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USE OF THERMAL IMAGING AND LASER SCAN IN UPDATING THE WATER

MANAGEMENT DATABASE Zboril Ales, Fojtik Tomas, Uhlirova Katerina, Zednickova Drahomira Key words: Laser scan, Aerial thermal imaging, GIS 1. Introduction The Ministry of Environment of the Czech Republic established the T. G. Masaryk Water Research Institute, public research institute. The Institute was founded in 1919. (http://www.vuv.cz)

The primary task of the institution is research on the state, use and changes in aquatic ecosystems and their linkages in the landscape and the associated environmental risks, technical support for water conservation, flood prevention and management of waste and packaging, based on that research. The above-mentioned activities use Hydroecological Information System (HEIS) as a unified information system to support the government administration in water management linked to national information system and other subsystems of the Unified Environmental Information System (JISŽP) for resolution of all issues. An integral part of HEIS is a digital database of water management data as a geographical representation of territorial identification phenomena. 2. Digital base of water management data

Digital base of water management data (DIBAVOD) is a thematic extension of the Fundamental Base of Geographic Data (ZABAGED®), which is binding on the government administration and the Government of the Czech Republic in the field of geospatial data. The content of DIBAVOD is described by 75 object categories that are purposefully divided into 10 groups:

A - Basic phenomena of surface and ground waters (rivers, reservoirs, hydrological structures,...) B - Specialized classification of surface and groundwater (water catchment areas, water bodies, ...) C - Protected areas (water resources protection zones, swimming areas, ...) D - Floodplains (floodplains of five, twenty and one-hundred year floodwaters, protective water flow levees, ...) E - Measuring and control sites for surface water (hydrological stations, water monitoring, ...) F - Measurement and control sites for groundwater (springs, wells, ...) G - Structures of the water-use subsystem (sewage, water, hydro-electric plants, ...) H - Extraction and discharge points (groundwater drawing points, discharge and drawing sites for surface waters) I - Structures on waterways (weirs, fish ladders, locks, waterfalls, ...) J - Meteorological observation structures (precipitation stations, climate and synoptic stations...) Objects are stored in Oracle as SDO geometries and users generally use ESRI tools.

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Financial and time-consuming maintenance and updating of the basic database of water management structures leads us to searching for more efficient and faster methods. In this paper we focus on two methods: air thermal imaging and laser scan (ALS). 3. Laser scan Aerial laser scanning (ALS) is currently one of the most modern technologies for the acquisition of spatial geographic data. It is used in particular for creating a digital relief model (DRM/DTM), which represents only natural ground, and a digital surface model (DSM), which includes not only the terrain but buildings and vegetation cover as well. Data on the Earth's surface are obtained by using laser beam broadcasts in the form of pulses from the scanner, which is located on the aircraft carrier Fig. 1. ALS has its own source of radiation and is therefore not dependent on sunlight (as is photogrammetry). Reflections from the surface are recorded - including both land and buildings from the earth's surface. Distance from of the point from the carrier is determined by the time that elapses between the sending and reception of the reflection of the beam from the ground or other objects back into the scanner. The location of points in the coordinate system is also determined by the position and inclination of the aircraft (scanner) at the time of transmission of the beam and the known direction of the beam. These values are measured using GPS devices and an inertial navigation system. [2, 3] Fig. 1: Using ALS (1 – Aerial laser scanner, 2 – The planned flight path, 3 – The beginning coordinate reference system, 4 – The beginning of the height reference system The reflection of the laser beam can be a single or multiple. The multiple reflections (with a significant height difference) occur primarily in forests and on edges of buildings. In over forests, part of the energy beam is usually reflected by high vegetation, while the rest penetrates below. A part is again reflected, for example from low vegetation, and the remaining part of the beam gets to the ground and back into the scanner. It is reported that approximately 10 to 25 % of the beam penetrates

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the forest canopy. In terms of the permeability of vegetation, the best time for the data collection is during a period of dormancy. Another condition is the absence of snow.

