Working with time

The temporality of spatial data can add another dimension in finding patterns and relationships in your analysis.  ArcMap comes with a suite of tools that allows you to “time-enable” your data layers, assuming that it comes with a date attribute.

The following tutorial takes a sample database for crime in Westwood (taken from http://crimemapping.com) over a 2 month period, and plots it on an interactive, temporal view in ArcMap.

Step 1: Loading your data onto ArcMap

  1. Download the tutorial data, unzip it to a local drive
  2. Open ArcMap and load the data (crime.shp)
  3. Symbolize the crime data by categories, choosing “type” as the value field, click on the “add all values” button, and choose a symbol style that looks better than the default “non” circle provided by ESRI.
  4. Go to the label tab, and label each feature by “type”
  5. Add a base layer of your choice

Step 2: Time enabling your data

  1. Open the attribute table for the crime data.  Inspect the table, and notice the “date” field
  2. Open the property window for the crime layer and click on the “time” tab
  3. Click on the checkbox to “enable time on this layer”
  4. Click on the “calculate” button.  This will calculate the time bounds for this layer.
  5. Set the “Time step interval” to 1 day, allowing us to inspect the data one day at a time.
  6. Click OK

Step 3:  Visualizing data over time

  1. Click on the Time Slider button
  2. Push the play button, and inspect the map.  What do you see?
  3. Click on the options button
  4. Under the “Time Display” tab, enable “Show time on map display” and choose a date display that you like.
  5. Under the “Playback” tab, set the speed to a desired setting and check the  box next to “Refresh the display…”  This will allow you to drag the time slider interactively.
  6. Click OK and play with the time enabled data. What trends do you see?

Step 4: Adding Directional Distributions

  1. Open ArcToolbox, and navigate to Spatial Statistics Tools, Measuring Geographic Distributions, and double click on Directional Distribution.
  2. For Input Feature Type, choose “crime”, for Case Field, choose “date”.  Make sure to save the output to a local folder of your choice, and name it “crime_distribution.shp”
  3. When the new layer is loaded to your map, go to its properties and click on the “Time” tab
  4. Enable the time on the layer, click on “calculate”, and set the time interval to 1 day
  5. Go to the Symbology tab, click on the single symbol, fill color to red, and the outline color to “no color”
  6. Go to the Display tab, and set the Transparency to 80%
  7. Click OK, and play the time slider again.

 

Step 5: Post To the Course Website

Post a screenshot (something similar to the picture above) to your Lab 10 blog.

Leave a Reply

Your email address will not be published. Required fields are marked *