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You can start working on your copy of Exercise 6 by accepting the GitHub Classroom assignment.
Exercise 6 is due by Wednesday 12th of December at 4pm (day before the last practical session!).
You can also take a look at the open course copy of Exercise 6 in the course GitHub repository (does not require logging in). Note that you should not try to make changes to this copy of the exercise, but rather only to the copy available via GitHub Classroom.
Defining the graph extent¶
First, combine the point data sets, for example, by using the Pandas append() method (adds rows from one DataFrame to the other). Then, specify the extent Polygon using a convex hull or a bounding box + a little buffer (the buffer enables the routes to go beyond the extent of the point layers!). When creating the buffer, remember that the coordinates are in decimal degrees!
Option 2 - Bounding box: Specify a Polygon that represents the bounding box of the combined points;
- First, define the bounds:
- Once you have all origin and destination points in one GeoDataFrame,
- you can get the corner coordinates of the bounding box from the total_bounds of the geometry-column.
- Note: the resulting coordinates from the total_bounds are in this order: [xmin, ymin, xmax, ymax]
- Next, you need to define a shapely polygon based on the bounding box coordinates.
- In order to create the shapely Polygon, we need to organize the bbox coordinates into a list of coordinate pairs for example like this:
- bbox_coords = [[xmin, ymax], [xmin, ymin], [xmax, ymin], [xmax, ymax]]
- You can create the list of coordinate pairs based on the total bounds. Store the total bounds first into a list, and then create the coordinate pairs.
- You can insert the coordinates into the list one by one. If bounds is a list that contains the total bounds of our input coordinates, then we can get xmin like this: bounds.
- Finally, buffer the bounding box polygon (eg. adding 0.05 decimal degrees to the extent using Shapely’s buffer method)
Option 2 - Convex hull: - Specify a Polygon that represents the convex hull of the combined points like we did in Lesson 1
- First, create a MultiPolygon of the points (eg. using unary_union)
- Then, you can access the convex_hull of that MultiPolygon object
- Finally, buffer the convex hull polygon (eg. adding 0.1 decimal degrees to the extent using Shapely’s buffer method)