The data acquired by ALS is in the form of a so-called point cloud. These are irregularly spaced point data, which after removal of gross errors represents a digital surface model (DSM). With the assistance of automated filtering and classification processes, reflections from buildings, vegetation, solid ground, and gross errors are distinguished. The filtered data for "solid" terrain then serves as the digital relief model (DRM). [3] The view, (2D and 3D), of the filtered and classified layers of terrain, vegetation and buildings is shown in Figure 2. The area with no data defines the watercourse surface.

Fig. 2: Aerial photo, points from the ALS-1. Terrain, 2. Surface of buildings 3. Surface vegetation

The advantages of ALS are primarily in the high density of data measured in a short period of time, in the possibility of use even in poor visibility and high data accuracy. The data obtained can be used either directly in the form of so-called 3D point cloud for visualization or documentation of the current status or, after partial processing, in vector form as detailed data to use, for example, for design.

In the Czech Republic the most important collector and processor of ALS data to date is the company Geodis. Their most important customers in the area of aerial laser scanning include power companies (E.ON, RWE), ENVIA, Deutsche Bahn, ČEPS and Ředitelství silnic a dálnic a Povodí s.p. (The Directorate of Roads and Highways and Waterways). The main projects are primarily focused on documentation of catchment water flows and processing of 3D models with flood analyses, measuring of the digital model of the highway with high accuracy (MH = 36mm), models of airports, models of smaller streams to obtain a cross-section of the trough, modeling of flood situations, forest modeling for monitoring vegetation growth and forest development, exact models of a city with a high resolution orthophotographic map (pixel 5 cm), model of surface over transit gas pipelines, 3D measuring of electrical transmission grids 3D systems and their protection zones or models of airports and railways. For these projects, MK II equipment by the Swedish company Topeye is used.

Since 2010, a unique planar aerial laser imaging project for the purpose of creating a new surface model (DSM) and digital relief model (DRM) has been taking place in the Czech Republic. Altimetric databases to date have been derived from the original military survey conducted from 1952-1957 and from topographic mapping at a scale of 1:10 000, conducted in 1957-1971 (see Table 1.), and their accuracy, detail and

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non-homogeneity are limiting factors for many activities (modeling, design, GIS application).

Vectorized basic 10 contours saved as 3D objects stored in DGN format, supplemented by terrain edges of embankments, excavations, banks, tanks, etc. Elevation models in the form of an irregular network of TIN obtained by the stereo-photogrammetry method. It is processed using ALS in exposed terrain, urban as well as wooded areas. Table 1: Overview of Elevation Data Name Description Precision (mean error) ZABAGED® - elevation Vectorized Basic map

1:10 000 contours saved as 3D objects stored in DGN format

0,7-1,5 m in exposed terrain 1-2 m in urban 2-5 m in wooded areas

ZABAGED® - advanced elevation

Updated and refinemented contours Basic map 1:10 000, supplemented by terrain edges of embankments, excavations, banks, tanks, etc

0,7-1,5 m in exposed terrain 1-2 m in urban 2-5 m in wooded areas

ZABAGED®- grid 10x10 m Derived model in the form of a grid (GRID) 10x10 m

1,5-2,5 m in exposed terrain 2-3 m in urban 3-7 m in wooded areas

DMR 2,5 generation MO ČR

Elevation model in the form of a grid (GRID) 100x100 m

3-5 m in exposed terrain 5-8 m in urban 10-15 m in wooded areas

DMR 3 generation MO ČR Elevation model in the form of an irregular network of TIN obtained by the stereo-photogrammetry method.

1-2 m in exposed terrain 1-2 m in urban 3-7 m in wooded areas

Digital surface model It is processed using ALS It is processed using ALS The project to create a new DRM and DSM is implemented in the collaboration of three institutions: Czech Office for Surveying, Mapping and Cadastre, Ministry of Defence, Ministry of Agriculture. Imaging of the territory of the Czech Republic is divided into three stages of Figure 3.

