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Wave Interference Evaluation Supporting System A transmission line may cause the interference in television and microwave communication. The purpose of this subsystem is to predict the wave interference caused by the determined transmission line. The system has functions as shown in Figure 4.



Methodologies
Suitability Map and Optimum Route The existing process of the site selection is evaluated and as per the need, the environmental information can be classified into categories like, natural, social and technical environment. Each of these categories contains layers as mentioned below.

• Environment containing habitats of endangered species, national parks, etc
• Social environment containing view points, scenic areas, cultural assets, temples, shrines, agricultural promotion area, forest area, cities, district for urban planning, airports, etc.
• Technical environment contained faults, dangerous district for collapse, areas of snowfall, thunderstorm, salty breeze, wind pressure, etc.

An index should be introduced to represent the relative difficulty of the route construction, based on the experience of engineers. The index may be defined as:

Index = 4 [Negative Control Point (The route must not pass through)]

Index = 3 [Route construction is strictly regulated, or has a great impact.]

Index = 2 [Route construction may be permitted, or has a moderate influence.]

Index = 1 [Route construction has a slight influence.]

Index = 0 [No problem for route construction.]

The index number can be assigned to each polygon feature of the environmental database, according to the difficulty of route construction. For point or line features, a sort of buffer procedure can be performed using GRID function, and the index number can be assigned according to the distance from the center. The suitability map can be created by overlaying and summing up all indexed layers. This procedure will utilize GRID functions, and is shown in Figure 5.



The resulted suitability map can be considered to represent a sort of impedance for route construction. Using GRID COSTDISTANCE functions, the optimum route can be computed based on the suitability map as shown in Figure 5.

Determine Tower Height In the detailed route, height of each tower can be determined to minimize the cost of construction of the whole route. It can be accomplished as shown in Figure 6.

• First, the possible combination of tower height should be computed for each span. The required clearance of wire should be ensured over the ground and structures.
• Then, the combinations of tower height are joined along the whole route. The result is constructed as a network model with a turntable. The cost of each turn is computed, which depends on the tower height and the tower type.
• Finally, the optimum path can be derived using NETWORK PATH command, based on the cost at each turn. The resulted path corresponds to the most cost-effective tower height combination.

Profile along the Detailed Route Once the detailed route is determined, the profile along the route can be plotted as one of the final results. This plot includes the profile along the route, the structures under wires, the required clearance, the dip of wires, and the towers. Figure7 shows an example of the profile plot. Those features are plotted using specific command modules of the GIS software. The curves of structures, clearance and wire dip can be computed.



Estimate the Construction Cost The cost estimation can be accomplished using a spreadsheet package. The specifications of towers and wires, can be read by the spreadsheet. Further, in-house can be used to create a ledger of the route or to estimate the construction cost.

Conclusion
Several extensions can be incorporated into the system. The extensions include the automatic siting of each tower, the use of the result of detailed-field surveying and the simulation of realistic views using CAD/GIS packages.

Reference
Masahiko Murata,Systems Engineering Center, PASCO Corporation, TOKYO, JAPAN

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