I have been reading about the various expeditions of Harry St John Bridger Philby and was wondering how he would have added detail to him maps . I understand that he carried a prismatic compass, theodolite, and a chronograph watch by which he could find his longitude, latitude.
He mentions how he prepared a piece of paper by sketching on it the relavent lines of longitude and latitude for his travels. I presume that each time he took a reading of his longitude and latitude he would mark his location on the map but how would he have filled in details such as cliffs, mountains and mountain ranges from ground level with any level of accuracy?
Basically, he'd take or estimate a bearing from one or more known positions, and then sketch in the features based on what he could observe or had been told by other travelers. The level of accuracy thus depended on his talent as an observer, as a reporter, and as a draftsman. His understanding of physical geography might also come into play: knowing that certain kinds of mountains or plateaus have certain kinds of terrain, streams, and trails through them would let him make informed guesses about unseen territory.