Book Image

Learning Geospatial Analysis with Python

By : Joel Lawhead
4 (1)
Book Image

Learning Geospatial Analysis with Python

4 (1)
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. It is an approach to use statistical analysis and other informational engineering to data which has a geographical or geospatial aspect. And this typically involves applications capable of geospatial display and processing to get a compiled and useful data. "Learning Geospatial Analysis with Python" uses the expressive and powerful Python programming language to guide you through geographic information systems, remote sensing, topography, and more. It explains how to use a framework in order to approach Geospatial analysis effectively, but on your own terms. "Learning Geospatial Analysis with Python" starts with a background of the field, a survey of the techniques and technology used, and then splits the field into its component speciality areas: GIS, remote sensing, elevation data, advanced modelling, and real-time data. This book will teach you everything there is to know, from using a particular software package or API to using generic algorithms that can be applied to Geospatial analysis. 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. "Learning Geospatial Analysis with Python" will round out your technical library with handy recipes and a good understanding of a field that supplements many a modern day human endeavors.
Table of Contents (17 chapters)
Learning Geospatial Analysis with Python
About the Author
About the Reviewers

Performing selections

The previous subsetting example is one way to select data. There are many other ways to subset data for further analysis. In this section we'll examine some of them.

Point in polygon formula

We briefly discussed the point in polygon formula in Chapter 1, Learning Geospatial Analysis with Python as a common type of geospatial operation. You'll find it is one of the most useful formulas out there. The formula is relatively straightforward. The following function performs this check using the Ray Casting method. This method draws a line from the test point all the way through the polygon and counts the number of times it crosses the polygon boundary. If the count is even, the point is outside the polygon. If it is odd, then it's inside. This particular implementation also checks to see if the point is on the edge of the polygon:

def point_in_poly(x,y,poly):
   # check if point is a vertex
   if (x,y) in poly: return True
   # check if point is on a boundary
   for i in range...