name change

pylot/core/active/seismicArrayPreparation.py

@@ -0,0 +1,665 @@
+import sys
+import numpy as np
+from scipy.interpolate import griddata
+
+class SeisArray(object):
+    '''
+    Can be used to interpolate missing values of a receiver grid, if only support points were measured.
+    Input file should contain in each line: ('traceID' 'receiverLineID' 'number of the geophone on recLine'  'X'  'Y'  'Z')
+
+    Can be used to generate a velocity grid file (vgrids.in) for FMTOMO with a topography adapting gradient.
+
+    Can be used to generate an interface file for FMTOMO (right now only interface.z used by grid3dg) for the topography.
+
+    Supports vtk output for sources and receivers.
+    Note: Source and Receiver files for FMTOMO will be generated by the Survey object (because traveltimes will be added directly).
+    '''
+    def __init__(self, recfile):
+        self._receiverlines = {}
+        self._receiverCoords = {}
+        self._measuredReceivers = {}
+        self._measuredTopo = {}
+        self._sourceLocs = {}
+        self._geophoneNumbers = {}
+        self._receiverlist = open(recfile, 'r').readlines()
+        self._generateReceiverlines()
+        self._setReceiverCoords()
+        self._setGeophoneNumbers()
+
+    def _generateReceiverlines(self):
+        '''
+        Connects the traceIDs to the lineIDs 
+        for each receiverline in a dictionary.
+        '''
+        for receiver in self._receiverlist:
+            traceID = int(receiver.split()[0]) 
+            lineID =  int(receiver.split()[1]) 
+            if not lineID in self._receiverlines.keys():
+                self._receiverlines[lineID] = []
+            self._receiverlines[lineID].append(traceID)
+
+    def _setReceiverCoords(self):
+        '''
+        Fills the three x, y, z dictionaries with measured coordinates
+        '''
+        for line in self._getReceiverlist():
+            traceID = int(line.split()[0]) 
+            x = float(line.split()[3]) 
+            y = float(line.split()[4]) 
+            z = float(line.split()[5]) 
+            self._receiverCoords[traceID] = (x, y, z)
+            self._measuredReceivers[traceID] = (x, y, z)
+
+    def _setGeophoneNumbers(self):
+        for line in self._getReceiverlist():
+            traceID = int(line.split()[0]) 
+            gphoneNum = float(line.split()[2])
+            self._geophoneNumbers[traceID] = gphoneNum
+
+    def _getReceiverlines(self):
+        return self._receiverlines
+
+    def _getReceiverlist(self):
+        return self._receiverlist
+
+    def getReceiverCoordinates(self):
+        return self._receiverCoords
+
+    def _getXreceiver(self, traceID):
+        return self._receiverCoords[traceID][0]
+
+    def _getYreceiver(self, traceID):
+        return self._receiverCoords[traceID][1]
+
+    def _getZreceiver(self, traceID):
+        return self._receiverCoords[traceID][2]
+
+    def _getXshot(self, shotnumber):
+        return self._sourceLocs[shotnumber][0]
+
+    def _getYshot(self, shotnumber):
+        return self._sourceLocs[shotnumber][1]
+
+    def _getZshot(self, shotnumber):
+        return self._sourceLocs[shotnumber][2]
+
+    def _getReceiverValue(self, traceID, coordinate):
+        setCoordinate = {'X': self._getXreceiver,
+                         'Y': self._getYreceiver,
+                         'Z': self._getZreceiver}
+        return setCoordinate[coordinate](traceID)
+
+    def _getGeophoneNumber(self, traceID):
+        return self._geophoneNumbers[traceID]
+
+    def getMeasuredReceivers(self):
+        return self._measuredReceivers 
+
+    def getMeasuredTopo(self):
+        return self._measuredTopo
+
+    def getSourceLocations(self):
+        return self._sourceLocs
+
+    def _setXvalue(self, traceID, value):
+        self._checkKey(traceID)
+        self._receiverCoords[traceID][0] = value
+
+    def _setYvalue(self, traceID, value):
+        self._checkKey(traceID)
+        self._receiverCoords[traceID][1] = value
+
+    def _setZvalue(self, traceID, value):
