Topographer

“ Where such rigid geodetic operations were instituted previous to the hydrographic survey of the coasts and waters, they furnish the hydrographic surveyor, not only with the correct outlines of the coast, but also with the precise position of the landmarks upon which he may base his work, or, in other words, a skeleton for the same. But, when such surveys are not existing, he is compelled to lay down the coast-line also, with its detail as far inland as there are landmarks auxiliary to navigation, thus performing the labors of the topographer as well as those of the hydrographer. ”

“ These ridges have no existence in nature. The heads of the rivers which flow toward the Arctic Ocean on the one side, and toward the Pacific on the other, lie intermingled on the surface of a vast plateau; they rise in the same marshes. But, in the European topographer’s imagination, the highest mountain ridges must run along the chief water-partings, and the topographers had drawn there the highest Alps, of which there is no trace in reality. Many such imaginary mountains were made to intersect the maps of Northern Asia in all directions. ”

“ Prof. now took observations for time and latitude in order to fix with accuracy the geographical location of the camp in Flaming Gorge, and to check the estimates of the topographers as they sighted the various stretches of the river. It has been found that estimates of this kind are quite accurate and that the variation from exactness is generally the same in [5] the same individual. Hence one man may underestimate and another may overestimate, but each will always make the same error, and this error can be readily corrected by frequent observations to determine latitude and longitude. ”

“ It cannot be too strongly insisted on that geographical surveys are functions of both civil and military operations. Very much of such work is also possible where a country lies open to exploration, not actively hostile, "but yet unsettled and adverse to strangers. .The geographical surveyor has to fit himself to all such conditions, and it may happen that a continuous, compre- hensive scheme of triangulation as a map basis is impossible. Under such circumstances other expedients must be adopted to ensure that accuracy of position which cannot be attained by the topographer unaided. ”

“ Much the same may be said of the dikes of cooled magma which have been injected along preëxisting fractures.
The base of the geological map.—Modern topographic maps form an important part of the library of the serious student of physiography; they are the gazetteer of this branch of science. Every civilized nation has to-day either completed a topographic atlas of its territory, or it is vigorously prosecuting a survey to furnish maps which represent the relief with some detail, and publishing the results in the form of an atlas of quadrangles. ”

“ If the geology be other than of the very simplest character—and this will generally be true of mountainous regions—it is not only necessary to fix the geographical positions of rock masses, but their elevations as well. In other words, the map must not only be a plan, but special elevations must be represented, known as geological sections. The most satisfactory representation—and this will be essential for all difficult areas—will be one which shows not only special elevations, but the topographic relief of every point in the area. ”

“ The great value of the modern topographical map is becoming, however, universally acknowledged, and every highly civilized nation has either completed or has in preparation sectional topographical maps of its domain on such a scale as is warranted by its financial condition and its state of development. Thus there is now being accumulated a vast library of geographical and to some extent geological information, of which the student of geology must be prepared to make use. ”

“ On the map of Germany (1:100,000) a slope of 50° is shown in solid black while stippled hachures are used for gentle slopes up to 10°. Instead of shading lines following the greatest slopes, lines following the contours and varying in their thickness and in their intervals apart, according to the slope of the ground to be represented, may be employed. This method affords a ready and expeditious means of sketching the ground, if the draughtsman limits himself to characteristically indicating its features by what have been called “form lines.” ”

“ The main topographic features are represented for a moderate distance from the coast, with such detail as is useful, depending on the scale of the chart. Elevations are given in figures for prominent summits, islands, and rocks; the general configuration of hills and mountains is represented by contours on large scale charts or by hachures or shading on small scale charts. Rivers, streams, lakes, marshes, towns, roads, prominent buildings, and other important topographic features are shown by appropriate symbols. ”

“ The complete atlas will consist of several thousand folios, each of which contains a topographical and a geological map of a small section of country, and will be named after some well-known town or natural feature within the limits of the district named. The topographical maps will show the reliefs, drainage, and cultures of the districts, indicated by the usual or definite conventional marks. The geological maps will show on distinct sheets the areal geology, or the areas occupied by the various rocks of the district; the economical geology, or the distribution of useful minerals ”

“ Great generalizations are not often completed at a single step, and it is enough that every effort at advance should have part of its movement in the right direction. What I wish to show is that topographic form was regarded in the days of our eastern surveys, even by our first master of American topography, as a completed product of extinct processes. Topography revealed structure, but it did not then reveal the long history that the structure has passed through. ”

“ It needs but little imagination to foretell that houses would be mere specks, roads, faint lines, and forests, masses of color, in other words, that it would be more instructive to consult the general map, on which all details are magnified to be clearly visible and topographic features brought out with great distinctness than to attempt to trace with unaided eye, from the image of objects at a distance of twenty-four miles, the course of streams or roads through forest or moor, or to judge of the relative elevations or modeling of the ground from the values of light and shade. ”

“ As a work of art, graphically delineating the configuration of a district of surpassing beauty and variety of scenery, it will, perhaps, possess greater interest to the ordinary observer than any scientific value of accuracy and completeness could give it. If a person were called upon to construct an ideal map which should group together specimens of all types of topographical form and the conventional signs known to the draughtsman, he could hardly derive from his imagination a chart more comprehensive than this. ”

