This protocol Deliverable 2.4 of Work Package 2 (WP2) of the emc2 project, presents a methodology to calculate and assess the population catchment areas around urban street networks. The Population Potential in Catchment Area (PPCA) protocol is presented through a paper published on the SoftwareX journal. It is a Python-based workflow using OpenStreetMap (OSM) and Global Human Settlement (GHS) data and employing Google Earth Engine for data acquisition and morphometric analysis. Through a series of four automated steps, the protocol cleans, processes, and classifies geospatial data, ultimately yielding refined population estimations within defined catchment areas. This protocol enables researchers and urban planners to assess the population that can be potentially accessed on foot using the street network, within given distances. The protocol allows this assessment in any city across the world with minimal input requirements, focusing mostly on bounding box coordinates. This resource was produced within the emc2 project, which is funded by ANR (France, grant ANR-23-DUTP-0003), FFG (Austria, grant FO999905461), MUR (Italy, grant 2024/0017648) and Vinnova (Sweden, grant 2023-02581) under the Driving Urban Transition Partnership, which has been co-funded by the European Commission.