+        self._checkKey(traceID)
+        self._receiverCoords[traceID][2] = value
+
+    def _setValue(self, traceID, coordinate, value):
+        setCoordinate = {'X': self._setXvalue,
+                         'Y': self._setYvalue,
+                         'Z': self._setZvalue}
+        setCoordinate[coordinate](traceID, value)
+
+    def _checkKey(self, traceID):
+        if not traceID in self._receiverCoords.keys():
+            self._receiverCoords[traceID] = [None, None, None]
+
+    def _checkTraceIDdirection(self, traceID1, traceID2):
+        if traceID2 > traceID1:
+            direction = +1
+            return direction
+        if traceID2 < traceID1:
+            direction = -1
+            return direction
+        print "Error: Same Value for traceID1 = %s and traceID2 = %s" %(traceID1, traceID2)
+
+    def _checkCoordDirection(self, traceID1, traceID2, coordinate):
+        '''
+        Checks whether the interpolation direction is positive or negative
+        '''
+        if self._getReceiverValue(traceID1, coordinate) < self._getReceiverValue(traceID2, coordinate):
+            direction = +1
+            return direction
+        if self._getReceiverValue(traceID1, coordinate) > self._getReceiverValue(traceID2, coordinate): 
+            direction = -1
+            return direction
+        print "Error: Same Value for traceID1 = %s and traceID2 = %s" %(traceID1, traceID2)
+                        
+    def _interpolateMeanDistances(self, traceID1, traceID2, coordinate):
+        '''
+        Returns the mean distance between two traceID's depending on the number of geophones in between
+        '''
+        num_spaces = abs(self._getGeophoneNumber(traceID1) - self._getGeophoneNumber(traceID2))
+        mean_distance =  abs(self._getReceiverValue(traceID1, coordinate) - self._getReceiverValue(traceID2, coordinate))/num_spaces
+        return mean_distance
+
+    def interpolateValues(self, coordinate):
+        '''
+        Interpolates and sets all values (linear) for coordinate = 'X', 'Y' or 'Z'
+        '''
+        for lineID in self._getReceiverlines().keys():
+                number_measured = len(self._getReceiverlines()[lineID])
+                for index, traceID1 in enumerate(self._getReceiverlines()[lineID]):
+                    if index + 1 < number_measured:
+                        traceID2 = self._getReceiverlines()[lineID][index + 1]
+
+                        traceID_dir = self._checkTraceIDdirection(traceID1, traceID2)
+                        traceID_interp = traceID1 + traceID_dir
+
+                        coord_dir = self._checkCoordDirection(traceID1, traceID2, coordinate)
+                        mean_distance = self._interpolateMeanDistances(traceID1, traceID2, coordinate)
+
+                        while (traceID_dir * traceID_interp) < (traceID_dir * traceID2):
+                            self._setValue(traceID_interp, coordinate,
+                                          (self._getReceiverValue(traceID_interp - traceID_dir, coordinate)
+                                           + coord_dir * (mean_distance)))
+                            traceID_interp += traceID_dir
+
+    def addMeasuredTopographyPoints(self, filename):
+        '''
+        Use more measured points for a higher precision of height interpolation.
+        Input file should contain in each line: ('point ID'  'X'  'Y'  'Z')
+        '''
+        topolist = open(filename, 'r').readlines()
+        for line in topolist:
+            line = line.split()
+            pointID = int(line[0])
+            x = float(line[1])
+            y = float(line[2])
+            z = float(line[3])
+            self._measuredTopo[pointID] = (x, y, z)        
+
+    def addSourceLocations(self, filename):
+        '''
+        Use source locations for a higher precision of height interpolation.
+        Input file should contain in each line: ('point ID'  'X'  'Y'  'Z')
+
+        Source locations must be added before they can be written to vtk files.
