Figure    2A IN  ANSWERING  QUESTIONS  2-8  THROUGH  2-11, USE THE CHAIN OF QUADRILATERALS IN FIGURE 2A AND THE TABLES IN APPENDIX II. 2-8. The size of the angle ABD is 1. 37° 2. 51° 3. 57° 4. 60° 2-9. What is the length of the line DB? 1. 500 ft 2. 531 ft 3. 548 ft 4. 554 ft 2-10. What is the length of line CE? 1. 646 ft 2. 608 ft 3. 697 ft 4. 709 ft 2-11. What is the length of line BF? 1. 452 ft 2. 487 ft 3. 520 ft 4. 561  ft Learning  Objective:  Identify  the construction and uses of various targets and signals as related to triangulation. 2-12. What minimum number of reference markers must be used for triangu- lation stations of first-order precision? 1. One 2. Two 3. Three 4. Four 2-13. What is the difference between a primary triangulation station and a secondary triangulation station? 1. The secondary station is used as a control point; the primary station  is  not 2. The secondary station is an instrument station; the primary station  is  not 3. The primary station is an instrument station; the secondary station is not 4. The primary stations are set up on monuments only; the secondary stations can use any point 2-14. A tripod target is the most satis- factory target to use because of which of the following qualities? 1. Its accuracy 2. Its durability 3. Its ease of construction 4. Each of the above 2-15. One of the disadvantages of using a bipod target is that it 1. is difficult to transport 2. must be strongly guyed 3. is extremely difficult to construct 4. cannot  be  used  when  first- or second-order precision is required 2-16. For accuracy, you should perform first-   and second-order triangu- lation surveys (a) during what time of day and (b) using what type of signals? 1. (a) At night (b) signal lights 2.  (a)  At  night (b)  heliotropes 3.  (a)  In  daylight (b)  target  sets 4. (a) In daylight, while overcast (b)  nonilluminating  bipod signals Learning  Objective:  Identify  the procedures used in triangulation surveying and recognize their importance. 9