JSSUA1

(All values in metres unless otherwise indicated)

LINE	BF	IS	FS	HPC	INITIAL RL	ADJ. (mm)	ADJ. RL	REMARKS
1	1.717			30.947	29.23	-	29.23	OBM 1 RL 29.23m AOD
2		1.432			29.515	-2	29.51	A
3	2.918		1.716	32.149	29.231	-2	29.23	B(CP)
4		2.272			29.877	-4	29.87	C
5	0.816		0.953	32.012	31.196	-4	31.19	D(CP)
6	1.436		3.005	30.443	29.007	-6	29.00	E(CP)
7	1.246		1.391	30.298	29.052	-8	29.04	CP
8		1.353			28.945	-10	28.93	F
9		1.462			28.836	-10	28.83	G
10			0.628		29.670	-10	29.66	OBM 2 RL 29.66m AOD
	8.133		7.693

The RLs were calculated using the following procedure.

1) For level position I1 = RL of OBM1 + staff reading at OBM1
                         = 29.23 + 1.717
                         = 30.947 m


   RL of A = HPC at I1 - staff reading at A
           = 30.947 - 1.432
           = 29.515 m 


   RL of B = 30.947 - 1.716
           = 29.231 m


2) B is a change point, it is necessary to calculate new HPC for position I2
	
   HPC at I2 = RL of B + staff reading at B from I2
             = 29.231 + 2.918
             = 32.149 m


   RL of C = 32.149 - 2.272
           = 29.877 m


   RL of D = 32.149 - 0.953
           = 31.196 m

3) The procedure is repeated for positions I3,I4 and I5 until the RL
   of OBM 2 is calculated.

4) The calculations must be checked then. For the HPC method, the check is 

			Total of FS - Total of BS = Known RL of start point - 

                                       calculated initial RL of end point



   For this example, 

           Total of FS - Total of BS = 7.693 - 8.133 = -0.440 m 

           Known RL of start point - calculated initial RL of end point

                     = 29.23 - 29.670

                     = -0.440 m


   If the check is not satisfied exactly then the calculations are in error and
   should be repeated.