+        '''
+        topolist = open(filename, 'r').readlines()
+        for line in topolist:
+            line = line.split()
+            pointID = int(line[0])
+            x = float(line[1])
+            y = float(line[2])
+            z = float(line[3])
+            self._sourceLocs[pointID] = (x, y, z)        
+
+    def interpZcoords4rec(self, method = 'linear'):
+        '''
+        Interpolates z values for all receivers.
+        '''
+        measured_x, measured_y, measured_z = self.getAllMeasuredPointsLists()
+
+        for traceID in self.getReceiverCoordinates().keys():
+            if type(self.getReceiverCoordinates()[traceID]) is not tuple:
+                z = griddata((measured_x, measured_y), measured_z, (self._getXreceiver(traceID), self._getYreceiver(traceID)), method = method)
+                self._setZvalue(traceID, float(z))
+
+    def _getAngle(self, distance):
+        '''
+        Function returns the angle on a Sphere of the radius R = 6371 [km] for a distance [km].
+        '''
+        PI = np.pi
+        R = 6371.
+        angle = distance * 180 / (PI * R)
+        return angle
+
+    def _getDistance(self, angle):
+        '''
+        Function returns the distance [km] on a Sphere of the radius R = 6371 [km] for an angle.
+        '''
+        PI = np.pi
+        R = 6371.
+        distance = angle / 180 * (PI * R)
+        return distance
+
+    def getMeasuredReceiverLists(self):
+        '''
+        Returns a list of all measured receivers known to SeisArray.
+        '''
+        x = []; y = []; z = []
+        for traceID in self.getMeasuredReceivers().keys():
+            x.append(self.getMeasuredReceivers()[traceID][0])        
+            y.append(self.getMeasuredReceivers()[traceID][1])
+            z.append(self.getMeasuredReceivers()[traceID][2])        
+        return x, y, z
+
+    def getMeasuredTopoLists(self):
+        '''
+        Returns a list of all measured topography points known to the SeisArray.
+        '''
+        x = []; y = []; z = []
+        for pointID in self.getMeasuredTopo().keys():
+            x.append(self.getMeasuredTopo()[pointID][0])        
+            y.append(self.getMeasuredTopo()[pointID][1])
+            z.append(self.getMeasuredTopo()[pointID][2])        
+        return x, y, z
+
+    def getSourceLocsLists(self):
+        '''
+        Returns a list of all measured source locations known to SeisArray.
+        '''
+        x = []; y = []; z = []
+        for pointID in self.getSourceLocations().keys():
+            x.append(self.getSourceLocations()[pointID][0])        
+            y.append(self.getSourceLocations()[pointID][1])
+            z.append(self.getSourceLocations()[pointID][2])        
+        return x, y, z
+
+    def getAllMeasuredPointsLists(self):
+        '''
+        Returns a list of all measured points known to SeisArray.
+        '''
+        mtopo_x, mtopo_y, mtopo_z = self.getMeasuredTopoLists()
+        msource_x, msource_y, msource_z = self.getSourceLocsLists()
+        mrec_x, mrec_y, mrec_z = self.getMeasuredReceiverLists()
+
+        x = mtopo_x + mrec_x + msource_x
+        y = mtopo_y + mrec_y + msource_y
+        z = mtopo_z + mrec_z + msource_z
+        return x, y, z
+
+    def getReceiverLists(self):
+        '''
+        Returns a list of all receivers (measured and interpolated).
+        '''
+        x = []; y =[]; z = []
+        for traceID in self.getReceiverCoordinates().keys():
+            x.append(self.getReceiverCoordinates()[traceID][0])
+            y.append(self.getReceiverCoordinates()[traceID][1])
+            z.append(self.getReceiverCoordinates()[traceID][2])
+        return x, y, z
+       
+    def _interpolateXY4rec(self):
+        '''
+        Interpolates the X and Y coordinates for all receivers.
