Find the flattest route between any two points in SF

San Francisco’s infamous hills now have a routing tool that prioritizes minimizing climbing, changing how you plan urban travel.

Drew Edwards has launched Flatten SF, a web application that calculates the flattest walking and biking routes in San Francisco. The tool utilizes 160,000 street segments, incorporating USGS 1-meter lidar elevation data and the Overture/OpenStreetMap street graph. Users can adjust a slider to find a balance between route distance and climbing, from the shortest possible path to the flattest viable option. The application computes routes within the browser and includes offline search capabilities for San Francisco streets, addresses, and places. Stairways are accommodated for pedestrian routes but excluded for cyclists. The tool visualizes the trade-offs between distance and cumulative elevation gain.

This application represents a significant advancement in urban navigation tools by integrating detailed elevation data directly into route calculation, moving beyond traditional shortest-path algorithms. The ability to dynamically adjust the distance-to-climbing trade-off offers a novel way for users to experience the city, potentially encouraging more walking and cycling by mitigating the physical exertion previously associated with SF's topography. The browser-based computation and offline data also suggest a trend towards more accessible and self-contained mapping solutions.

The methodology behind Flatten SF could inform the development of similar tools for other hilly cities, as well as for niche applications like accessibility routing for wheelchairs or strollers. By making elevation a primary, adjustable factor, Edwards' work highlights a gap in current mapping services that often overlook the qualitative aspects of travel beyond pure distance or estimated time. This could pressure existing platforms to incorporate more nuanced routing criteria.