Mapping

“ For mapping, do not take a case of instruments unless they are really good; have rather a few good ones wrapped in a chamois skin, a small ivory rule on which the eighths of an inch serve for miles, a pair of good dividing compasses, a good circular protractor transparent marked, from 0 to 360, a small parallel rule, HHH. pencils, a cake of blue for rivers, and carmine for roads, with a couple of sable pencils and a fine incorrodible metallic pen, will enable you to make a very complete and reliable map. ”

“ The symbols shown, however, will cover all the ordinary requirements of miscellaneous mapping. Though the plate shows more than one symbol for some features the symbol most commonly used is given first and should be preferred. The center of each symbol should mark the location of the feature symbolized. Symbols are not always platted with sufficient care. On small-scale maps they are difficult to locate and unless great care is taken in platting them they are likely to be several miles out of place. All symbols should be located precisely where they belong. ”

“ In mapping, charting, and geodesy, the inconsistent application of algebraic sign to geographical references and the angular reference of azimuthal systems is a potential trouble area in scientific data collection. The following conventions have wide use in the standardization of scientific notation: Longitude references are positive eastward of the Greenwich meridian to 180°, and negative westward of Greenwich. Latitude references are positive to the north of the equator and negative to the south. ”

“ Relief Maps are intended to present a representation of the ground which shall be absolutely true to nature. The object, however, can be fully attained only if the scale of the map is sufficiently large, if the horizontal and vertical scales are identical, so that there shall be no exaggeration of the heights, and if regard is had, eventually, to the curvature of the earth’s surface. Relief maps on a small scale necessitate a generalization of the features of the ground, as in the case of ordinary maps, as likewise an exaggeration of the heights. ”

“ Every map is a sketch, which is corrected by the geometric location of a greater or less number of points. Assuming entire accuracy in the location of the points, that is, assuming that the errors of location of the points are not perceptible upon the map, the measure of accuracy of the map consists in the number of these geometric locations per unit of surface, per square inch, if you will, of the map. The greater the number of these locations the greater the accuracy of the map, but however numerous they may be the map itself is a sketch, the points located being simply mathematical points. ”

“ RUSKIN'S MAPS
Reading the map is as great a pleasure to some people as reading a story-book. You will see them pore over the atlas for an hour together, going on dream-journeys. It is a cheap way of globe-trotting, and gets rid of the discomforts; only one must have imagination to turn the wriggling hair-lines into vistas of river scenery, and the woolly-bear shading into forested crests and peaks against the sunset. It needs a good deal of imagination to get over the ugliness of most modern maps; but why should maps be ugly? ”

“ Such is the conception of an accurate map which is an attempt to produce on a plain surface or sheet of paper, a horizontal projection of objects on the ground, which will show the relative positions of every detail on any desired scale with as little distortion as possible, and on which distances may be measured in any direction, and areas computed with a degree of accuracy only limited by the scale. ”

“ 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. ”

“ Study a good map—a quadrangle of the U. S. Geological Survey, for instance. Note what things are represented, and how representation is made: study the map, until it is thoroughly understood.
There are three factors with which the map-maker deals: direction, distance, and elevation. With the first, he must always reckon, and usually with the second and the third as well.
Direction is fundamental. Suppose there are three dominant points in the area to be mapped, relatively situated as here indicated. ”

“ The degree of generalization in the geologic and other detail to be shown on a map usually involves a corresponding degree of generalization in its base. Absolutely true generalization means the same degree of omission of detail for each kind of feature. If a base map on a scale of 1 mile to 1 inch, prepared with the usual detail, were placed before a camera and reduced to a scale of 16 miles to 1 inch, the lines representing the smaller tributaries of streams and the smaller water bodies, as well as many other features, would probably be so greatly reduced in length as to be illegible. ”

“ And like a diagram or map, it is in a way artificial since it gives weight to one element at the expense of the others. But again like the diagram or map, the thing it shows is a fact, a fact which is more readily grasped by this artificial device than by bald statement. Maps do not take the place of photographs, nevertheless they have their own peculiar place in making intelligible the make-up of the physical world. ”

“ The modern map, well and thoroughly made, records faithfully every fact concerning the surface of the earth now known to man, and there is very little about it that scholarly geographers do not now know. In addition to the modern map’s accuracy, it is as much more attractive than its forebears to the eye as the beautiful color pictures now used in textbooks are seen to be when compared with the muddy wood cuts that appeared in schoolbooks a century or more ago. ”

“ Each of the three distances of each of the three compartments should be made to show the objects conspicuous to the eye from the summit of the Rigi, and those, too, which though not conspicuous, are yet of sufficient interest to be worthy of notice. With such a map before you, you would almost be able to construct, and put together, the view for yourself. He alone understands a scene, who has in his mind distinct images of all its parts, and of the relation of each to its environment. ”

“ Map Projections are dealt with separately below. It will suffice therefore to point out that the ordinary needs of the cartographer can be met by conical projections, and, in the case of maps covering a wide area, by Lambert’s equal area projection. The indiscriminate use of Mercator’s projection, for maps of the world, is to be deprecated owing to the inordinate exaggeration of areas in high latitudes. In the case of topographical maps sheets bounded by meridians and parallels are to be commended. ”

