Tham khảo tài liệu 'mapping geomorphological environments phần 3', khoa học tự nhiên, công nghệ môi trường phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Mapping Geomorphological Environments Among the most common types of analyses is statistical analysis. Most GISs have tools for calculating statistical parameters and for the creation of graphs. However if the user desires he can easily extract an information layer or the result of a search into another file form and import it in a purely statistical program. Of course the possibility of importing the statistical results within the GIS is also available. GIS has the capacity to spatially represent descriptive informations by using symbols for each geographic entity. Thus a torrent s colour may change in reference to its class and its shading density may change in accordance with the value of the drainage frequency in such a way that the spatial distribution of the descriptive information would be immediately understood. This feature is enabled within thematic cartography and four basic methods are followed 1. Individual Values The method of individual values is used to represent features with distinct values. The distinct values Grouping of branches on the basis of their length. can be either string characters . geological ages or numbers. Some examples of values can be the 1st Class of a torrent but also the value Crystal limestones of a geological formation. Depending on the descriptive information the appropriate symbolism is selected. 2. Ranges It is usual to group information in ranges when expressed in continuous values such as altitude slope direction etc. There are many grouping methods such as equal ranges or equal width ranges. ơass . in ------ n Representation of the branch class by different symbolisation and colour. Usually a drainage network s branches may be grouped based on their length and then each range is represented by a different tint. In the following example the branches have been grouped in a way that each range contains an almost equal number of branches. Through this method drainage density and frequency can be depicted. 3. Statistical
