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researchers are highlighted in this paper as the problem statement to introduce the
D16 algorithm.
D16 was initially derived to overcome the weakness of the SFD model espe-
cially in D8 algorithm, yet when introducing some rules and new equations on the
model, the results show a surprising positive enhancement toward the current
accuracy of D8 algorithm. D16 algorithm had shown enhancement in accuracy,
reliability and consistency of the flow direction results compared to D8 algorithm.
The problem related to flow divergence in a ridge area also being enhanced by D16
via the additional eight flow direction options from D8 algorithm.
Based on three sources of raster data used with various testing methods, D16
algorithm had shown that it is capable to produce better accuracy, flow divergence,
smoothness, edge reliability, and better result of generalisation and produce a
stagnant state of rain water compared to D8. Although the construction of D16
seems to be a bit complicated with many new equations introduced compared to
D8 algorithm, a new automated approach can be derived easily with D16 algo-
rithm as discussed in Figs. 18 , 19 and 20 .
In the nutshell, all the testing methods used in this study have shown a positive
enhancement compared to D8 algorithm. Thus, this algorithm, hopefully, fulfils
the accuracy demand from other field professions, which are somehow related to
the water flow modelling. However, because of the complexity of equations
applied in D16 as well as an external program in ArcGIS software, this study
cannot afford to measure and compare in terms of processing time for both
algorithms. However, the authors believe that the upturn of machine or computer
technology today is capable to perform D16 algorithm much faster compared to
the D8 algorithm when it was introduced and implemented over 28 years ago.
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