PMS AG Photo Mess Systeme


An Overview about the 3D Photogrammetry and the Rectification with ELCOVISION 10

The usage of photogrammetry is recommend whenever larger data sets (details) are to be stored in the photo and if only small amounts of time are available at the object. The possibility to do the measurements even years later and the automatically given documentation rank likewise among the advantages of the photogrammetry.

The fundamental advantages of the photogrammetry can be summarized thus as follows:
  • Non-contact measurement of the object
  • All documentation and information for the measurement is saved at the moment when the picture is taken
  • The evaluation is chronological and spatially independent from the moment the pictures were taken. This means the evaluation could be done even years after the images were taken.
  • The only condition to the object is that you must be able to photograph it.
The Photographs of the Object

The object is preferably photographed with a calibrated camera. For scale information we measure the length of at least one distance or we simply photograph a well known distance like a gauge rod. Many photogrammetric evaluations particularly larger objects use a few control points for the definition of the system of coordinates and to ensure the accuracy. These control points can be measured using ELCOVISION 10 ElTheo.
The object is photographed freehand as the situation permits. Lifting platform are usual aids or the use of helicopter or a small aircraft. Even model helicopters are used for photograph campaigns in difficult terrain.

The Preparations for the Evaluation of the Pictures

In a first step the pictures were réseau measured and orientated.Here the program computes the points of view of the cameras at the time the photo was taken.
During orientation the pictures can be combined together in any order. ELCOVISION 10 does not need any further information like approximate values for the camera point of view for the orientation process.
The final global orientation (bundle adjustment) with up to 1000 pictures ensures a homogeneous accuracy level by the entire photo block. All measurements and scale information are computed balanced with each other and a homogeneous photo block results. Also possible measuring errors or point mistakes are uncovered and displayed to the user. As welcome by-product the so-called new points are computed. These points are the very exactly computed 3D coordinates of the object points used for the orientation. These points are very usefull e.g. as a skeleton for the CAD drawing.

The Evaluation of the Photo Block

After the orientation procedure the photo block is loaded into a CAD program. This is done very easily using one of the CAD plugins of ELCOVISION 10 which were available for many different CAD of programs. All drawing functions of the CAD of system become thereby also measuring functions for the measurement from pictures. The plugins for AutoCAD offers also extensive possibilities for the production of 3D orthophotos apart from the conventional line evaluation.

The Rectification Module ELCOVISION 10 ELSP

Like the 3D - photogrammetry ELCOVISION 10 the rectificiation module ELCOVISION 10 ELSP can use any kind of images.
Beside a point-wise rectificiation during a line evaluation in a CAD system you can also compute a pixelwise rectified orthophoto within seconds. You can define any number of rectification planes per image. The rectification planes can be cut out in arbitrary manners. This ensures that only valid parts of the images are rectified. A orthophoto can be built up from as many as desired images and rectification planes. You can save the images in any supported digital image format or printed out true to scale.