The aim of the study is to develop methods for the detection of patch borders based on ortophotos and airborne laser scanning data. The solution is expected to decrease manual workload. There are no restrictions on selecting algorithms or hardware. However, the solution must be applicable for the entire country and must be based on freeware libraries. Download the poster about the topic
Forested land near to cities has a potential for recreational activities. Land use planning requires information about forest structure – species composition, stand density, age, etc. Remote sensing data in combination with land information systems can be used to estimate the forest structural variables. The estimates can serve as direct for planning or can be used as a starting point for more detailed field inventories.
Forest clearcut mapping with satellite images is part of Estonian national environmental monitoring programme. Tartu Observatory carries out this sub-programme for last ten years. Landsat images from US archives, that have been traditionally used for clearcut mapping for fifteen years, have been supplemented by European Space Agency's Sentinel-2 images in the last years. Landsat images have a 30 m spatial resolution, Sentinel-2 images have a 10 m resolution. The study would help to better understand, what steps in post-classification image treatment would be necessary to yield in similar clearcut mapping results in case where the initial data are from either Landsat or from Sentinel-2 images. The new knowledge obtained will be applicable in Estonian environmental mapping programme. Working package is a GIS package, IDRISI and MapInfo are recommended. Facilities of Tartu Observatory and Estonian University of Life Sciences will be used.
Estonian coastal areas of the Baltic Sea and the two major shallow lakes are overgrown by helophytic macrophyte belt, dominated by common reed (Phragmites australis). Images from two medium spatial resolution satellites, Landsat OLI and Sentinel-2 MSI have been used to monitor the macrophyte expansion. An original non-parametric image interpretation methodology has been applied on late summer images. Results from the two different satellite scanners that have different spatial resolution give slightly different results. A study will be initiated, what steps would be necessary to the data processing flow to fit the results from different satellites into one single time series. Area of interest could be one of the two Estonian large islands, one of the two Estonian large shallow lakes or a stretch of the Baltic Sea coast. Working package is a GIS package, IDRISI and MapInfo are recommended. Field work at lakeshore or at seashore during field work season could be envisioned. Facilities of Tartu Observatory and Estonian University of Life Sciences will be used.
Spectral properties of woody parts of trees have been less studied compared to leaves, yet reflectance of bark is highly variable between species. Bark spectra are available only for a few species in public databases. The measurements were collected using different approaches: in situ or in laboratory; using direct sunlight or artificial source; with contact probe, integrating sphere or no fore optics.
The aim of this work is to carry a comprehensive intercomparison of the various approaches for a wide range of targets with a goal to identify the most suitable one for measuring bark reflectance spectra. Next, the methodology will be applied to create a spectral library and significantly boost the available bark spectra by sampling over 70 different tree species present in Agali Arboretum in Jarvselja, Estonia. The results can be of practical use to the community for various tasks, e.g. interpreting the signal obtained from Earth Observation, reconstructing scene elements in radiative transfer models, or evaluating the attractiveness of given species to bark and timber beetles.
The overstory and understory vegetation in forest ecosystems need to be treated differently in carbon cycle modeling, because carbon fixed through net primary productivity has different residence times for different components. However, there are currently no existing satellite products that provide separate or simultaneous estimates of overstory and understory leaf area index (LAIo and LAIu). The proposed research would focus on estimating and validating understory LAI component via several independent pathways including Earth Observation data, in situ remote sensing techniques and radiative transfer modelling. The results would help to answer the question how significant fraction of canopy LAI is represented by understory – the major source of uncertainties in global LAI products.
Observation and modeling of start of growing season (SOS), end of growing season (EOS), and growing season length provide essential information on how terrestrial vegetation responds to climate changes. The estimation of SOS and EOS utilizes seasonal patterns in satellite vegetation indices (VIs). The conducted research would identify the most suitable method to track understory phenology signal, and explore to what extent are satellite phenology metrics influenced by understory plant phenology.
The spherical mean of the shoot silhouette-to-total leaf area ratio (STAR) and the shoot transmission coefficient (c) are two key structural parameters in radiative transfer models for calculating canopy photosynthesis and leaf area index. The current standard optical methods for estimating these parameters are rather tedious and time-consuming, which results in limited knowledge about their role and variation. The goal of this research is to explore and assess the potential of novel techniques (e.g. 3D laser scanning, tomography) for the effective estimation of needle shoot structure.
