How accurate is FATMAP?




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    edoardo raparelli

    So you don't use the digital elevation models available for the countries covered by your maps but you derive an elevation model with 10 meters resolution (worst case) from aerial or satellites images. But when I look at the slope map it seems that its resolution is much less than 10 meters. Do you smooth it to make the layer more nice? I also noticed that the slope of some zones changes when zooming in and out. Is it caused by the algorithm used to calculates the slope which captures different features when changing the zoom? Sometimes the slope at a fixed zoom also changes when moving the map.

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    Hi Edoardo, thanks for your question! 

    We gather our high-res satellite imagery from various providers that cover different areas of the world, and so that means that the resolution of the map varies depending on which areas of the map you are looking at. Most of central Europe and the US are covered with 2m to 5m resolution and the rest of the world around 10m resolution.

    As you describe above, this means the elevation model is calculated depending on this resolution and which area of the world you are looking at.

    Also as you say above, the slope will change depending on your zoom level. This is how we maximise the performance of the map on your browser or on the app. So essentially, when you zoom in, you will see more detail, and therefore the elevation model will be more accurate. 

    We are actually working on a way to improve this by maximising both the accuracy of the elevation model, keeping the high-resolution detail of the maps and a high performance of the web and app.

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    edoardo raparelli

    Many thanks for clarifying what I asked.

    I really appreciate the way you decided to generate the DEM, that's really clever.

    I think that if you find a way to keep at least the slope layer at the highest detail regardless of the zoom this app will be a MUST HAVE for anyone who practices outdoor activities.

    Anyway, thanks for the already amazing results!

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