What are these sets of three numbers in my Minecraft server log?

I'm referring to the floating-point-esque numbers in parentheses that appear after the entity ID, at the end of the lines indicating that a player has logged in:

2011-04-21 23:49:37 [INFO] burpen [/192.168.1.2:45001] logged in with entity id 120884 at (26.5, 118.62000000476837, 72.5)
2011-04-21 23:49:45 [INFO] burpen [/192.168.1.2:45006] logged in with entity id 121098 at (25.5, 118.62000000476837, 83.5)
2011-04-21 23:49:53 [INFO] burpen [/192.168.1.2:45013] logged in with entity id 121638 at (20.5, 72.62000000476837, 79.5)

I believe these started appearing after the 1.5 server update, or one of the updates since then. I initially thought they denoted player location at time of login, but they don't match up with the values shown when I press F3 immediately after logging in. Moreover, the numbers change even when the player doesn't move (the three example lines were generated by standing in the same spot and repeatedly logging in/out).

I realize they might be part of some internal testing at Mojang that was left in for the most recent update(s), and in that case, they might not be terribly important. But if otherwise, I'm curious to see if anyone knows what these are.

Those are absolutely player coordinates — the .62 in the middle (y) coordinate is a dead giveaway. If you check your position using F3 while standing on any full block, you'll see your y coordinate always ends in .62000… (or occasionally .619999…). This is because the player's coordinates are reported from the "eyes" — the point where the camera sits in first-person view. A player's eyes are 1.62 blocks/meters above the ground.

Now, as to why they aren't accurate, I couldn't say. My best guess is that it's related to the "spawn radius" in SMP. When you die (or log in for the first time), you don't spawn at a fixed point in the world; there is about a chunk-sized area in which you can appear. It's possible that, when a returning player is added to the world, they are either initially placed in the spawn zone before being moved to their real location, or alternatively that the spawn radius is applied to their entry coordinates and reported in the log, but discarded before the player fully enters the world.

Update: A bugfix listed in Notch's blog post on the changes coming in 1.6 supports this theory:

• Fixed players spawning in the wrong location and quickly lerping to the correct location

("Lerping" refers to linear interpolation, the type of math which controls player movement.)