This option is started by picking a node such as in {INFO}NODES above. It is possible to change those quantities displayed in cyan in the right-hand panel, including the type of node. When an interior node is changed into a boundary node ( by Picking "Interior"), presumed connections to two neighbouring boundary nodes are displayed for confirmation or correction. The user will be prompted to enter a depth for the affected node and has the option of entering a depth or permitting automatic linear interpolation of depth relative to depths at the two neighbouring boundary nodes. The latter calculation is carried out on the basis of distance and as if the three nodes are in a straight line.