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Fig. 3: Bands air laser scanning in the Czech Republic (ALS) Aerial laser scanning has the following basic parameters: the maximum mean height over the terrain varies between 1,250 - 1,500m and the average canopy of adjacent scanning bands is 40-50% which achieves a density of points of at least 1 point / m 2 with a mean error of length measurement of spatial turf up to 0.10 m. 1. A DRM in the form of bars 5 x 5 m with an average mean error of height σ = 0.30 m (the result of automated pre-processing). Deadline: end 2012 2. DRM in an irregular network of points (TIN), with a mean elevation error of σ = 0.18 m in the exposed terrain, and σ = 0.30 m for the wooded areas (final semi-automatic data processing) Deadline: end 2015 3. DSM in an irregular network of selected elevation points (TIN), with a mean elevation error of σ = 0.40 m for precisely defined spatial objects (buildings) and the σ = 0.70 m for diffuse objects precisely (forests and other elements of plant cover, soil) Deadline: end 2012 [1] The Water Research Institute analyzed the technological possibilities of the use of ALS results to update selected elements of the digital database of water management data. This mainly concerned the identification of barriers located in watercourse channels, with a focus on small waterways, obtaining more precise geometry of waterways and comparing terrain models in relation to the creation of boundaries of the water basin formations of small streams. Further, the suitability of using the ALS data in coastal zones as an input to hydrodynamic models for determination of flood plain areas was assessed. For use in water management, the behavior the laser beam near the water surfaces is essential. Scanners appropriate for nation-wide mapping use a laser with near-infrared radiation. From the spectral characteristics of water, it is known that water almost fully absorbs this radiation. If the purpose is to find the border of the water surface (such as the flood line) or determine the geometry inundation territory, this wavelength is very convenient. In the data, the water surface will appear as an area

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of very low point density. The approximate surface level can be determined from the heights of points reflected directly from the banks. To map the surface of the water you must use green or blue-green area of the spectrum, which is not absorbed by water and so can pass down to the bottom of it and be reflected back. There are systems in the world for mapping of coastal waters using the principle of dual use as infrared radiation (surface mapping), as well as using green-blue radiation concurrently. The system is called DIAL - Differential Absorption Lidar. For very clear water and a calm surface, mapping can, theoretically, be carried out up to a depth of 50 m. For these systems a significantly lower flight altitude (200-400 m) is necessary [4] Description and characteristics of the data The solution utilizes test data from sites in Eastern Bohemia. The area that was targeted by ALS, has an area approximately 47 km 2.The altitude is in the range from 268-425 m / M. The area is relatively intensively farmed. Arable land covers nearly 60% of the area, forest area, 20%, 10% is used residentially and 7% is permanent grassland. The site is not excessively sloped: 65% of the area has a slope of under 5% and 22% has slope from 5-10% From a water management perspective, attention was focused above all on the flow of the Dědina. The length of the section that flows through the surveyed territory is approximately 9 km. The character of the flow is natural with a channel width of 6-8 m. In urban Dobruška the channel has been modified for a section that is about 1 km, in a trapezoidal shape, fortified with stone set in concrete with three transverse stabilization level drops with heights from the lower surface level of 0.5 m, 0.7 m and 0.3 m. At the time of the field survey (for orientation these elevations will be cited, even though the surface level differences are, of course, slightly different and dependent on the current status of water). Bottom width of this section ranges from 2 to 6 meters. Normal water depth is 15 cm; only just below the level drops there are relatively deep pools. Experimental ALS data collection in this area took place on April 24 and June 26, 2008. Data was obtained from a height of 1,200 – 1,500 m and cloud density is approximately 1.2 points / m 2

The data was primarily acquired in a WGS-84 coordinate reference system and at an ellipsoidal elevation. It was provided in the UTM display mode (zone 33N) in ASCII text format (X, Y, Z). At the Water Research Institute workstation, it was subsequently transferred to the S-JTSK East North and Balt elevation system, a coordinate system used as a standard (in the Czech Republic). Elevation values are rounded to the nearest millimeter, nevertheless, the stated accuracy is in the following overview of examined data.

