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DAT-241: Geospatial Data Analysis

The following table maps course session dates, lesson topics, references, and content links for DAT-241: Geospatial Data Analysis

course date wk no. session links learning objectives out-of-class work
DAT-241 Tue
1 Identify feature and ground elements on a map, designate as point, line, polygon, or raster. 1. Choose a high-quality map of your choosing, upload image to one drive, and complete an analysis row in the table (feel free to upload a separate in shared drive if you don't like typing in spreadsheet)
2.Attemp an install of the "most stable" desktop version for your OS. Keep track of bugs, look them up online if you can
DAT-241 Tue

Map Feature Discovery Exercise Review

Spatial data types


ESRI Shapefile(s)

Compare map extents using conversion algorithms for various coordinate systems

Edit a KML file containing spatial data and demonstrate fidelity to the KML standard by displaying the KML data on a map

QGIS Setup Basics

Add kml file
  1. Layer menu bar - add layer - add vector layer - then choose your kml file - add
Install baselayer plugin
  1. Menu bar: Plugins - Manage and install Plugins - Search for QuickMapServices - select it from the search results - click "Install Plugin"
  2. Once the plugin is installed, you'll get a side panel, probably defaultingn to the right side of screen. If you don't see the plugin search window, navigate to View - Panels - QMS Search
  3. You could search for something like "street" and see a bunch of street layers

Layer Styling Basics

  1. Navigate to wprdc.org and browse data sets that are of type: KML or geoJSON. Download a few that look interesting.
  2. Add to a QGIS project
  3. Rename layers logically
  4. Choose styling to make features stand out from the basemap
  5. Practice reordering or changing symbols to allow several feature layers to coexist happily.
  6. Take a screen shot of your tinkering and upload to our shared one drive directory, inside the week2 sub-directory. The root is linked below.
DAT-241 Tue

Map projections and Intro to QGIS

Question: What types of distortion of map features occur as projection systems change? What evidence demonstrates these distortions?

  1. Open google Earth and create a test set of about 6 polygons of rectancular and triangular shape which span different axes of the earth. So we want some test features that travel across 1/4 or more of the earth's surface, some extended horizontally parallel with the equator (cutting lines of longitude) and some extending vertically cutting many lines of latitude.
  2. Once you have your chosen test shapes, export the file as a KML and upload to your group's directory in the cloud drive.
  3. All other group members can then download the test file for use in QGIS
  4. Each Member: Create a new project in QGIS named ProjectionComparison
  5. With your group, choose 6-8 different projection systems for your project using: Project >> Properties >> CRS tab >> Predefined CRS
  6. Look for naming patterns in the CRSs listed and choose from a variety of different core types, using the filter tool to shave down to a certain type of projection, i.e. "Cylindrical" or "Conic"
  7. Create a recording system--perhaps a Shared word doc in OneDrive--where you can experiment with projecting your features using several Coordinate Reference Systems in QGIUS. We want to caputre with screen shots the outputs of various projections with some simple explanatory text about what you're seeing.

Target completion for next week 23-FEB

Research the key features of the projections you choose to analyze to add depth to your conclusions;

DAT-241 Tue

Session Recordings

QGIS Demonstrations

Use vector analysis tools to count points by polygon, generate new quant attibutes, and style feaures based on feature attributes

Choose a polygon and point layer to conduct a similar type of analysis as we did with the trees by neighborhood. Distill down an inquiry question to pursue and see if you can style your map with that inquiry in mind. Tinker with the Choroplet shading algorthms (equal count, natural breaks, etc.) Take a screen clip of your map and upload to our shared drive: week4_pointsInPolygons directory.

DAT-241 Tue

Spring'21 Session Recording

Join flat file US census data with TIGER shapefile spatial data and create choropleth maps to investigate an inquiry question of your choosing.

Develop a (rough) inquiry question related to the spatial patterns in US census/ACS data, such as: Where in PA is the gender wage gap the greatest in construction and human services industries?

  1. Choose a region of interest to you, perhaps a whole state, or just a sub-section, or just blocks in a county.
  2. Choose a table using American Fact Finder that speaks to your inquiry question. Download that table, clean it up keeping only columns of interest to your inquiry. Don't forget to organize your data sets and don't just dump everything in Downloads.
  3. Load your spatial data into QGIS. Load in your flat file as demonstrated. Try the join on the GEO-ID column.
  4. Use the field calculator tool to generate a computed field related to your inquiry, such as subtracting male wages from female wages
  5. Visualize your data using sensible styling to draw the eye into your pattern of interest.
  6. Upload a screen shot and brief description in a text file of the patterns you discovered to our shared cloud drive week5 directory.
DAT-241 Tue


QGIS and Map Layouts

Tool demos

  • Intersection: vector >> Geoprocessing >> Intersection. This acts like a "cookie cutter". Be sure to create a new file for your layer and not a temporary layer.
  • Export selected features only: use edit >> select and click on features you want to export (click with ctl for multi-select). Then, right click your layer in the layer pane, export >> Save Selected Features As...
  • Use Vector >> geoprocessing >> clip to trim points inside a polygon layer
  • Dissolve polygons to get an "outline" shape: Vector >> geoprocessing >> dissolve. You can dissolve on a categorical field value if your dataset supports it (i.e. the features are classified based on a category set)

Create map layouts with supporting features: legend, title, source, insets, etc.

