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CLaRiNet 0.1 beta >> Ordering streams and traversing networks > FindNetworkTransition

# FindNetworkTransition

Locates the cells verifying a transition criterion when moving downstream in a channel network.

### Calling Sequence

    CELLS = FindNetworkTransition ( handle_ras , handle_fdr , a , b , outlet , niter )

### Arguments

hr

  integer: handle on the raster which will be used to define the transition criterion.

fdr

  integer: handle on the flow direction grid to be used.

a,b

  floats: the transition criterion will be verified when the expression (a * #Raster# + b) switches from positive to negative when moving downstream.

outlet

  integer: record number (absolute reference in the raster, as returned by `XY2rec`) of the outlet cell.

nit

  integer: number of times that the search for transitions can be performed recursively.

CELLS

  output: vector containing the record numbers of the cells verifying the transition criterion.

### Description

Locates the cells verifying a transition criterion when moving downstream in a channel network.

### Exemples

if the raster `elev` contains elevation data, then the contour line `Z=Z0` in the catchment having its outlet at cell `outlet`, is given by the set of cells verifying the following transition :

`1 * #elev# - Z0` switching from positive to negative when moving downstream, i.e. :

`CZ0 = FindNetworkTransition ( elev , fdr , 1 , -Z0 , outlet , 1)`

### See Also

- XY2rec

### Authors

- Nicolas LE MOINE

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