Book Image

QGIS Blueprints

By : Ben Mearns
Book Image

QGIS Blueprints

By: Ben Mearns

Overview of this book

Table of Contents (14 chapters)
QGIS Blueprints
About the Author
About the Reviewers


Next, we will move on to preparing this data relationship for the Web and its spatiotemporal visualization.

TopoJSON is a variant of JSON, which uses the topological relationships between the geometric features to greatly reduce the size of the vector data and thereby improves the browser's rendering performance and reduces the risk of delay due to data transfers.

An example of GeoJSON

The following code is an example of GeoJSON, showing two of our State House Districts. The format is familiar—based on our previous work with JSON—with sets of coordinates that define a polygonal area grouped together. The repeated sections are marked by ellipses (…).

  "type": "FeatureCollection",
  "crs": { "type": "name", "properties": { "name":   "urn:ogc:def:crs:OGC:1.3:CRS84" } },

  "features": [
    { "type": "Feature", "properties": { "STATEFP": "42", "SLDLST": "181", "GEOID": "42181", "NAMELSAD": "State House District 181", "LSAD": "LL", "LSY": "2014", "MTFCC": "G5220", "FUNCSTAT": "N", "ALAND...