Fix target misfit

SimPEG/Directives.py

@@ -149,7 +149,7 @@ class TargetMisfit(InversionDirective):
     @property
     def target(self):
         if getattr(self, '_target', None) is None:
-            self._target = self.survey.nD
+            self._target = self.survey.nD*0.5
         return self._target
     @target.setter
     def target(self, val):

SimPEG/Maps.py

@@ -1,7 +1,7 @@
 import Utils, numpy as np, scipy.sparse as sp
 from Tests import checkDerivative
 from PropMaps import PropMap, Property
-
+from numpy.polynomial import polynomial
 
 class IdentityMap(object):
     """