Find The Flattest Route Between Any Two Points In SF

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Flatten SF is a browser-based tool for finding and comparing routes between points in San Francisco. It uses USGS 1-meter lidar elevation data and an Overture/OpenStreetMap street graph to show the trade-off between walking distance and cumulative climbing.

Flatten SF, a browser-based route planner, lets users compare paths between points in San Francisco by walking distance and cumulative climbing. The tool calculates routes over more than 160,000 street segments using elevation and street-network data, giving users a way to weigh a shorter trip against a less steep one.

The site says its routes are computed in the user’s browser using USGS 1-meter lidar elevation data and a street graph drawn from Overture and OpenStreetMap. Users enter starting and ending points and move a slider across routes that balance distance against climbing. Place, address and intersection search for San Francisco is built into the page and works offline, according to the site.

Flatten SF describes the slider as covering routes that are not beaten by another route on both distance and climbing. Moving it toward flatter options does not shorten the route or add climbing, the site says. The measure is cumulative elevation gain along the path, rather than simply the difference in elevation between the endpoints.

Routing rules differ by travel mode: stairways are permitted for walking and excluded for biking. The site also displays faint lines for other routes in the distance-versus-climbing trade-off. It credits the project to Drew Edwards and links to its source, data and full analysis.

Compare Climbing With Walking Distance

San Francisco’s elevation changes can make two routes between the same locations feel quite different. Flatten SF makes that trade-off visible, allowing people to see whether avoiding a climb means walking farther and choose a route that fits their preferences. That may be useful for pedestrians and cyclists, though the source does not report user numbers, measured travel-time savings or accessibility outcomes.

The tool’s approach also makes a distinction that can be easy to miss in ordinary directions: a route’s total climbing is not captured by comparing only the elevation at its start and finish. A path can climb and descend repeatedly while ending near its starting elevation. By showing cumulative gain, the planner gives a more direct measure of the uphill effort along a route.

Elevation Data Shapes the Routes

The planner combines a street network with detailed elevation measurements. The source identifies USGS lidar at a 1-meter resolution as its elevation input and Overture/OpenStreetMap as the basis for the street graph. It says more than 160,000 street segments are used in its calculations.

Flatten SF frames its route choices as a distance-and-climbing trade-off. Its description says the flattest route worth walking is determined using a stated preference: one foot of climbing costs 200 feet of walking. The site says that beyond this point, the alternatives stop being routes. This is a modeling choice built into the explanation, not a claim that every traveler values climbing in the same way.

““every route that nothing else beats on both counts, from the shortest path to the flattest one worth walking””

— Flatten SF

Limits of the Route Data

The source does not give a publication or launch date, explain how recently the street graph or elevation data were updated, or describe how it handles temporary closures, construction, private paths or changes to street access. It also does not provide independent accuracy testing or explain how elevation estimates are affected by data gaps.

The 200-foot walking cost for each foot of climbing is presented as the tool’s routing rule. The source does not say that this reflects every user’s comfort, mobility or travel needs. Route results should therefore be understood as comparisons generated by the site’s model, not as a guarantee that a path is suitable for every person or current street condition.

Try a Route and Review the Data

Users can enter two San Francisco locations on the Flatten SF site and move the slider to inspect the available distance-and-climbing trade-offs. The site links to its source, data and full analysis for readers who want to examine how the routes are built. The provided material does not announce a future update, expansion to other cities or additional release date.

Key Questions

What does Flatten SF do?

It calculates routes between locations in San Francisco and lets users compare distance with cumulative climbing.

What data does the planner use?

The site says it uses USGS 1-meter lidar elevation data and a street graph based on Overture and OpenStreetMap, covering more than 160,000 street segments.

Does the tool include stairways?

According to the site, stairways are allowed for walking routes and excluded for bike routes.

What does cumulative climbing mean?

It is the total uphill gain along the route. It can differ from the elevation change between the starting point and destination because a route may climb and descend along the way.

Is the flattest route always the best choice?

The tool shows route trade-offs according to its model, including a stated cost of 200 feet of walking for each foot of climbing. The source does not establish that this rule matches every traveler’s needs, so users should review the route details and conditions.

Source: hn