+        '''
+        for coordinate in ('X', 'Y'):
+            self.interpolateValues(coordinate)
+
+    def interpolateAll(self):
+        self._interpolateXY4rec()
+        self.interpZcoords4rec()
+
+    def interpolateTopography(self, nTheta, nPhi, thetaSN, phiWE, method = 'linear', filename = 'interface1.in'):
+        '''
+        Interpolate Z values on a regular grid with cushion nodes to use it as FMTOMO topography interface.
+        Returns a surface in form of a list of points [[x1, y1, z1], [x2, y2, y2], ...] (cartesian).
+
+        :param: nTheta, number of points in theta (NS)
+        type: integer
+
+        :param: nPhi, number of points in phi (WE)
+        type: integer
+
+        :param: thetaSN (S, N) extensions of the model in degree
+        type: tuple
+
+        :param: phiWE (W, E) extensions of the model in degree
+        type: tuple
+        '''                                       
+
+        surface = []
+        elevation = 0.25 # elevate topography so that no source lies above the surface
+
+        if filename is not None:
+            outfile = open(filename, 'w')
+
+        print "Interpolating topography on regular grid with the dimensions:"
+        print "nTheta = %s, nPhi = %s, thetaSN = %s, phiWE = %s"%(nTheta, nPhi, thetaSN, phiWE)
+        print "method = %s, filename = %s" %(method, filename)
+
+        thetaS, thetaN = thetaSN
+        phiW, phiE = phiWE
+
+        measured_x, measured_y, measured_z = self.getAllMeasuredPointsLists()
+
+        # need to determine the delta to add two cushion nodes around the min/max values
+        thetaDelta = (thetaN - thetaS) / (nTheta - 1)
+        phiDelta = (phiE - phiW) / (nPhi - 1)
+
+        thetaGrid = np.linspace(thetaS - thetaDelta, thetaN + thetaDelta, num = nTheta + 2) # +2 cushion nodes
+        phiGrid = np.linspace(phiW - phiDelta, phiE + phiDelta, num = nPhi + 2) # +2 cushion nodes
+
+        nTotal = len(thetaGrid) * len(phiGrid); count = 0
+        for theta in thetaGrid:
+            for phi in phiGrid:
+                xval = self._getDistance(phi)
+                yval = self._getDistance(theta)
+                z = griddata((measured_x, measured_y), measured_z, (xval, yval), method = method)
+                # in case the point lies outside, nan will be returned. Find nearest:
+                if np.isnan(z) == True:
+                    z = griddata((measured_x, measured_y), measured_z, (xval, yval), method = 'nearest')
+                z = float(z)
+                surface.append((xval, yval, z))
+                count += 1
+                progress = float(count) / float(nTotal) * 100
+                self._update_progress(progress)
+
+                if filename is not None: 
+                    outfile.writelines('%10s\n'%(z + elevation))
+                
+        return surface
+
+    def generateVgrid(self, nTheta = 80, nPhi = 80, nR = 120,
+                      thetaSN = (-0.2, 1.2), phiWE = (-0.2, 1.2),
+                      Rbt = (-62.0, 6.0), vbot = 5.5, filename = 'vgrids.in',
+                      method = 'linear' ):
+        '''
+        Generate a velocity grid for fmtomo regarding topography with a linear gradient starting at the topography with 0.34 [km/s].
