Planetary defences

Planetary Shields

Star Wars planetary shields

Star Wars does have theatre shields, like one protecting Rebel base on Hoth in TESB, but there is no evidence of planetary shields in canon. Some say that dialogue supports planetary shield on Hoth, but there are some problems with planetary shield:

1) If shield was stopping orbital bombardment, and ships could pass through it, Empire just needed to send several bomber squadrons and/or Star Destroyers to bombard Rebel base from under the shield. Also, there would be no need to drop shield to allow escaping transports to pass throught shield.

2) If such shield can stop ships, how Empire landed troops on planet? Shield was clearly still operable by time General Veers ordered walkers to shoot at shield generator.

Also, let's get closer look at dialogue:

VEERS: My lord, the fleet has moves out of light-speed. Com-Scan has detected an energy field protecting an area around the sixth planet of the Hoth system. The field is strong enough to deflect any bombardment.

Later:

VADER: Make ready to land out troops beyond the energy shield and deploy the fleet so that nothing gets off that system. You are in command now, Admiral Piett.

So, whatever that "energy field" was, it was not planetary shield.

As for RotS novelization, it does support planetary shield but that goes against higher canon (movies). For details, see here.

CONCLUSION: We have absolutely no evidence of planetary shields in Star Wars canon.

Star trek planetary shields

Planetary shields as existed in Trek as far back as TOS. The first example being the shield protecting the Tantalus penal colony in "Dagger of the Mind" that at the very least blocked transporters. The second and more formidable one appears in "Whom Gods Destroy" which was projected from the Elba II Asylum dome and was powerful enough to resist the firepower of the E-1701's main phaser banks even at it's weakest point on the side of the planet opposite the asylum.

This is dialogue from "Whom Gods Destroy":
SCOTTY: "Sensor readings."
SULU: "Forcefield is weakest on far side of the planet."

Nothng conclusive is mentioned throughout the movies, TNG and DS9, though in episodes like "Gambit, Part 1", there is at least theater coverage shielding for a small scientific outpost along with phasers and possibly photon torpeodes. However VOY's "Year of Hell, Part 2" implies strongly that even relatively primitive starfaring civilizations ought to have them, and "Nightingale" actually shows one in operation protecting the Kraylor homeworld from bombardment and invasion by the Annari fleet blockading it.

Also, episode "The Chase" from TNG shows that one Vor'Cha class Attack Cruiser is able to destroy life on entire world, down to last mollecule, by using chain reaction - that means that full planetary shields must be in use, beacouse theatre shields would be useless. Also, in TNG episode "Chain of Command", main problem with Cardassian bioweapon-delivery system was not that it can deliver microbes over great distance without carrying missile or ship, but rather that it can do so without target realizing it (and raising shields). "Die is Cast" also seems to confirm existence of planetary shields:

TAIN: "...and begin massive bombardment..."
GARAK: "Well, that should more than take care about the Founders."
TAIN: "Yes, unless Founders have some planetary defences we don't know about" (emphasis mine). Within context, it is clear that he was talking about planetary shields.

Also, Breen attack on San Francisco caused only slight damage, most likely bleedthrought from planetary shield.

Active defences

Star Wars

Hoth ion cannon

Rebel Ion canon on Hoth seems to be able to not only completely disable Star Destroyer, but also to bypass/defeat shields. One way or another, it is clear that Imperial and Star Wars shields in general are vulnerable to disruption or penetration by electronic shots, since shields did not seem to affect ion pulses fired by canon, and Star Destroyer was left completely powerless and adrift.

Star Trek

We don't knaw what kind of planetary defences Federation has, but we can guess when looking Federation's neighbours.

Cardassians deployed weapon platforms. These seemed to be fairly recent development from their alliance with Dominion, but again Federation is more advanced but more peace-loving state. Better guess would be orbital stations - we seen some Starbases, like Spacedock (in orbit around Earth) and Starbase 375. Also mentioned are "antiquated" PDS on Betazed, that were inadequate in stopping Dominion attack without fleet support. However, we never see PDS in action, probably due to budgetary reasons.

These might be planetary-based phaser emitters and torpedo launchers, since we know that Cardassians have designed special type of disruptor for planetary defence and according to non-canon technical manuals, phasers used by Sovereign and Prometheus class starships were originally used for planetary defence.

Star Trek active planetary defences

Star Trek passive planetary defences

Star Wars active planetary defences

Star Wars passive planetary defences