There are a considerable number of maps, the creation of which is related to field studies. The field variation of a given phenomenon can be demonstrated with an appropriate surface view of the issue. Physical-geographic, and socio-economic phenomena can be presented on maps in many ways. Their selection depends mainly on the phenomenon being presented, and on the characteristics of the method itself. Geographiccan be presented by the method of appropriate signs located in the points of occurrence of these phenomena, where each point corresponds to a certain number. The points symbolize objects occupying such a small area that they usually do not fit on the scale of the map, for example, towers, trees, monuments.
The superficial extent of phenomena is reflected by range lines, and the degree to which they are covered by a colored, or graphic, background. Surface marks represent objects whose size and extent can be fully represented at the map scale, e.g. lakes, swamps, forests, etc. In capturing a phenomenon related to a certain space, it can be presented either in the form of a specific symbol within a given area, i.e. by means of a cartodiagram. The degree of intensity of a given phenomenon can also be presented by means of a color scale in relation to a certain unit of area, that is, by means of a cartogram. Linear signs present only the length of an object, since its width is of little importance, or does not fit within the scale of the map. The isarithmic method is also very common. Special methods, such as arrows, directional lines or isochrones, are used to represent the phenomenon of movement.
On maps, several methods of cartographic presentation are often used simultaneously. Methods of presenting phenomena have been divided into qualitative referring to non-measurable features, informing only about the occurrence of a phenomenon ( range, area, signature methods), and quantitative showing the intensity of a phenomenon. The cartogram, cartodiagram, isoline, and dot methods can be included in this group.
Signature method
The main idea of the signature method is the use of localized symbols on the map in the form of appropriately selected signs or geometric figures representing the size of the phenomena under study, or objects. Their grouping is marked on the map mostly in a compact form. Signatures can differ from each other in shape, color, or size. By shape we divide them into geometric, letter, symbolic, and pictorial. Geometric signatures are the most widespread due to the simplicity of their construction, ease of reading, and interpretation. Linear signatures are used less frequently. They are more often found on maps depicting social and economic phenomena. Symbolic signatures usually have a simplified shape of the depicted object. In order to distinguish the depicted objects, signatures of different colors and shapes are used. Using signatures of different color but the same shape, certain differences between objects belonging to one group are marked. The size of signatures is often represented by a scale used to present the size of a given phenomenon in given absolute numbers. The scale of signatures can be represented in a proportional way, when there is a relationship between the size of a given phenomenon and the size of a given signature. The scale can also be arbitrary, when the size of the signature does not directly relate to the size of the phenomenon. The signature method can be used to represent the dynamics of the development of a phenomenon by means of increasing signatures, i.e. signatures that reflect the change of a phenomenon in a continuous manner. The sizes of the signatures depend on the scale and the purpose of the map in question.
Cartogram method
This method presents a given phenomenon by means of its average values within the boundaries of a given territorial unit. In the case of a phenomenon that differs only in the magnitude of occurrence in a given area (e.g., population density), it is presented on the map by relative values, i.e., the ratio of the magnitude of the phenomenon to the unit of area, e.g., population per km2 . In order to illustrate the intensity of a given phenomenon, each administrative unit is covered on the map with a hue, or dotting, or a chevron, with the color chosen so that a change in the intensity of a given phenomenon corresponds to a change in the intensity of a given hue. The tint, or marks, cover the entire area of the map. Thus, a cartogram is a map divided into territorial units, on which the intensity of a given phenomenon is depicted by surface graphic methods. The element that illustrates the intensity of a given phenomenon is the graphic scale. To emphasize the change in the intensity of a phenomenon, different shades (from light to dark) of a single color are most often used than several colors. Despite the great popularity of the cartogram, this method gives the impression of uniformity that the intensity of the phenomenon presented does not change within the area unit. However, within each territorial unit, a given phenomenon is characterized by a certain degree of variation. Another disadvantage of the cartogram method is the arbitrariness of the choice of scale, which can change the picture of the occurrence of a given phenomenon. This demonstrates the low precision of this method. Another disadvantage of this method is that it gives the impression of a radical change in the intensity of a given phenomenon on the border of two territorial units, which in reality is not the case in the vast majority of cases. Cartograms do not reflect the actual distribution of phenomena, and their intensity in space. They refer only to the average value of a phenomenon for a given territorial unit.
Cartodiagram method
The cartodiagram method involves placing a diagram on a map within the territorial boundaries of the occurrence of a phenomenon. This diagram gives the magnitude of a given phenomenon in absolute numbers, and thus gives its summary characteristics within the boundaries of separate administrative units. However, the diagram, as in the cartogram method, does not completely reflect the differences occurring within a given territorial unit.
