Recover myself from Dilate and Erode for noise reduction
First of all, are you using gray-scale morphology?  If so, then I would threshold the map first, to get a binary image, and then apply binary morphology to fill in gaps and get rid of the noise.

Second, instead of erosion and dilation, try opening and closing, which are higher order morphological operations. Opening is erosion followed by dilation with the same structuring element.  Closing is dilation followed by erosion.  

A good thing to try is to do an opening to get rid of the noisy specks, and then do a closing to fill in the gaps.  This will simplify your process to three operations: threshold, open, close.  So you would only need to tune three parameters: the threshold and the two structuring elements.