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Qualitative and quantitative interpretation of remote sensing data on the stage of primary forecast in project of exploration in rare-metal and
noble metal province Movchan I. , Iakovleva A.
Качественная и количественная интерпретация данных
дистанционного зондирования на стадии первичного прогноза в
проект освоения редкометалльных и благородных металлов
провинции
12
Мовчан И. Б. , Яковлева А. А.
Мовчан Игорь Борисович /Movchan Igor - кандидат геолого-минералогических наук, доцент,
кафедра геоэкологии;
2Яковлева Александра Анатольевна /Iakovleva Alexandra- кандидат физико-математических
наук, доцент,
кафедра высшей математики,
Национальный минерально-сырьевой университет «Горный», г. Санкт-Петербург
Аннотация: 8-полосный образ WV-2 спутника дистанционного зондирования является основой применения исходного спектра и структурной перестройки алгоритмов, разработанных для решения задач геологоразведки и первичной прогноза. Основные методы интерпретации являются системы автоматизированного линеаментного декодирования, волновой анализ на аналитическом продолжении.
Abstract: 8-band image of WV-2 satellite remote sensing is the base of application of original spectrum and structural reconstruction algorithms which are developed for solution of problems of geological survey and primary forecast. Main methods of interpretation are computer-aided lineament decoding, wave analogies in analytical continuation.
Ключевые слова: линеамент, сечение, спектр, индекс, прогноз.
Keywords: lineament, cross-section, spectrum, index, forecast.
Geological survey of mineral deposits with application of modern surface methods has the ecological and economic risks. Main part of near-surface deposits is supposed to be discovered. The potential resources include just hidden geological objects which are masked or placed at the significant depths. High price of traditional geological-geophysical methods causes their using within limited areas for evaluative works and certifications. Appearing remote sensing system, providing the stereoscopic multispectrum images of extra-high resolution, allows looking below the Earth surface on the mining depths of geological substratum.
The efficient technology of remote sensing data application in geology is formed by the set of subsequent transforms and reductions of original images and initial geological information. The precision of their parameters fitting and organization of procedures consequence define the optimization of computing tools and rationality degree of its application.
In this paper the first element of original satellite image processing is its radiometric and geometrical reducing which is not considered in details. Next important item is the set of indirect detections discovered in 8-band DG image which admit tracing main landscape components. The last ones are considered as the factors of lithological substratum masking.
The dense vegetable cover mapped within the whole territory of Russia is traded on the typical absorption band of chlorophyll. The peculiarity of processing consists in the
invariance of spectrum heterogeneities of vegetable cover which are caused by geological heterogeneities located by correlation with ferro-aluminosilicate index.
The surface humidification is considered as the high-amplitude modulator of landscape reflecting ability. Relatively homogeneous hydrological conditions reflect the present hydrogeological and structural-tectonic situation, but humidification caused by abundant atmospheric precipitation masks whole underlying surface.
Algorithmic computation is developed in 9-dimensional spectrum space, formed by 8 bands of 2 meters resolution as well as by panchromatic band of 0.5 meter resolution. In the ideal case this space includes additionally the corresponding stereoscopic pair which increases the stability of low-amplitude signal and supplements the information about the heterogeneity of indicatrix of reflection of underlying surface and about its morphology. The structure of final multidimensional matrix defines one of required components taking into consideration the variability of illumination conditions, density of mapped vegetable cover and the intensity of other overlying factors. The procedure includes the composition of file of spectrum vector absolute values in each point of investigated area, centration of required component and composition of file of non-standardized computed index. The standardization is based on the model, developed with consideration of characteristic curve of spectrum bands, and finally it is detailed on the reference areas. In this paper the values of reference areas with snow aren’t used.
The geological forecast takes into account the geochemical indexes (for instance, Fe-Al-Si and reductive-oxidative ones) and geomorphological component of satellite image. The space-related analysis of spectrum heterogeneities ordering (connectivity of signature families on the spectrum characteristics) and analysis of structural homogeneity of Fourier spectrum are realized within segmented area. On its base we implement the metallogenic forecast and reconstruction of geological structural cross-section.
On the stages of structural (qualitative) interpretation of multispectrum image and its recomputing into the geological space one has to estimate the positions of signal extremum and extremum of horizontal gradient and to compute the space-related stationarity parameters. The advantages of 8-band DG satellite image are:
- the work with high-contrast representations of landscape and geomorphological anomalies of different genesis;
- minimization of spline-interpolation procedures with increasing the precision of structural forecast;
- significant details of structural cross-sections marking the element of structural control of primary ore deposints.
