posted 5 years ago
Works suprisingly well!
Although I would be sceptical about accuracy and precision just for the following reasons:
I guess these tools are based on freely available earth surface data provided by satellites. The best of these datasets (Alos Palsar, to my knowledge), has a resolution of 12.5 m. So a countour interval of 2 m, based on data with a resolution of 12.5 m, is purely based on interpolation and NOT real. Might be enough though for basic planning ...
These free data are always in the form of "digital elevation models", and they represent the entire elevations of the surface at sight, including buildings. So if you live in an urban setting, the contours you get might be very inaccurate or even false due to the buildings around you. On the contrary, the "digital terrain models" have buildings and vegetation removed in post-processing, but this is very difficult to achieve with satellite data and is never the case for free datasets.
Cheerio
Lukas