Ex31-2 In a traverse ABCDE, the length of the sides DE and EA could not be measured.
Line |
AB |
BC |
CD |
DE |
EA |
Length (m) |
480 |
626 |
470 |
? |
? |
WCB (m) |
99° 00' |
31° 05' |
301° 20' |
235° 00' |
153° 25' |
Determine the missing data.
Figure Example 31.2
Solution :
Let us consider the closed traverse ABCD. Let the line DA is having length and bearing (WCB) be l and q respectively.
Line
|
Length (m) |
WCB |
Latitude (m) |
Departure (m) |
AB |
480 |
99° 00' |
- 75.088 |
474.090 |
BC |
625 |
31° 05' |
535.261 |
322.678 |
CD |
470 |
301° 20' |
244.408 |
-401.454 |
DA |
l |
q |
l cos q |
l sin q |
Thus in closed traverse ABCD,
å Latitude = 0 or, l cos q + 704.581 = 0 or, l cos q = - 704.581
å Departure = 0 or, l sin q + 395.314 or l sin q = - 395.314
Now in the D ADE,
a = Bearing of DE - Bearing of DA
= 235° 00' - 209° 17' 43" = 25° 42' 17"
b = Bearing of EA - Bearing of DE
= 153° 25' - (235° 00' - 180°) = 98° 25'
g = Back bearing of DA + (360° = back bearing of EA)
= (209° 17' 43" - 180°) + (360° - (153° 25' + 180°)
= 55° 52' 43"
= 676.104m
and
= 354.229m
