The second option, BOUNDARY, brings up the following sub-menu:
which permits a variety of editing operations on boundary nodes.
ADD, DELETE and MOVE are essentially similar to the functions of the same names in {TOP.INDIVID.INTERIOR}, but since here they are applied to boundary nodes, provisional connections to the two presumed neighbouring boundary nodes are displayed for the user to confirm or correct, as in the case of {TOP.INDIVID.INTERIOR}CHANGE above. N.B. This DELETE option should not be used for complete deletion of an island, which requires more radical changes to the NODE file. Instead, use DELISL in {TOP.GROUP.BOUNDARIES} , described later.
This option allows the user to replace any designated string of boundary nodes with a fresh selection of nodes from a boundary data file in DIGIT format. Selection may be made on the basis of distance between points or by choosing every Nth digitized point. The following information panel is displayed:
Pick [NONE] under "DIGIT File Name:" as the first operation in this panel. Enter the file name of the DIGIT file to reselect from to the following prompt. The asterisk indicates which selection criterion is in effect. To reselect a stretch of boundary nodes, first Pick the first and last nodes on the stretch to be replaced. The Noder will then search the digitized boundary data file and display the points which it identifies to be the first and last points of the corresponding stretch of digitized boundary data. On confirming this identification, the user can make a fresh selection of nodes by Picking RESELECT. Once reselection of the nodes is complete the new nodes will be displayed and the user may save or cancel the reselection at the following prompt. If the reselection is saved a prompt will appear asking if depth for the reselected nodes should be interpolated or assigned from the DIGIT file used. DISPLAY provides the usual windowing facilities. Pick DONE to leave this procedure. The final option in the panel permits some saving of time in the case of very large digitized boundary files. If it is known that the blocks of data (digitized data or nodes) representing islands are in exactly the same order in both the DIGIT and NODE files being used, then some search time can be saved by toggling NO to YES. Do not use this facility if islands have been deleted with the Noder without corresponding updating of the digitized boundary file.
The LINE option permits replacement of a stretch of boundary with a straight line of new boundary nodes, the total number of which is under the user's control. This operation is useful for straightening up lines of boundary nodes representing docks, wharfs, etc. Another application is in creating a line of nodes to represent a new open boundary when an outlying part of a model domain is removed for any reason.
The user is prompted to Pick two existing boundary nodes which demarcate the beginning and end of the stretch to be replaced. Existing intervening nodes are deleted and the user is prompted to enter via the keyboard how many new boundary nodes are to be placed (at equal intervals) along the straight line joining the two designated end nodes. The proposed new configuration is then displayed for confirmation or cancellation. Two methods of setting depths at the new nodes are offered, manual entry, node by node, via the keyboard, or by linear interpolation between the depths at the designated end nodes.
This permits setting new depths along a stretch of boundary by linear interpolation between depths at nodes at each end. The user is asked to Pick two nodes, one at each end of the length of boundary where depths are to be set. Note that it is incorrect to Pick the same node twice when wishing to reset depths on a whole boundary, e.g. an island. Instead, Pick two adjacent nodes. The nodes on the stretch of boundary identified by the program as lying between the specified end nodes are then shown in yellow. Note that the wrong part of the boundary may be shown, due to ambiguity as to which is the first and which is the last node. If this happens, enter N (No) and the remaining part of the boundary (presumably the required part) will be shown in yellow. When the choice of boundary stretch is confirmed, a new panel will be displayed, in which the end nodes are identified by red and blue and their current depths are displayed. If either of these depths is incorrect, Pick the current value and enter a new one. Then when ACCEPT is subsequently picked, linear interpolation of depth is carried out on the basis of distance (arc length) along the boundary.
This option deletes all the boundary nodes associated with an island, that is, complete removal of an island from the node file. The user selects the island to be deleted by Picking any boundary node of the island.
At present,the NODER offers no method of adding a new island; to do this, add the required boundary nodes in the correct order into the NODE format file using a text editor. The string of new nodes should be preceded by a record giving the number of nodes added, and the total number of nodes and number of islands in lines 1 and 2 of the file should be amended.
The DISPLAY option provides control over windowing and is described in
detail in DISPLOT. See Section 
The INFO option permits viewing and changing of various node attributes, as detailed in the section on {TOP}INFO.
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