• Classified point clouds (1.2 point / m 2) – for example, terrain layer, buildings,

vegetation, etc. median error = 0.18 m. • Digital relief model in the form of DRM 4G (5 x 5 m), mean error = 0.30 m The main calculations and analyses were performed in ArcGIS 9.3 using the extensions Spatial Analyst, 3D Analyst, ArcHydro, ETGeoWizard and XTools Pro.

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Refinement of the geometry of the watercourse Waterways are very well recognizable in ALS data. It turned out that the positional accuracy of existing data on streams are inadequate compared with ALS data and inconsistent with runoff paths generated from the digital terrain model from the ALS data. The differences are sometimes up to 20 meters. The differences have several causes:

· ZABAGED ® and DIBAVOD datasets correspond to a scale of 1: 10 000 · The high degree of generalization of the flow lines · Opacity of dense vegetation accompanying the waterway on the orthophoto

Fig. 4: Comparison of the existing watercourse dataset with the ALS data Figure 4 shows a case where the axis of the watercourse of the current database does not pass through the axis of the channel and at several locations it is even outside the channel. The riverbed is visible from both the ALS points and the TIN model created. This is because in this case, the opacity of the accompanying vegetation on the orthophoto image. Refinement of data on watercourses must precede other analyses. Currently, an automated generalization process is being developed for the flow axis from DMT data from ALS. Identification of transverse bottom drops in a watercourse To find the transverse bottom drops a necessary condition is the exact flow axis and an accurate as possible terrain model. This means a TIN from the point cloud for the terrain layer. Figure 5. shows the TIN section of the flow with two degrees (elevation 0.5 and 0.7 m) including their details. Values at points with a step of about 5 m indicate altitude (right) and elevation difference from the point situated below (left). Points closest to the steps are highlighted in red. In the lower right corner is a photo of the upper level (0.7 m). A part of the picture is a longitudinal profile of the surface of the flow of the displayed the section where the level jumps are noticeable. In this way it was possible to establish all levels. More difficult was determining the height of a slip that has a height of about 0.3 m and which is located less than 3 m from an unfiltered out bridge. Despite this fact, it was possible to identify the step. The results show that on the basis of the ALS data the cross barriers with a height of 0.3 m can

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be located. Another aim will be to automate the method and apply it to the flows of a different nature.

Fig. 5: Identification of 2 levels with the help of DMT (TIN) and the longitudinal profile of water surface Basis for establishing floodplain areas ALS belongs among classic geodetic surveying of profiles of the flow channel, valley profiles and photogrammetric mapping of inundations as one of the basic methods of acquiring geospatial data for hydraulic models. The continuously increasing accuracy and data density of ALS begs the question whether these data could at least partially replace the expensive and technically demanding geodetic survey. In the area of interest, it is possible to assent to mutual comparison of elevation data because in 2002 a flood zone was established on the flow of the Dědina and photogrammetric mapping was included among the geodetic documents (only the lower part of the stream) along with geodetic detailed profiles of the flow channel and valley profiles (1999). The entire situation, including the subsequently described comparisons, is shown in figure 6. Analyses were carried out in an area where the most elevation data is available for a DSM created on the basis of aerial laser scanning (ALS), photogrammetric (FOT) and ZABAGED ® elevation (ZAB). All grids have a resolution of 5 m. The resulting differences are highlighted in color in the right section of Figure 6. They indicate that ALS is an average of 0.36 m below the FOT with a standard deviation of 0.33. Positive values on the left side are caused by an error that occurred during the test scan. Differences between ALS and ZABAGED ® are larger and more uncertain and the mean difference value is also -0.36 m. The indicative deviation is 0.56. As could be expected, larger differences are especially apparent in areas of the watercourse channel, especially in comparison with ZABAGED ®. ZABAGED ® Elevation does not include the geometry of channels of smaller streams.

