Added import of z0 for transmission line.

gprMax/input_cmds_multiuse.py

@@ -16,6 +16,7 @@
 # You should have received a copy of the GNU General Public License
 # along with gprMax.  If not, see <http://www.gnu.org/licenses/>.
 
+from gprMax.constants import z0
 from gprMax.exceptions import CmdInputError
 from gprMax.geometry_views import GeometryView
 from gprMax.materials import Material, PeplinskiSoil
@@ -265,7 +266,7 @@ def process_multicmds(multicmds, G):
                 raise CmdInputError("'" + cmdname + ': ' + ' '.join(tmp) + "'" + ' z-coordinate is not within the model domain')
             if positionx < G.pmlthickness[0] or positionx > G.nx - G.pmlthickness[3] or positiony < G.pmlthickness[1] or positiony > G.ny - G.pmlthickness[4] or positionz < G.pmlthickness[2] or positionz > G.nz - G.pmlthickness[5]:
                 print("WARNING: '" + cmdname + ': ' + ' '.join(tmp) + "'" + ' sources and receivers should not normally be positioned within the PML.')
-            if resistance <= 0 or resistance > 376.7:
+            if resistance <= 0 or resistance > z0:
                 raise CmdInputError("'" + cmdname + ': ' + ' '.join(tmp) + "'" + ' requires a resistance greater than zero and less than the impedance of free space, i.e. 376.73 Ohms')
                     
             # Check if there is a waveformID in the waveforms list