Specific mapping and creation of DTM:

Specific surveying means vector plotting in pairs of stereo-images.

The principle of this procedure is connecting of a special photogrammetry SW with the CAD program. The photogrammetry SW used in our company is PHODIS (ZEISS), SUMMIT EVOLUTION (INPHO) and DEPHOS (DEPHOS). The first two are connected to a CAD program MicroStation (BENTLEY) and the third works in its internal format, which is further imported in the format *.dgn into MicroStation.

  

With regard to the SW used by us we prefer format *.dgn; however, currently there is no problem converting to other formats (such as *.dwg, *.dxf) according to the customer’s requirements.

In most orders, the client supplies, together with other documentation, the data model for plotting. I.e., the client defines individual elements which are to be included in the future specific map. Following the submitted model a sample is plotted which is sent for assessment and when correctness is confirmed the order is further processed.

Besides a purpose-specific map, another product of plotting may be a digital terrain model (hereinafter referred to as DTM). Unlike in the case of a purpose-specific map, when creating a DTM, only elements modelling the terrain are plotted (i.e., roads, terrain fractures, water courses …) and further a regular network of height points is created which reliably represents the course of terrain between terrain fractures. The dimension of the network of height points (10m – 100m) depends on the scale of images and the required precision of DTM. Out of the wide range of uses of DMT we may mention the formation of contour plans, calculation of yardage, visualisation of flood areas …

Automatic data collection DTM (depending on the required precision) may be applied for large areas from an aerial survey. This procedure is significantly faster but it is necessary to check the data acquired in this way and to edit them. This procedure may be used especially for formation of small scale orthophoto plans and collecting of data for various visualisations.

We use the MATCH T (INPHO) program for automatic data collection.

The accuracy of plotting depends on the image scale, quality of input data (image quality and resolution, triangulation calculation…) and the skills and experience of a drawer. In general, the following chart may be applied.

Image scale
Final map scale
Attainable accuracy
Resolution of orthophoto
20 000
5 000
50 cm
20 cm
10 000
5 000
25 cm
20 cm
8 000
2 000
20 cm
10 cm
4 000
1 000
15 cm
10 cm
2 500
500
10 cm
10 cm

Hypsographic digital model of riverbed.

3D modelling

Automatic aerotriangulation

Orthophoto maps

Specific mapping

Surveying of facades

Contact

Adress:

SFP-carto
Radobyčická 10
301 00 Pilsen
tel./fax +420 377 970 901
info@sfp-carto.cz

česky/english

SFP - Aerial & terrestrial photogrammetry, © 2007, made by: ERB Production