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Another comparison concerned the flow of cross sections and inundations. About 40 geodetically measured profiles were available for the entire section, the average distance of which was about 200 meters. The elevation of all available resources was related to the location of the individual geodetically measured points. Compared were the altitudes of the geodetic measurements (GEO), the aerial laser scanning (ALS), photogrammetric mapping (PHO) and from the ZABAGED ® grid, 10 x 10 m improved altimetry (ZAB). In addition, an extra ALS data profile (step 0.5 m) was added to determine how the ALS reflects off the line of terrain fracture and inundation territory. Fig. 6 includes in its lower part 4 typical cross sections from different areas. There is satisfactory agreement of ALS and GEO.

Fig. 6: Comparison of ALS data with geodetic and photogrammetric measurement In most cases, the height measured using photogrammetry lies above and the height measured by laser scanning below the geodetic survey height. In the field of photogrammetry, the average height differences in the trough are about 0.36 meters GEO - ALS and 0.57 m FOT - GEO. For the inundation area, these values are approximately 0.25 m in both cases (sections A and B). In the middle section the ALS values range from 0.30 to 0.40 m below the GEO values (profile C). In contrast, there

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was excellent agreement with profiles on the top of the stream - the valley in the forest (profile D). A smaller scale and grid resolution of 10 meters corresponds to ZABAGED ® profiles. The results of the comparison of digital terrain models and profiles could indicate a systematic ALS error. It should be borne in mind that the shapes of channels geodetically surveyed might not be fully current due to the surveying having been acquired in 1999. Apart from analyzing the differences of different DTM data, contours (equidistant 2 m) were generated from the ALS data and compared with the current contours of ZABAGED ®. The resulting maps, related to differences in land use (forest, arable land, urban), are shown in Fig.7. They indicate that significantly more accurate elevation occurs mainly in the forest. In other cases, the differences do not exceed the margin of error, which is half the distance between contours.

Fig. 7: Comparison of ZABAGED ® layers and ALS A flood zone was established in the area of interest in 2001 for the Dědina watercourse, which flows through the city of Dobruska. The section of the stream that flows through the territory concerned has a length of 8.4 km. The resulting flood lines relate to flood scenarios with a maximum flood flow of Q 20 and Q 100 The data on the basis of which the floodplain was defined, was lent by the Elbe River s.p., based in Hradec Kralove. They are:

1. The photogrammetric survey (lower part of the stream: from the mouth of the Dědina to Orlice all the way through to the county of Pulič)

2. Geodetic survey a. Detailed profiles of flow channels (lower flow: from the mouth of the

Orlice to Pulič) b. Profiles in the valley where photogrammetric scanning was performed

(upper part of the stream: Pulič onwards)

Each data source and the areas issuing from them are shown in Figures 8 and 9.

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Fig. 8: Aerial view of the area of interest

Fig. 9: Summary of available data in the area of interest on the basis of the DMT

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Comparison of DMT

An external supplier created Altitudinal and topographic evaluation of aerial surveying imagery and processing of a digital terrain model for the Elbe River. A detailed point field was available with a mandatory point connection line. The distance of points ranges from about 3 m to 20 m depending on the segmentation of the surface (see Figure 10)

Fig. 10: photogrammetric capture points in the vicinity of Pulič and the Dědina waterway

To evaluate the accuracy of elevations in this area, a comparison of the DMT from the data of the laser measurements with the other two digital terrain models was assented to. These are:

1.DMT Photogrammetry 2. Current DMT, created from the contours of ZABAGED ®

Due to the resolution of the photogrammetric data, data was selected that had already been processed from, meaning DRM points in a regular grid with a spacing of 5 meters. Grids with a resolution of 5m, and whose values were subtracted from each other, were created from both point contours using an intermediate TIN product.

