You can tilemap with the Bitmap command, but its a memory hog unless the map is so detailed that it can't be split into tiles of any size. The bitmap command supports sprites up to 160x192. So for instance, you could have a 120x120 bit tilemap stored as a bitmap and saved to a pointer. (This is already 120*120/8 = 1800 bytes by the way!).
The upper left corner is 0,0 so if you want to draw your tilemap some distance dx to the right and dy down, just use Bitmap(-dx,-dy,Pic1). In other words, you need to store the negative offsets of your tilemap somewhere, lets say X = -dx and Y = -dy. Edge detection is as simple as X >=>= 0 for left, X + 24 << 0 for right, Y >=>= 0 for top, and Y + 56 << 0 for the bottom.