Petermann was responsible for drawing most of the maps in the first few years of the journal. His strength was in the analysis and evaluation of all sources available. As such one can say that the indication 'Originalkarte' (original map) in many titles was well earned, for few slavishly copied what explorers or other experts had sketched. German geographers, like Hermann Wagner (1840–1929), claimed that in other geographical journals explorer's maps were just copied instead of having them evaluated by cartographers first. Maps based on recent exploration reports were always, when possible, complemented with route maps from previous expeditions. He did not like to infer or extrapolate from the sources, for that might give inaccurate measurements, so many of his maps show large blank spaces. How right he was in this respect was demonstrated in 1911 when Julien Thoulet drafted bathymetric maps for the territory of France. In these four maps he draws hypothetical isobaths, which are based on respectively 15, 31, 154, and 308 altitude measurements per for France and the adjacent territories. (A reasonable number of measuring points for precipitation and temperature maps would be 1,500 and 600 per 100,000 km² respectively to create acceptable isoline maps for these phenomena). These give schematic negative relief maps, which hardly even approximate the true relief of the territory. Thoulet wanted to show that the few bathymetric measurements available for the vast oceans would only vaguely approximate the true relief of the ocean floors. Petermann must have had the same idea intuitively for his exploratory maps. He was keen, however, to introduce spot heights and spot depths in the maps he drafted in order that others could benefit from them.