DESCRIPTION | DOWNLOAD | SOURCE CODE | EXAMPLE | DEPENDENCIES | DISCLAIMER

coastline

DESCRIPTION

The subroutine "coastline" finds the oceanic grid nodes situated next to land grid nodes. These oceanic nodes will hereafter be referred to as coastal nodes. A series of "connected" coastal nodes will be referred to as a coastline. The 'nodeno' coastal nodes which are found, i.e., the coastline, are returned in the vectors 'xcoastal[nodeno]' and 'ycoastal[nodeno]'.
A sequence of coastal bands may be produced by multiple calls to this subroutine. First call the subroutine to get the "coastalmost" nodes. Then, reset values for the coastalmost nodes to > specialvalue, and call the routine again. Repeat this algorithm to find any number of bands that are "parallell" to the land.
Warning! Special values due to other circumstances than dry nodes in the range <1:xmax,1:ymax> should be removed. Otherwise, an erroneous coastline may be returned!

DOWNLOAD

SYNTAX

subroutine

coastline

( mxm,maxnodes,xmax,ymax,value,specialvalue,corner, clockwise,remove,two,xbounds,ybounds,goodcorner, nodeno,lake,xcoastal,ycoastal )

INPUT, OUTPUT VARIABLES

Input:

mxm	(i)	-	the declared dimension of the model (see also the note for 'value[,]' below).
maxnodes	(i)	-	the declared dimension of the output vectors 'xcoastal[]' and ycoastal[]; i.e., the maximum no. of coastal nodes which can be stored by calling "coastline".
xmax, ymax	(i)	-	the actual dimensions of the model.
value	(RR)	-	array containing an output field from the model. Note: a border (of width 1) must be added around the (maximum) model domain.
specialvalue	(r)	-	it is assumed that dry nodes (i,j) are characterized by 'value[i,j]' >= 'specialvalue'
corner	(i)	-	denotes the corner from which search for a coastline is started. It is assumed that the corner is a dry node (on the continent for which the coastline will be determined). The corners are numbered according to the stecil: 4  3 1  2
clockwise	(l)	-	.true. if "coastline" is to search for a coastline in a clockwise manner; .false. if an anticlockwise search will be performed. Below, dry nodes are black, and the previously encountered coastal node is white. If 'clokwise' is .true., the next coastal node will be red; if 'clockwise' is .false., the next coastal node will be green.
remove	(l)	-	If 'remove' is .false., the output coastline will consist of every node which is recognized as a coastal node. Note: this may result in the same node being entered twice in the output coastline. If 'remove' is .true., some nodes may be eliminated from the coastline (see 'two' below). See the example below for a sample domain and resulting coastlines.
two	(l)	-	has no effect if 'remove' is .false. Otherwise, if 'two' is .false., and there are coastal nodes which are encountered more than once, the intermediate entries in 'xcoastal[]' and 'ycoastal[]' are removed along with the duplicate. If 'two' is .true. (and 'remove' is also .true'), when a new coastal (oceanic) node is found, only the first and the last neighbouring coastal nodes will be accepted. Intermediate entries are removed. See the example below for a sample domain and resulting coastlines.
xbounds, ybounds	(I)	-	the bounds outside which the search for a coastline will be terminated. (xbound[1],ybound[1]) and (xbound[2],ybound[2]) are the lower, left corner and the upper right corner, respectively, of the (sub-)domain of interest. (If xbound[1] = ybound[1] = 1 and xbound[2] = 'xmax' and ybound[2] = 'ymax', the entire domain will be considered).

Output:

goodcorner	(l)	-	will be .true. if the values of 'corner' and 'clockwise' lead to a successful search of the coastline; otherwise, the output value of 'goodcorner' will be .false.
nodeno	(i)	-	the number of coastal nodes which were detected.
lake	(l)	-	will be .true. if a closed coastline is been detected; otherwise .false.
xcoastal, ycoastal	(I)	-	the (x,y) nodal locations of the 'nodeno' coastal nodes.

DEPENDENCIES

No external.

EXAMPLE

Domain:


Color code:


	land (dry)
	ocean (wet), never part of coastline
	ocean (wet), always part of coastline
	ocean (wet), part of coastline when 'remove' is .true. and two is .false.
	ocean (wet), part of coastline when 'remove' is .false.


In the domain above, the routine "coastline" will detect the continental coastline, provided that
• either 'corner' = 2 and 'clockwise' = .false.
• or 'corner' = 3 and 'clockwise' = .true.

Output coastline:


'remove'=.false.
'remove'=.true., 'two'=.false.
'remove'=.true., 'two'=.true.

DISCLAIMER

ALTHOUGH THE PROVIDED SOFTWARE HAS BEEN USED IN A NUMBER OF APPLICATIONS, I CAN TAKE NO RESPONSIBILITY OF ERRORS THAT MAY ARISE WHEN USING THIS TOOL.

... however, if a problem occurs, please do not hesitate to inform me, and I'll do my best to help you out!