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Results of the DMT comparison were as follows:

Fig. 11: Comparison of ALS and the photogrammetric

Fig. 12: Comparison topogrid ZABAGED ® and photogrammetry

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Fig. 13: Comparison topogrid ZABAGED ® and ALS

Fig. 14: Comparison of photogrammetry and ALS

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Profile comparison In Region 1 (length of the flow of about 2.1 km) 10 geodetically surveyed

profiles were available. The elevation of all available resources was related to the location of individual points of the geodetically surveyed profiles. Compared were the altitudes of the geodesic measurements, the photogrammetric, aerial scanning and topogrid, created from contours of ZABAGED ®. In most cases, the altitude of the generated profiles followed the order: photogrammetry, geodetic surveying, laser scan. Approximate height differences are document in table 2. Table 2: Average height difference, in the trough outside the trough

Height difference - average (m) In the trough Outside the

trough

Geodesic measurements – laserscan 0,36 0,27

Photogrammetry - geodesic measurements 0,57 0,24

Discussion New altimetry mapping using the ALS method will bring quality altimetry information that will find application in many fields of human activity. From the perspective of water management the accuracy and density of the new elevation data will facilitate development and updating of existing data (DIBAVOD). In addition to this, it opens the way to various automated methods. The basis will be the specification of the watercourse network, including updating of distances. For the identification of high-rise buildings on and over the flow of water (i.e. grades, weirs, bridges, etc.) the automatic process could contribute analysis of the longitudinal profile of the water. ALS data will become the most essential of the geodetic materials and will play a major role in the mapping of flood hazards and risks, which are required by the European directive. From analysis of test data it follows that after removal of systematic errors, the data should be appropriate for determining the geometry of flooding and the channels some of the smaller rivers, where water depth is low. In the case of large watercourses, it is necessary to carry out further research and consider using other methods for mapping underwater terrain. Precise DRM will make irrefutable sense in determining the distribution boards and catchment areas, which are essential to determining the volume of precipitation. Accuracy and density of the DRM will enable processing of studies and planning documents for the preparation of retention tanks (for example, flood prevention measures, water accumulation, etc.). DRM will provide sufficiently detailed data for various modeling in the field of surface and groundwater. Certain restrictions are high demands on hardware with regard to the enormous volumes of data processed.

4. Aerial thermal imaging

Infrared imaging falling into the category of imagery for remote surveying of the ground is contactless measurement of surface temperature of the monitored object with infrared cameras. The infrared camera’s detector measures the electro-magnetic radiation radiated in the infrared spectrum by the object. Numerically this band can

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be expressed in the wavelength range λ = 0.75 micron to 1 mm. The fact that radiation depends directly on the surface temperature of the object (as described by Planck's law, Wien's law of sliding, the Stefan-Boltzman law), this temperature allows the camera to calculate and display. Camera detected radiation is affected by the emissivity of the body, radiation reflected from the monitored object that was created in the environment, and absorption of radiation during movement through the atmosphere.

The object may be hiding underground and only affect surface temperature. Infrared photography is quite strict regarding weather conditions in which the measurement is made. Clouds and their shadows, wind of 3 m / s, high soil moisture all have negative effects and in some applications vegetation and / or direct sunlight can have a negative effect. The optimum periods for most imaging applications are autumn and winter. Infrared scanning is appropriate to carry out before dawn and with no snow. These conditions greatly limit the use of thermo graphic imaging methods. The number of days suitable for imaging is very narrow. Sometimes it is hard to satisfy all these conditions and it may happen that the required imaging cannot be carried out at all.

Therefore, it is necessary during image analysis to determine what is being monitored using selected method. Thermographs can be particularly useful for study of expression of temperature contrasts. The resulting temperature map obtained through thermal scanning is influenced by the properties of the object itself and the characteristics of the environment in which the tracked object is located.

The infrared camera ThermaCAM PM 695 is located in the plane in the gyro suspension because of the narrow camera angle and minimizing the impact of turbulence on the captured ground. Gyroscopic suspension offsets the negative effects of flying and maintains the axis of infrared cameras in an upright position (perpendicular to the ground).

