diff --git a/gprMax/cmds_multiple.py b/gprMax/cmds_multiple.py
index e68097c6..eb14b284 100644
--- a/gprMax/cmds_multiple.py
+++ b/gprMax/cmds_multiple.py
@@ -53,7 +53,7 @@ class UserObjectMulti:
     def __str__(self):
         """Readable user string as per hash commands."""
         s = ''
-        for k, v in self.kwargs.items():
+        for _, v in self.kwargs.items():
             if isinstance(v, tuple) or isinstance(v, list):
                 v = ' '.join([str(el) for el in v])
             s += str(v) + ' '
diff --git a/gprMax/fractals.py b/gprMax/fractals.py
index 14fee38b..d6956de1 100644
--- a/gprMax/fractals.py
+++ b/gprMax/fractals.py
@@ -130,6 +130,12 @@ class FractalVolume:
         self.nx = xf - xs
         self.ny = yf - ys
         self.nz = zf - zs
+        self.originalxs = xs
+        self.originalxf = xf
+        self.originalys = ys
+        self.originalyf = yf
+        self.originalzs = zs
+        self.originalzf = zf
         self.averaging = False
         self.seed = None
         self.dimension = dimension
diff --git a/gprMax/gprMax.py b/gprMax/gprMax.py
index 76bbcc7e..54b4f642 100644
--- a/gprMax/gprMax.py
+++ b/gprMax/gprMax.py
@@ -25,7 +25,7 @@ from .contexts import Context, MPIContext
 from .utilities import setup_logging
 
 logger = logging.getLogger(__name__)
-setup_logging(level=25)
+setup_logging(level=20)
 
 def run(
     scenes=None,
diff --git a/gprMax/subgrids/base.py b/gprMax/subgrids/base.py
index 3728a580..948c04d6 100644
--- a/gprMax/subgrids/base.py
+++ b/gprMax/subgrids/base.py
@@ -16,11 +16,13 @@
 # You should have received a copy of the GNU General Public License
 # along with gprMax.  If not, see <http://www.gnu.org/licenses/>.
 
+import logging
 import numpy as np
-from scipy.constants import c
 
 from ..grid import FDTDGrid
 
+logger = logging.getLogger(__name__)
+
 
 class SubGridBase(FDTDGrid):
 
@@ -65,6 +67,7 @@ class SubGridBase(FDTDGrid):
 
     def main_grid_index_to_subgrid_index(self, i, j, k):
         """Calculate local subgrid index from global main grid index."""
+        logger.debug('SubGridBase has no i0, j0, k0 members.')
         i_s = self.n_boundary_cells_x + (i - self.i0) * self.ratio
         j_s = self.n_boundary_cells_y + (j - self.j0) * self.ratio
         k_s = self.n_boundary_cells_z + (k - self.k0) * self.ratio
diff --git a/gprMax/subgrids/multi.py b/gprMax/subgrids/multi.py
index ace79cce..8a5cfb05 100644
--- a/gprMax/subgrids/multi.py
+++ b/gprMax/subgrids/multi.py
@@ -16,8 +16,12 @@
 # You should have received a copy of the GNU General Public License
 # along with gprMax.  If not, see <http://www.gnu.org/licenses/>.
 
+import logging
+
 from ..receivers import Rx
 
+logger = logging.getLogger(__name__)
+
 
 class ReferenceRx(Rx):
     """Receiver that mimicks a receiver in coarse grid.
@@ -27,6 +31,8 @@ class ReferenceRx(Rx):
         position as the coarse grid.
     """
 
+    logger.debug('ReferenceRx has no offset member.')
+
     def get_field(self, str_id, field):
         """Return the field value at the equivalent coarse yee cell.
 
diff --git a/gprMax/subgrids/precursor_nodes.py b/gprMax/subgrids/precursor_nodes.py
index 5d19241c..43a6c0d1 100644
--- a/gprMax/subgrids/precursor_nodes.py
+++ b/gprMax/subgrids/precursor_nodes.py
@@ -16,11 +16,12 @@
 # You should have received a copy of the GNU General Public License
 # along with gprMax.  If not, see <http://www.gnu.org/licenses/>.
 
