Photogrammetric work-cameral processing of space, aerial and ground surveys in order to create an image of the terrain in orthogonal projection.
The process of preparing the final product (digital and/or paper orthophotoplans and orthophotos of the area of interest) includes:
- Selection of raw data.
- Preliminary analysis of raw data.
- Detailed technical design of processing.
- Photogrammetric processing of initial data.
- Export of obtained materials.
- Control of work execution.
- Generation of documentation and products for further work.
Detailed technical design of image processing:
In the detailed technical project, the recommended methods of processing shall be specified and technically justified. It is necessary to consider the nature of the terrain and buildings, the quality of images, density and location of points of geodetic networks and survey justification, equipment with photogrammetric devices and software.
At detailed technical design the scheme of works on photogrammetric condensation of a basic network and the scheme of works on drawing up of originals of maps (plans) are constituted. The choice of photogrammetric processing of images is justified.
Depending on the volume and quality of planned high-altitude training in the technological scheme of office processes can be envisaged:
- Photogrammetric thickening of the survey justification (with sparse field preparation of images) and subsequent collection of digital information about the terrain from single images or stereo pairs oriented according to photogrammetric thickening.
- Processing of single images or stereo pairs oriented directly on the field training points (with continuous binding of images) or contour points identified on existing images of previous years or on maps (plans) of a larger scale.
Detailed technical design of photogrammetric condensation includes the selection and designation of points of the photogrammetric network, as well as the preparation of the network diagram.
Photogrammetric processing includes:
- Creating of a swivel mounting.
- Performing internal orientation of images.
- Performing mutual orientation of images.
- Performing external orientation.
- Creating a DEM (under condition of using stereo images).
- Orthorectification of data.
- Creation of a seamless mosaic.
- Alignment of mosaic color characteristics.
- Export of orthoimages.
- Quality control.
Reference data (reference points) for photogrammetric condensation are the points of the state geodetic network, geodetic networks of condensation and points of the survey geodetic network identified on the pictures, as well as additional information obtained by onboard devices directly in the aerial survey flight.
Construction and processing of DEM — after orientation of the model or images information about the relief and / or contours in a sequence determined by the nature of the mapped area are collected. Next, 3D vectorization is carried out in stereoscopic mode, the construction of 3D models of objects.
Orthophotographic image — a photographic image of the terrain in orthogonal projection, obtained as a result of orthophototransformation.
As a result of digital transformation, the original image is converted into a digital image of the terrain, which is an orthogonal projection of the terrain on the horizontal plane.
- Digital image of the original photo.
- Values of elements of internal and external orientation of images.
- Digital terrain model (DTM).
Scope of using photogrammetry:
The main applications of digital transformation are topography and cartography. In creating and updating maps for various purposes from aerospace images, transformed images of the terrain in the map projection are created. These images can be created as a result of processing a single image or from images located in a route with overlaps. Another area of application is GIS, where the data obtained as a result of photogrammetric processing, thematic mapping (decryption) of objects is performed. Digital transformation is performed with the accuracy corresponding to the requirements of current regulations to the accuracy of maps of the corresponding scale.
- High measurement accuracy.
- Large amount of information about the object.
- Objectivity and reliability of measurement results.
- Possibility of obtaining in a short time information about the state of the entire object and its individual parts.
- Ability to study stationary and moving objects, transient or slow-passing processes.
- Ability to perform visual assessment of objects.
- Research of objects by remote method (significant when staying in the area of the object is unsafe for life).