The structural reconstruction has the form of combined algorithm computing, from one side, the spectrum signal transforms and, from another side, the structural peculiarities of signal on the base of eigen values of dispersion matrix. The result is the set of structural-lineament maps (Fig. 1), reflecting the modern tectonics of polygon at the different levels of generalization (different levels of details). This stage of processing satellite image includes the primary forecast and geological mapping under minimum a priori information condition. The forecast itself is in tracing hypothetical ore-controlling structural elements within the investigated area, these elements classification with discovering the law of space location of reference objects (ores and deposits of different ranges) [1].
Fig. 1. The example of lineament structural mapping on the 8-band DG image (on its low-
frequency component)
Spectrum processing is focused on the finding the conditionally independent harmonics in the spectrum plane which admits the correct separation of optical density field of satellite image on the different-frequency components. Computing the absolute values of horizontal gradient vector and consequent location of positions of extremum of initial field and its horizontal gradient is the main procedure for mapping the small vicinities of lineament reconstructions. The lineament is the smoothed and linearized element of landscape reflecting the geological fractures of modern activation and near-surface structural-rock complexes. The dispersion matrixes mentioned above are used for transform the quasicontinuous field of optical density into the discrete lineament field. The last one has the «closed» image, formed by smoothed structural elements like linear, arch, S-shaped etc. ones with natural shifts of ancient lineaments with regard to young ones. Within the lineament field one can select the elements of discordant structures, circular structures of different ranges, the wide spectrum of their spacial relations, in particular, the grouping and attraction to the definite linear (axis-like) zones. We proved these structural peculiarities together with reference objects are classified as ore-controlling ones and are parametrized in the problem of primary forecast.
The quantitative (in geological space) continuation of 8-band DG image reduces the initial field of optical density into the cluster map of the areas of space-related stationary. The last one is the area of constant amplitude-frequency composition of field which is considered in the terms of ultimate depth of geological (density and structural) heterogeneities. Our corresponding algorithm traces in the cross section the elements of stratification, syn-forms and anti-forms as well as the steeply-dipping structural objects associated with fractures (Fig. 2) [2].
Fig. 2. The application of wave analogies for reconstruction of structural cross-section on the base of special stationary analysis of 8-band DG image. Background is real geological cross-section. Foreground is the result of analytical continuation of optical density field ofpanchromatic band
Within considered region reflected on the figures one can see the correlation or reconstructed structural elements of cross-section with the structural elements of geological cross section formed on the base of geological survey and drilling data. The deep recomputings are based on the wave analogies and is represented as the set of internal waves which is finally considered as structural half-tone cross section like seismic time-related cross section.
Our research results consist of our original algorithms and the family of interpretation criteria, from one side, and the analysis of interpretational properties of 8-band DG image of high resolution. Their combination gives the interpretation system of new generation applied to both potential and non-potential fields processing under minimum a-priori information condition.
RESUME: multifunctionality and global character of used methods and algorithms
application
The data of satellite WV-2 with use of algorithms of spectrum separation and frequency filtering, confirmed by field operations as well as final mathematical models of natural processes allow to get the next full-colored and high-detailed spectrum synthesis: «biotic» synthesis, «hygrophyte» synthesis, «lithological» synthesis, «reductive-oxidative» synthesis, synthesis of «landscape stereotype», synthesis of «land-using», «anthropogenic» synthesis. Application of described algorithms in particular problems including photogrammetric ones increases the signal-to-noise merit by: spectrum stationarity of informative signal; generating the mask of regular noises; continuous character of histogram of final transformations. Using our original algorithms one can expand the original set of DG production up to 10 bands plus spectrum and synthesized bands of 0.5 m resolution. Considered investigations are on the initial stage because of requirement of confirming field works, defining reference samples and final confirmation of derived parameters on the base of field works.
References
1. Movchan I. B. Formal criteria of decoding and interpretation of structure of satellite slide and airphotos //The proceedings of International Conference MatGeos-08, Friberg, Germany. June, 2008. - 6 p.
2. Yakovleva A. A. Structural reconstruction of geological half-space on potential fields under conditions of a priori information minimum // The proceedings of International Conference MatGeos-08. Friberg, Germany. June, 2008. - 7 p.
