Install error

[OZ1SEJ]

I followed the installation instructions on Ubuntu 20.04:

git clone https://github.com/aduvenhage/ais-decoder.git
mkdir ais-decoder-build
cd ais-decoder-build
cmake ../ais-decoder -DCMAKE_BUILD_TYPE=RELEASE

The last command gave me an error:

$ cmake ../ais-decoder -DCMAKE_BUILD_TYPE=RELEASE
CMake Error: The source directory "/home/steen/radio/ais-decoder/ais-decoder" does not exist.
Specify --help for usage, or press the help button on the CMake GUI.

I typed cd .. and the cmake command worked. So I'm not sure what the -build directory is for.