+
+        :param: nTheta, number of points in theta (NS)
+        type: integer
+
+        :param: nPhi, number of points in phi (WE)
+        type: integer
+
+        :param: nR, number of points in depth
+        type: integer
+
+        :param: thetaSN (S, N) extensions of the model in degree
+        type: tuple
+
+        :param: phiWE (W, E) extensions of the model in degree
+        type: tuple
+
+        :param: Rbt (bot, top) extensions of the model in km
+        type: tuple
+
+        :param: vbot, velocity at the bottom of the model
+        type: real
+        '''
+
+        def getRad(angle):
+            PI = np.pi
+            rad = angle / 180 * PI
+            return rad
+
+        def getZmax(surface):
+            z = []
+            for point in surface:
+                z.append(point[2])
+            return max(z)
+
+        R = 6371
+        vmin = 0.34
+        decm = 0.3 # diagonal elements of the covariance matrix (grid3dg's default value is 0.3)
+        outfile = open(filename, 'w')
+
+        thetaS, thetaN = thetaSN
+        phiW, phiE = phiWE
+        rbot = Rbt[0] + R
+        rtop = Rbt[1] + R
+
+        # need to determine the delta to add two cushion nodes around the min/max values
+        thetaDelta = abs(thetaN - thetaS) / (nTheta - 1)
+        phiDelta = abs(phiE - phiW) / (nPhi - 1)
+        rDelta = abs(rbot - rtop) / (nR - 1)
+        
+        # create a regular grid including +2 cushion nodes in every direction
+        thetaGrid = np.linspace(thetaS - thetaDelta, thetaN + thetaDelta, num = nTheta + 2) # +2 cushion nodes
+        phiGrid = np.linspace(phiW - phiDelta, phiE + phiDelta, num = nPhi + 2) # +2 cushion nodes
+        rGrid = np.linspace(rbot - rDelta, rtop + rDelta, num = nR + 2) # +2 cushion nodes
+
+        nTotal = len(rGrid) * len(thetaGrid) * len(phiGrid)
+        print "Total number of grid nodes: %s"%nTotal
+
+        # write header for velocity grid file (in RADIANS)
+        outfile.writelines('%10s %10s \n' %(1, 1))
+        outfile.writelines('%10s %10s %10s\n' %(nR + 2, nTheta + 2, nPhi + 2))
+        outfile.writelines('%10s %10s %10s\n' %(rDelta, getRad(thetaDelta), getRad(phiDelta)))
+        outfile.writelines('%10s %10s %10s\n' %(rbot - rDelta, getRad(thetaS - thetaDelta), getRad(phiW - phiDelta)))
+
+        surface = self.interpolateTopography(nTheta, nPhi, thetaSN, phiWE, method = method, filename = None)
+        zmax = getZmax(surface)
+
+        print "\nGenerating velocity grid for FMTOMO. Output filename = %s, interpolation method = %s"%(filename, method)
+        print "nTheta = %s, nPhi = %s, nR = %s, thetaSN = %s, phiWE = %s, Rbt = %s"%(nTheta, nPhi, nR, thetaSN, phiWE, Rbt)
+        count = 0
+        for radius in rGrid:
+            for theta in thetaGrid:
+                for phi in phiGrid:
+                    xval = self._getDistance(phi)
+                    yval = self._getDistance(theta)
+                    for point in surface:
+                        if point[0] == xval and point[1] == yval:
+                            z = point[2]
+                    if radius > (R + z + 1):
+                        vel = 0.0
+                    # elif radius > (R + z - 15): ########### TESTING
+                    #     vel = (radius - z - R) / (Rbt[0] - rDelta - zmax) * 1.0 + vmin     ##########################
+                    else:
+                        vel = (radius - z - R) / (Rbt[0] - rDelta - zmax) * vbot + vmin     ##########################
+                    count += 1
+                    outfile.writelines('%10s %10s\n'%(vel, decm))
+
+                    progress = float(count) / float(nTotal) * 100
+                    self._update_progress(progress)
+                    
