Many of us know web mapping services which allow displaying maps with real view of the Earth’s surface. On these maps you can see a direct view of residential, industrial, agricultural or natural areas. A disadvantage of these web services is low spatial resolution, old data, distortion or objects positional offset from the real geographic position. Imagery from these maps services (Pic.1a) only resembles orthophoto maps (Pic.1b). However, they don’t show real vertical view, but an oblique one.
Pic.1 Comparison of oblique (a) and vertical orthophoto image (b)
Orthophoto map is in reality a map layer which represents a vertical view of the Earth’s surface in each pixel. The procedure to create such a map consists of image capture in regular overlaying pattern and height over ground (resulting spatial resolution of the map depends on the height over ground, camera sensor resolution and lens focal length, its units are cm/px). These images are then processed to create a mosaic. This process consists of a several steps like the camera lens correction and images orthorectification in order to create a real map without any oblique views. Such map layer enables uniform scale in each pixel, distance measurements or surface area calculations.
With the help of technologies related to unmanned aerial vehicles our company is able to create orthophoto maps:
- With high spatial resolution (<1 cm/px)
- With a large area covering
- In various spectra (RGB, NIR, multispectral)
- With very precise georeferencing and scale (the definition of the exact position of maps using the coordinates of the actual geographical position, uniform scale of the map in each area, the positional accuracy of the maps up to 2 cm)
- With the update to customer specification (fast and flexible acquisition of current images and the establishment of current orthophoto maps)
- For hard to reach or dangerous places without direct access to the area
Among the disciplines that practice using orthophoto maps includes the following:
- GIS (Geographic Information Systems) – an essential input for additional software works such as the measurement of distance, infrastructure design, urban planning, etc.
- Construction – land-use planning and control
- Cartography – creation of maps
- Agriculture – monitor the status of agricultural land, evaluation of the crop’s condition, irrigation efficiency, fertilizers and sprays
- Archaeology – digitalization and input for ground plan drawings
- State administration – monitoring and control of different areas of interest (black dumps, illegal buildings, project documentation)