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News — 16 September, 2021

Before-After Maps: Visualizing OSM Mapping Contribution Over Time

Adding map data on OpenStreetMap transforms a blank canvas into a visual representation of places and communities where people live. However, it is often difficult to compare side by side how the map has changed over time.

The geospatial team at Kathmandu Living Labs often talked about how comparing map changes could help them reflect on the work they have done and compare data before and after their mapping contributed to a certain area. We believe hundreds of small organizations and/or volunteer groups working in mapping might have the same need.

This need was then passed on to our tech team, who developed an online tool, Before-After maps. This tool shows map data of the same place at two different points in time. The main idea behind its development is to visually compare how a particular area looked at two different years, side by side. These maps show the effort put in between “before” and “after” a particular time period.

We wanted to make generating before-after maps simple and accessible for everyone. Normally, it is a manual process, can be time-consuming, and may require technical knowledge of things such as — but not limited to — Maperitive, OSM data formats, tile hosting, etc. With this application, we hope that generating such maps and showcasing impact will be easier for the organizations and/or volunteer groups working in mapping.

The developer of the Before-After tool, also the Tech Lead at Kathmandu Living Labs, Saurav Bhattarai, shares:

“The manual process of creating Before-After maps requires both time and effort. It also needs a bit of technical skill, which everyone may not possess. With this tool, anyone can generate Before-After maps for the desired place with little effort and technical knowledge.”

In our eight years of experience working on the ground and interacting with multiple mapping organizations all over the world, we have learned that most organizations working in mapping lack the technical capacity to create in-house before-after maps as an output. A mapping team with in-house tech teams is usually an exception rather than the norm. Just because everyone is not able to do this doesn’t mean they shouldn’t be able to.

The tool is an amalgamation of some pre-existing open source initiatives, which you can find more about in the About section. The map style for the generated before-after maps is provided by Baato.

At present, the tool allows you to search for a geographic location and compare past years against current OSM data. Once the user has entered their details, they will receive an email with a link to their map.

So far, the comments on the Before-After tool have been encouraging:

KLL Feedback 2.png

KLL Feedback 1.png

However, we are still in the early phases of the development of the tool and are eagerly seeking feedback as well as contributors to improve it. For your valuable suggestions, please reach out to us at

You can find more information about Kathmandu Living Labs at