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Program Manipulation

Manual correction of a trace. Scaling

If the quality of the scanned image is good enough, the recursive segment selection will may not be required, and well digitized trace may be formed during just one pass. On the contrary if the observed part of the seismogram is barely visible at the screen, or there are some empty intervals on the plot (fig. 5.1.a), the automated selection of segments cannot be made full enough

Defective part of seismogram and image after axis selection

In this cases the automatically created line will be drawn far from true function curve To overcome this shortage a user may apply a manual correction of the trace. For this goal one must activate the Set points mode and pick a number of points instead of pale part of line, so a new curve will be plotted through the new points. When the Set points button is pressed, the choice interpol button is highlighted and a user may set the mode of approximation: linear interpolation or square spline interpolation . Then he may start setting the points onto positions of the curve supposed

Setting must be performed from left to right. The initial point must be as close to existing curve as possible, and the last point must be on the drawn curve too. First, all points are connected by the straight lines. After all points are picked, a user has to set Edit trace mode to perform the approximation and then Refresh main window; after that a plot will be cleaned from the previous auxiliary lines

spline interpolation

linear interpolation

The final editing the trace may be performed in the Edit trace mode. In this mode one should move along the line, drawn before, with the small steps and make often clicking by the left mouse button. Every click causes the deviation of line to the pointed coordinates and spline approximation predecessor and consequent little parts of existing line

manual editing of line and resulting curve image

For more delicate approximation, a user may perform this job in enlarged scale mode. For this purpose one must press the Scale button and select the power of image zooming (as an integer power of two). The image will be immediately enlarged and the user should take some efforts to find an interesting fragment of the canvas in the graphic window After such correction of a trace, a user should return to ordinary scale (=1) and check the final result (fig. 5.7). On the figure, the edited part of the curve is enclosed into the small rectangular frame. This manual correction process may be repeated as many times as required. This enables the user to gradually improve the line to be saved

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