surveying iii (topographic and geodetic surveys) - Modern Prepper

(1) To test the theodolite for proper vertical collimation, level the instrument carefully, bring theimage of the vertical circle into view by turning the changeover knob (13), sight the horizontal crosshaironto a clearly defined object, and record the reading. Reverse the telescope, resight the object, andrecord the second reading. Halve the second reading and add 90 minutes. This should result in exactlythe same reading obtained in the first position. If it does not, a collimation error or index error of thevertical circle exists.(2) To adjust the vertical circle to the proper reading, place the telescope in the first position.Set the micrometer scale to the proper seconds reading obtained in the vertical collimation check. Directthe telescope on the object. Use the vertical slow-motion screw (14) and bring into coincidence thegraduation lines which give the proper reading. Turn the collimation level adjusting screw (21) to bringthe level bubble to center. Repeat the measurement of the vertical angle, as with the collimation check,and add the two readings. The sum of the readings should now be within 10 seconds of 180 minutes. Ifit is not, repeat the entire correction procedure.PART C: TRAVERSING AND TRAVERSE TYPES3-14. General. Traversing is a form of control survey that is used in a wide variety of surveys.Traverses are a series of established stations linked together by the angle and distance between adjacentpoints. The angles are measured by theodolites, and the distances are measured by EDME. The AISItotal station combines both of these functions. Detailed information pertaining to traverse design, datacollection, and limitations are discussed in the SSGCN.a. Starting Control. The purpose of a traverse is to locate points relative to each other on a commongrid. Surveyors need certain elements of starting data such as the coordinates of a starting point and anazimuth to an azimuth mark. Surveyors should make an effort to use the best data available to begin atraverse. Survey control data is available in the form of existing stations (with the station data publishedin a trigonometric list) or new stations that were established by local agencies who can provide thestation data.b. Open Traverse. An open traverse (Figure 3-13, page 3-28) originates at a starting station,proceeds to its destination, and ends at a station whose relative position is not previously known. Theopen traverse is the least-desirable traverse type, because it does not provide the opportunity forchecking the accuracy of the fieldwork. All measurements must be carefully collected, and everymethod for checking position and direction must be use. The planning of a traverse should alwaysprovide for closure of the traverse.3-27 EN0593