Written by Ian Amitin
I woke up and did what I assume most Americans do to start the day; I checked my phone. I’m not proud of this habit. The routine of checking my phone involves a look at the latest news from NPR. My eyes opened just a little bit wider when I read the headline of the second article down: “Maps Show A Dramatic Rise In Health Insurance Coverage Under ACA.”
Ah sweet, a temporal map! thought this nerd, as I examined the article glowing in my face.
Indeed, it was a temporal map of the rate of insured per capita by county of the United States. This find was particularly timely because I had been looking for interesting temporal web maps for a couple of days with little to show for it. This map was simple. It had a time bar, and told a simple story. Perfect for mass consumption.
I need to make one.
So I researched…
… And researched…
… And then tried an exercise.
Finally feeling confident, I decided to try to make the simplest of time enabled web maps... and got nowhere. I was stuck in a cycle of google searches, failed ArcMap table joins, AGOL not giving me an option to enable time functionality, and swearing to myself for days.
In cases such as the one I found myself in, I have a method to get myself out. I go to the boxing gym, punch things, get punched, feel better, then go back to work the next morning. Low and behold it worked. I guess my sparring partner knocked some sense into me and I recognized that I was going about my table join the wrong way. I needed to perform a one-to-many join, instead of the standard table joins and appends that proved worthless in this situation.
I ended up using the Make Query Table tool to complete a Join of US median income data by year with a simple polygon shapefile of the United States.
Although the join seemed to work, the names of my output attribute table fields had changed. The field that used to be called ‘Date_’ was now called ‘IncomeB’… Why, Arc, why?!
I knew from my research that I had to enable time on my layer by opening the layer properties and navigating to the ‘Time’ tab, then clicking ‘enable time on this layer’.
As it turns out, this step is only important for making a time-enabled map within ArcMap. What was truly important was formatting my time field so that ArcGIS Online can understand that this layer contains time data. To do this, I used the Convert Time Field tool.
This gave me a new field that I named ‘Time_Conv’.
With my data now formatted to be recognized in AGOL as containing time, I exported my data into a new folder and then compressed that folder, because AGOL can only upload shapefiles in .zip folders.
Finally, I was ready to make my temporal map in ArcGIS Online. I started by uploading my data into the ‘My Contents’ section as a Hosted Feature Layer. It was very important for me to upload data as a Hosted Feature Layer, otherwise AGOL would not recognize that my data contained a time attribute. We are able to do this because PCC now has hosting privileges.
With my data hosted in AGOL, I clicked on my file name and enabled my time settings.
After time settings are set, making a map in AGOL was easy and intuitive. I modified the thematic characteristics of my map by clicking Details > Change Style, and then selecting an attribute and display theme. I selected my attribute for Annual Median Income (‘income1’) and made a simple 5-class choropleth map using natural breaks to classify significant changes year over year.
At the bottom of my map I found a time bar and small button to the right that will allowed me to configure my time bar settings.
While less than great, I had finally built a temporal web map! I high-fived everyone in the tutoring lab.
My experience in making the simplest of temporal web maps was frustrating, but like trying most GIS tasks for the first time, now that I have made it work once, I feel much more optimistic about making better maps in the future.
My first temporal web map.