Error Angle Measurement

General Basic field operations performed by a surveyor involve linear and angular measurements. Through application of mathematics (geometry and trigonometry) and angle measurement calculator spatial information knowledge,the surveyor converts these measurements to the horizontal and vertical

Angle Measurement Worksheet

relationships necessary to produce maps, plans of engineering projects, or Geographical Information System/ Land Information System (GIS/LIS). angle measurement problems The highway surveyor must be adept at making the required measurements to the degree of accuracy required. Various types of engineering works require various tolerances in the precision of angle measurement formula the measurements made and the accuracies achieved by these measurements. The use of common sense and development of good surveying practice in all phases of a survey cannot be overemphasized. All conditions that may be encountered in the "real world" during the actual field survey cannot be covered in any manual. A manual may specify certain techniques, such

Angle Measurement Of Polygons

as a certain number of repeated operations, to achieve a required accuracy. The surveyor must then often use judgment based on the equipment being used and the field conditions encountered, to modify those techniques. Some field conditions (heat waves or wind for example) may make it impossible to perform some operations to a consistent degree of accuracy. 3.2 Accuracy and Precision 3.2.1 Accuracy Accuracy is the degree of conformity with a standard or accepted value. Accuracy relates to the quality of the result. It is distinguished from precision that relates to the quality of the operation used to obtain the result. The standard used to determine accuracy can be: An exact known value, such as the sum of the three interior angles of a plane triangle is 180°. A value of a conventional unit as defined by a physical representation thereof, such as the international meter. A survey or map value determined by superior methods and deemed sufficiently near the ideal or true value to be held constant for the control of depe

more accurate measurements, we look for better instruments and better procedures. The theodolite is an instrument for measuring horizontal and vertical angles. It has long had the same general angle measurement game look. A sighting telescope rotates on a vertical axis. A circular scale rotates angle measurement online on this same axis to measure the horizontal angle. A second axis, the trunnion axis, moves with the instrument and

Angle Measurement Sensor

is perpendicular to the vertical axis. The trunnion axis allows the scope to pivot up and down, and it has a scale to measure the vertical angle. One major design improvement came http://www.state.nj.us/transportation/eng/documents/survey/Chapter3.shtm with the invention of the transiting theodolite. With this innovation, the telescope was able to swing all the way over on the trunnion axis. This in itself did not reduce any of the inherent error in the instrument, but it gave surveyors the means of doing so. When the scope is inverted, the instrument error is still there, but most of the error reverses http://whistleralley.com/surveying/theoerror/ direction. By taking the mean of an even number of observations, half direct and half inverted, the error is turned against itself and greatly reduced. In common usage among American surveyors, a transit is an older-style instrument with a compass and exposed metal scales, while a theodolite usually has no compass and has enclosed glass-plate scales, which are read with a built-in microscope or an electronic micrometer. Strictly speaking though, they are both theodolites and they probably are both transits. Nearly all modern surveyors’ theodolites are transits. Non-transiting theodolites are still manufactured, mostly for builders working on small sites. Detailed below are four instrument misadjustments that can lead to significant error. The error formulas below may be indeterminate for certain unrealistic values of the variables. Keep in mind that the calibration errors (α, β, γ, ε) are near 0°, and the zenith angle, φ, cannot be near 0° or 180°. Theodolite errors: The trunnion axis is not perpendicular to the vertical axis. The line of sight is not perpendicular to the trunnion axis. The vertical axis is not plumb. The vertical angle collimation is out of adjustment. Errors: The trunnion axis i

3) The flatness of the surfaces being viewed by the autocollimators. This factor is a large contributor to measurement error and http://starrett-webber.com/AG31.html uncertainty. NOTE: The type of autocollimator used in the measurement will have a great influence on the resulting measurement. Different kinds of autocollimators may give different results. How this is possible will be shown below. If the surface in not ideally flat, the angle of reflection may be different than the angle of incidence. The autocollimators used by Webber angle measurement Gage have a 2-inch diameter beam and are manually read. The return image in visually centered between two target lines. The reading is taken off a micrometer dial. For reference and Calibration Grade blocks, the beam nearly covers the whole area of the block. The angle indicated by the autocollimator is the average returned over the entire surface of the error angle measurement angle block. Autocollimators which have narrower beams such a laser autocollimators may give different readings than autocollimators that cover the entire surface. The average reflected image in this picture is different than the average reflected image of the picture above. Positioning of the autocollimator may also effect the readings of an angle block. This is another effect due to flatness of the block. If the beam of the autocollimator is not centered on the angle block, different readings may result. The measurement uncertainty factor (k=2) due to flatness is estimated to be given by: U = WF / (4.85 B) where U is expressed in arc seconds and W = maximum dimension of the angle block (Width or Length) in inches, or equal to B if W is smaller than B F = measured flatness of the angle gage block surface in microinches B = Beam diameter of the autocollimator in inches. Note: 1 arc second is approximately 4.85 microinches of taper per inch. 4) Pyramidal Error. The pyramidal angle is the deviation from 90°, forwar