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Teal dots on a flat sheet, each ringed in amber, the rings merging into one region that a straight slate line cuts through

Coverage, from a live feed to a policy number

One transport authority's question — is the cycle-hire scheme where people are? — worked from a live docking-station feed to a coverage figure a minister can quote, with the projection mistakes met on the way.

Spatial Analysis

Steps
6
Each assumes the one before it
Time
~3 h
At the problems' own estimates
XP
1,110
Before hint costs and speed bonuses
Progress
0/6
Start the pathBegins with Which boroughs is the cycle-hire scheme actually in?

What you will be able to do

Take a live point feed and an administrative boundary layer and produce a defensible coverage report against a policy target: supply per area, walk-distance coverage per unit, the projection choices that make those numbers true, the indexed query that keeps the app responsive, and the tile budget that takes the map offline.

The sequence

Each step assumes the one before it.

  1. Up nextWhich boroughs is the cycle-hire scheme actually in?Up nextJoin 799 docking stations to 33 boroughs and rank them by docks per square kilometre.beginnerDifficulty: beginner130 XP~25 min
  2. 2Docks and bikes per borough, in one queryA point-in-polygon join with GROUP BY — and the outer join that keeps the boroughs with nothing to count.beginnerDifficulty: beginner150 XP~25 min
  3. 3How much of Inner London is a five-minute walk from a dock?Buffer, dissolve and clip: the covered share of each Inner London borough at a 400 m walk.intermediateDifficulty: intermediate240 XP~45 min
  4. 4The buffer that shrank on the way to the mapQuantify what a 400 m buffer drawn in EPSG:3857 actually covers on the ground in London, and how much of the coverage report it loses.intermediateDifficulty: intermediate200 XP~30 min
  5. 5Redirect the rider at an empty dockFor every station with no bikes, the nearest station that has one, and the walk in metres — with the KNN operator so it stays fast at 799 stations or 79,000.intermediateDifficulty: intermediate250 XP~40 min
  6. 6How many tiles does an offline London need?From a bounding box to a tile count: size the offline basemap for a field app across zoom 10–15.beginnerDifficulty: beginner140 XP~25 min

Where it leads

Spatial Analysis is examined in the Open-Data Analyst — Associate, which issues the Kharita Certified Open-Data Analyst (Associate) (KODA-A1). The problems here are the practice; the assessment is the same kind of problem, under time.