Automatic aerotriangulation:

The result of any triangulation (manual, semiautomatic or automatic) is elements of exterior orientation of images necessary for further processing of data from the images.

In photogrammetry in general the elements of exterior orientation are presented by the coordinates of the centre of the entrance pupil X0, Y0, Z0 and the three slopes of the image ω, φ, κ – all these for each picture. The calculation of the necessary values may be performed for the whole block of images and this offers at least two advantages.

Quality – in a regular procedure the whole block is compact, there are fixed connections of pictures even with triple overlapping and rows are connected with greater strength as well (identical points are located at up to six images. This applies to the standard longitudinal overlapping 60%).

What is also important is the financial aspect. Especially with large blocks, it is possible to substantially decrease the price of pre-flight preparation by decreasing the number of control points. With semi-automatic and automatic methods (in principle a manual intervention is always necessary) connecting points are searched for on the basis of correlations and they may be quite numerous. However, what matters is the quality of their placement and the results of the search must be checked.

Example: a block of 300 images, 25 control points (positional and height ones), 10 height only control points, about 20,000 connecting points. This block is fixed, it is relatively connected by a large number of points and absolutely placed in a coordinate system – the number of control points is sufficient.

 

As well as in our SW, the majority of special programs for AT include various tools for checking the calculation and searching for faults in materials and individual steps of the calculation. Here too (as well as elsewhere) the quality of the result is conditioned mainly by the quality of the input data.

Just a few notes regarding output formats. As we bought PHODIS from ZEISS (Germany) as the first station, we used mainly the exchange format Phorex and PATB. Currently, we process AT via the program MATCH AT, where the results may also be in other formats such as BINGO, SOCKET SET, Z/I, etc.

  

  

Today it is also possible in many programs which work with pairs of stereo images to set the elements of the exterior orientation for individual images in a text form. However, the most viable solution is export and import of a whole project which we use in our office. One of our software programs is Evolution from INPHO (Germany); here of course it is possible to perform direct importing of whole projects from MATCH AT.

The accuracy of triangulation depends on the image scale and the quality of the input data (quality and resolution of images, method of signalling and positioning of control points …). 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

 

3D modelling

Automatic aerotriangulation

Orthophoto maps

Specific mapping

Surveying of facades

Contact

Adress:

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

česky/english

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