# Creating land use layers

I have a land use layer which includes 36 different individual classes. Using the raster calculator I have been able to extract 1 of the different classes and make a new layer (landuse=[number of the land use class]). I want to put multiple of these classes together to create one layer e.g. a general forest layer, and tried using the AND function. This however is not working and only acknowledges the first number in the equation (e.g. landuse = 1 AND 2 AND 3) only the land use equivalent to 1 is produced. Does anyone have any ideas?

• I'm almost sure you mean `landuse = 1 OR landuse = 2 OR landuse = 3`? Jul 22, 2022 at 11:37
• Order of precedence is rough on beginners, especially with Boolean operators.. Look at the `IN` operator (`field IN (1,2,3)`) Jul 22, 2022 at 11:41
• @Vince I'm pretty sure the raster calculator can't handle `IN`?
– Erik
Jul 22, 2022 at 12:11

Currently your telling the calculator to include everything where `landuse equals 1` and where `2` and where `3`. Now your old math teacher comes around the corner and asks "Three what? Bananas? Apples? Gas stations?"
After showing him (nicely) out the door you provide more details to your algorithm, e.g. `landuse = 1 AND landuse = 2 AND landuse = 3`. While this might work out, your programming tutor strolls in and has a nervous breakdown, since basically you're looking for pixels where the landuse is 1, 2 and 3 at the same time.
You hand him a calming tea, seat him on the condo and return to your expression, replacing your `ANDs` by `ORs`, while also shortening it a bit: `landuse = (1 OR 2 OR 3)`.
• And then someone versed in Boolean logic points out that `1 or 2 or 3` resolves to `True`· and the expression to `landuse == 1`. This is the place for the `IN` operator.. Jul 22, 2022 at 12:07
• @Vince I noticed that too, but @Erik's high reputation makes me think the raster calculator interprets `landuse = (1 OR 2 OR 3)` correctly as the equivalent of SQL's `landuse IN (1,2,3)`. The OP's original query parses as `(landuse=1) OR 2 OR 3`, effectively confirming that non-zero zero constant are truthy Jul 22, 2022 at 12:16