INSTRUMENT TO SET OUT RIGHT ANGLES CROSS STAFF Open cross staff French cross staff Adjustable cross staffContd . . . OPTICAL SQUAREOBSTACLES IN CHAINING Various obstacles may be classed as,CHANING FREE VISION OBSTRUCTEDCHAINING OBSTRUCTED VISION FREECHAINING AND VISION BOTH OBTRUCTEDCONVENTIONAL SYMBOLSTO PLOT A CHAIN SURVEYCHAIN AND COMPASS TRAVERSING In traverse surveying the directions of survey lines are fixed byAngular Measurements Unlike CHAIN SURVEY - forming a network of triangles LENGTHS measured with chain or tape ANGLES measured with Angular Instruments Running of check lines is not necessary.TRAVERSE Traverse means to cover a distance or to passthrough a line. May be classed asCLOSED TRAVERSEUNCLOSED / OPEN TRAVERSECLOSED TRAVERSE A traverse is said to be closed when a complete circuit is made when it returns to the starting point forming a closedpolygon (Fig.1) when it begins and ends at points whose positions on planare known (Fig.2) The work may be checked and "balanced. Suitable for locating the boundaries of lakes, woods, etc. And for the survey of moderately large areas.Fig.1Fig.2Fig.3UNCLOSED OR OPEN TRAVERSE Atraverseissaidtobeopenorunclosedwhenitdoesnotform a closed polygon. (Fig. 3) It consists of a series of lines extending in the same generaldirection and not returning to the starting point. Suitable for survey of a long narrow strip of country e.g. thevalleyofariver, thecoastline, alongmeanderingroad, orrailway etc.METHODS OF TRAVERSING The chief methods by which the direction of the survey lines maybe determined are as follows : By the Chain Angles. By the Free or Loose Needle Method. By the Fast Needle Method. By the Measurement of Angles betweenSuccessive Lines.ANY QUERIESthank you . . . !