Технические науки/ Горное дело

Ystykul Karagoz Abubakirovna

karagozy@mail.ru

Kazakh National Research Technical University after K.I.Satpaev, Kazakhstan

Eugene Levin

Michigan Technological University, USA

Seredovich Vladimir Adolfovich

Novosibirsk State University of Architecture and Civil Enginering

Blagoveshenskyi Viktor Petrovich

Institute of geography Republic of Kazakhstan

TECHNOLOGY OF MEASURING OF AVALACHE SLOPES WITH USE OF TERRESTRIAL LASER SCANNING FROM CIS COUNTRY VIEW

Introduction

Humans have had a great interest in avalanches since ancient times, back when they frequently caused loss of life and livestock, destruction of houses, etc. However, people were not able to discover the nature of, and especially how to control avalanches, in those days. While many troubles have been caused by avalanches, a complete avalanche disaster inventory has yet to be created. The death records of avalanche victims have been retained in the annals, manuscripts, books and human memory.

The first mentions of avalanche disasters are found in ancient descriptions of the campaigns of Alexander of Macedon in the mountains of Central Asia and over the Hindu Kush into India [1].

The Alps is home to the longest record of avalanche disasters, with written evidence from the antique and the early Middle Ages. The first genuine medieval document reporting a death due to avalanche was part of the retinue of Bishop Rudolph, Christmas in the year 1129 sent to Rome through the Great St. Bernard [2]. The Russians had to deal with avalanches in the Alps too. The army under the command of A.V. Suvorov was going from Italy to Switzerland in the autumn of 1799. The army suffered minor casualties from avalanches at the St. Gotthard pass and in narrow mountain valley on the way to devil's bridge. There is a monument devoted to Suvorov's soldiers not far from devil's bridge, in an alcove, carved into a steep mountain slope. Avalanches overlap it every winter.

In the twentieth century, the largest avalanche disaster occurred again in the Alps during the First World War, on the Austro-Italian front. According to the subsequent estimates six thousand soldiers died from avalanches, more than people that’d died from the result of military action [3]. Avalanche disasters are not the privilege of the Alps in Europe. Lists of victims have been maintained in Iceland, Norway, Bulgaria and other countries. However, the Alps remain as the primary location where avalanches occur. One of the most horrible disasters happened in the French Alps in 1970: the avalanche that struck the hotel in Val d'isere killed about two hundred tourists and the other one pulled down the health resort for children near Saint-Gervais, burying 80 people - children and staff [3].

Avalanche danger area covers 124 km² [4,5] in the mountainous regions of Kazakhstan. The volumes of the avalanches in the area can reach 1 million square meters. Human settlements, ski resorts and roads are threatened by avalanches. Eighty seven people died in avalanches within the territory of Kazakhstan over the past 64 years. Mostly tourists such as climbers and skiers face the threat of avalanches. Forecasting avalanches, preventive descents and defenses are used as avalanche protection policies.

Neglecting the avalanche danger can lead to quite severe consequences and significant destruction of infrastructure, and cause human casualties. Therefore, research on the identification of avalanche sites is very important. One of the avalanche areas in Kazakhstan is Ile Alatau (Fig.1) and Altay [4].

There are avalanche areas along highways Ust-Kamenogorsk – Zyryanovsk , Ust-Kamenogorsk – Samara and on the railway Ust-Kamenogorsk – Zyryanovsk in Altai. By the ski resorts of Chimbulak, Almatau (Fig. 2), the Akbulak, the rink Medeu, the road through the valleys of the rivers Bolshaya and Malaya Almatinka, Esik and Turgen. Marked hiking trails and climbing routes are also threatened by avalanches in the Ile Alatau mountains. The number of avalanche areas which cause danger will be increased in connection with the construction of new ski resorts. A major ski resort of international class going by the name of "Kokzhailau " is planned to be built for the winter Universiade close to Almaty in 2017.

Scale - 1: 25 000

Figure 1. Fragment of map of avalanche hazard in Almatau

1 – avalanche road: less than 1 – 10 year; 2 – before 10 till 50 year; 3 –more than 50 year; 4 –less than 10 year; 5 –before 10 till 50 year; 6 – less than 50 year; 7 –forest; 8 – road of avalanche; 9 – watershed; 10 – house

Three methods of research are used to explore and describe avalanches, as well as to identify unhazardous avalanche areas: 1) forwarding; 2) map 3) interpretation. Experience in the application of these methods showed their advantages and disadvantages. Below is the examination of each of these methods.

