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Tibor Lajos
I would like to recommend acomplex measurement systemthat makes it possible to get aperfect comprehensive overviewof your lake. Thanks to theimprovement of the technicaland IT devices, in the last decadeI managed to develop ameasurement procedure for thisspecific task. The expressive andeasy understandable display ofthe processed data have gotspecial emphasis during thedevelopment of themeasurement procedure. Myactivity contribute with technicalsupport for water specialists,emergency managementorganizations and fishermen.
Lake bed mapping
The display of the several physicalparameters is being realized withcoordinate grid contour maps. Themeasurement takes places with multi-channel sonar that is set for the specificconditions in all the cases. The depth isrepresented by numbers and contourlines on the map which is created fromthe processed data. Depth dependentcolor helps in interpretation. Thedeeper the area, the cooler color isapplied. The visible depth on the mapmeans the top of the sediment! Theaccuracy of the displayed depth valuesare more precise than 10 cm. Thedisplay of map detail is only limited bythe poster size.
A map file with KMZ extension isproduced for the lake area. By openingthe file in the „Google Earth” app thelake bed map appears on the map. Wecan measure distance, and the locationof the user can be shown as well.
Surface hardness of the lake bed
This type of map is significant fromfishing point of view. Surfacehardness of the lake bed isdisplayed with the gray colorshades. White color means thehardest surface, while black showsthe softest one. During themeasurement, the map is createdfrom the reflection of the multi-frequency ultrasound. Sedimentmap is absolutely necessary forwater maintenance.
Sediment thickness
Ultrasounds of different frequenciespenetrate into the sediment and reflectdifferently. For given water temperatureand sediment, the calibration is made withoptoelectric device at necessary number oflocations. Due to the differentdetermination method of the sediment indifferent fields, according to mymeasurement the top of the sediment,where the light transmittance ends and thebottom is the rigid soil. In case of favorablelake bed and weather conditions, it’spossible to determine separately theamount of fixed and moving sediment. Thethickness of the sediment is displayed onthe map with shades of gray colors. Thearea without sediment is white, and blackcolor indicate the area with the thickestsediment. The largest measured value isrepresented on the map. Every shademeans 10 cm deviation.
Introducing the measurement of the sedimentThe reflection properties of ultrasounds with different frequenciesmakes it possible to determine the thickness of the sediment. Reflectionoccurs at the boundaries of the media with different sound propagationvelocities. The short wavelength signals return from the boundary layerof water and sediment, suitable for determining the surface of the lakebed. The high-wavelength ultrasonic sound penetrate deeper into thesoft medium and reflects from the boundary of the stable soil structure.The thickness of the sediment can be accurately determined from thetime difference of the return signals. Ultrasonic sound measurementsare carried out on the whole area of the lake. Control points aredetermined according to the preliminary sediment map at the thickestsediment layer locations. At his places, checking and calibration of theresults are made by manual probe. Depending on the environmentalimpact of the lake, a very soft movable sediment layer is formed abovethe soft sediment layer. Flows can change the distribution of thismedium. Measurement under flow-free conditions can be carried outwith an opto-probe. The upper limit of the soft movable layer can bedetected where the light transmittance of the water disappears. Thebottom, where physical resistance is observed. The surface hardness ofthe sediment can be determined from the magnitude of the reflectedshort-wave ultrasound. Hard surface results in strong signals withmultiple recurrence. From the softer layers, weaker signals are detectedwithout secondary reflection. The evaluation of the results are displayedin the form of sediment map.
Determination of water area parametersThe following parameters of the water area are determined from the measurement data.
• Whole water surface
• Lake water volume
• Coastline length
• Average water depth
• Deepest point
• Average thickness of the sediment
• Sediment volume
Parameters in layers
The general parameters of the lake is not sufficient for biological investigations. It is necessary to know the area of waterlayers and the volume of water within layers. In the possession of the data, it is possible to determine the current weightalgae and the amount of water that participate in the oxygen production. Similarly significant to know the amount anddistribution of the sediment. It matters how big is sediment the area that the light can reach, what is the amount thatsediment in which the healthy decomposition process can occur and where can develop dangerous gar production.