+        outfile.close()
+
+    def exportAll(self, filename = 'interpolated_receivers.out'):
+        recfile_out = open(filename, 'w')
+        count = 0
+        for traceID in self.getReceiverCoordinates().keys():
+            count += 1
+            x, y, z = self.getReceiverCoordinates()[traceID] 
+            recfile_out.writelines('%5s %15s %15s %15s\n' %(traceID, x, y, z))
+        print "Exported coordinates for %s traces to file > %s" %(count, filename)
+        recfile_out.close()
+
+    def plotArray2D(self, plot_topo = False, highlight_measured = False, annotations = True):
+        import matplotlib.pyplot as plt
+        plt.interactive(True)
+        plt.figure()
+        xmt, ymt, zmt = self.getMeasuredTopoLists() 
+        xsc, ysc, zsc = self.getSourceLocsLists()
+        xmr, ymr, zmr = self.getMeasuredReceiverLists() 
+        xrc, yrc, zrc = self.getReceiverLists() 
+
+        plt.plot(xrc, yrc, 'k.', markersize = 10, label = 'all receivers')
+        plt.plot(xsc, ysc, 'b*', markersize = 10, label = 'shot locations')
+
+        if plot_topo == True: 
+            plt.plot(xmt, ymt, 'b', markersize = 10, label = 'measured topo points')
+        if highlight_measured == True:
+            plt.plot(xmr, ymr, 'ro', label = 'measured receivers')
+
+        plt.xlabel('X [m]')
+        plt.ylabel('Y [m]')
+        plt.legend()
+        if annotations == True:
+            for traceID in self.getReceiverCoordinates().keys():
+                plt.annotate(str(traceID), xy = (self._getXreceiver(traceID), self._getYreceiver(traceID)), fontsize = 'x-small')
+
+    def plotArray3D(self, ax = None):
+        import matplotlib.pyplot as plt
+        from mpl_toolkits.mplot3d import Axes3D
+        plt.interactive(True)
+
+        if ax == None:
+            fig = plt.figure()
+            ax = plt.axes(projection = '3d')
+
+        xmt, ymt, zmt = self.getMeasuredTopoLists() 
+        xmr, ymr, zmr = self.getMeasuredReceiverLists() 
+        xin, yin, zin = self.getReceiverLists() 
+
+        ax.plot(xmt, ymt, zmt, 'b*', markersize = 10, label = 'measured topo points')
+        ax.plot(xin, yin, zin, 'k.', markersize = 10, label = 'interpolated receivers')
+        ax.plot(xmr, ymr, zmr, 'ro', label = 'measured receivers')
+        ax.set_xlabel('X'); ax.set_ylabel('Y'); ax.set_zlabel('elevation')
+        ax.legend()
+
+        return ax
+            
+        
+    def plotSurface3D(self, ax = None, step = 0.5, method = 'linear'):
+        from matplotlib import cm
+        import matplotlib.pyplot as plt
+        from mpl_toolkits.mplot3d import Axes3D
+        plt.interactive(True)
+
+        if ax == None:
+            fig = plt.figure()
+            ax = plt.axes(projection = '3d')
+
+        xmt, ymt, zmt = self.getMeasuredTopoLists()
+        xmr, ymr, zmr = self.getMeasuredReceiverLists()
+
+        x = xmt + xmr
+        y = ymt + ymr
+        z = zmt + zmr
+
+        xaxis = np.arange(min(x)+1, max(x), step)
+        yaxis = np.arange(min(y)+1, max(y), step)
+
+        xgrid, ygrid = np.meshgrid(xaxis, yaxis)
+
+        zgrid = griddata((x, y), z, (xgrid, ygrid), method = method)
+
+        ax.plot_surface(xgrid, ygrid, zgrid, linewidth = 0, cmap = cm.jet, vmin = min(z), vmax = max(z))
+
+        ax.set_zlim(-(max(x) - min(x)/2),(max(x) - min(x)/2))
+        ax.set_aspect('equal')
+
+        ax.set_xlabel('X'); ax.set_ylabel('Y'); ax.set_zlabel('elevation')
+        ax.legend()
+
+        return ax
+
+    def _update_progress(self, progress):
+        sys.stdout.write("%d%% done   \r" % (progress) )
+        sys.stdout.flush()
+
+    def receivers2VTK(self, filename = 'receivers.vtk'):
+        '''
+        Generates vtk files from all receivers of the SeisArray object.
