SIMBOL IMAGE PROBLEMS IN AUTOMATED MAP COMPILATION AND UPDATING DIGITAL TOPOGRAPHIC MAPS

N.F.Vasilkova

FGUP The Center "Sibgeoinform"

info@sibgi.ru

 

The digital topographic map assumes a graphic display of topographical objects and signatures for map presentation maintenance according to the existing conventional signs and further graphic output.

Let's list only some difficulties at the construction of algorithms for display of map objects geometry.

The most labour-consuming is display of the rocks areas. For their display it is necessary to break a rock figure into some components and by means of algorithms to connect among themselves in a uniform complex.

It is a lot of such complex conditional images of objects, which, depending on the form, arrangements and figure, have the individual form not repeating never more.

It is possible to carry to labour-consuming objects:

Ice breakages and rocky coast;

Glaciers and snowfield;

Complexes of ravines and gullies;

Landslips;

Lava streams;

Barrows and hillocks;

The areas of coastal shallows and banks;

The areas of dangerous coast;

Reeves;

Complexes of sluices, sediment bowls, open pits and coal cuts;

Cult structures with shape of domes;

Frontiers with frontier marks and earth marks; etc.

It is also necessary to consider displays of many linear objects, represented a line of the certain width. So in scale of 1:50 000 lines width of highways is increased up to 1mm; the width of highways is increased up to 1,4mm. Railways are represented by thickness of 0,5mm. More often these roads go on banks or dredging which are displayed by lines with teeth which width on a map makes 1mm.

According to the Manual Unit I: Average errors in plan position on maps of subjects images and contours concerning strong points should not exceed 0,5mm. It means that cartographers in the given situation do not put the admissible accuracy.

The same occurs at display of the rivers and channels in two lines which are artificially extend.

The same principle is applied and to linear glades.

The map is more all loaded in the built up territories of cities.

The same is necessary by fonts completion at transition from one scale to another which sizes underline:

     gradation of settlements on number of inhabitants;

     importance of an object;

     navigability of the rivers.

The font shows:

     type of settlement;

     political-administrative value of settlements;

     the basic or second name of an object.

The given requirements are not actual at occurrence of digital production, as all characteristics can be entered into semantics of object.

Earlier maps made in the traditional way have included errors of blueprint installation, manual maps frame construction. Items of the State Geodetic Control in this case were put on coordinates which were moved in plane from actual position, nevertheless other objects of a map remained in the places.

Accumulation of errors in plan position has made inadmissible limits that have come to light at work on updating.

As a result of the aforesaid, it is possible to draw a conclusion, that accuracy and reliability are lost on a digital topographic map and there is a number of additional works and time expenses on objects display completion.