Alejandro José Vitale

Structure-from-Motion Approach for Characterization of Bioerosion Patterns Using UAV Imagery

The aim of this work is to evaluate the applicability of the 3D model obtained through Structure-from-Motion (SFM) from unmanned aerial vehicle (UAV) imagery, in order to characterize bioerosion patterns (i.e., cavities for roosting and nesting) caused by burrowing parrots on a cliff in Bahía Blanca, Argentina. The combined use of SFM-UAV technology was successfully applied for the 3D point cloud model reconstruction. The local point density, obtained by means of a sphere of radius equal to 0.5 m, reached a mean value of 9749, allowing to build a high-resolution model (0.013 m) for resolving fine spatial details in topography. To test the model, we compared it with another point cloud dataset which was created using a low cost do-it-yourself terrestrial laser scanner; the results showed that our georeferenced model had a good accuracy. In addition, an innovative method for the detection of the bioerosion features was implemented, through the processing of data provided by SFM like color and spatial coordinates (particularly the y coordinate). From the 3D model, we also derived topographic calculations such as slope angle and surface roughness, to get associations between the surface topography and bioerosion features.

Preliminary Analysis of Waves in the Coastal Zone of Monte Hermoso and Pehuén Co, Argentina

Abstract Delgado, A.L.; Vitale, A.J.; Perillo, G.M.E., and Piccolo, M.C., 2012. Preliminary analysis of waves in the coastal zone of Monte Hermoso and Pehuén Co, Argentina. Coastal geomorphology is significantly influenced by waves because they are a major agent in removing and transporting sediments. Furthermore, any kind of human coastal activity is influenced by waves. Consequently, it is essential to know about the wave distribution of the coastal areas. The aim of this study was to analyze the waves at Monte Hermoso and Pehuén Co coastal zone, Buenos Aires, Argentina. The study was based on data obtained from an oceanographic tower located on the coast of the study area, between April 2007 and July 2009, analyzed annually and seasonally. The major occurrence and frequency of the significant wave heights (Hs) and the period of significant waves (Ts) were studied. The main percentages of Hs occurred between 0.25 and 1.5 m and were related to Ts between 0 and 16 seconds. The highest Hs rates were observed in spring, whereas the lowest ones in winter. Theoretical distribution probabilities were applied and the Weibull distribution was the most appropriate fit for the data, presenting a shape parameter of 0.82 and a scale parameter of 1.73. Joint probability analysis of Hs and Ts showed that summer and spring have similar patterns with larger probabilities of locally generated waves, whereas, contrary to what it is normally expected, winter has the larger percentage of swells because of the large number of calm-wind days. Finally, the Ursell number and the flux intensity parameter were obtained to demonstrate that the waves have been able to transport the typical sediments at the tower site toward the sea.

Influence of climate variations on Chascomús shallow lake thermal conditions and its consequences on the reproductive ecology of the Argentinian Silverside (Odontesthes bonariensis—Actinopterygii, Atherinopsidae)

It is well known that water temperature directly affects fish reproduction. The aim of this study was to develop a predictive model to determine water temperature conditions on a typical Pampas shallow lake (Chascomús, 35°36′S, 58°02′W) from local climate variables (specifically air temperature and rainfall). In addition, this model was used to assess the variability of local climate and water temperature conditions in this lake over the last 47xa0years, and predict possible effects on pejerrey reproductive phenology. The temperature model showed a good fit demonstrating a direct influence of the local climate into the lake water temperature. As consequence of a demonstrated warming in Chascomús City, an average increase of 1.4°C was evident in Chascomús lake over the analyzed period, which was mainly due to a thermal increase during the warmer seasons (spring, summer, and autumn). This pattern of warming drove to a shortening in the pejerrey spawning season length, estimating a decrease of 19xa0days over the period of 47xa0years. Thus, this study showed that a tight association between the climate variability and the change in fish reproductive phenology can occur in species inhabiting shallow lakes.

Image Processing Spreadsheet

Consider an hypothetical image processing system, where a given target is to be identified. The usual sequence of steps consists on an image equalization to adapt to the illumination situation. Then the image is binarized, allowing a morphological filter to correct the noisy edges and shapes by means of an indeterminate sequence of openings or closings. The resulting image can then be segmented and recognized. If the results are unsatisfactory, then the processing parameters in any of the previous steps must be changed, perhaps by trial and error. For instance, the binarization threshold can be raised or lowered, and the following steps must be performed again to see the results. This is obviously cumbersome, tedious and error prone. The Image Processing Spreadsheet PDICalc is a simple but powerful combination of two different and widespread software technologies. Its benefit comes from enabling users to build an image processing pipeline, considering each step separately, and visualizing the results of modifying the parameters of each step in the final image. A spreadsheet based user interface eliminates the tedious and repetitive interaction that characterizes current image processing software. Users can build a processing template and reliably repeat often needed processing without the effort of redevelopment or recoding. In the cited example the user simply creates the processing template, defining each cell of the spreadsheet as the result of applying a given processing step on another cell. This template can be then reused with any input image, can be stored for future processing sessions, and every step can be trimmed precisely to achieve the desired results. Our implementation considers most of the image processing techniques as its building blocks. Arithmetic operators are overloaded to represent per pixel operations. We included also equalization and histogram correction, arbitrary convolution filtering, arbitrary morphological filtering (with programmed repetition), Fourier operations, and several segmentation techniques.

Low-cost monitoring buoys network tracking biogeochemical changes in lakes and marine environments – a regional case study

Abstract Lakes, rivers, estuaries and ocean waters control many important natural functions at the regional-global level. Hence, integrative and frequent long-term water monitoring is required globally. This paper describes the main features and innovations of a low-cost monitoring buoys network (MBN) deployed in a temperate region of Argentina. The MBN was designed to record extended time series at high-frequency, which is of great value for the scientific community, as well as for decision-makers. In addition, two innovative designs belonging to two versions of moored buoys (i.e. shallow waters and coastal marine waters) were presented. It was shown that the cost of either of two versions of the buoy is low, which can be considered as the main advantage.

Aplicação de Eletrônica Open Source para Estudar Ilha de Calor em Alta Frequência

A new measurement system based on open source electronics (Arduino) was designed to obtain high frequency data to study Urban Heat Island (UHI). The instrument registers geo-referenced information of air temperature, relative humidity, barometric pressure and altitude above sea level in a moving vehicle. The device was designed to analyze the UHI in Bahia Blanca city, Argentina. Measurements were made with the method of urban transects during different days of summer and winter. The spatial distribution of air temperature was associated with wind direction and speed. Relative humidity was low in the downtown area and high in the periphery and the estuarine coast. In conclusion, the device allowed to study the Urban Heat Island in the city. Its use will be useful for urban planning because the measurements are very fast and accurate.