Tile-by-tile movement

I just bought T2D yesterday, and I've gone through the basic tutorial and done some of the strategy
tutorial. Now I'm trying to figure out how to do tile-by-tile movement, as in a game like
X-Com or Ultima. I have a box moving around on the map I created in the strategy controller, but it
isn't aligned with the tiles. It's moving 4 units at a time in each direction, as I expect, but it's not
moving from tile center to tile center.

Here's my code to create the map:

function LoadWorldMap()
{
$tilesize = 4;
new ScriptObject(worldMap);
worldMap.map = new t2dTileMap(Map) { scenegraph = $strategyScene; };
worldMap.map.loadTileMap("~/data/tilemaps/worldMap.map");

worldMap.grassLayer = addLayer(worldMap.map, 0);
worldMap.grassOverLayer = addLayer(worldMap.map, 1);

}

function addLayer(%map, %num)
{
%layer = %map.getTileLayer( %num );
%layer.setPosition( "0 0" );
%layer.setTileSize( $tilesize SPC $tilesize );
%layer.setLayer(30);
%layer.setGroup(10);

return %layer;
}

Here's the code to intialize a player:

function CreatePlayer()
{
$player = new t2dStaticSprite() { scenegraph = $strategyScene; };
$player.setPosition("-2 -2");
$player.setSize($tilesize SPC $tilesize);
$player.setImageMap(boxImageMap);
$player.speed = 4*$tilesize;

...
}

And here's one of my move functions (bound to 'w'):

function moveUp(%obj)
{
if (%obj.moving)
return;

%obj.moving = true;
%obj.moveTo(%obj.getPositionX() SPC (%obj.getPositionY() - $tilesize), %obj.speed,
true, true, true, 0.01);
}

Can anyone help me figure out what I'm doing wrong?

Thanks,
Chris