Leaf-level photosynthetic responses are scaled to canopies based on the amount of photosyntheticaly active radiation (PAR) incident on the leaf surfaces. Shoots of conifer forests are distinct foliage units. Very often, needles are tightly grouped in shoots, making it impossible to infer the amount of needle surface area from optical measurements. The pool of reported needle-to-shoot area ratios for various conifer species is very limited; and assumptions or their extrapolation to different species can introduce serious errors.
Here conducted work would involve both in situ as well as laboratory element and would significantly expand the list through obtaining the needle-to-shoot area ratios for conifer species from Agali arboretum in Jarvselja, Estonia.
Angular distribution of leaves is a major determinant of radiation transmittance through the canopy. Leaf inclination angle distribution plays a fundamental role in the leaf projection function (commonly referred to as G-function), which is in turn a key variable for the indirect quantification of leaf area index (Ross 1981).
To date, relatively few measurements of leaf inclination angle have been reported for different tree species; compilation of large datasets has long been hampered due to issues in consistently applying existing methods to tree canopies, difficulty of applying direct methods in the field and unsatisfactory ability of these methods to reproduce measurements and to collect a representative number of leaves.
Recently, Ryu et al. (2010) proposed a robust and affordable method based on leveled photography to provide reliable leaf inclination angle measurements in broadleaf trees, which are comparable to direct measurements (Pisek et al. 2011). Pisek et al. (2013) and Raabe et al. (2015) used this method to compile a dataset of leaf inclination angles for selected temperate and boreal broadleaf tree species.
Using the leveled photography approach and collected photos of different species in botanical gardens around the world, the conducted work would produce the largest existing dataset of leaf inclination angle measurements.
Suspended sediments in water decrease the quality on waters but also influence to the transport of nutrients and chemicals in natural aquatic environment. Particles origins may vary – the large amount is coming from the cities together with waste water but also with rain fall or ressupended from sediments in shallow water. Several may provide such information and the goal of the work is to validate some of these. Use of standard software processing schemes together with field data will be learned during the practical work.
The underwater light climate is affected by particles present in the water column. Boreal small lakes are generally turbid with phytoplankton, suspended matter and coloured dissolved organic matter as the main absorbers. This study focuses on the variation of absorption by those substances, whereas laboratory work is also required. According to European Water Framework Directive there are 8 lake types in Estonia. The purpose of this study is to investigate if and how the absorption parameters vary seasonally in different lake types.
QAA and GSCM models are widely used in the remote sensing applications to derive bio-optical properties of water. The input for the models is the remote sensing reflectance and output are the absorption and scattering coefficients that describe the optical properties of the waters. These coefficients are in turn the input for higher order algorithms (e.g. chlorophyll a concentration) or are essential parameters for deriving primary production or modelling carbon cycle. Therefore their derivation from remote sensing data is with high importance. The topic involves testing the QAA and GSCM models on the bio-optical and validating the results on the Sentinel-3/OLCI products. The results obtained during this project could be further proceed in the master studies.
EU Water Framework Directive (WFD) requires all EU member states to monitor and report the ecological status of the waterbodies larger than 0.5km2. To classify the ecological status of the water, the phytoplankton parameters form an essential group, from where the chlorophyll a, phytoplankton biomass, cyanobacterial biomass, the intensity and frequency of the blooms can be monitored by Sentinel-3/OLCI data. The aim of the topic is to derive and compare the WFD compatible products from in situ and Sentinel-3 data and continue the time series that have been already produced earlier.
During the thesis, the students has to compile a set of conditions a satellite sensor has to meet in order to use the data for water remote sensing. Afterwards a list of missions that are currently active or planned to the near future are researched in order to find missions that meet the previously compiled criteria. The list must include possible positive and negative aspects of using the sensor under investigation. As the end result - a list of satellites will be created that is currently missing and the scientist of the field can benefit from the research.
The idea is to "play" with a radiation transfer model to see how concentration changes in different greenhouse gases affect their radiation forcing at different altitudes.
The aim of this project is to investigate changes in temperature due to absorption of infrared radiation for different projectd carbon dioxide concentrations using atmospheric radiative trasfer model FUTBOLIN.
Measurements of diffuse UV radiation started in Tõravere at summer 2016. First analyses of collected spectra will be carried out and changes in spectra due to changes in climate factors will be investigated.
The aim of this project is to give an overview of available information on UV radiation for Tõravere and compare the results with spectral measurements carried out at Tõravere.
The aim of this project is to give an overview of information about available ozone products from satellite measurements for Estonia, analyze recent ozone values in Estonia and find larger deflections from the average values (for example 2011).