Anywhere in the lines between the compressor and the expansion valve is the "high pressure" side of the system. You can install the high pressure port anywhere between the compressor and the expansion valve, but obviously common sense tells us that you don't want the port to be 1-2" from the compressor outlet., Perhaps a minimum of 8-12" away. Measuring the HP after both condenser and dryer is fine as well, if placement on your car aircon design allows for that. This will mean slightly higher refrigerant pressures post-compressor pre-condenser, something we try and avoid at the higher tropical temperatures we operate in, since that may affect both compressor and condenser life. With daily temperatures usually exceeding 32C, aircons are in operation literally when the engine is running, so component lives matter (#CLM).
As a comparison, this is the pipe routing on a factory-fitted on my Lotus Elise S1. These are pipes fitted directly to the compressor body.
I am not trying to dictate, nor am I pretending that fitting the ports next to the compressor is a "must", but merely stating a fact that's where the factory had them fitted.