![]() ![]() Before trying to derive the conversion see if either of the systems have a built in conversion tool, this should be able to convert the data correctly. Thus converting from GSLIB to Vulcan is a simple matter of inverting the sign of the last angle. Vulcan also considers a 90 degree offset in the bearing as a consequence of labeling the X axis as the principal axis. For example, Vulcan considers the X axis to be the major axis, and the Euler angles rotate about the ZYX axes, with positive clockwise bearing, positive upwards plunge and a positive upwards dip. In some cases it may be simple to convert between conventions. ![]() Given the three different axes to rotate about, and the dozens of possible sequences, along with the different sign conventions, and even different principal axes, it can be difficult to convert between formats accurately. This is not the only convention out there. GSLIB considers the Y axis as the principal axis and the Euler angles rotate about the ZXY axes, with positive clockwise, positive upwards, and positive downwards. \left[ \begin = R^T\) which means that rotations may be reversed very easily by simply multiplying by the transpose. Which may be expressed in matrix notation as When orienting a new coordinate system any point \((x, y)\) may be transformed into a rotated point \((x', y')\) using the following equations: This angle is measured positive clockwise from the Y axis (North). In geologic modeling we generally consider the azimuth, or bearing, which is denoted \(\alpha\). A single angle may be used to describe the rotation. Orienting an object or coordinate system is substantially easier in 2D than in 3D. The underlying principles explained here will also allow for modelers to transform between different conventions. ![]() This lesson will use and explain the conventions behind the GSLIB (Deutsch
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