-import sys
-
+import logging
 import numpy as np
 from scipy import interpolate
 
+logger = logging.getLogger(__name__)
+
 
 def calculate_weighting_coefficients(x1, x):
     c1 = (x - x1) / x
@@ -28,7 +29,7 @@ def calculate_weighting_coefficients(x1, x):
     return (c1, c2)
 
 
-class PrecusorNodesBase:
+class PrecursorNodesBase:
 
     def __init__(self, fdtd_grid, sub_grid):
         self.G = fdtd_grid
@@ -66,7 +67,6 @@ class PrecusorNodesBase:
         self.initialize_magnetic_slices_array()
         self.initialize_electric_slices_array()
 
-
     def _initialize_fields(self):
 
         # Initialise the precursor arrays
@@ -276,7 +276,7 @@ class PrecusorNodesBase:
             setattr(self, obj[0], f)
 
 
-class PrecursorNodes(PrecusorNodesBase):
+class PrecursorNodes(PrecursorNodesBase):
 
     def __init__(self, fdtd_grid, sub_grid):
         super().__init__(fdtd_grid, sub_grid)
@@ -402,7 +402,7 @@ class PrecursorNodes(PrecusorNodesBase):
         return f_1, f_2
 
 
-class PrecursorNodesFiltered(PrecusorNodesBase):
+class PrecursorNodesFiltered(PrecursorNodesBase):
 
     def __init__(self, fdtd_grid, sub_grid):
         super().__init__(fdtd_grid, sub_grid)
diff --git a/gprMax/utilities.py b/gprMax/utilities.py
index 180f248e..68341386 100644
--- a/gprMax/utilities.py
+++ b/gprMax/utilities.py
@@ -324,10 +324,7 @@ def get_host_info():
             pass
 
         # Hyperthreading
-        if threadspercore == 2:
-            hyperthreading = True
-        else:
-            hyperthreading = False
+        hyperthreading = True if threadspercore == 2 else False
 
         # OS version
         osversion = platform.platform()
@@ -341,14 +338,17 @@ def get_host_info():
     hostinfo['osversion'] = osversion
     hostinfo['hyperthreading'] = hyperthreading
     hostinfo['logicalcores'] = psutil.cpu_count()
+
     try:
         # Get number of physical CPU cores, i.e. avoid hyperthreading with OpenMP
         hostinfo['physicalcores'] = psutil.cpu_count(logical=False)
     except ValueError:
         hostinfo['physicalcores'] = hostinfo['logicalcores']
+
     # Handle case where cpu_count returns None on some machines
     if not hostinfo['physicalcores']:
         hostinfo['physicalcores'] = hostinfo['logicalcores']
+
     hostinfo['ram'] = psutil.virtual_memory().total
     hostinfo['ompthreads'] = 1
 
@@ -366,13 +366,17 @@ def set_omp_threads(nthreads=None):
         # Should waiting threads consume CPU power (can drastically effect
         # performance)
         os.environ['OMP_WAIT_POLICY'] = 'ACTIVE'
+
     # Number of threads may be adjusted by the run time environment to best
     # utilize system resources
     os.environ['OMP_DYNAMIC'] = 'FALSE'
+
     # Each place corresponds to a single core (having one or more hardware threads)
     os.environ['OMP_PLACES'] = 'cores'
+
     # Bind threads to physical cores
     os.environ['OMP_PROC_BIND'] = 'TRUE'
+
     # Prints OMP version and environment variables (useful for debug)
     # os.environ['OMP_DISPLAY_ENV'] = 'TRUE'
 
@@ -531,27 +535,7 @@ def detect_gpus():
     return gpus
 
 
-# def check_gpus(gpus):
-#     """Check if requested Nvidia GPU(s) deviceID(s) exist.
-
-#     Args:
-#         gpus (list): List of GPU object(s).
-#     """
-
-#     # Check if requested device ID(s) exist
-#     for ID in deviceIDs:
-#         if ID not in deviceIDsavail:
-#             raise GeneralError(f'GPU with device ID {ID} does not exist')
-
-#     # Gather information about selected/detected GPUs
-#     gpus = []
-#     for ID in deviceIDsavail:
-#         gpu = GPU(deviceID=ID)
-#         gpu.get_gpu_info(drv)
-#         gpus.append(gpu)
-
-
 def timer():
     """Function to return time in fractional seconds."""
-    logger.debug('"thread_time" not currently available in macOS and bug (https://bugs.python.org/issue36205) with "process_time"')
+    logger.debug('"thread_time" not currently available in macOS and bug (https://bugs.python.org/issue36205) with "process_time", so use "perf_counter".')
     return timer_fn()