Expeditionary method. The essence of this method is that the expedition is included to study the area which charts avalanche hazard maps and avalanche cadaster according to geomorphological, geobotanical and other characteristics. To carry out an expedition is preferred in the spring or summer, because in winter the traces of avalanche activity of the past years are hidden under the snow. It is necessary to collect all the published information about previous avalanches in the area prior to beginning the field work for choosing the topographic base in meeting the practical goals of the expedition

Depending on time of the year field work occurs, the expedition is equipped with appropriate equipment, food and uniforms. Based on the information collected under this program an avalanche inventory is compiled and appended to the map of avalanche danger, which is based on this topographic base. Mapping avalanche risk using this method over large areas has a number of disadvantages: the high cost of conducting field research; large complexity; the difficulty of defining the boundaries of the catchment and ways of avalanches.

The cartographic method. The core of this method lies describing of the paths of avalanches and avalanche catchment areas in the analysis of topography according to the topographic maps. The cartographic method has the advantage compared with the method of surveying, namely: 1. possibility of accurately defining the area of catchment and its nature, the paths of avalanches, slope angles and slope etc., which is very important for calculations of possible impact force and distance of snow avalanches. 2. Cost effective. The disadvantages of cartographic method include: the impossibility of the survey in nature, as there are no changes on the map in the study area that occurred after the release of those topographic maps; the impossibility of obtaining by the remnants of snow cornices data on the nature of snow accumulation and direction of the prevailing winds [6].

Aerial method. In addition to traditional techniques, investigations of avalanche zones may also includes aerial methods. Above ground methods include aerial photography and laser scanning (altimetry), used usually in combination. Airborne methods of monitoring objects have a number of advantages over spaceborne: high precision products, adjustability of equipment and shooting options; partial or complete exclusion of works on geodetic substantiation; high automation level; the possibility of technical and economic planning with the whole complex of aerial surveys.

It is necessary to formulate the organizational and economic aspects on the use of manned aerial systems for monitoring small areas of avalanche sites.

1. The cost of equipment for a comprehensive aerial survey and data processing programs is quite high and ranges from 1.5 to 2 million. Only large organizations are able to purchase and use such equipment, those specializing in high-volume supply of information about remote sensing.

2. The weight of the navigation and airborne radar equipment (lidar) together is 200 kg or more, which requires to be adapted for shooting aircraft (An-3, Cesna, etc.) or helicopters (Mi-8T, etc.).

3. The use of manned equipment assumes the availability of a well-developed field infrastructure: airfield, depot and equipment maintenance, certified pilots, dispatcher and maintenance personnel.

4. Obtaining and processing large amounts of information leads to the creation of separate structural units: mapping and surveying teams, groups, post-processing of survey data. Again, this is only available for large specialized organizations.

Costs of narrow strip of avalanche site laser scanning is significantly higher than just a simple area scanning. Therefore, to use ALS on extensive grounds and terrestrial laser scanning (TLS) on the local level is ultimately advised per [7].

The analysis of existing methods for modeling snow avalanches has shown that the majority do not meet our practical needs. Low adequacy of physical/mathematical representation of the avalanche, description in nature, and the low accuracy of prediction. can be included as disadvantage of these existing methods. Some methods cannot be implemented in particular conditions. Therefore, nowadays identification of appropriate and accurate methods of modeling and forecasting and analysis of snow avalanches is highly important.

The proposed method for modeling and forecasting snow avalanches can determine the area, speed, and power of avalanches with high accuracy. For example the software RAMMS, developed by the Swiss Institute of Snow and Avalanches, is highly adequate in terms evaluating the physics of avalanches [8].

The second order dynamics equation forms the basis for numerical solutions. The height and speed of the snow flow is calculated on specially designed digital three-dimensional terrain models [8]. Important survey information is displayed while using the program In this model, the resistance to the flow of the snow is taken in two types: power dry Coulomb friction with coefficient µ, and the forces are proportional to the square of the speed of movement of the snow mass, c the coefficient ξ. The frictional resistance will be:

(1)

ρ - the density of the stream;

g– free fall acceleration;

а is the average angle of the slope in the given point;

H– the height of the stream;

U– flow velocity (speed).

This model is best suited to describe the movement of very large avalanches consisting of dry snow. At the same time, RAMMS is not capable of describing wet avalanches and those of small volume. The authors suggest that a small avalanche can be modeled by increasing the values of the coefficients µ and ξ, but this requires pre-setting models. An additional disadvantage of this model is that the movement of snow is not described at the avalanche front, in the field of small moving mass, and large coefficients of resistance.

