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Placement of WAAS Reference Station (WRS) for Indian airspace
Calculate the distance between the WRS We have mentioned a solution given by Gauss. Its limitations is that the distance d between the WRS station should be smaller than 50 Km . For longer distance Bessel’s Mid latitude formulas is suggested. One Second = 1.855/60 = 0.04 Km  Fig :4 – Plan I Used Hero formula to calculate the area of isosceles triangle which are the part of the WRS monitored area. S= (a + b + c) / 2 Where a, b, c are the sides of the triangle Area of triangle = [s (s-a) (s-b) (s-c)]1/2 When station is connected to each other, the final shape of the monitored area is irregular shape. To ease out the calculation of WRS monitored area, the isosceles triangle pattern has been considered for calculating the monitored area of the WRS station. The area calculation of Plan I &II and the station coverage diagram as Fig (4) & (5) The total Area covered by plan-I = 8185051.789 Km2 The total Area covered by plan-II = 5007448.85 Km2 It is evident that Plan –I monitored area is much higher than Plan II monitored area due to increased in number of WRS stations. To prepare the coverage diagram for both plans, for sake of simplicity thumb of rules has been followed. The coverage of the each WRS is calculated based on averaging of sides of triangle and also taken least value of the average as same station sharing or the part of the other triangle. The coverage diagram of Plan-I and Plan –II are placed as Fig (4) and Fig (5). In plan-I, Entire Indian Airspace is covered and monitored area is calculated including bowing effect coverage. The bowing effect will be more prominent between station 1&2, 2&3, 3&4, 4 & 5, 5 & 6, 6&9 , 9 &10 , 10&1, 11&9. Some of the station coverage is overlapping due to more number of stations in less area. The WRS coverage will over lap to each other WRS coverage. The station (12) &(14) will not play major role as station will fall within the monitoring station of the other station. Therefore, station (12) and (14) can be utilized for WMS. The coverage diagram for plan-II as shown Fig (5) does not cover entire Indian air space. This plan needs to more WRS to cover entire airspace. The additional WRS required for plan-II are either at Lucknow or Patana . There is less overlapping of correction signal compare to plan-I .  Fig :5 – Plan II |