Lines, solids, and signatures are used as plot elements. Line cartodiagrams are excellent for presenting phenomena and objects, where length is the predominant element. Circular or star cartodiagrams are used to illustrate phenomena that occur cyclically. Circular diagrams are often used to show the overall value of a phenomenon, which is expressed by the area of the circle, as well as the percentage of its components.
Surface cartodiagrams mostly use geometric figures: triangles, squares, rectangles and circles, the sizes of which are proportional to the size of the phenomenon they present. The most common in this group are rectangular cartodiagrams, with the help of which good comparability is achieved, since one side can have a constant value, while the height of the bar indicates a certain value. Square or circular diagrams, despite their simplicity of construction, are less commonly used. Three-dimensional solid diagrams are often used in popular publications, but less often in scientific papers.
The volume of the presented solid is proportional to the size of the presented phenomenon. For a more precise presentation of quantitative relations, figures of equal shape a different size are more often used. The main disadvantage of the cartodiagram method is the inaccurate presentation of the location of a given phenomenon. Also, the diagrams, covering certain parts of the map, give the impression that the phenomenon runs according to the boundaries of the diagram. The cartodiagram method is widely used because of its simplicity of construction, and ease of perception.
Point method
Another method of presenting phenomena on thematic maps is the point method, which illustrates the intensity of a phenomenon in relation to an area. It is based on the assumption that a certain number of units of a given phenomenon or object corresponds to a point of a certain size. Here one selects the so-called “weight” of a point, that is, the number of units of a given phenomenon corresponding to one point. This selection depends on the scale of the map. With the help of the point method, a fairly faithful picture of the distribution of the phenomenon is obtained. The simplicity and demonstrability of the point method allow it to be widely used. Using different colors of points, it is also possible to show not only the quantitative, but also the qualitative side of a phenomenon. Population maps can show nationality differences by using a different color for a particular nation.
Isoline method
This method was developed in 1846 as the so-called equidistant line method. The isoline (isarithmic) method is based on the assumption that a phenomenon occurs uniformly within a given area. Phenomena are represented by lines connecting points with the same values. These lines are called isolines (isarithms). These lines are determined by averaging the values between different measurement points. The most common isoline is a level. Frequently used isolines are also:
- Isotherms – lines connecting points of equal temperature
- isohyets – lines connecting points of equal rainfall totals
- isochrones- lines connecting points of equal occurrence of a given phenomenon
- isohypse (level) – lines connecting points of equal height
- isohalines – lines connecting points of equal salinity
- Isobaths – lines connecting points of equal depth (in relation to bodies of water)
- isoheles – lines connecting points of equal insolation
- Isobars – lines connecting points of equal atmospheric pressure
- Isotachy-lines connecting points with the same value of velocity at a given moment.
The main disadvantage of the isarithmic method is that the vast majority of isolines are not based on data derived from measurements, but on a series of averaged points obtained by interpolation. Thus, isarithms simplify the picture of the presented phenomena. The main advantages of this method include the replacement of the boundaries of territorial units appearing in cartograms with harmonious isolines.
To distinguish individual isarithms from each other, their values are usually described on a map. Often, in order to plasticize the arrangements of isarithms, appropriate graphical scales are used, with the help of which colors are selected to represent them between individual isarithms.
Range method
This method for showing the spread of a phenomenon without taking into account its intensity. For this purpose, range lines are used, with which it is possible to mark the extent of not only one, but also several phenomena simultaneously on a single map by using different colors of lines. Range lines show that a given phenomenon occurs in the area it covers. However, using this method it is possible to reflect only the approximate location of the phenomenon. It does not have to occur in the entire area covered, by the lines.
Range lines are very often used to represent the distribution of animals and plants on zoogeographic and phytogeographic maps. Colored, dotted, or graphed areas can also be used to present the level of spread. The range method can be used to capture the absolute distribution of a phenomenon when it falls within a range plot, or its relative distribution. The extent of a phenomenon can be defined by lines, or by description, when the range boundaries are not specified.
Surface method
This method is also called the chorchromatic method, or the qualitative background method. It is an expanded take on the range method. It involves dividing the area into fields (mutually exclusive extents) that are qualitatively different, there are no overlapping areas, such as a land use map, administrative map. The map area is divided into regions, it can represent regionalization. Regions are delineated on the basis of previous indicators, predetermined criteria. The surface method is used to present qualitative characteristics of phenomena. Marking quantitative characteristics is used rarely, and consists in delineating different surfaces and marking colors on them with a color scale, or hatching. Then the least intense color informs and weak intensification. The occurrence of several phenomena on the same surface is reflected by a combination of the above methods. Range, and surface methods are often used in conjunction with signatures.