Tham khảo tài liệu 'earth sciences part 10', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 350 Earth Sciences such as thickness and grade are already known should be used to estimate these parameters at points where no sampling is available. This process can be named as data extension. Data can be extended thru two-dimensional planes or three-dimensional space. During extension process square or rectangular grids wireframes are imposed onto area. Triangulation is another type of artificial net applied on field. Then extension methods such as inverse distance square geostatistics and artificial neural networks are applied. Gridding Although there are several methods to figure underground treasures such as aerial and seismic surveys drill holes are still the most reliable and decisive data givers. In plan view they look as irregularly distributed point data. Grid is a regular network formed by triangle square or rectangles generally. It is the result of a regular mesh need. Irregularly distributed sample points get a regular form if node points are assigned parameter values such as thickness and grade. In other words thickness and grade values are estimated at node points which results in a regular data structure Fig. 4 . Plenty of node points are generated by superimposing a wireframe grid onto a field Knudsen 1990 Parker 1990 . Fig. 4. Assignment to node points. Irregularly distributed sample values drill holes are extended distributed to field by several approaches a. Classical methods triangle polygon b. Inverse distance methods c. Geostatistical methods d. Artificial intelligence neural networks These methods are generally employed to assign node values by using drill holes. Nodes are aligned through triangular or rectangular grids networks Fig. 5 Fig. 6 . Calculation of coordinates of grid nodes is a simple mathematical process. Let number of nodes in X direction is n and in y direction is m. Total number of nodes on grid is mxn. If each point is represented as p i j I i 1 2 . n j 1 2 . m then p i j s are function of Xi and yi coordinates p i j f
