The process of digital topographic maps creation

The creation of digital topographic maps includes following main stages:

• automatic conversion of original cartographic information into digital form;
• symbolization of digital cartographic information and automatic creation of digital maps.

Development of user's database control system for working with digital topographic maps

The first stage

In the first stage the problem of receiving on the basis of original cartographic information (aerospace photographs, disjointed original and colored drawing map's prints) vector digital model of a map - the base of a digital topographic map is solved.

This problem is solved in the following ways:

• by means of digitizing original cartographic information on the map-case (digitizer) in the way of tracking object's contours, preparing and bringing in semantics, structuring of digital information;
• by means of scanning original cartographic information with subsequent automatic or interactive vectorization and recognition of raster representation on the display, input of required semantics and structuring of digital information.

At the same time for automation recognition and vectorization of raster representation very efficient is to use mechanism of cartographic expert system for tuning and training software at given parameters of locality and maps recognizable elements and objects. Present scanner technologies of automatic raster digital information getting provide automation of recognition 90% on relief, 50-60% in hydrography and growth by using published map originals. Approximate efficiency - 70-100 hours for one nomenclative list.

The second stage

In the second stage following problems are solved:

• symbolization of vector model;
• creation of a digital topographic map according to the degree of load;
• control and editing of symbolized digital topographic maps;
• receiving of archival graphical symbolized copy of a digital topographic map.

The notion of symbolization process is in appropriation to each object the code (N) corresponding to a conventional sign from the library of conventional signs in accordance with classified code, object's characteristics and its meaning. This process is carried out automatically depending on the scale and the type of a digital map. At the same time unified library of conventional sings and types is formed. Each conventional sign has its own digital description - vector or (and) raster. Besides for following visualization a group of deduction sequence of cartographic representation is prepared.

The level of load

One of the significant characteristics of a digital topographic map is the level of load. Original depiction, for example, for a digital topographic map with the scale 1:50000 are taken as basis. Further each object according to its significance receives one of the load levels (1, 2, 3, 4). Such approach provides readability of cartographic depiction on the display practically in every its territorial coverage within the whole nomenclative list.

The creation of a digital topographic map according to the degree of load is realized on the display in interactive mode in the windows, beginning with the most little window, within which all objects are read, with the following window upsizing through the method "quadrotree". At the same time load coordination and objects' brief between windows is provided within one nomenclative list or between adjacent nomenclative lists for each degree of load. For solving this problem it is efficient to use mechanism of cartographic expert system for taking decisions about objects' selection optimization in the degree of load taking into account a number of factors. This solving requires mechanism of establishment space-logical connections.

When forming digital topographic maps due to the degree of load, program and visual control and information editing is carried out, which, basically, comes to the placement of objects' names. The process of map creation ends with receiving symbolized graphical copy in series for each degree of load, beginning with the first (with more important objects).

Digital map creation is carried out in universal data structure, that provide an opportunity of vector information recording in consecutive as well as in chain-nodal representation, in raster view, supplemental information and also creation of the section of present users. The technology is realized through the complex of automatized work places, united in local network.

Methods and technologies of maps creation

Dataware technologies of digital maps creation include:

• classification and coding system of cartographic information;
• rules of digital description of cartographic information;
• system (of library) of conventional signs of digital maps;
• data format of digital maps.

To the main methods of map creation belong:

• methods of automatic recognition of images (raster depictions, got while scanning);
• methods of cartographic generalization with the use of graph theory and logical-procedural approach, mechanism of expert system;
• methods of multimedia software;
• methods of expert systems;
• methods of space-logical connections' establishment.

All main qualities and advantages of digital topographic maps manifest while using them. Therefore together with digital maps a user may be given a digital map database control system, which carries out following main tasks:

• creation and running digital map database;
• work with cartographic representation:
  • display, ranging, cartographic representation movement in arbitrary direction;
  • control of dynamic window and the degree of visual depiction load;
  • receiving information about objects;
  • depiction editing;
  • managing of classifier and library of conventional signs;
  • creation, storage, mapping a user layer and its editing on digital maps;
  • managing of user's classifiers of conventional signs library ( for example, library of special conventional signs);
  • depicting of cartographic representation on plotter or other devices;
• connection with standard database;
• user's interface, which is used to solve applied informative and calculated tasks.

It must be noted, that the creation technology of digital maps and user's system of database control is realized on one and the same program module, which allows unifying software and dataware on the whole.