“ The lines should preferably run across the long axis of an area, not parallel to it, and the predominating trend or general direction of the areas of one geologic formation on a map should decide the direction of the lines for all areas of that formation on the same map, even if the rule must be violated on some of the minor areas.
An effort should always be made to produce a pattern that is subordinate in strength to the main lines of the base map on which it is drawn. In black and white maps, as in colored maps, unlike patterns should be placed next to each other. ”

“ On the other hand, the draftsman, in reproducing a section that represents the structure along a given line or zone, may be able to make the outcrops coincide with the topography and the formation boundaries shown on the map, but the structure, or the interpretation of it to be given, should be carefully worked out by the author. All essential facts relating to bedding, folding, faulting, crosscutting dikes and veins, or other significant details should be indicated with precision. No attempt need be made to draw firm, steady lines so long as the essential facts are clearly expressed. ”

“ We read how the truths have appealed to his own consciousness. It stands where the relief map itself stands, as representing the delineator’s own mental image of such structure.
There are no lines drawn in this map that contradict or confuse the meaning; all is direct, truthful and clear in statement of fact. Each line has its own particular meaning. If represents direction. Applied to land surface, a vertical line means a perpendicular mountain or side wall of plateau, horizontal lines indicate level areas, and oblique lines a sloping surface. ”

“ The topographical survey of a country is defined by Sir A. Scott Waugh to imply ‘the measurement and delineation of the natural features of a country, and the works of man thereon, with the object of producing a complete and sufficiently accurate map. Being free from the trammels of boundaries of properties, the principal lines of operations must conform to the features of the country, and objects to be surveyed.’
The only safe basis for the topographical survey of a country is a system of accurate triangulation. ”

“ If the bed dips steeply down, the line will be narrower,—if but slightly inclined, it will be broader; the breadth of such a line (which may be coloured to taste) always varying with the thickness of the stratum and the angle which it makes with the horizon. In a district where faults and curvatures along with trap-rocks abound, the mapping becomes more complex, but the principle remains the same—a curved stratum on the ground making a similarly curved band on the map, and a fault or dislocation of a set of beds producing, in the same way, a corresponding break in the lines traced. ”

“ When the maps are coloured, and each child has her own, they may then be taught how to read a map so coloured. The teacher will draw from the class that if the contour lines come close together the ground slopes very rapidly, but that the slope is more gradual when the contour lines are more widely separated—that the greatest height of the land lies near the greater ocean, and that the more gradual slope is towards the smaller ocean, and that this allows of the development of larger but slower rivers than those flowing down the steeper slope. ”

“ These publications are illustrated with well-selected half-tones and carefully prepared black and white maps based on the accurate topographic maps issued by the Geological Survey.
The first need of the intelligent traveler is a map of the area he is about to traverse. Fortunately excellent maps of almost all the larger parks are for sale by the United States Geological Survey at nominal prices. Maps have been published of Yellowstone, Yosemite and Glacier national parks on a scale of 2 miles to the inch ”

“ Topography. The land area on most charts is distinguished from the water area by a stipple or tint; on some charts the topographic features have, however, been depended upon to bring out the land from the water. The solid shore line is the high-water line, and should be clear on the chart; the area between high and low water is sanded or otherwise shaded on all charts. The relief of the land is represented by hill shading or by contour lines which are the successive curves of elevation on the land. ”

“ To see the sketch-map of a previously unsurveyed country grow upon the paper is an intense satisfaction. The aspect of every peak gives rise to a twofold problem. Can it be climbed, and if so by what route? How should it be depicted on the map? These questions are ever present. The solution of them is the thought of every hour, the first point of interest in every view. As it is with the explorer, so to a less extent is it liable to be with every climber; for all climbers are to some extent explorers, even though they are but exploring previously described and mapped territory. ”

“ A geologist who requires a base map that includes new topographic data should address a request for its preparation to the chief geologist, who, through the Director, will refer the request to the topographic branch. ”

“ Great care is necessary in the selection of stations that will be suitable both for the extension of triangulation and the purposes of closely overlooking topographical details. In order to obtain means for correctly orienting the photographic views when plotting the map from them, it is usual, whilst making the exposures, to observe two or three points in each view with the alt-azimuth attached to the camera, in order to ascertain the horizontal and vertical angles between them. ”

“ His routes always lie along valleys, whose sides cut off the distant view and whose bends often prevent him from looking either ahead or back. When he climbs a peak, [96] assuming him to have a clear view, which is rare, he beholds a wide panorama, it is true, but, save in the foreground, it consists of a throng of peaks, whose summits alone are visible over intervening ridges. If, following tradition, he laboriously fixes the position of some of them, it is lost labour, for the mere dotting upon a map of the points of a lot of peaks tells a geographer nothing. ”

“ When dealing with maps not drawn on an equal area projection we substitute quadrilaterals bounded by meridians and parallels, the areas for which are given in the “Smithsonian Geographical Tables” (1894) , in Professor H. Wagner’s tables in the geographical Jahrbuch, or similar works.
It is obvious that the area of a group of mountains projected on a horizontal plane, such as is presented by a map, must differ widely from the area of the superficies or physical surface of those mountains exposed to the air. Thus, a slope of 45° having a surface of 100 sq. m. ”

“ By watching a given section of ridge, while the sun is moving across the sky, all a sunny day, and by using a map at first to discover what the different sky signs as they become visible actually mean, and also how much they reveal of the unseen topography as displayed in the map, it is possible for some men to train their sight to discriminate fairly closely between a number of even more complex signs, and to ascertain actual details as to the character and direction of unseen walls and crests, the location of unseen snow summits, and the length of far ridges. ”