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, 

 6 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? 