  1. Develop or intensify a inquiry question using US Census/ACS data, ideally comparative in nature. Possibly side-by-side maps of compared areas in your layout. Declare you intent in our tracker
  2. Use joins and processing tools to trim your data and symbolize your maps as appropriate.
  3. Export your layout as a PDF or JPG and either post to a git repo or cloud drive. Prepare to share next week!
DAT-241 Tue


Vector Layer Analysis

  • Buffers and area overlap analysis

In-Class Exercise Steps

  1. Create a blank project called busAccessZones in QGIS
  2. Retrieve the Port Authority bus route layer from the WPRDC.org
  3. Lets secure contextual layers for identification of regions with poor bus coverage, so perhaps Pittsburgh Neighborhoods
  4. With your blank project, click prohject >> properties >> CRS and choose a projected coordinate system, such as the: WGS_1984_Web_Mercator_Auxiliary_Sphere
  5. Let's inquire which neighborhoods have the least to access to rapid, express, and key corridor routes. TO do this, let's select only these types of features in our route layer. Open the attribute table. Then click the column header for serviceType to sort by service type. Hold down control and control + shift to select only these three types of routes
  6. With only our rapid, express, and key corridors selected, right click the layer in the layer pane, export >> export selected features >> and name the file logically.
  7. Create a polygon buffer around all of our Port Authority routes: Vector >> Geoprocessing tools >> Buffer. Once in your tool popup, select the Port Authority routes as your layer, and set buffer distance to 0.25 miles.
  8. Consider turning on a base layer with the Quick OSM plugin: Eric used the ESRI World Topo base layer.
  9. We now want a new polygon layer of only the neighborhood areas that are not within 1/4 mile of an express, rapid, or key corridor route. Create this with vector >> Geoprocessing tools >> Symmetrical Difference tool.
  10. In our case, since the bus routes extend beyond PGH city limits, we need to clip the low-service area symmetical difference layer to only the extent of PGH Neighborhoods. Do this with vector >> geoprocessing tools >> clip
  11. Style the result layer and add supporting layers, such as neighborhood centers, etc.

TODO for week 7

Use the buffer tool around a point, line, or polygon layer of your choice to investigate the impact of the some attribute of your chosen layer on the surrounding area. For example, one idea would be to look for so-called food deserts by creating a buffer of walking distance around known supermarkets. Another idea would be use the recreation layers in the WPRDC, such as playgrounds, ball fields, green fields, etc. Investigate the question of which areas in a given study area have the most access to child-friendly spaces. Create a buffer of safe child walking distance to playgrounds, pools, or recreation sites and identify low-service areas (less ideal areas to raise children who want to play).

Create a simple map layout and upload to the week7_buffers shared drive subdirectory.

DAT-241 Tue


Applied spatial algorithms

PA Crash Data set

Road Safety mini-projecet

Which sections of road in PA do you classify as most dangerous? Which sections of road are good candidates for increased safety implements such as lighting, guardrails, speed tracker signs?

Suggested steps: Review the PA Crash data points to decide which ones to use in your analysis. Build a map with a reasonable buffer around PA roads such that crashes can be counted with the "Count points in polygon" tool as demonstrated tonight and previously.

Helpful notes

  • Eric's PA road buffer is stated in degrees, so his 200 foot buffer was encoded as 0.000549 degrees inside the buffer tool.
  • Eric used the weight field in the count points in polygon tool to add additional data depth to the analysis. See tool settings.

For post-spring break

Prepare a draft export of your map and also a short written summary of your findings for sharing with peers on the class after spring break. Upload your images to our week8_roadSafety shared drive

DAT-241 Tue
- Spring break: No Class all week! Renew, rejuvinate, refactor! Catch up if you're behind.
DAT-241 Tue

Session Recording

Digitizing 311 Service Zones Project

Strategically create vector features on a map based on patterns discovered in supporting data sets. Use generated features to continue pursuing spatial inquiry.

Completion target for 311 vector project: Class start of 20-APR-2021

DAT-241 Tue

Session Recording

LandSat 8 Primer and Raster Data

Project Worktime

Download and symbolize raster data from the USGS LandSat 8 sensor array

Finalize your 311 service zones and create a presentable set of map layouts which depict your suggested priority zones for the City of Pittsburgh Department(s) which you chose to analyze.

DAT-241 Tue

311 Project Sharing

Geocoding and Shortest Path Algos

Prep postgreSQL install

DAT-241 Tue

Spatial Databases

  • PostgreSQL basics
  • PostGIS extension installation
  • Connecting to PG Admin
  • Spatial query visualization
DAT-241 Tue

Spatial Database project worktime

DAT-241 Tue
14 Final session; final project sharing Push revised work to your git repository