As a result of wind effect, the survey airplane is not always moving parallel to the flight path, and the aircraft can drift up to15 degrees. To eliminate the adverse impact on the outcome of drift, compensation is necessary. To compensate for drift, navigation devices,

Fig. 15: ThermaCAM camera

The gyro suspension and AEROcontrol all work together. Precise GPS navigation allows for shooting along a pre-planned route. The data record on the spatial position and the infrared camera angles are used for subsequent georeferencing (the location in the coordinate system) thermal records. Source infrared data is stored in formats IMG or FFF, and must be prepared for interpretation. For the processing of thermo-vision images, 5 parameters are entered: emissivity, reflected temperature, atmospheric temperature, relative humidity sensor and the distance from the object, whereas a major role is played by temperature reflected (depending on cloud cover) and the emissivity of the object (depending on the material of the object). This means a choice of an appropriate scale and output color temperature range (IRON, RAIN, GRAY...). Thermograph records can be presented in the same way as other

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topographic map bases. By georeferencing thermal imaging records they are placed in the coordinate system. Thermograph records are specific positions and thus it is possible to present scale, measuring distance and area. Presentation along with other map data is available both in printed form and in various software platforms (CAD, GIS...). Map background or background an orthophotomap improves orientation in the thermal image record. For certain types of tasks where the required rate of assessment can be implemented method called direct georeferencing (using only the elements directly measured GPS / INS without the use of other maps).

Measured or popular objects can be:

• Pipelines: water distribution, heat distribution, gas, oil....Searching for pipelines stored under or above the ground and their location. Analysis of distribution, diagnostics, malfunction detection, prevention of accidents, quality control, pipe insulation.

• The heat loss of buildings: registering losses of heat from the roofs and walls of buildings, surface imaging of urban agglomerations.

• Landfill waste deposits, stockpiles, dumps, contamination, environmental liability

• Geology, searching for tectonic faults, contamination.

• Water works, dams, pollution of water bodies, and sources of pollution of water bodies.

• Climate analysis, monitoring of urban agglomerations in the tropical days.

• Underground structures, old mining works, and archeology.

• Monitoring the status of animal populations.

Fig. 16: Water pipe about 2 m below the surface

GEODIS has been involved with thermal imaging since 1994 and has undertaken a large number of projects. At present, it is using infrared cameras with a resolution of 640 x 480 pixels. Angle of view perpendicular to the direction the aircraft is 10 to 24 degrees depending on the camera and lens. In the context of rising energy prices and the costs of long-distance transport with the aide of long-distance hot-water lines, efforts are increasing to map these networks and managed them well. Current development of thermograph imaging supports the energy saving and environmental protection in connection with global warming which is also the focus of EU programs.

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It is a modern data collection method that is used not only by public institutions, but is applied in everyday commercial practice. The thermo-vision records conceal a lot of interesting information. The data must be properly handled, understood and interpreted. [8]

The following examples present the possibilities of interpretation of aerial thermal imaging for users engaged in river networks. In contrast to orthophotos, figures 17 and 18 enable one to clearly identify the tributaries into the main stream, including the temperature difference between the two streams and the exact trajectory of the axis of water flow.

a) b)

Fig. 17: Inflows into waterways

a) b)

Fig. 18: Trajectory of axes and watercourses) thermal image, b) orthophoto

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Control authorities monitoring the discharge of wastewater into watercourses are able to use aerial thermal imaging to objectively locate sewage outlets, which are not identifiable from the orthophoto, or from local investigation, because of discharges below the minimum level of water flow. (Fig. 19)

Fig. 19: Identification of the discharge of wastewater into the stream

Finally, you can locate cross barriers in the trough as various thresholds, stabilizers, or objects in the trough weirs. (Fig. 20)

a)

b) Fig. 20: Identification of the weir and inflow

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5. Conclusion Aerial laser scanning and thermal imaging is currently a relatively expensive method of obtaining the source data. But when taking into account the wide range of potential uses of input data across the entire range of needs of state and local governments, private companies and research institutions, government agendas and monitoring (in general), it can be stated that the initial investment is paid back many times over. The condition is good imaging parameters and technological lines of evaluation to make the results the most useful for potential users. The policy of free access to the results is another condition for successful use and evaluation of all potential products of the project. The TG Masaryk Water Research Institute, Academy of Sciences is in cooperation with the Land Survey Office to find the optimal use of technological procedures of the ongoing project of ALS for the need of protecting water and updating water data. This paper outlines the possibilities of ALS and its subsequent evaluation in relation to:

1. More specific location of watercourses 2. Identification of barriers in the riverbed of a watercourse in connection with the determination of the water level 3. Assessment of the suitability of the ALS data in coastal zones as input to hydrodynamic models to determine floodplain areas 4. Possible quality assessment over elevation data.

