Hello Sakari_N,

I'm trying to trace fences where I see them, give or take. Since I am airmchair mapping only, can't do surveys in Finland, I don't have local knowledge and some details may be off. I do the mapping in hope that it's easier for someone local to do a survey and modify my version than doing the whole thing from scratch.

It's also sort of a drawing aid for me in some cases: houses are often parallel with fences and in turn with streets, and to pick up the base vector I find it easier and more precise to do it from long fences than short walls or street centers that are imaginary; neighboring blocks often have the generic base vectors of fences and walls lined up, and sometimes even property boundaries line up between adjacent blocks. This in turn helps me figuring the extent of some houses especially when they are under trees.

About the details...

Sometimes I see a fence starts at one corner of a property and I see the end of it in another corner but at the resolution of the aerials available here I can't see the fence in the middle along the given edge, but I find it very unlikely that it just missing in the middle, so in those cases I sometimes imply short middle sections. 

Similarly, with building corners under trees I sometimes can't decide whether the building is rectangular with a corner shaded out or has a more complex floorplan; whether a building touches (or even replaces) the fence or there's a tiny gap; or whether two very closely placed buildings share a wall or they are just really close, within a meter. I regard these all limitations of the aerial based mapping.

About fences, I also cant determine whether they are really fences or walls or hedges (or hedge grown over a fence).

Properties fully surrounded with fences: I don't have local knowledge, but I assume most of the cases it's not a big gap in the fence but a small gate, usually put on the node where the driveway crosses the fence. 

(Unfortunately the actual gate is typically not visible on the aerials in this region.) 

If you have alternative sources or local knowledge, please feel free to add the details, remove fence segments that the subpixel shadow on the aeriel made me think is there but is not.


Thanks!

