A proximity sensor system adapted for a marine vessel , the system comprising: one or more proximity sensors , each at a sensor location on the marine vessel and configured to measure proximity of objects and generate proximity measurements ; characterised by : a memory storing a first two-dimensional vessel outline of the marine vessel with respect to a point of navigation (P n ) for the marine vessel and at least a second two-dimensional vessel outline of the marine vessel with respect to the point of navigation (Pn), wherein the second two-dimensional vessel outline represents a cross-section of the marine vessel closer to a waterline than the first two-dimensional vessel outline ; a processor configured to: receive the proximity measurements measured by one or more proximity sensors on the marine vessel ; identify an object height (h) for at least a closest subset of the proximity measurements ; determine an appropriate two-dimensional vessel outline for each of the closest subset of proximity measurements based on the respective object height (h); identify four linearly-closest proximity measurements (90+x, 90-x, 90+y, 90-y) based on the appropriate two-dimensional vessel outline , including one closest proximity measurement in each of a positive X direction, a negative X direction, a positive Y direction, and a negative Y direction; and generate a most important object (MIO) dataset identifying the four linearly-closest proximity measurements (90+x, 90-x, 90+y, 90-y). a marine vessel , the system comprising: one or more proximity sensors , each at a sensor location on the marine vessel and configured to measure proximity of objects and generate proximity measurements ; characterised by : a memory storing a first two-dimensional vessel outline of the marine vessel with respect to a point of navigation (P n ) for the marine vessel and at least a second two-dimensional vessel outline of the marine vessel with respect to the point of navigation (Pn), wherein the second two-dimensional vessel outline represents a cross-section of the marine vessel closer to a waterline than the first two-dimensional vessel outline ; a processor configured to: receive the proximity measurements measured by one or more proximity sensors on the marine vessel ; identify an object height (h) for at least a closest subset of the proximity measurements ; determine an appropriate two-dimensional vessel outline for each of the closest subset of proximity measurements based on the respective object height (h); identify four linearly-closest proximity measurements (90+x, 90-x, 90+y, 90-y) based on the appropriate two-dimensional vessel outline , including one closest proximity measurement in each of a positive X direction, a negative X direction, a positive Y direction, and a negative Y direction; and generate a most important object (MIO) dataset identifying the four linearly-closest proximity measurements (90+x, 90-x, 90+y, 90-y). receive the proximity measurements measured by one or more proximity sensors on the marine vessel ; identify an object height (h) for at least a closest subset of the proximity measurements ; determine an appropriate two-dimensional vessel outline for each of the closest subset of proximity measurements based on the respective object height (h); identify four linearly-closest proximity measurements (90+x, 90-x, 90+y, 90-y) based on the appropriate two-dimensional vessel outline , including one closest proximity measurement in each of a positive X direction, a negative X direction, a positive Y direction, and a negative Y direction; and generate a most important object (MIO) dataset identifying the four linearly-closest proximity measurements (90+x, 90-x, 90+y, 90-y). <EOS>