Effects of laser beam alignment tolerance on lidar accuracy

One of the major lidar error sources not yet analyzed in the literature is the tolerance of the laser beam alignment with respect to the scanning mirror. In this paper, the problem of quantifying these errors is solved for rotating polygon mirror type lidar systems. An arbitrary deviation of the beam from its design direction–the vector of beam misalignment–can be described by two independent parameters. We choose these as horizontal and vertical components of the misalignment vector in the body frame. Either component affects both, horizontal and vertical lidar accuracy. Horizontal lidar errors appear as scan line distortions—along and across track shifts, rotations and scaling. It is shown that the horizontal component of misalignment results in a scan line first being shifted across the track and then rotated around the vertical at the new center of the scan line. Resulting vertical lidar error, being a linear function of the scan angle, is similar to that produced by a roll bias. The vertical component of the beam misalignment causes scan line scaling and an along track shift. The corresponding vertical error is quadratic with respect to the scan angle. The magnitude of these effects is significant even at tight alignment tolerances and cannot be realistically accounted for in the conventional calibration model, which includes only range, attitude and GPS biases. Therefore, in order to attain better accuracy, this model must be expanded to include the beam misalignment parameters as well. Addition of new parameters into the model raises a question of whether they can be reliably solved for. To give a positive answer to this question, a calibration method must utilize not only ground control information, which is typically very limited, but also the relative accuracy information from the overlapping flight lines.     

The adsorption and interaction of long-chain fatty acids and heavy metals at the mercury electrode/sodium chloride solution interface

The reduction of heavy metals (cadmium, lead and zinc) in the presence of long-chain fatty acids (lauric, oleic and linoleic) in 0.55 mol dm^?3 NaCl and 0.03 mol dm^?3 NaHCO₃ at pH 8.7 has been studied by differential pulse polarography. The increase of the peak height of investigated metals by up to tenfold the value obtained in electrolyte without fatty acid is due to adsorption of metal ions at the electrode surface. The accumulation of metal increases with the increase of adsorption time (at potentials more positive than the reduction potential of the particular metal) and with increase of salinity. The heavy-metal adsorption depends on the concentrations of both metal ions and fatty acids. The interaction of heavy metals with the unsaturated fatty acids in the bulk and/or in the adsorbed layer at different natural interfaces could be of considerable importance in an understanding of the fate and distribution of heavy metals in the natural aquatic environment.     

Boninite volcanic rocks from the mélange of NW Dinaric-Vardar ophiolite zone (Mt. Medvednica,Croatia) – record of Middle to Late Jurassic arc-forearc system in the Tethyan subduction factory

Mineralogy and Petrology - In the Late Jurassic to Early Cretaceous ophiolite mélange from the Mt. Medvednica (Vardar Ocean) blocks of boninite rocks have been documented. They emerge as...     

Northern Adriatic phytoplankton response to short Po River discharge pulses during summer stratified conditions

A 275‐km‐long transversel Northern Adriatic profile from the mouth of the Po River (Italian Adriatic coast) to the Kvarner region (Croatian coastal island area) was investigated in three successive case studies in August 2008, 2009 and 2010. The short Po River pulses in August result in the surface advection of riverine water, nutrients and phytoplankton from the western to the eastern side of the Adriatic. This surface spreading exhibits inter‐annual variability depending on the riverine discharge in the preceding period. The Po River discharge pulse in August 2010 in particular resulted in an extraordinary tongue‐like advection of riverine water, nutrients, and phytoplankton towards the Eastern Adriatic coast. The phenomenon was detected using both satellite imagery and classical oceanographic measurements. In the advective water, toxic dinoflagellates were most abundant in August 2010, when the influence of the Po was greatest.     

