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# Week 7

Extracting historical geodata.

Due date (changed) November 6.

For this week, we’ll be collaboratively digitizing some historic geodata.

In class

1. Download a map of the world from http://www.naturalearthdata.com/downloads/50m-cultural-vectors/

2. Set your CRS as the world.

3. Download Boston-Area shapefiles from benschmidt.org/GIS.zip

4. Load them in QGIS.

# 1. Choose your map

We’re using maps of Roxbury from 1915.

https://www.flickr.com/photos/mastatelibrary/albums/72157634973616960

You’ve selected one already.

# 2. Georectify the map

Using some of the Boston shapefiles we’ve seen in class, georectify your map.

You’ll need something to use as a base layer! I’ve given you to download a set of roads; but there are a variety of other sources out there that may work as well. http://wsgw.mass.gov/data/gispub/shape/eotroads/eotroads_35.zip

Abby Mullen has posted a list of instructions for georectification online One additional note: be sure to choose ‘polynomial 2’ as the method; otherwise, you might end up with a weirdly warped map.

# 3. Create a polygon layer.

Follow the directions here to make the layer. Make sure the attributes for each object include:

Be sure to follow the typology here exactly; don’t make the column for ‘type’ uppercase, for example! But do make sure it’s a polygon layer, not a line layer, since buildings have shapes.

1. id
2. type let’s try for a five-type taxonomy. Enter the term exactly as it appears below.
• Commercial
• Residential
• Industrial
• Government
• Communal (churches, YMCAs, etc.)
1. name: The label for the object on the map.

# 4. Trace the five larges buildings in your map to the polygon layer.

Again, follow the directions here.

# 5. Save the exported shapefile into a new folder.

That folder will have several files in it; one that ends with .shp, one that ends with .prj`, and so forth.

Zip the entire folder and mail it to me–we’ll try to assemble all these pieces together into a partial map of Roxbury 100 years ago.