In connection with the aerial thermal imaging, it is recommended to apply the results in the field of water management in relation to:

1. Location of discharge (waste) water into surface waters 2. Identification or precise trajectory axes watercourses 3. Mapping cross barriers and stabilization of objects in the bed of the stream using a terrain model generated from ALS.

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6. Illustrations Fig. 1: Using ALS Fig. 2: Aerial photo, points from the ALS-1. Terrain, 2. Surface of buildings 3. Surface vegetation Fig. 3: Bands air laser scanning in the Czech Republic (ALS) Fig. 4: Comparison of the existing watercourse dataset with the ALS data Fig. 5: Identification of 2 levels with the help of DMT (TIN) and the longitudinal profile of water surface Fig. 6: Comparison of ALS data with geodetic and photogrammetric measurement

Fig. 7: Comparison of ZABAGED ® layers and ALS Fig. 8: Aerial view of the area of interest Fig. 9: Summary of available data in the area of interest on the basis of the DMT Fig. 10: photogrammetric capture points in the vicinity of Pulič and the Dědina waterway Fig. 11: Comparison of ALS and the photogrammetric Fig. 12: Comparison topogrid ZABAGED ® and photogrammetry Fig. 13: Comparison topogrid ZABAGED ® and ALS Fig. 14: Comparison of photogrammetry and ALS Fig. 15: ThermaCAM camera Fig. 16: Water pipe about 2 m below the surface Fig. 17: Inflows into waterways Fig. 18: Trajectory of axes and watercourses) thermal image, b) orthophoto Fig. 19: Identification of the discharge of wastewater into the stream Fig. 20: Identification of the weir and inflow 7. Bibliography [1] Brázdil, K. (2009): The project of creating a new elevation of the Czech Republic, volume 55/97, 2009, No. 7, pages 145-151, Geodetic and Cartographic horizon. [2] Sima, J. (2009): The ABCs of Aerial Laser Scanning, 2009, Issue Number 3, pages 22 - 25, GeoBusiness. [3] Dušánek, P. (2008): Creation of Digital Terrain Models from Aerial Laser Scanning and its use for updating the ZABAGED ® Elevation. DP. Technical University in Prague. [4] Dolansky, T. (2004): Lidar and Aerial Laser Scanning, Acta Universitatis Purkynianae 99 Geoinformatics Studies, J. E. Purkyn University Usti nad Labem, 2004, ISBN 80-7044-575-0 [5] Brázdil, K. The Project of Creating a New Elevation of the Czech Republic. Geodetic and Cartographic Horizon 7 / 2009, pgs. 145-151 [6] Uhlir, K., Zboril, A., Possibilities of Using Laser Scanning for Surface Water Management Purposes.Water Management 12/2009 - VTEI 6 / 2009, pgs. 11-15 [7] János, M., Infrared View from an Airplane ItCAD 02/2010, pgs. 18-19.

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Contents 1. Introduction..................................................................................................... 1 2. Digital base of water management data......................................................... 1 3. Laser scan...................................................................................................... 2 4. Aerial thermal imaging.................................................................................... 15 5. Conclusion...................................................................................................... 20 6. Illustrations...................................................................................................... 21 7. Bibliography.................................................................................................... 21

Contacts T. G. Masaryk Water Research Institute, public research institute Podbabska 30/2582 160 00 Prague 6 Czech Republic Zboril Ales, zboril@vuv.cz Fojtik Tomas, fojtik@vuv.cz Uhlirova Katerina GEODIS BRNO Zednickova Drahomira