Experiences with forest maps

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6266
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Experiences with forest maps

Post by 6266 » Wed Aug 24, 2022 9:00 am

I like to share my experiences with making forest maps.

Started with the usual method using OSM, that is good in Europe, but in USA it was very bad. So I tried some other sources.

First I tried the National map and replace all dark green as forest. Looked good in the beginning, but is no way because there is text and other lines on it you can see in the forest.

Found then globeland30, a 30 m map from China in only a few colors: Forest, fields, towns, water, maybe roads, I don't remember. Used it for GTA, I was happy with it. But there was necessary to work on each airport with it. Because the date of the texture and the forest map was not the same, there were lots of places with trees but in the texture were houses or building areas.

Now in my actual project Uruguay I had to see, that globeland30 isn't available any longer. Tried OSM with the same bad result like in GTA. Found now a really easy source. I use the texture itself.

So I copy all tiles to another place and use Imbatch for manipulation

Replace all white with 20 % tolerance to black
Replace two green colors what are trees in the texture with 3 % tolerance to white
Replace another green color from the texture with 80 % tolerance to black

Get than tiles in only two colors: white for trees, black for no trees

Reducing the tiles to 2048 x 2048, renaming to b9999.bmp, making dark s9999.bmp files and copieing all to terragen\ForestMaps in the landscape.

I needed to try 3 times, first I had to add the second green, then I had to add the replace of the white. Each transfomation with Imbatch needs 5 minutes on 600 tiles. The only thing I had to correct were trees on the sea and on bigger lakes, maybe that can be adjusted better, but it was one hour to correct it. So I mad the whole forest map for a 600 tiles landscape in one day, some hours machine labour, and maybe 2 hours for experimenting and correcting. Until now I made 10 airports with no need to correct the forest map. I think it's a good way to do it.

Biggest advantage is, that it's only one source. Where a tree is in the texture, there is a tree in the forest map too

Here a picture from the trees, couldn't do it better by hand in my opinion
forest.jpg
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dgtfer
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Re: Experiences with forest maps

Post by dgtfer » Wed Aug 24, 2022 11:50 am

For the US you can use the National Land Cover Database, with its 30m resolution, it's a good base, that you can improve with adequate textures selection. I built my West Coast sceneries like that.
Image

6266
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Re: Experiences with forest maps

Post by 6266 » Wed Aug 24, 2022 1:10 pm

Thanks for that hint
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6266
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Re: Experiences with forest maps

Post by 6266 » Sun Sep 11, 2022 11:16 am

Next step with the method to use the texture as base for the forest maps. This method has the disadvantage to fill some water places with trees. And if I don't fill the water I get holes in the dark places of the forest.

So in my newest project I made forrests with holes. Then I tried a second run to replace only one dark color in the holes to make conifers. What I got are mixed forests, not perfect, but nice enough. And the water is still water without trees. With more knowledge about colors it could be made surely even better ...
mixed.jpg
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bluefang
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Re: Experiences with forest maps

Post by bluefang » Fri Sep 23, 2022 5:50 am

dgtfer wrote:
Wed Aug 24, 2022 11:50 am
For the US you can use the National Land Cover Database, with its 30m resolution, it's a good base, that you can improve with adequate textures selection. I built my West Coast sceneries like that.

For the US west of the Mississippi, the NLCD works ok - because the contrast between trees, land, and crops is abrupt and obvious - however, try anything along the east coast (US) and, well, it just falls apart.

The problem is that there are a lot of areas that are "green" in color which are not trees. The algorithm seems to fall apart with our lush vegetation variety - from swamps to non-forest weed fields to tree lined highways - it just doesn't work. I truly wish it did. I probably spent ~200 hours painting forest maps for my little tiny 6x6 scenery - and I am still not satisfied.

The best way to illustrate the issue is by example... here is a sample landscape tile in my scenery - so far no AI or satellite based service has been able to properly identify the trees in this tile:

example-trees.jpg
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Image

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6266
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Re: Experiences with forest maps

Post by 6266 » Fri Sep 23, 2022 6:57 am

This is the forest map of your excample with my method. The method is very fast, I need 10 - 15 minutes for to define it, to change 600 tiles then takes 5 - 10 minutes. To get an acceptable result I usually need 3 tries. So ca 1 hour manual work, and som hours for the landscapeseditor to create the forest maps for a 600 tiles (24 x 25) landscape.

Question 1: What is an acceptable result? Perfection costs a lot of time

Question 2: Do you need perfection in a forest map? I like trees in a landscape. A landscape without trees isn't a good landscape. But how close does it have to be to reality? Most important in my opinion is to create an imagination of trees. If you create a landscape, it's yours. And if there is a tree in the middle of a deep see, so what, then there is a little island in your landscape, but not IRL. This wrong tree doesn't really disturbe the flying.

My first changing of a forest map in a copy of an existing landscape was a row of trees at the border of an airfield. I was happy with the result. Later I saw a picture from that airport IRL where they have cutted all this trees ...

(only my 5 cent)
trees.jpg
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NickB
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Re: Experiences with forest maps

Post by NickB » Thu Jan 05, 2023 7:09 pm

In Condor_Tiles, I've been experimenting with 'DetecTree', and it works quite well when the landscape textures are uniform, but not as well when tiles are in different seasons or dates. I've made some notes on the process.
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