Lecture 21 - Networks and Automated Geoprocessing Workflow (Network Analyst and ModelBuilder)

What is Network Analyst?

A tool for conducting spatial analyses that rely on underlying transportation networks

Examples:

• Finding the fastest route

• Determining a service area

• Pairing delivery addresses with vehicles in a fleet

An example of how practical this can be

Consider an example of delivering goods to grocery stores from a central warehouse location. A fleet of three trucks is available at the warehouse. The warehouse operates only within a certain time window—from 8:00 a.m. to 5:00 p.m.—during which all trucks must return back to the warehouse. Each truck has a capacity of 15,000 pounds, which limits the amount of goods it can carry. Each store has a demand for a specific amount of goods (in pounds) that needs to be delivered, and each store has time windows that confine when deliveries should be made. Furthermore, the driver can work only eight hours per day, requires a break for lunch, and is paid for the amount spent on driving and servicing the stores. The goal is to come up with an itinerary for each driver (or route) such that the deliveries can be made while honoring all the service requirements and minimizing the total time spent on a particular route by the driver.

________: To run Network Analyst, we must have a network dataset– a GIS dataset that defines the transportation network

This includes not only the geography of all the possible routes (lines), but also all of the information about junctions (intersection points).

One-way traffic, speed limits, and other complexities can be incorporated as well.

Network datasets

_________: Tools to conduct repetitive spatial data processing tasks automatically, without running it manually.

Geoprocessing: a set of operations used to manipulate, analyze, and manage geospatial data

Examples:

• Buffering

• Overlay analysis (intersect, union, clip)

• Spatial joins

• Data conversion

• Raster processing (reclassification, extraction, map algebra, etc)

In ArcGIS Pro: ModelBuilder

In QGIS: Graphical Modeler

• Add a tool

• Add an input dataset

• Add another tool, and add your previous output dataset as the new input

  • Drag the arrow, or select from drop down menu

• Auto layout

• Save

Automating Geoprocessing Workflows

_______: A programming tool that allows to create, edit, and manage geoprocessing workflows.

• Combines multiple GIS tools into a single workflow model.

• Connects the output of one tool directly as the input for another.

• Saves, shares, and re-runs workflow automatically.

• Parameterizes models (reusable for different study areas or species).

Imagine I had spent days or even weeks running multiple steps of complex spatial analysis. I had to work through several steps of overlay, buffers, selections, etc., all in the correct sequence.

Then, I come to find out that one of the parameters in one of my earliest steps needed to change, affecting everything downstream in the process.

Network Analyst allows you to automate this process.

It also makes a convenient visual to show/remember your work.

Model Builder