If the two persons have the same height, intersect the other person's eyes with the black line on the sighting window. The "line" either is the horizontal projection of an inclined linear object, or a horizontal line on an inclined plane. Hold the compass as follows: Both short and long si
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Both short and long si The position of 'E' and 'W' are reversed on the circular card; 'E' lies left of the 0o mark i. The angle between the true north and the magnetic north is called magnetic declination. For example, a primary linear structure such as the crest of ripple marks or bbrunton casts on a bed may be folded around the axis of a fold.
The Breithaupt compass is one example. Read the strike and dip of the great circle. Articles needing additional references from January All articles needing additional references.
Using the compass as hand level on a Jacob Staff The compass can be used as hand level, mounted on a Jacob Staff to measure the true stratigraphic thickness of a lithostratigraphic unit e. In this position, we are looking edgewise along the plane. Measuring the bearing of a line between two points Commonly we want to measure the trend and plunge of a line connecting two points, e.
This preference, especially in North America, is because Brunton provides a precise sighting-clinometer and hand level capability, and can be used at both waist and eye levels; advantages that are absent in other brands such as Silva which lacks a leveling system for sighting bearings Compton, The true direction of the trend may be indicated by the white or the black needle; the color depends on how we hold the compass sighting arm away or toward our bodyand on which way we are facing in the field looking north or south.
Now, with the bulls-eye bubble centered, record the number that either end of the compass needle is showing. First, measure the plane i.
For example, if a set of slickenlines striations plunges e. Overall Size L W H: Please help improve this article by adding citations to reliable sources. Put the two thumbs under the sighting arm on the box; the two index fingers on the edge of the lid, and the center fingers behind the horizontally positioned box.
Thus, we need to know how to measure linear and planar comapss of all kinds, such as sedimentological and structural fabric elements, and map lithostratigraphic boundaries such as contacts. The homogeneity in each domain reflects two major facts: This is in excellent condition. Start at the lower contact of a stratigraphic unit.
Center the bull's eye level, and intersect the edge of the plane with the black line in the sighting window don't try to align the black line with the edge because it tilts the box unless the plane is vertical. The azimuth scale uses three digits, with north at o or o, and south at o.
The convention for direction of inclination is down, i. To figure out which one, we should be aware of the local geographic directions, that is, know the direction of north or south in the field at all times.
The attitude of both linear and planar objects has two general components: While the rectangular side of the box is still completely touching the layer, slowly turn the compass and reread the dip. Once all three are lined up and the compass is level, the reading for that azimuth can be made.
Thus, both trend and plunge are scalars; together they define the line vector.
January Learn how and when to remove this template message. Magnetic declination is constant along the so-called isogonic lines.
See Compton, for maintaining the compass. The zero rbunton is the pointer used for magnetic declination adjustment. Read the plunge directly from the scale in the compass the same way you read dip.