T&A Survey Drone Services projects
The goal of the drone survey was to map a secondary channel of the river Vecht by performing an photogrammetric revision analysis covering the entire area. The Waterschap constructed the secondary channel in 2015. A natural process will gradually change the course of the channel due to the development of a meander. The information obtained from the photogrammetric survey clearly shows the current position of the secondary channel, making it possible to closely monitor its future natural development.
SmartPlanes fixed-wing drone
Since the research area is about 2 km long, the Waterschap decided the best way to perform the survey was from the air. T&A Used the SmartPlanes Freya, a fixed-wing drone which is particularly suitable for the 3D mapping of large areas.
The more than 2.000 photo's that were taken during the survey have been processed with photogrammetric software into photographic images with XYZ-information. The scale, hight and color contrasts of the images have been corrected and processed into a point cloud. From this point cloud a Digital Elevation Model (DEM) and an orthophoto (below) were calculated.
Currently entire fields are preventatively sprayed with fungicide on a regular basis. Early detection of incipient fungus infection in wheat is important as it can significantly reduce the use of fungicide. If detected early, farmers can treat fungi locally.
Using a portable IR spectrometer, we have taken spectral measurements of wheat leaves with different levels of Fungus infestation, ranging from healthy to strongly affected. The spectra (plot with spectra) indicate that there are systematic spectral changes with increasing deterioration of the plants’ health. A very good indicator seems to be the “red-edge” position (plot with pointdata).
The most efficient way to make a rapid assessment of the condition of a wheat field is the use of drones to collect spectra through hyperspectral imagery. To prove this, a test flight was done using the Aibotix multirotor with a normal RGB camera. The great advantage of the multirotor is that it can fly slowly and low enough to create an image with a resolutions so high that it is possible to map individual leaves. This is important, as our study has shown that the leaves of one single plant can have different spectral properties. Flying at higher speed and elevation will decrease the spatial resolution, mixing spectra from different materials (also soil). As a result the sensitivity of the measurement will drop significantly.
Top right: Aibotix in action
Bottom left: Image showing the vegetation greenness
Bottom right: Spectral characteristics (Red edge position) of wheat leaves at different levels of fungus infestation.
As part of the EU-FP7 IMPACTMIN study, this area was investigated using a combination of remote sensing data (Satellite imagery, UAV technology, airborne hyperspectral imagery, gammaray data) and a variety of field data, including spectral measurements on soils and rocks.
The area exhibits in many ways very high levels of risk to the environment and local population. The aim of the study was:
- Monitoring the stability of the pit-wall.
- Detection and delineation of underground coal fires which can spread to the dumpsites or cause chemical reactions producing hazardous gases. The burning of the coal also destabilizes the steep slopes even more.
- Delineation of the horizontal and vertical extend of the landfill. The mine was used as public solid waste dump during the 1992-1995 war. Illegal waste dumping still continues. There are reports of radioactive waste dumped in the area before, during and after the war.
- Inspection of sewerage and discharge systems, wich are generally in poor conditions.
- Determination of the grade and extend of soil and groundwater pollution. Waterborne pollutants are a serious concern for the environment and public health.
- Detection and delineation of other landfills in the vicinity of the mine. Large quantities of waste are reportedly being dumped illegally at roadsides, rivers, abandoned mines (including Vihovici), posing a threat to public health and the environment.
Top: 3-D model of the Vihovici open pit mine
Middle: Digital elevation model of the Vihovici open pit area
Bottom: Example of spectral mapping of polluted soils. The inset shows some examples of reflectance spectra of soils at different locations. The numbers refer to the sample locations on the image.
As part of the EU-FP7 IMPACTMIN study subsidized by the European Commission, this area was surveyed using a combination of remote sensing data (Satellite imagery, UAV technology, airborne hyperspectral imagery, gammaray data) and a variety of field data, including a detailed spectral study of soil, rocks and vegetation.
The combined remote sensing data were used to characterize:
- The open pit area: mineralogy, geochemistry, geomorphology
- The tailings dam area: Mineralogy, geochemistry, tailings dispersal into einvironment
- The acid drainage from the mine and the tailings dam.
- The acid generating/buffering potential of various geologic formations in the area.
- Condition of soils, farmland and forest areas: soil mineralogy and vegetation stress.
Middle right: Acid mine drainage with pH<1, running off into the local surface water system.
Mapping of Acid drainage related secondary iron minerals by:
Top left: Smartplanes natural color image
Top right: Worldview 2 satellite image, resolution 50 cm
Bottom left: Hyperspectral images from manned aircraft, resolution 50 cm
Bottom right: Drone aerial photograph, resolution 5 cm
In the Republic of Georgia, pesticides like DDT and Parathion were widely used over the last decades in order to increase food production. After the Stockholm Convention (1975), these pesticides were banned in many countries. As a consequence, large stocks of POP pesticides were collected into a hazardous waste dumpsite in a remote area in the Lagluja Mountain region, Marneuli district of eastern Georgia. The dumpsite is located on top of a hill. The POP pesticides were stored in underground containers (so-called sarcophaguses), trenches and pits. The landfill contains an estimated 2.700 tons of pesticides. Similar dumpsites are found all over the former Sovjet Union.
Because of the political change from communism to a more market-oriented and decentralised government system, control over Lagluna Mountain deteriorated. In the succeeding years driven by economics, POP pesticides have been stolen from the landfill. Opening up the dumpsite has had devastating consequences not just to the soil but the environment at large posing serious health threats to the public.
Sarcophaguses have been reopened to obtain usable pesticides. In addition, the scrap value for the reinforcing rebar made these coffins target for demolition. Throughout this mountain region, pesticides continue to be found in rusted, leaking or even open steel drums.
The area is often used as a grazing area for herds of cattle and goats. The animals had free access to the dumpsite and in the dry season were suspected of drinking from stagnant pools of water. Today, the landfill is fenced off.
T&A Survey Drone Services was asked by Tauw Group to make an aerial assessment of this 4 hectare area, responding to an RFP by U.N. Development Program. The pollution was clearly visible on the surface. The Remote Sensing images show an amazingly detailed overview of the landfill. The images were used to perform a detailed survey of the underground and to create several sanitation concepts. The Remote Sensing images were geo-referenced, making it possible to make accurate estimations of the amount of pollutant in various parts of the landfill.
Top right: Preparing the Smartplane for the launch
Bottom left: Colour coded elevation model with 5 cm resolution generated using UAV-photogrammetry
Bottom right: 3D-view of a part of the dumpsite. Note some excavated sargophagi on the left side.