这是一个非常好的问题。答案要求一个可视化三维空间倾斜平面,垂直平面沿直线方向一致的利益,并跟踪我们的兴趣会使倾斜平面垂直的平面和倾斜平面相交。提供的地图上,我们可以很容易地确定两个地质单元,x和y,地形高程轮廓在400和300英尺,结构轮廓表示单位x, x单位联系单位y(单元的底部x, y)的单位,单位和底部y。假定单位w以上,和z下面,是无名的。北表示,毕业1000英尺范围内,在250英尺的分歧。使这个练习更容易我们需要以下- -起草直尺量角器工程师的规模(假设我们的地图规模成正比)——绘图铅笔(2或2 h) -乙烯基橡皮擦的灵敏度/修正起草刷有助于保持起草表面清洁的解释,在此,将使用和解释手工测量,过程将清楚。一块起草牛皮纸或描图纸放在我们的地图有时容易处理和纠正错误或注意计算。首先,*我们必须确定这些单位*的倾斜和罢工structure-contouring接触的表面。一个显而易见的选择是使用x和y之间的接触边界单元。请注意,这种接触穿过300英尺海拔地形等高线地图3位置。因此,接触的海拔高度是300英尺在这些位置。我们可以徒手草图轮廓* *结构通过这三个点,但他们足够接近被沿着一条直线,我们可以使用直尺素描在一个300英尺的轮廓线结构轮廓通过这些点。 The alignment of this contour is along the *strike* of the contact between units x and y. Take note of the compass alignment of this contour, *and take note of the compass alignment of our line of interest, A - A'.* The following were determined from the map: 1) alignment of A - A' is N 60 deg E (or S 60 deg W), and 2) alignment of 300 ft structure contour, N 75 deg E (or S 75 deg W). The dip of the x - y contact is to the northwest. In other words, the dip of the x - y contact is perpendicular to the northeast - southwest alignment of the strike. To continue, we note that the contact of interest crosses the 400 ft topographic elevation contour at 4 locations, all essentially in a linear alignment parallel to the 300 ft structure contour. We, therefore, use our straight edge to again sketch-in the parallel alignment of the 400 ft-elevation structure contour. The dip of this contact is determined by the arctan(rise/run), wherein the rise = 100 ft, run determined from the map distance between 400 and 300 ft contours = about 400 ft. Note the dip is to the *northwest,* or 14 deg at N 15 deg W. In other words, the dip is perpendicular to the strike, and by using the rise/run we have determined the dip angle is approximately 14 deg. Second, we take note of some simple 3-dimensional geometry related to the dip and strike of our contact of interest, and the direction of our line of interest. We are interested in knowing the apparent dip traced by of our line of interest on the x - y contact surface. The line of strike is a horizontal line that has no dip, and we know the rise and run used to determine the contact dip. Essentially, any line of strike (such as a *tangent* to a structure contour) defines a level line. The path of our line of interest is tilted against the contact surface. Imagine we are facing down-dip while standing on our line of interest where it crosses the 300 ft structure elevation contour. To the left, our line of interest can be seen tracing a path that is rising gently along the surface of the x - y contact; to the right descending gently along the contact surface. Consequently, from where we stand, we can scribe an imaginary circular arc on the contact surface that crosses our line of interest and the line of strike of our contact surface and immediately determine the apparent dip of the trace our line of interest on the contact surface. The radius of the circular arc will be the distance of the run used in determining the dip. A known fact: The line of dip on our contact is aligned down-elevation *perpendicular to the strike.* Consequently, the apparent *vertical rise (or fall)* of our line of interest *along the plane of the x - y contact* will be the sine of the angle between the line of interest and strike of the x - y contact **times** the known vertical rise (100 ft) of the contact dip. This gives an vertical rise (or fall) of about 26 ft. Taken along a run of 400 ft, the vertical angle is the arctan(26/400), or about 3.7 deg. Along our line of interest, the magnitude and direction of this apparent **dip** is 3.7 deg at N 60 deg E.
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