How to specify installation location

I need to deploy an application via PS & SCCM.
How is the best method of telling PS that the msi is in the same directory as the PS script?
I can’t hard code the install directory as that will be determined by SCCM.

I read that this is the correct method, however it’ errors out for me.

$scriptpath = $MyInvocation.MyCommand.Path
$dir = Split-Path $scriptpath

Error is ‘Split-Path : Cannot bind argument to parameter ‘Path’ because it is null.’

In scripts you have the built in automatic variable $PSScriptRoot pointing to the directory of the script.