Ground control points (GCPs) are used in the process of indirectly georeferencing Unmanned Aerial Systems (UAS) images. A minimum of three ground control points (GCPs) is required but increasing the number of GCPs will lead to higher accuracy of the final results. The aim of this study is to provide the answer to the question of how many ground control points are necessary in order to derive high precision results. To obtain the results, an area of about 1 ha was photographed with a low-cost UAS, namely, the DJI Phantom 3 Standard at two different heights, 28 m and 35 m above ground, the camera being oriented in a nadiral position, and 50 ground control points were measured using a total station. In the first and the second scenario, the UAS images were processed using the Pix4D Mapper Pro software and 3DF Zephyr, respectively, by performing a full bundle adjustment process with the number being gradually increased from three GCPs to 40. The third test was made with 3DF Zephyr Pro software using a free-network approach in the bundle adjustment. Also, the point clouds and the mesh surfaces derived automatically after using the minimum and the optimum number of GCPs, respectively, were compared with a terrestrial laser scanner (TLS) point cloud. The results expressed a clear overview of the number of GCPs needed for the indirect georeferencing process with minimum influence on the final results.

This study compares the normalized difference built-up index (NDBI) and normalized difference vegetation index (NDVI) as indicators of surface urban heat island effects in Landsat-8 OLI imagery by investigating the relationships between the land surface temperature (LST), NDBI and NDVI. The urban heat island (UHI) represents the phenomenon of higher atmospheric and surface temperatures occurring in urban area or metropolitan area than in the surrounding rural areas due to urbanization. With the development of remote sensing technology, it has become an important approach to urban heat island research. Landsat data were used to estimate the LST, NDBI and NDVI from four seasons for Iasi municipality area. This paper indicates than there is a strong linear relationship between LST and NDBI, whereas the relationship between LST and NDVI varies by season. This paper suggests, NDBI is an accurate indicator of surface UHI effects and can be used as a complementary metric to the traditionally applied NDVI.

Basic principles for assessing phytotoxicity are the same whether the test compound is a heavy metal, herbicide, fungicide, insecticide or other toxic compounds. The difference lies not in the method of evaluation, but in the experimental program and working methodology. In this paper the phytotoxic effects of heavy metals, Cr (VI) and Cd (II) on plants germination and growth were studied. Stock solutions of the two heavy metals were prepared at a concentration of 1000 mg/L, in distilled water. Diluted working solutions were prepared for experiments, with the following concentrations: 30, 60, 90, 120, 150 and 300 mg/L. Heavy metal solutions were used in the phytotoxicity tests, by taking 3 mL for each metal ion, and soaked in Whatman filter paper discs placed in Petri dishes. This way the interaction between the liquid phase in soil (soil solution) in which various concentrations of heavy metals are dissolved and the environmenta (in particular the vegetation) are simulated. Lepidium sativum was used as test plant, by conducting germination tests for three days of exposure. Lepidium sativum is a sensitive test species, widely used in the toxicity tests because it is rapidly growing, it is cheap and easy to analyze. The seed germination, root length and dry biomass of plants were assessed. It was found that metal ions have inhibitory effect on seed germination process of L. sativum. Root development is affected by both the tested metal ion and its concentration. The dry biomass reflects the toxicity of metal ions tested, which is dependent on the type of metal ion and its concentration. The study shows that the tested plant experiences a important toxicity stress due to the exposure to heavy metals.

Nowadays, Unmanned Aerial Systems (UASs) are a wide used technique for acquisition in order to create buildings 3D models, providing the acquisition of a high number of images at very high resolution or video sequences, in a very short time. Since low-cost UASs are preferred, the accuracy of a building 3D model created using this platforms must be evaluated. To achieve results, the dean's office building from the Faculty of “Hydrotechnical Engineering, Geodesy and Environmental Engineering” of Iasi, Romania, has been chosen, which is a complex shape building with the roof formed of two hyperbolic paraboloids. Seven points were placed on the ground around the building, three of them being used as GCPs, while the remaining four as Check points (CPs) for accuracy assessment. Additionally, the coordinates of 10 natural CPs representing the building characteristic points were measured with a Leica TCR 405 total station. The building 3D model was created as a point cloud which was automatically generated based on digital images acquired with the low-cost UASs, using the image matching algorithm and different software like 3DF Zephyr, Visual SfM, PhotoModeler Scanner and Drone2Map for ArcGIS. Except for the PhotoModeler Scanner software, the interior and exterior orientation parameters were determined simultaneously by solving a self-calibrating bundle adjustment. Based on the UAS point clouds, automatically generated by using the above mentioned software and GNSS data respectively, the parameters of the east side hyperbolic paraboloid were calculated using the least squares method and a statistical blunder detection. Then, in order to assess the accuracy of the building 3D model, several comparisons were made for the facades and the roof with reference data, considered with minimum errors: TLS mesh for the facades and GNSS mesh for the roof. Finally, the front facade of the building was created in 3D based on its characteristic points using the PhotoModeler Scanner software, resulting a CAD (Computer Aided Design) model. The results showed the high potential of using low-cost UASs for building 3D model creation and if the building 3D model is created based on its characteristic points the accuracy is significantly improved.

Chromium and cadmium are heavy metals that occur naturally in the environment and especially in soils. Their toxic effect is more pronounced at high concentrations and it depends on the oxidation states. While Cr (III) is considered an essential trace element for the metabolism of living organisms, Cr (VI) has a higher mobility and is easily soluble in soils and can be leached into surface water or groundwater, and taken up by plants. That leads to a toxic and carcinogenic effect to humans via inhalation for long exposures. The concentrations and the form of heavy metals in soils and the behavior of their free ions in soils solution are influenced by soil pH, organic matter (OM) content, cation exchange capacity (CEC), and clay mineralogy. This work presents the toxicity effect of two common heavy metals that can be found in soil (chromium and cadmium) on two microbial strains, which are also isolated from soil: Azotobacter sp. and Pichia sp. Batch tests where made using different concentrations of the selected heavy metals and culture medium: for Azotobacter sp. strain was used a Sabouraud medium and for Pichia sp. strain a YEPD medium (Yeast Extract, Pepton, Dextrose). The dry weights of the microbial culture were used to determine the microbial growing, calculated in percent inhibition of dry weight versus concentrations of metal ions.