“ My 'Handbook of the Stars' has been prepared to aid the student in the construction of such maps.
In selecting maps it is well to be able to recognise the amount of distortion and scale-variation. This may be done by examining the spaces included between successive parallels and meridians, near the edges and angles of the maps, and comparing these either with those in the centre of the map, or with the known figures and dimensions of the corresponding spaces on a globe. ”

“ 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. ”

“ For in the schoolroom, as far as the study of the map went, we began with the symbol and stuck to the symbol. No teacher of geography I ever had, except the master I referred to, took the pains to ascertain whether I had any sense of the facts for which the symbols stood. Outside the study of maps, geography consisted of statistics: tables of population, imports and exports, manufactures, and degrees of temperature; dimensions of rivers, mountains, and political states; with lists of minerals, plants, and plagues native to any given part of the globe. ”

“ The habit of locating the events recorded, of tracing upon the map the route of an army, or the line of an important road or canal, and observing the impediments or natural obstructions to be overcome, with the great advantages to be derived therefrom, together with inferences as to the time and labor required, has the effect of making the study of history of living interest, especially if the map used indicates such surface structure. ”

“ Geometry grew out of the practice of surveying, and now embodies many of the laws and principles of the science. There are several distinct systems of surveying, classed according to the purposes contemplated. It is astronomically employed in determining the figure of the earth by the actual measurement of arcs. A fair knowledge of mathematics and trigonometry is required in what are known as coast surveys. Land surveying is of the plainest kind, and employed in finding the contents of areas, or in dividing large tracts into lots of smaller dimensions. ”

“ The time came when it was decided to republish, and I sent in my manuscript, and the map along with it, to Messrs. Cassell. The proofs came, they were corrected, but I heard nothing of the map. I wrote and asked; was told it had never been received, and sat aghast. It is one thing to draw a map at random, set a scale in one corner of it at a venture, and write up a story to the measurements. It is quite another to have to examine a whole book, make an inventory of all the allusions contained in it, and with a pair of compasses, painfully design a map to suit the data. ”

“ A structural map suitable to all grades of pupils, the lower as well as the higher grades, seems highly essential; especially should it be one that is adapted to the teacher’s use while before the class—one to teach from. This should be entirely different from a reference map. It should plainly show the great facts of physical geography or surface structure, as well as some detail, and this in a simple form. For the lower grades there should be no lines to mark the political divisions, neither should there be any names of countries, states, or cities to designate localities. ”

“ It does not copy nature, but gives us a simplified representation of it, which is no misrepresentation, but such as sharpens our vision in view of the complexities of reality,—like the ideal picture which the geographer draws in his map, as a means not to deception but to more effective guidance, he meanwhile assuming, that they who are to profit by the map will know how to read it, i.e., to interpret it in accordance with nature. ”

“ 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. ”

“ In preparing an original geologic map a letter symbol, such as has been just described, or a number should be put in the proper place in the explanation, and the same symbol or number should be repeated at one or more places on the map within the areas to which it refers. Each area that is indicated by a color should be marked with the proper symbol in order to make its identification sure, for light colors especially are likely to fade and mixed colors can not be discriminated with certainty. ”

“ As this new light comes to the student, he looks with interest and eagerness to see the plan of it all. We do not mean to say that he sees in the map before him an actual correspondence to the earth’s surface structure, that [40] is, forms that are reproductions in miniature of mountain range and valley, but he sees a representation of them calculated to arouse his imagination to a lively degree. He is enabled to picture to himself great slopes crowned by lofty mountain peaks, and the meeting of their lower edges where mighty rivers flow. ”

“ But we have chosen our example of a greater breadth than can often be required, on purpose [558] to shew how high the errors can ever arise; and how they may, if it is thought needful, be nearly estimated and corrected.
Write down, in a vacant space at the bottom of the map, a table of the errors of equidistant parallels, as from five degrees to five degrees of the whole latitude; and having taken the mean errors, and diminished them in the ratio of radius to the sine of the mean inclination of the line of distance to the meridian, you shall find the correction required ”

“ The size of a symbol must depend on its importance on the map bearing it. On a map that shows numerous mines, for instance, the crossed hammers or the symbols for shafts should be not only visible but conspicuous. The draftsman who is to make such a map must know beforehand how much his drawing will be reduced in reproduction and must make the symbols in proportion to the reduction. The symbols shown in Plate II (p. 20) should be used in all the Survey's illustrations where they are appropriate. ”

“ The amount of literature which is devoted exclusively to the subject of topographical drawing and sketching, as distinguished from the actual field-practice, is very scarce. When the surveyor has completed the collecting of all the data which are necessary for the obtaining of an exact reproduction on paper of the area which has been surveyed, the question arises, Which are the best methods by which these data can be graphically reproduced in a map, so as to give the reader the best possible idea about the exact formation of the ground surveyed, whether it be a farm, a county, or a State? ”