Table 10.

Similarity in extracted values and isoline zones for the different parameters from various datasets in comparison to the T50A dataset

Sl. No.	Dataset	Difference class from T50A values	Average elevation			Relative relief			Slope			Drainage density			Averaged totals	Remarks
			Difference class range (m)	% Basin area	Total %	Difference class range (m)	% Basin area	Total %	Difference class range (degrees)	% Basin area	Total %	Difference class range (km / sqkm)	% Basin area	Total %
1	A30	Immediate greater	−100 to 0	47.19	85.42	−250 to 0	40.06	99.26	−10 to 0	80.85	94.23	−2 to 0	11.55	50.20	82.28	Very high match
		Immediate lesser	0 to 100	38.23		0 to 250	59.20		0 to 10	13.38		0 to 2	38.65
2	A90	Immediate greater	−500 to 0	25.60	52.87	−250 to 0	38.53	72.24	−10 to 0	38.65	58.52	−2 to 0	32.01	70.78	63.60	Low match
		Immediate lesser	0 to 500	27.27		0 to 250	33.71		0 to 10	19.87		0 to 2	38.77
3	C30	Immediate greater	−100 to 0	50.75	65.55	−250 to 0	53.80	93.97	−10 to 0	70.93	82.41	−2 to 0	9.22	47.82	72.44	Moderate match
		Immediate lesser	0 to 100	14.80		0 to 250	40.17		0 to 10	11.48		0 to 2	38.60
4	C90	Immediate greater	−500 to 0	27.04	54.62	−250 to 0	42.15	69.62	−10 to 0	37.41	50.80	−2 to 0	32.32	71.20	61.56	Low match
		Immediate lesser	0 to 500	27.58		0 to 250	27.47		0 to 10	13.39		0 to 2	38.88
5	S90	Immediate greater	−100 to 0	48.74	86.23	−250 to 0	62.39	98.94	−10 to 0	80.68	87.65	−2 to 0	39.68	76.85	87.42	Very high match
		Immediate lesser	0 to 100	37.49		0 to 250	36.55		0 to 10	6.97		0 to 2	37.17
6	T50D	Immediate greater	−100 to 0	60.61	94.12	−250 to 0	94.88	99.86	−10 to 0	82.81	84.76	−2 to 0	48.77	78.48	89.31	Highest match
		Immediate lesser	0 to 100	33.51		0 to 250	4.98		0 to 10	1.95		0 to 2	29.71
7	T250A	Immediate greater	−500 to 0	46.95	74.96	−250 to 0	30.60	47.43	−10 to 0	31.43	52.04	−2 to 0	48.55	71.57	61.50	Lowest match
		Immediate lesser	0 to 500	28.01		0 to 250	16.83		0 to 10	20.61		0 to 2	23.02
8	T250D	Immediate greater	−500 to 0	47.16	74.93	−250 to 0	38.64	58.79	−10 to 0	29.67	42.83	−2 to 0	41.85	79.06	63.90	Low match
		Immediate lesser	0 to 500	27.77		0 to 250	20.15		0 to 10	13.16		0 to 2	37.21

Differences for each dataset are computed parameter-wise by subtracting from the corresponding values of that same parameter in the T50A database for each of the 1154 grids and isopleth classes are then demarcated on basis of this difference. Thus the immediate greater class (where T50A values are higher) and immediate lesser class (where T50A values are lower) together show areas which are more closely approximate to the values of the surveyed T50A database. If these two ranges combined, cover a greater proportion of the basin area, it implies then that that dataset matches well with the surveyed topographical map database, in terms of the parameters extracted and their ensuing isopleth zones. Perfect matching would give a narrow difference class range around zero covering the total basin area