Catchment Area Analysis

The Question

“What is the actual walkable area our customers come from?”

The Model

Isochrone-based Catchment (de Smith et al., Ch. 7)

C(t) = { x : travel_time(x, store) ≤ t }

C(t) = set of all points reachable within time t
5 min walk = primary zone (~400m, daily customers)
10 min walk = secondary zone (~800m, destination diners)
15 min transit = tertiary zone (MTR from Central, Admiralty)

Source: de Smith, M., Goodchild, M. & Longley, P. — Geospatial Analysis (6th ed.)

Why Not a Simple Radius?

Sheung Wan has a topography problem. The catchment is NOT a circle:

• North: Bounded by the harbour (no residential past Connaught Road)
• South: Steep hill to Mid-Levels (walkable downhill, painful uphill)
• East: Transitions to Central, different character
• West: Sai Ying Pun, more residential

The real catchment is pear-shaped: wider west, pinched north.

Applied to 14 Wa In Fong East

Zone	Time	Boundary	Population	Character
Primary	0-5 min	Possession St to Centre St	~8,000	Mixed elderly + office
Secondary	5-10 min	Hillier St to Sai Ying Pun	~24,000	More residential, younger
Tertiary	10-15 min / 1 MTR stop	Central, HKU, Mid-Levels	~80,000+	Office, students, visitors

Tip

The catchment shape depends on your target customer. Office workers use different routes than tourists. Delivery extends the catchment to 2km+ (see Constraints).