Each planetary hex facing has room for 4 ground bases. Of these 4 bases only 2 of them may be Ground Combat Bases- all heavy weapons bases and Phaser-4 bases fit into this category. Major worlds may have 1 Ph-4 base per hex side. Populated worlds may have 1 Ph-4 base on every other hex side. Only populated and major worlds may have Ph-4 bases. All other worlds may have 2 GCBs per hex side and 2 other bases which may include Ph-1 bases, drone defense bases, fighter bases, drone bases, power stations, and the like.
Ground bases armed with only Ph-3s may use the HardToSee attribute. Ground bases with weapons other than Ph-3s may not. Fighter or PF capability counts as a weapon, and a Special Sensor counts as a weapon, but a single Ph-G counts as a Ph-3 for this purpose. Any ship that can see into a sector containing an armed ground base will know that there is a ground base there, but not on which planet it is.The exception is Ground Warning Stations (GWSs) on outer planets. They may use the HardToSee attribute in the script.