You may think the above 3D contour map of Loch Ness was derived from some modern sonar study or similar. However, the data points used to generate the image were from the 1903-04 bathymetric survey of the loch conducted by Murray and Pullar. The total number of soundings was 1700 and those have been fed into the plotting software which you can examine at this link. Similar maps for Loch Morar, Lomond and Leven can be viewed as well as the 2D representations.