Fish stock estimationThe main advantage of the hydro acoustic method that the measurementhappens for the whole lake by without disturbing the fishes stock. Duringthe measurement, a program classifies the fish in three categoriesaccording to their size. The measured numbers quantifies the estimatedfish stock mass, for which the owner of the lake provide the average massof the fish categories. For each individual return signal, the measureddistance is registered as well. From these data the mass of the fishes canbe determined. The algorithm has been developed on production lake,containing fishes with the same size. The limit of the measurement rangeis 2 x 70 m, but the smallest deviation in the results, 10 5 can be reachedwith 20-25 m range. Firstly the data in connection with the mapping areameasured. Due to this procedure, the fishes goes into deeper areas thatmakes them easier to detect. The fish stock / hectare is used to determinethe fish stock. It’s necessary for the measurement that the average depthof the lake exceeds 2.5 m. At shallower average depth, the fishes movessignificantly in transversal direction due to the sound of the measurementboat. In shallow water, the few degrees of hidden data below the watersurface can lead to significant data loss.
Cross sectional imagesOnly the numbers and graphs that express the fish stock are not so representative. Water specialist, fishermen can easierinterpret the cross sectional image that is created by the 74°radars. The proportion and density of the fishes becomesvisible.
Fish Map
Besides the number andcategories of the fishes thelocation is also recorded.With the help of themeasured data, thepositions of the fishes canbe displayed for themoment of themeasurement. The fishesavoid the deep areas withthick sediment, especiallyin case of decreasingatmosphere pressurebecause of the soluble gasin the water. In most of thecase, this area is only fewpercentage of the lake thatcould be degassed even byhand.
Photographic imageThe program draws a realistic photographic image from the reflections of the lake bed. Larger objects, large fishes are recognizable in the picture. In case of fishes, characteristic shape can be separated from the surroundings, and ultrasonic shadow appears. It is possible to determine the dimensions and exact coordinates of the objects.
Composite imagePhotographic image and lake bed map are displayed together with their information. The contours and the colors helps you to see the lake bed in 3D.
Animation
A spectacular, 3D terrain model is created from maps to fit into the surroundings, every point of the lake bed can be identify. You can display any information, planned object, status you want to reach in the future. The video is made in Full HD (1920x1080) resolution.
Demonstration film with aerial video
The maps are inserted into aerial video, On demand,narrator provides information about the water area.
Phases of project implementation
Return of completed and signed order form. Obtaining required
licenses.
Selecting a date by prior arrangement. Data
collection takes place on a pre-planned route on the
lake, with a specially designed vehicle.
Full documentation will be completed in 1-3 weeks.
It is sent electronically via e-mail. The questions that arise at this stage will be
answered.
Payment will be made in one amount with online
transfer after the approval of the documentation.
Contact information
Order Measurement Documentation Invoicing
Phone: +36 30 740 6932
E-mail: [email protected]
Facebook: Tibor Lajos
Details of the measurement
On-site consultation
Discussion of conditions that make transport
difficult. Description of the artwork needed to
record the current water level.
Lake bed data collection
The transportation on the lake is carried out with a
small power, excellent condition four stroke
engine. Firstly the shoreline is recorded,
after that the main area of the water is covered with parallel ways. During this
time, fishing is not possible.
Sediment investigation with
probeCalibration for sediment composition is done with an optoelectronic probe
at the required amount of locations.
Fish stock data determination
During the measurement the transport is carried
out with an electric motor. The distance between the parallel ways depends on the average water depth
of the lake.
Checking the data
Before removing the measurement vehicle
from the water, all data from the instruments are
saved. Testing and checking the data carried
out on a computer.
