SURVEYING 



27 



7. Determine the distance to a visible but inaccessible object. 

 Use two similar right-angled triangles. Fig. 9. 



8. Prolong a line beyond an obstacle. 



There are several ways to accomplish this, but the use of similar 

 triangles is the only method suggested. 



Let A B be points in the line to be prolonged beyond O, an obstacle. 

 Make A B C a right-angled triangle. Prolong A C to F, making C F 

 equal A C, and C E equal E F, and B C equal C D. Extend D E to I, 

 3 making DG and G I equal to A C, also 



extend F G to H, making G H equal F G. 

 Then H I are points in the extended line 

 AB. 



Base 



Fig. 9. Sketch showing 

 method of measuring to an 

 inaccessible point. 



Fig. 



10. Sketch showing method of extend- 

 ing a line beyond an obstacle. 



9. Make a survey of the lot on which the schoolhouse stands, 

 locating buildings, etc. 



10. Make a survey of the home farm or a part of it, as assigned by 

 the instructor. 



11. Make a survey of a lot or a field having an irregular side, by 

 taking offsets at regular or irregular intervals, dividing the field into 

 trapezoids. (See method of calculating areas of tracts with irregular 

 sides) . 



QUESTIONS 



1. How is a tract of land divided in making a chain survey? 



2. What care should be taken in making field notes of a survey? 



3. What care should be taken in marking permanent corners? 



