Aerial images Interpretations

Flight picture gives an excellent overview of the area of ​​interest, it’s a “frozen” image of the view from the aircraft just at the moment of exposure. It allows you to go back and study in detail the individual sections of the image and compared with photos taken at other times of the same section to detect any changes between shooting sessions. By determine the position of a number of points in the image, and the ground level and the altitude is known, the image can be oriented in a coordinate system with good precision, so that it becomes possible to use this as a basis to digitally plot surfaces, lines and points in one or more GIS layers with the same coordinate system.

Through aerial images are photographed so that they overlap, typically ca. 60% in the direction of flight and about 25% laterally toward the adjacent flight paths, they can be joined for larger images (orthophotos). They can also be used separately in different image interpretation system. When considering the overlapping area in such a system sees images taken from different angles of the left and right eyes. It makes you look in stereo and can even measure heights. When the aircraft had time to move significantly longer between shots than the distance you have between your eyes becomes the height scale a bit exaggerated, but it makes the only possible measure height a little safer.

The new technique of digital aerial imagery has allowed the time from shooting until the images after privacy audit, are available has been shortened considerably. National Land Survey estimates that one-third of Sweden’s surface is photographed each year. Normally the varying time of year so that every second shooting takes place after the deciduous trees blossomed and every before leafing. Which of photography are that you choose depends on what you want to interpret the images. Applies the canopy cover / overgrowth or ground vegetation then you want after all that leaf will be blooming on trees and shrubs and ground vegetation started to grow, so that it can easily be seen in CIR photos (IRF image = Infrared radiation is red in color picture). When it comes to facilities on the ground as roads, ditches, houses, etc. so they can often be obscured by foliage so that they are not interpretable. Its best to interpret vegetation in the pictures from June and July and happily at midday, so that the shadows are as short as possible. Information on planned and executed the shooting reported on the surveying site. There are also a number of private companies in the market that can offer aerial photography in cases where no surveying default images work.

Some examples of the interpretation of aerial missions that we have done in recent years are shown below:

Follow-up of the LIFE MIA project.
Interpretation of crown cover of trees and shrubs as well as share fir tree layer at two points in time, before and after the performed actions.
A more detailed presentation of the LIFE MIA project. (here)

Monitoring of protected areas on Gotland.
Aerial Interpretation of tree and shrub coverage. A more detailed presentation of the follow-up on Gotland. (here)

Aerial Interpretation of facilities within Gräsö eastern archipelago.
Digitization of plant surfaces (house, other buildings, docks, piers, etc.) before the reserve formation 2011-06-28 / 29 and 2013-05-17, and the compilation of interpreting the results in Excel with summaries per island and plant type. A more detailed presentation of the facility’s interpretation of Gräsö eastern archipelago. (here)

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