- 2075 Baisakh · 8 marks
Gale's table, coordinates of all points
Short answer
Using Bowditch rule from C (1000N,1500E), coordinates are: A (972.637N, 1333.995E), B (1030.036N, 1367.756E), C (1000.000N, 1500.000E), D (993.467N, 1565.935E), E (920.688N, 1542.047E). Linear misclosure 0.3657 m, 1/1530.
Prepare the Gale's Table and find the co-ordinates of all the points if the co-ordinate of C is (1000N, 1500E) from the following data.
| S.No | Line | Length (m) | Bearing (WCB) |
|---|---|---|---|
| 1 | AB | 66.60 | 30°30' |
| 2 | BC | 135.70 | 102°48' |
| 3 | CD | 66.30 | 95°40' |
| 4 | DE | 76.60 | 198°8' |
| 5 | EA | 214.30 | 284°1' |
The bearings are given directly, so the Gale's table starts from the latitudes and departures. Bowditch's rule is used to balance the traverse, and the coordinates are then run from C (1000 N, 1500 E).
Step 1: Latitude and departure
| Line | Length (m) | Bearing | Latitude | Departure | Corr. lat | Corr. dep |
|---|---|---|---|---|---|---|
| AB | 66.600 | 30°30' | +57.385 | +33.802 | +0.0140 | -0.0412 |
| BC | 135.700 | 102°48' | -30.064 | +132.328 | +0.0285 | -0.0840 |
| CD | 66.300 | 95°40' | -6.547 | +65.976 | +0.0139 | -0.0410 |
| DE | 76.600 | 198°08' | -72.796 | -23.840 | +0.0161 | -0.0474 |
| EA | 214.300 | 284°01' | +51.904 | -207.919 | +0.0450 | -0.1327 |
| Sum | 559.500 | -0.117 | +0.346 | +0.1174 | -0.3464 |
Step 2: Closing error
Step 3: Bowditch correction
The corrections are in the last two columns above (their sums cancel the errors). Adjusted values:
| Line | Adj. lat | Adj. dep | Adj. length (m) | Adj. bearing |
|---|---|---|---|---|
| AB | +57.398 | +33.761 | 66.591 | 30°28' |
| BC | -30.036 | +132.244 | 135.612 | 102°48' |
| CD | -6.533 | +65.935 | 66.258 | 95°39' |
| DE | -72.780 | -23.888 | 76.599 | 198°10' |
| EA | +51.949 | -208.052 | 214.440 | 284°01' |
Step 4: Coordinates of all points
Starting from C = (1000.000 N, 1500.000 E), add the adjusted latitude and departure of CD, DE, EA and AB in turn:
| Station | Northing (m) | Easting (m) |
|---|---|---|
| A | 972.637 | 1333.995 |
| B | 1030.036 | 1367.756 |
| C | 1000.000 | 1500.000 |
| D | 993.467 | 1565.935 |
| E | 920.688 | 1542.047 |
Check: B plus the adjusted BC returns exactly to C (1000.000 N, 1500.000 E).
Answer: A (972.637 N, 1333.995 E), B (1030.036 N, 1367.756 E), C (1000.000 N, 1500.000 E), D (993.467 N, 1565.935 E), E (920.688 N, 1542.047 E); misclosure 0.3657 m, 1 in 1530.
✓ Answer checked by Claude Opus 5.5 (high effort)
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