Determination of the apparent copper complexing capacity of seawater by anodic stripping voltammetry

A new experimental technique using differential pulse anodic stripping voltammetry with a thin-film mercury electrode and efficient mixing of the electrolyte for the apparent copper complexing capacity of seawater is proposed. The effects of some factors such as type of electrode and cell, pH of the solution, potential of deposition, time of equilibration, and influence of a non-ionic surface active agent on the measurements are examined. Experimental results for the apparent copper complexing capacity of seawater are calculated presuming 1:1 inert complex formation. By using EDTA as a model ligand, it is shown that the proposed procedure with efficient mixing of the solution excludes any appreciable kinetic influence upon the electroanalytical results.     

Draconids 2011: Outburst Observations by the Croatian Meteor Network

The predicted Draconid meteor shower outburst during October 2011 had been observed by a portion of the Croatian Meteor Network whose stations encountered clear weather. A total of 95 Draconid orbits have been calculated from 18 contributing stations, and in this paper we present results for 63 orbits obtained from the fully automatic observation and processing pipeline. Two methods of trajectory estimation were applied, showing better fit results using a linearly changing velocity model versus a constant velocity model. The estimated mean radiant position has been found to be at RA = 262.6°, Dec = +55.7°, with estimated geocentric velocity Vg = 20.7 km/s.     

Zadar on the Crossroad of Nationalisms in the 20th Century

Zadar, the ex capital of Dalmatia (South Croatia), within the borders of Austro-Hungarian Monarchy, reached the 20th century as a well developed administrative and governing centre. It is a city situated on the eastern (Croatian) Adriatic coast, with an almost 3000 years old tradition and rich cultural and art heritage. After the disintegration of Austria-Hungary, the Kingdom of Slovenes, Croats and Serbs was proclaimed (later: the Kingdom of Yugoslavia). Zadar, as a separate enclave (in Italian named Zara), was annexed to the Kingdom of Italy. It was the result of the Treaty of Rapallo, by which Zadar was separated from its region. This alienated enclave covered 57 km² and there were about 20,000 inhabitants. In this way, the normal regional function of Zadar was interrupted which lasted untill the end of WW II. It was a period of isolation, economic stagnation, smuggling, political marginality and military-strategical importance. Zadar became not only one of the symbols of the failure of Croats to create their independent state after Austro-Hungarian disintegration but also a symbol of the realisation of nationalistic aspirations of the Kingdoms of Italy and Serbia. In the first place Zadar lost its function as a leading governmental and strong economical centre of South Croatia (Dalmatia). The great majority of Croatian inhabitants had to leave the city. Thousands of Italians immigrated, which led to a complete change in the ethnic structure. The most disastrous consequence was the air-raid destruction of Zadar during WW II., in which about 5000 people died. After the destroyed town had been returned to the motherland Republic of Croatia, the restoration took a long time. The borders of Zadar district were often changed, its territory reduced or increased. Since Croatia gained independence, the role of this geographic area has become politically extremely important. Today, Zadar numbers 80,000 inhabitants. The recent NATO intention of installing a logistic basis near it (1998) also proves that strategic and geopolitical interests, regarding this city and its region, continue.     

The influence of surfactants on the measurements of copper and cadmium speciation in model seawater by differential pulse anodic stripping voltammetry

Model systems consisting of a heavy metal ion (Cu²⁺ or Cd²⁺), complexing ligand (EDTA or NTA), a surfactant (9,12-octadecadienoic acid, C₁₈H₃₂O₂, i.e., linoleic acid), and a surfactant which is at the same time a complexing ligand (tert-octylphenol etoxylate, C₈H₁₇(C₆H₄)(OC₂H₄)_9–10OH, i.e., Triton-X-100) in seawater and NaCl solution were used in order to investigate the influence of the surfactant adsorption (on the electrode surface) on the heavy metal speciation measurements. The samples were titrated with either the metal, complexing ligand or surfactant and were measured by differential pulse anodic stripping voltammetry. It was shown that the surfactant adsorption exerts a strong influence upon the overall metal redox process and, thus, changes considerably both the apparent complexing capacity and the conditional stability constant of the system. Considering the presence of high concentrations of surfactants in polluted seawaters, the danger of measuring the apparent complexing capacity with the anodic stripping voltammetry method, without a detailed knowledge of surfactant properties and influence upon the system, is discussed.