Multiple grounds

[nutmegzzzz]

I'm currently designing a PCB for a camera system that utilizes 3 different grounds (Analog, Digital and Chassis).

ov7940db_1.1_SCH.pdf

[MP]

For best results, you would treat all three as 3 separate circuits and then tie them all together at a single point at the chassis. Otherwise, you could have interference between you analog and digital circuitry.

MP

[nutmegzzzz]

First time working with PCB design so please bear with me. 

Instead of having a single ground plane with all grounds connected, Can I use that layer to wire the appropriate grounds together and then bring them all to the top layer and wire with 0 ohm jumpers.  Is this appropriate or am I still going to cause a problem not having a single ground plane?  I should mention the eval board for this chip uses 2 layers with no power or ground plane.

Also because I am using two power supplies (3.3V and 1.8V), instead of having a power plane (originally I was going to have just 3.3V), can I use this layer for various power connections thus saving space on the top and bottom layer.

Thanks for your help MP,

[MP]

It is not a good board layout practice to use a board layer for this purpose.

MP