GEOG 301 - Intro to GIS and Maps

Lab 13: Point symbols and bivariate maps.

The purpose of this exercise is to introduce you to different methods of using graduated circles (or other point symbols) to map your data. For this lab, you will be using the GIS software ArcMap. The first part of the exercise will be straightforward graduated symbol mapping using

We will be using two datasets: One of WA State, the other of the Lower 48. The WA data will be the same as you've been using. You should have that. In that same geodatabase is the US states data. Make everyone's life easier and put all your data and saved files in a single subdirectory on your flash drive.

The first part of the exercise will be a relatively straightforward mapping exercise using the US dataset (named CFY17_st). Note, for simplicity, ignore AK and Hawaii in mapping throughout this lab. However, you will probably want to change the projection, as the Pro default kind of stretches the US out east-west. Remember doing that for the Colombia lab?

OK. Fire up Pro with a new project and map.

As you are doing this lab - SAVE FREQUENTLY! Seriously. This is true for everything you do on a computer, but GIS especially.

Now, I trimmed down the US 2017 data. Load the US dataset. If it won't work in Pro, load the states dataset instead (map - add data).

Click on the little box next to the file name - this will draw the map. Obviously, it is a map of the US, including state boundaries. There is a data file associated with this map. To view it, right click on the filename (left side of screen), goto 'open attribute table.' Here, you can browse the data. Some of the headings are a bit cryptic - you know as much as I do....

We will start with a simple proportional symbol map. Make sure the map is active (click on it). Right click on the "states" text in what sort of appears to be the legend and select 'symbology' tab. Then select proportional symbols. You will also have to select a column of data to map in the 'fields' 'value' box. In this case, you are drawing circles that are proportional to the data you have selected - so, for this map, you should have 48 different circle sizes. Interestingly, this new version of arc gives a maximum size which caps circle size. Which means that the circles aren't truly proportional (set the max size to <none> to see a truly proportional map). Play with the minimum and maximum/none size of the symbol. Also, play with the colors - remember, this map might be printed in black and white.

Make a layout and add all the usual proper cartographic stuff. Be sure to save this map as a pdf, as you will be printing it out (Map #1)

  1. As you played with the circle size options, how did they impact your map? In short, explain how the map changed as you played with these option.
  2. What's that 'appearance compensation' thing? You'll need to goto help to answer this. Or even onto the web (Google is your friend).

Next up, Graduated symbols. Select that option in symbology. After playing a bit, pick one of the columns of data to make a graduated circle map. Play with the number of circles and classification method. You'll note that this looks just like the classification options from the last two labs, only you're using circle size instead of color shade.

Just for giggles, let's now make this a multivariate map. Add the same dataset a second time (map - add data) (you should see two "states" layers over on the left). Make the second one a choropleth map- using data that is different than your graduated circle map. Add all the usual, proper cartographic stuff. Save as PDF and print this map (Map #2)

3. How does graduated circle mapping differ from the proportional symbols mapping options?

4.Why might you use this option rather than the proportional symbols option?

Now for the more complicated map. Which isn't possible in Pro. grrrrrr. Sure, two years ago they promised the functionality, but it's not there yet. So, this lab becomes much shorter and easier. Y'all can cheer now. :)

The idea was to make a proportional symbol map of WA with pie charts of other variables within the circles. Dang. Ah well.

Finally, just because, let's make a quick dot density map. Use the WA dataset this time. In the symbology tab, choose dot density. Pick something and map it! Be sure to choose something for which dot density makes sense (for example, I just did average household income, which makes no sense as a dot density map. Include all the proper cartographic bits. Save as pdf and print (Map #3)

Hand in all 3 maps and the answers to the 4 italicized questions above.