ORTRO

After the alignment of the images ORTRO can reconstruct a three-dimensional model, perfectly scaled, of reality, the scale is not deducible.

To estimate the exact scale, and introduce a real coordinate system, (Georeferencing), it is necessary to know the measures of two or more points, called Ground Control Point (GCP). We can set these measures manually associating them to the corrisponding pixel of the photos; ORTRO has several methods to simplify this task:

• Approximate georeferencing. Consists of extracting the coordinates of the projection centers from the EXIF information of each image. This first approximation of the model leads to an automatic raw collimation of each GCP, in the corresponding images.
• Incremental Bundle Adjustment. Ss performed progressively as you add new GCP to your model; camera calibration and alignement parameters are recalculated in real time. This minimizes the parallax residuals, and significantly increases the accuracy and the precision of measurements.
• The statistical measure of residuals.The georeferencing procedure produces always optimal or sub-optimal results and the highest quality possible, however the degree of congruence between the alignement and the measurements of the GCP can not be known a priori. To fully validate the quality of the model ORTRO provides an estimate of the error, for each control point, through the geometric reprojection technique

The control points can be typed manually or imported via an exchange metafile.

The georeferenced 3D model is ready for measuring. As the original source of the information consists of the images, they remain the most intuitive and effective means for collimating the geometrical details, even though, according to the contexts, different operating modes are available. Ortro supports all possible measurement mode, and gives the possibility to get accurate and precise values in each condition. Here are the main measuring methods supported:

• Integrated dense points cloud. ORTRO is able to automatically generate a dense cloud of three-dimensional points that models with great accuracy the details that appear in multiple frames. The output resolution is a function of the degree of overlap among the images, but not always, for various reasons, it reaches a uniform level sufficient to obtain the desired accuracy. When this is possible a real three-dimensional coordinate can be associated to each pixels of the image and the data collection can be done using a single image at a time. If you have a high definition laser scanners cloud, ORTRO can automatically import and register it with the one built by the photos, increasing dramatically the precision obtainable.
• Homologous images. If the dense cloud is not sufficient for a precise acquisition in the area of interest, the relief of some points could be jeopardized. ORTRO provides an alternative technique for the measurement of important points, based on the method of the homologous images. You select the point of interest on one image where it is well visible and ORTRO automatically chooses the other images where the same point can be located collecting its in exact pixel position. The matching on homologous images is done with a sophisticated interactive algorithm-assisted procedure to ensure the minimization of residual errors.
• Stereo vision. The stereoscopic method is one of the earliest and most established systems for 3D data collection from images. In the ORTRO development team operates the best spcialist in stereovision having realized several stereo photogrammetric applications; many customers have been working with those softwares for many years. The stereoscopic method is particularly effective                                         for images acquired from aircraft or drone, in these cases the overlapping frames, which must exceed 60%, allows to work with pairs of images in a 3D immersive environment obtained wearing                                         special glasses. ORTRO manages a wide collection of stereoscopic equipment, from the simplest ones consisting of just Red Cyan glasses (anaglyph technique) to the most professional that include                                         OpenGL stereoready graphics cards, active and passive eyewear, and virtually every type of screen on the market. The generation of stereo pairs (epipolar resampling and possible rotation                                         of frames) is obtained in a completely automatic way, their consultation takes place at continuous with the use of a control map using two main techniques fixed and moving floating mark.

Data collection is performed in a 3D CAD environment, Vector data can be inported and exported in the most popular vector formats

Ortro integrates many tools that facilitate the production of professional processed, exported in the most common exchange formats:

• Coloured dense point cloud.
• Texturized mesh .
• Ortho immages.
• Sections and profiles.
• Contour linees.
• Volume calculation.