Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: light measurements

Sortuj według:

Ogranicz wyniki do:

Redukowanie czasu obliczeń transformaty Hougha z wykorzystaniem preselekcji implementowane na GPGPU

Mazurek P.

Pomiary Automatyka Kontrola

2013

R. 59, nr 11

1171--1173

W artykule przedstawiono algorytm rzadkiego próbkowania okręgu dla transformaty Hougha, w celu preselekcji okręgów do dalszego przetwarzania. Rozwiązanie pozwala na skrócenie czasu obliczeń, rzędu dwóch razy dla implementacji z wykorzystaniem programowanej karty graficznej (GPGPU). Może ono być zastosowywane do wykrycia jednokolorowej kryzy wokół lustra sferycznego lub półsferycznego służącego do pomiaru oświetlenia. Dzięki temu można analizować obraz wideo zawierający pomiary z różnych obszarów.

The Hough Transform (HT) is a very powerful algorithm for the detection of shapes. It is used for the detection of the flange of a light probe (Fig. 1). GPGPU processing is necessary for HT computation. The proposed algorithm (Fig. 4) is based on the preselection of circles for further computation (Fig. 3). Selection of the circles based on a limited set of pixel samples allows reduction of the processing time up to two times. The reduction is dependent on the image content, but the test shows that the influence of the number of the tested radiuses is less. About one second of the processing time is necessary, so larger images need tens of seconds for computation (Fig. 5). This algorithm uses exhaustive search over all positions and radiuses. One of the interesting applications of the HT is the estimation of the position and diameter of a circle related to the flange of a light probe [2, 3]. Light probes are used for computer graphics applications and they allow application of the real world measurements of light using the Image Based Lighting (IBL) technique. The GPGPU implementation use CUDA based code (CUDA v4.0) [10,11] and 16x8 organization of threads is assumed. The technique proposed for the time and spatial synchronization of the multiple threads for more synchronous read operation from a global memory is applied [7]. The global memory is large and slow, so a GPGPU-global memory interface is the main bottleneck of the system. Synchronization of accesses allows coalescence read operations.

Zastosowanie zdjęć hemisferycznych w badaniach ekosystemów leśnych

Strzeliński P.

Roczniki Geomatyki

2006

T. 4, z. 4

93-112

The main aim of the study is to discuss basic assumptions of taking hemispherical photographs in the context of their practical use in forest inventory. The work encompasses methodology of taking digital hemispherical photographs. Hemispherical photographs are most often taken for research on ecological conditions of plants. Usually the aim of such research is to obtain information on the amount of light which reaches selected height above the ground. It is important to observe a few rules in taking photographs (overcast, camera leveling, sensitivity, shutter speed, maximum resolution). The best equipment for this purpose is a digital reflex camera and fish-eye lens with the angle 180°. Another solution is a digital reflex camera smaller than 35 mm with suitable converter which together with lens will allow to obtain circular photo with retained angle of 180°. Gap Light Analyzer and WinSCANOPY are the most frequently used software packages for analysis of hemispherical photos. The following elements are expected to be determined as a result of analyses based on hemispherical photographs: absolute amount of light registered at measurement levels, crown density structure, spatial variability of stand foliage, leaf area index, general description of crowns (crowns deformation, viability of lateral shoots) the condition of assimilatory organs (number of annuals, crown light and decrement of assimilatory organs, distortion and discoloration of assimilatory organs) relationship between tree density and natural regeneration The following attempts will be undertaken with the use of hemispherical photos: to estimate biomass of assimilatory organs, to estimate density of photons flow in the process of photosynthesis under canopies and in gaps of stand, to register the infrared scope of radiation (in order to examine assimilation organs in stands), to prepare a photomap of canopies. The study encompasses a brief review of literature, a list of possible devices with basic software.