Geoscience Reference
In-Depth Information
Fig. 2
General concept of flow direction
Flow Direction'' to increase the efficiency, accuracy and reliability of current D8
algorithm, used in many GIS and hydrology software which are related to SFD
models.
Apart from the requests of several related field applications for high accuracy
flow direction information, the demand for developing a new SFD algorithm is
encouraged by:
1. Some limitations of D8 algorithms stated by several researchers.
2. The need to increase the dispersion options of current SFD model.
3. The need for other state of water other such as a stagnant and a sink.
4. The reliability on accuracy by the D8 algorithm (Fig. 1 ).
Apart from limitations of SFD as well as D8 algorithm, there is a main factor of
deriving the new SFD algorithm. According to the 1st Law of Geography,
''Everything is related to everything else, but near things are more related than
distant things'' (Tobler 1970 ). The eight neighbour pixels used in this neigh-
bourhood analysis is definitely true and agree by this law, but we cannot ignore the
other parameter of this law on the distant thing.
The main difference highlighted between eight directions of existing SFD with
this new SFD algorithm is by adding eight additional directions for D8 algorithm
that fully obey the first law of geography as the name given ''D16'' algorithm. In
addition, some rules and equations are also introduced in this algorithm in order to
minimize the weaknesses of D8 algorithm.
1.2 Water Flow Direction Concept
Water flow direction is work based on the elevation difference and gravity
attraction to the lower height area. At any point (X, Y, Z) in all spatial referenced
system, a certain volume or drop of water (example from the rain) will have from
0-360 of horizontal direction to flow from one point to other point or place which
is lower than the current surface elevation. That is the nature of the world
Search WWH ::




Custom Search