Photogrammetria最新文献

The objective of this paper is to show how a sequence of elementary morphological filtering operations can lead to the correction of the stripping effect present on some level 1B SPOT images. The basic idea employed is to design the morphological filter using an a priori modeling of the stripes. The overall algorithm is divided in three steps. A binary image showing the high frequencies in the vertical direction is first obtained. Another binary image is then deduced which indicates the location of the stripes. Finally, the corrected image is obtained by morphological interpolation at the stripe location. The effect of each processing step is illustrated from an original image of the Porto Alegre city, south of Brazil, corrupted by the stripes.

The High-Resolution Imaging Spectrometer (HIRIS) is a JPL-facility instrument designed for NASA's Earth Observing System (Eos). It will have 10-nm wide spectral bands from 0.4 to 2.5 μm at 30-m spatial resolution over a 24-km swath. The spectral resolution allows identification of many minerals in rocks and soils, important algal pigments in oceans and inland waters, spectral changes associated with plant canopy biochemistry, composition of atmospheric aerosols, and grain size of snow and its contamination by absorbing impurities. The bands will have 12-bit quantization over a dynamic range suitable for bright targets, such as snow. For targets of low brightness, such as water bodies, image-motion compensation will allow gains up to a factor of 8 to increase signal-to-noise ratios. The sensor will be able to point ±26° crosstrack and +52°/−30° downtrack. In the 705-km orbit altitude proposed for Eos, the crosstrack pointing capability will allow 3–4 views during a 16-day revisit cycle.

Today, digital mapping is the method for production of large-scale maps in Denmark, and it is used in all the private mapping companies working for municipalities and utility companies. The rapid introduction of the modern technology is a result of the introduction of the use of natural gas all over the country. This project was financially big enough, and the technology for digital mapping was at a breaking point, so these two factors together made the change possible. The development of a data-exchange format was also an important tool in the process. The experience of digital mapping is described from the point of view of a private, photogrammetric mapping company.

We have experimentally studied the optical spectrum of daylight photographs of sinusoidal and other complex reflecting surfaces made out of paper coated with a thin layer of plastic. It is shown that the reflecting characteristics of the plastic layer are quite similar to those of the water surface. Hence, the paper models can be conveniently used to model the sea surface undulations. The main results of the present laboratory study are: The frequency of a sinusoidal surface is best estimated when the camera angle is about 45° and the illumination angle is also 45°. Clear skylight illumination produces more accurate estimates than those obtained with diffused illumination. The amplitude of the sinusoidal surface must be less than one third ($\text{1}\text{3}$) of its wavelength so that no higher harmonics are generated and the spectral peak height is proportional to the waveheight.

Finally, this study verifies through laboratory model studies some of the theoretical conclusions previously reported using order theory. The photographic method for studying the spectrum of the sea surface is perhaps the cheapest of all other methods used by oceanographers.