+        '''
+        outfile = open(filename, 'w')
+        traceIDs = []
+
+        for traceID in self.getReceiverCoordinates():
+            traceIDs.append(traceID)
+
+        nPoints = len(traceIDs)
+
+        # write header
+        print("Writing header for VTK file...")
+        outfile.writelines('# vtk DataFile Version 3.1\n')
+        outfile.writelines('Receivers with traceIDs\n')
+        outfile.writelines('ASCII\n')
+        outfile.writelines('DATASET POLYDATA\n')
+        outfile.writelines('POINTS %15d float\n' %(nPoints))
+
+        # write coordinates
+        print("Writing coordinates to VTK file...")
+        for traceID in traceIDs:
+            x = self._getXreceiver(traceID)
+            y = self._getYreceiver(traceID)
+            z = self._getZreceiver(traceID)
+
+            outfile.writelines('%10f %10f %10f \n' %(x, y, z))
+
+        outfile.writelines('VERTICES %15d %15d\n' %(nPoints, 2 * nPoints))
+
+        # write indices
+        print("Writing indices to VTK file...")
+        for index in range(nPoints):
+            outfile.writelines('%10d %10d\n' %(1, index))
+
+        outfile.writelines('POINT_DATA %15d\n' %(nPoints))
+        outfile.writelines('SCALARS traceIDs int %d\n' %(1))
+        outfile.writelines('LOOKUP_TABLE default\n')
+
+        # write traceIDs
+        print("Writing traceIDs to VTK file...")
+        for traceID in traceIDs:
+            outfile.writelines('%10d\n' %traceID)
+
+        outfile.close()
+        print("Wrote receiver grid for %d points to file: %s" %(nPoints, filename))
+        return
+
+    def sources2VTK(self, filename = 'sources.vtk'):
+        '''
+        Generates vtk-files for all source locations in the SeisArray object.
+        '''
+        outfile = open(filename, 'w')
+        shotnumbers = []
+
+        for shotnumber in self.getSourceLocations():
+            shotnumbers.append(shotnumber)
+
+        nPoints = len(shotnumbers)
+
+        # write header
+        print("Writing header for VTK file...")
+        outfile.writelines('# vtk DataFile Version 3.1\n')
+        outfile.writelines('Shots with shotnumbers\n')
+        outfile.writelines('ASCII\n')
+        outfile.writelines('DATASET POLYDATA\n')
+        outfile.writelines('POINTS %15d float\n' %(nPoints))
+
+        # write coordinates
+        print("Writing coordinates to VTK file...")
+        for shotnumber in shotnumbers:
+            x = self._getXshot(shotnumber)
+            y = self._getYshot(shotnumber)
+            z = self._getZshot(shotnumber)
+
+            outfile.writelines('%10f %10f %10f \n' %(x, y, z))
+
+        outfile.writelines('VERTICES %15d %15d\n' %(nPoints, 2 * nPoints))
+
+        # write indices
+        print("Writing indices to VTK file...")
+        for index in range(nPoints):
+            outfile.writelines('%10d %10d\n' %(1, index))
+
+        outfile.writelines('POINT_DATA %15d\n' %(nPoints))
+        outfile.writelines('SCALARS shotnumbers int %d\n' %(1))
+        outfile.writelines('LOOKUP_TABLE default\n')
+
+        # write shotnumber
+        print("Writing shotnumbers to VTK file...")
+        for shotnumber in shotnumbers:
+            outfile.writelines('%10d\n' %shotnumber)
+
+        outfile.close()
+        print("Wrote receiver grid for %d points to file: %s" %(nPoints, filename))
+        return
+
+
+    def saveSeisArray(self, filename = 'seisArray.pickle'):
+        import cPickle
+        outfile = open(filename, 'wb')
+
+        cPickle.dump(self, outfile, -1)
+        print('saved SeisArray to file %s'%(filename))
+        
+    @staticmethod    
+    def from_pickle(filename):
+        import cPickle
+        infile = open(filename, 'rb')
+        return cPickle.load(infile)