating line direction

In addition to distance, you'll often want to know the bearing of a line between its end points. We can calculate this line direction from one of the points using only the Python math module, as shown in the following calculation:

>>> from math import atan2, cos, sin, degrees
>>> lon1 = -90.21
>>> lat1 = 32.31
>>> lon2 = -88.95
>>> lat2 = 30.43
>>> angle = atan2(cos(lat1)*sin(lat2)-sin(lat1) *
>>>     cos(lat2)*cos(lon2-lon1), sin(lon2-lon1)*cos(lat2))
>>> bearing = (degrees(angle) + 360) % 360
>>> print(bearing)

Sometimes, you end up with a negative bearing value. To avoid this issue, we add 360 to the result to avoid a negative number and use the Python module operator to keep the value from climbing over 360.

The math in the angle calculation is reverse engineering a right triangle and then figuring out the acute angle of the triangle. The following URL provides...