144,000/12 = 12,000 feet2. Determine the ground coverage. Now thatyou know the altitude at which the mission must beflown to obtain a scale of 1/12,000, you can determinethe amount of ground coverage on each frame. Again,this information can be determined using the IFGAformula. Remember that the forward overlap requiredis 60 percent. The remaining 40 percent of the 9-inchnegative is usable imagery for GGF. You must first findthe size of the usable portion of the negative for GGF.This is accomplished as follows:0.40 9 = 3.6 inches of useable image area for GGF^{I}=^{G}so G =I AFAFG =3.6^{12,000}=3,600 feet12The amount of side lap required is 40 percent. Thisleaves only 60 percent of the useable negative imagearea for GGS. You determine the usable portion of thenegative for GGS as follows:0.60 9 = 5.4 inches of usable image area for GGSG= 5.4 _{}12,00012=5,400 feet3. Determine the total number of framesrequired. Next, you need to determine the total numberof frames required to complete the mission. You knowthat the area to be mapped is 10 nautical miles east andwest by 20 nautical miles north and south. Therefore,the strips will be flown north and south.The number of exposures per strip is determined bydividing the GGF into the length of the map. Firstconvert nautical miles into feet (1 nmi = 6,080 ft) andmultiply by 20 (length of area to be mapped).6,080 20 = 121,600 feetNext, divide by the GGF as follows: 121,600/3600= 33.77 or 34 frames per strip. Remember to add fourmore frames. This totals 38 frames for each strip.Now you must find the number of strips required.The area to be mapped is 10 nautical miles long.Calculate the number of strips as follows:10 (nautical miles) 6,080 (feet per nautical mile)= 60,800 feet60,800/5400 (GGS) = 11.25 or 12 flight stripsRemember to add one strip, so a total of 13 flightstrips is required.To determine the total frames required for themapping mission, you must multiply the number offrames required for GGF by the number of flight stripsrequired as follows:13 38 = 494 frames4. Draw flight lines on the chart. Your next stepis to draw the flight lines on the chart used to fly themission. The scale of this chart is 1/50,000.To determine the distance between the plotted lineson the chart, you must convert the GGS into inches, andthen multiply the GGS (in inches) by the scale of thechart as follows:5,400 (feet) 12 = 64,800 (inches) 1/50,000 =1.29 inchesThe distance between flight lines on the chart is 1.29inches apart. A multi-finger divider should be used todraw these lines.5. Determine the time interval between exposures.To determine the exposure interval, first convert theaircraft speed to feet per second. The true aircraft speedis operating at 140 knots, but there is a wind of 15 knotscoming from the north. Since the aircraft will be flyingin a north and south direction, the wind factor must betaken into consideration. At this time determine thecorrected airspeed in knots, then determine the airspeedin feet per second as follows:1. Corrected airspeed.a. Aircraft flying toward the northCorrected airspeed (140 knots - 15 knots = 125knots)b. Aircraft flying toward the southCorrected airspeed (140 knots + 15 knots = 155knots)2. To determine aircraft speed in feet per second,you must multiply the corrected airspeed by theconversion factor of 1.7.a. Aircraft flying toward the north = 212.5 feetper secondb. Aircraft flying toward the south = 263.5 feetper secondTo calculate the exposure interval, you must use thefollowing formula:T=^{D}_{S}4-25

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