Function to get the directory in which this script resides.

get-scriptdirectory.ps1

function Get-ScriptDirectory {
    $invocation = (Get-Variable MyInvocation -Scope 1).Value
    $script = [IO.FileInfo] $invocation.MyCommand.Path
    if ([IO.File]::Exists($script)) {
        return (Split-Path $script.Fullname)
    } else {
        return $null
    }
}