2000 Meters per Pixel

The images below are all exactly to scale, each pixel equals two kilometers to a side! Internet Explorer users may Click and Drag the starships to compare them as you like. In the background is the Earth's Moon also to exact scale for comparison. Have fun!

SHIP NAME/TYPE:		HALO
DIAMETER (Main Body):		10000 km.
BUILDER/COMMENTS:		Built by the mysterious 'Forerunners'. The back side looks a little bigger than the front in this image because of the isometric projection that I prefer to use, but this baby should be to scale. Big? Yes, but I wonder if Niven ever played Halo....
SOURCE:		Halo and Halo2, amazing games from Bungie and Microsoft Game Studios. The custom land and cloud maps used in this image were created by IRML, whose excellent Halo Mesh can be seen and downloaded here

Unicron

SHIP NAME/TYPE:		Unicron
DIAMETER (Main Body):		1000 km.
BUILDER/COMMENTS:		Unicron's builder is not described in the film. The size quoted above is based on pure extrapolation from the film, and is probably generous. I have seen sizes quoted anywhere from 3000km to "the size of a large planet", however the cartoon is extremely liberal with respect to scale and consistency. The Transformers seem to inhabit large asteroids rather than planets, which would mean that a large planet from their point of view may in fact be a large asteroid (Ceres is one of the largest known asteroids in our solar system and measures approximately 1000km in diameter, which is why I chose that size).
SOURCE:		Transformers: The Movie (1987)

Zentraedi Fulbtzs Berrentzs class Home Base, 1400 km high

SHIP NAME/TYPE:		Zentraedi Fulbtzs Berrentzs class Home Base
HEIGHT:		1400 km. This height is significant in that it reflects the length of the Japanese Isles.
BUILDER/COMMENTS:		Built by Zentraedi, under Supreme Commander Dolza. This is the version of the Zentraedi Mobile Command Base that appears in the television series.
SOURCE:		Robotech/Macross animated television series, image drawn by JR

Mothership from ID4, 800 km long

SHIP NAME/TYPE:		ID4 Mothership
LENGTH:		Approximately 800 km long. Please see notes
BUILDER/COMMENTS:		ID4 Aliens. Please see notes
SOURCE:		Independance Day (Film), image drawn by JR

Zentraedi Mobile Command Base, 1400km wide

SHIP NAME/TYPE:		Bodolza/ Zentraedi Mobile Command Base
WIDTH:		600 km, Verified by Egan Loo, Macross Compendium.
BUILDER/COMMENTS:		Built by the Zentraedi, the mobile command bases are among the most powerful ships in the known universe. They are each commanded by one ancient and gigantic supreme commander, who is integrally fused to the vessel. See Notes for further details.
SOURCE:		Macross: Do You Remember Love? (Animated Film), image drawn by JR

Death Star II from Star Wars, episode VI, 160km diameter (official size)

SHIP NAME/TYPE:		Death Star II/ Mobile Command Base
DIAMETER:		160km (official size, see http://www.theforce.net/swtc/ds/ for an alternate size theory and discussion.)
BUILDER/COMMENTS:		The Empire under Darth Sidious (human). Incorporated into the base is a laser-type weapon capable of destroying an entire Earth sized planet.
SOURCE:		Star Wars, Episode VI (Film)

Death Star from Star Wars, episode IV, 120 km diameter (official size)

SHIP NAME/TYPE:		Death Star/ Mobile Command Base
DIAMETER:		120km (official size, see http://www.theforce.net/swtc/ds/ for an alternate size theory and discussion.)
BUILDER/COMMENTS:		The Empire under Darth Sidious (human). Incorporated into the base is a laser-type weapon capable of destroying an entire Earth sized planet.
SOURCE:		Star Wars, Episode IV (Film)

V'Ger from Star Trek: The Motion Picture, 98 km long

SHIP NAME/TYPE:		V'Ger (Voyager VI)
LENGTH:		Approximately 98 km.
BUILDER/COMMENTS:		Originally built by humans and launched near the end of the 20th century for peacful reconnaisance purposes, the Voyager VI probe was intercepted by an evidently technologically advanced race who augmented the probe and sent it back to Earth under a new internal conciousness, resulting in a near cataclysm.
SOURCE:		Star Trek, the Motion Picture (Film, 1982 Paramount Pictures), image drawn by JR

Whale Probe from Star Trek IV, 74 km long

SHIP NAME/TYPE:		Whale Probe
LENGTH:		Approximately 74 km. There are numerous conflicting sources for the length of the Whale Probe, but extrapolation from the film has led me to accept this length as being the most likely.
BUILDER/COMMENTS:		Unknown, although the device was able to communicate with humpback whales.
SOURCE:		Star Trek IV, (Film, Paramount Pictures)

Marduk Base from Macross II, 50 km diameter

SHIP NAME/TYPE:		Marduk Mothership
DIAMETER:		Approximately 50 km. This is the stated length of the RPG version, although the movie version seems to be much larger. Further investigation is needed.
BUILDER/COMMENTS:		Marduk, the creators of the Zentraedi.
SOURCE:		Macross II, (Animated Film), image drawn by JR

Rama, 50km long

SHIP NAME/TYPE:		Rama
LENGTH:		50 km long, 20 km in diameter.
BUILDER/COMMENTS:		Large habitat ship
SOURCE:		Rendezvous with Rama, Arthur C. Clark, image drawn by JR

Vorlon Planet Killer from Babylon 5, approximately 45 km long

SHIP NAME/TYPE:		Vorlon Planet Killer
LENGTH:		Approximately 45 km. There are numerous conflicting sources for the length of the Vorlon Planet Killer, but extrapolation from the show has led me to accept this length as being the most likely.
BUILDER/COMMENTS:		The Vorlon
SOURCE:		Babylon 5, (Television Series)

Phobos, moon of Mars, 27km long at longest axis

SHIP NAME/TYPE:		Phobos
DIAMETER:		27 km x 23 km x 20 km
BUILDER/COMMENTS:		Moon of Mars
SOURCE:		Discovered in 1877, August 12 by Asaph Hall; photographed by 'Mariner 9' in 1971, 'Viking 1' in 1977, and the Russian 'Phobos' probe in 1988.