Therefore, currently searching accurate, convenient methods of modelling, forecasting, and analysis of snow avalanches is of high importance [8].

In snow and avalanche research, terrestrial laser scanning (TLS) is used increasingly to accurately map snow depths over an area of several km². Laser scanners emit a pulse of light in the near-infrared spectrum. The pulse hits the terrain or snow surface and is reflected. A photodiode in the scanner detects the returning pulse, and determines the distance to the target from the travel time of the pulse. The data from the reflected pulses are saved in a point cloud in the scanner’s internal coordinate system. When the exact global position of the laser scanner is known, and three translational and three rotational parameters exist, the point cloud can be registered in a global coordinate system (Prokop, 2008). Prokop (2008), Prokop et al. (2008), and Grünewald et al. (2010) report mean deviations between TLS data and reference tachymetry measurements of 0.04-0.1 m for target distances reaching 500 m, depending on the conditions and the laser used [9].

We used TLS snow data to obtain precise quantitative information about snow depths and snow redistribution. These data are derived by subtracting rasters from different scan campaigns. Then we correlated the snow depth and distribution data with the results of the terrainbased parameter and also compared the measured pattern of snow redistribution with windfield simulations[10, 11].

Active implementation and practice of TLS in various studies have shown highly accurate output results, quick shooting and processing, and fusion of new survey data with traditional methods [9].

The technology of TLS is an effective tool for modeling and the subsequent analysis of morphological properties of micro - and nanorelief and reliefoids (snow cover, vegetation). High-precision digital elevation models allow for proceeding to a qualitatively new level of morphological analysis [12].

Morphometric analysis of topography is the base of investigation (DEM). To identify potential areas of origin of avalanches the following criteria is selected: absolute and relative heights; slope; curvature in plan; the minimum area of the zone of origin; maximum unit of avalanche nonhazardous zone within avalanche hazardous territory.

Figure 3. The algorithm of automated selection of avalanche hearth with the use of morphometric analysis of the relief

Technological scheme of TLS-

1. Technical project planning.

2. Reconnaissance of the area. A rational way of creating and thickening survey ground takes into account the specific conditions of the area [13]. The location of the scanner and the placement of targets are outlined. The deadline of the work is clarified. We have chosen the center of origin of avalanches on the mountain slope and the installation location of the scanner (Fig. 5). The first survey was held on 05 A5pril 2015 when there was snow cover. The second survey was carried out on 02 July 2015 without snow.

1. Compilation scanner survey preparation.

2. Three-dimensional Terrain Laser Scanning.

1) Installation of the scanner onto a projected point with a tripod, the height is set to ensure maximum coverage of the area of interest in one scan (Fig.6)

2) Special stamps spread around the scanner, which show the points of operating survey object

3) Determination of the coordinates of the centers of special grades from the basic reference points of the network

4) Scanning of the terrain and objects around a point of scanner position

5) Identification and determination of approximate coordinates of the centers of special grades to further quick determination of their position on the scan

6) Scanning of special stamps with maximum resolution

7) Moving the scanner to the next scan point and repeating the steps 1-6.

Figure 5. Installation of the total station and scanner to projected point on a tripod

Laboratory work.

Terrestrial laser scanning data can be used to create a three-dimensional vector model of objects[15].

Data processing of laser scanner data is aimed at obtaining high-quality digital terrain models and their derived digital elevation models. The existence of such models is a prerequisite for the development of analytical tools, oriented on the investigation of surface geometry through a number of formalized procedures. According to the DEM the depth, cross section, height, volume, and speed of avalanches is determined and the potential to predict an avalanche is possible. The terrain model is mapped with orthophoto imagery and can be modified based on the identified errors [15].

Results.

Digital terrain modeling: digital elevation models (DEM) is one of the powerful and pervasive GIS functions. Under a DEM (digital elevation model) or DTM (digital terrain model) ) it is commonly assumed that representations of three-dimensional objects are in the form of three-dimensional data comprising many of the elevations and Z-samples at the nodes of a regular or irregular network or a set of records of contour lines or other structural lines [12].

Therefore, the concerns of high-precision monitoring of avalanche sites using TLS can be solved. A practical confirmation of the calculations is necessary. A Land-based survey of hazardous glacial processes in the highlands is currently taking place mainly at local areas with a limited observation period.

The issues of exploitation NLS systems: certification and registration of TLS, obtaining permits for filming, security and insurance photography are not considered in the article.

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