To be more precise, i have to make board (B1) that is used as amplifier and filter for input analog signal. This board uses +/-12V and GND (12VGND) as supply for amplifiers, and +5V and GND (5VGND) that supplies digital part. Digital part on this card is used to drive few LEDs, and some simple logic. Board (B1) is connected to separate DSP board (B2) with inputs for analog AGND and +5V and digital DGND.
I don't know if it is better to place plane on B1 that is connected to AGND around analog part, or plane should be connected to 12VGND aroung analog part. 12VGND connects to operational amplifiers power inputs. AGND on B1 is separated and will be connected to AGND on board B2. AGND on B1 is connected to inverting inputs on OPAMPs and is used as reference for analog inputs.