CTRP 0821 – Digital Mapping

CTRP 0821 – Digital Mapping | Lab Assignment #6 | October 29th, 2020

This lab assignment has two parts in total and is due at 3:29 pm on Thursday, November 5th. When finished, upload the completed assignment to Canvas.

 

During the past few months you have developed skills related to geo data acquisition, modification, analysis, and visualization through completing the in-class activities and lab assignments. While each of those activities and labs focused on an individual skill, this lab will test your ability to apply the knowledge collectively, in advance of the upcoming final project during which you will be responsible for implementing the cartographic process end-to-end (conceptualization to presentation).

 

The assignment aligns with the following Quantitative Literacy General Education Area Goals:

 

• Understand the mathematical models underlying digital maps. (V, A, B)
• Describe the geospatial and other technologies used to create digital maps. (V, A, C)
• Acquire spatial data from public and proprietary sources (VI, VII, E)
• Perform basic mapping and spatial statistical analysis. (IV, V, B, F)
• Evaluate the quality of spatial data, maps, and spatial analyses. (I, D)

 

Note 1: Now that you have experience using Carto in previous labs, these instructions will be less detailed than before. If you don’t remember how to perform certain tasks in Carto, just ask a classmate or the professor (or revisit instructions from a previous lab).

 

Note 2: It is expected that you now understand the mapmaking best practices we have discussed, including: symbology, classification, map elements, typography, and color. Make use of this knowledge in your work, as it is a significant part of your lab grade.

 

Part 1 – Finding Fresh Food in Philadelphia

 

In your final lab of the semester (congratulations!), you’ll be using spatial analysis to help answer an important question for a friend. Let’s say your friend comes to you and says:

 

“I need to buy some fresh food for my family. I would love to be able to shop at a farmer’s market, but I don’t have a car and I pay for my groceries with SNAP (the Supplemental Nutrition Assistance Program, also known as “food stamps”). Plus, I work an irregular schedule. Can you help me figure out where and when to shop?”

 

Luckily, your friend has you, an expert digital mapmaker with access to just the right datasets to solve this problem. You’re going to make a map that shows which farmers markets in Philadelphia are accessible by subway and accept SNAP payment, and style it by the day of the week that each market is open. Let’s get to it!

 

1. Download the SEPTA station and farmers markets datasets from Canvas and upload them to Carto. These have been cleaned up from the versions available on OpenDataPhilly.

 

2. Once the SEPTA dataset is uploaded, open it and you’ll notice a station called AT&T Station. This dataset is from 2014, but the station name was changed to NRG Station in 2018. Double click the name and edit it.

 

 

3. Create a new map with both the SEPTA stations and farmers markets datasets.

 

4. Some of the stations in the SEPTA dataset are now defunct (closed), so they won’t be of much use to us. Add an analysis to the layer to “filter by column value” and set it to hide all defunct stations according to the “line” attribute.

 

 

5. Your friend needs to find markets that are accessible via subway, but they don’t mind walking a little. Add a new analysis to the SEPTA layer and create a travel or distance buffer of a half mile around the stations. You can set the buffers to dissolve.

 

 

6. Now open the farmers market layer. First, we need to filter for those that accept SNAP benefits. Use the filter by column value analysis here and hide those with a value of “false.”

 

 

7. Finally, we need to find out which markets are within the half mile buffers from the subway. Add an “intersect and aggregate” analysis to the farmers market layer and target the buffers (not the stations).

 

 

8. Style your point color by the “day” attribute and select a qualitative color scheme. Be sure your color scheme is accessible to those with color vision impairment. Choose the point size, stroke size, and stroke color that looks best to you.

 

9. Add a pop-up for the other attributes you believe would be most helpful to your map user. Suggested attributes include name and address as well as day, time, and months of operation, as many farmers markets have a limited operating season.

 

10. Add a custom legend.

 

 

11. Drag and drop the days of the week to put them in the correct order. Click the “x” to delete the “others” item if present. Customize your legend text to describe the attribute being styled.

 

 

12. Return to your SEPTA buffer layer and click the icon that looks like an eye to hide your buffers.

 

 

13. Edit your basemap, title, metadata, and anything else needed to make a clear, legible map. Make sure all your text is precise and accurate.

 

Paste the URL (link) to your map here:

 

Then answer the following question:

 

1. According to your map, how many farmers markets are available to your friend on each day of the week, taking both SEPTA access and acceptance of SNAP payment into account?

 

 

 

Part 2 – Walkable Access to Healthy Food

 

For this part of the lab you are to make a web map of walkable access to healthy food in Philadelphia.

 

1. Download the data for walkable access to healthy food from OpenDataPhilly.OpenDataPhilly may indicate this data is archived, but you should still be able to download a Shapefile or GeoJSON version.Note: Download the version with the “Walkable Access to Healthy Food”in the title not “Low/No Access …”

 

1. Load the data into CARTO.

 

1. Style the map using the access_ attribute.

 

1. Apply the finishing touches to your map.

 

Paste the link to your finished map here:

 

After creating the map respond to the following:

 

1. From 2012-14, which areas of the city have low walkable access to healthy food?

 

2. From 2012-14, which areas of the city have high walkable access to healthy food?

 

3. In your own words, describe how the city determined what qualifies as low, moderate, and high access. Note: To answer this prompt you will first need to read the methodology section (pp. 63-68) of the Walkable Access to Healthy Food report available on Canvas.

 

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End of Lab