Advanced Photography Course

converting airspeed (in knots) to feet is 1.7 (kts

1.7 =

ft/sec). For example, when the airspeed is 125 knots,

the ground speed, in feet, is 212.5 feet per second (125

1.7 = 212.5).

Head winds and tail winds must also be considered.

When head winds are present, you should subtract the
head wind from the airspeed. Tail winds should be

added to the airspeed. For example, when the aircraft
is flying north at 125 knots and the wind is blowing from

the north at 10 mph, then the corrected airspeed is 115
knots (125 - 10= 115). When the air craft is flying south,
then the corrected airspeed is 135 knots (125 + 10 =

135). The corrected airspeed must be used to find the

ground speed, in feet.

For the time interval between exposures, the

following formula should be used:

T= D

Where

T = Time in seconds

D = Ground-gained forward

S = Ground speed in feet per second

NOTE: When the interval between exposures can

be accomplished in full seconds only, the tenths of a
second should be dropped. By doing so, slightly more
than the required 60-percent forward overlap is

provided. This can be advantageous.

SCALE OF THE FINISHED
MOSAIC MAP

The scale of the finished mosaic map is determined

by using the following formula:

S= 12A

Where

S= Scale

F = Lens focal length

A = Altitude

The answer derived by using this formula gives a

representative fraction (RF) in like-units. Notice that
you must convert the altitude to inches, since the lens
focal length is normally in inches. For example, you

used a 10-inch focal-length lens for a mapping mission
flown at 5,000 feet. You can determine the scale of the
finished mosaic as follows:

5,000

S= 6,000

The scale of the finished mosaic is 1/6,000 (1:6,000).

To reinforce the mission planning procedures, you

can use the following example:

You are assigned to assist in the mission

calculations required for a recon mapping mission. You

are briefed on the mission and the following
information is provided:

Area to be mapped is 10 nautical miles east and west

by 20 nautical miles north and south.

Forward overlap required is 60 percent.

Side lap required is 40 percent.

Lens focal length is 12 inches.

Negative size is 9

9 inches.

True airspeed of aircraft is 140 knots.

The wind is from the north at 15 knots.

The scale of the chart used to plan and fly the

mission is 1/50,000 (1:50,000).

The required scale is 1/12,000 (1: 12,000).

A graphic scale representing 3,000 feet is required
on the printed mosaic map.

1. Determine the altitude. The first step in this

problem is to determine the altitude at which the aircraft
must fly to obtain the required scale of 1/12,000. The
IFGA formula used to determine the altitude is as

follows:

I = G orA=FG

Since G (ground coverage) is not known, you must
substitute the required scale (1/12,000) for it. At a
required scale of 1/12,000, each unit of I (on the film
plane) records 12,000 units of G. Since A is measured
in feet, you must divide your answer by 12 to get the
units in feet.

A= 12

12,000 = 144,000 =144,000

Divide by 12 to get altitude units in feet

4-24

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Advanced Photography Course

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DOFMaster for Windows On-line Depth of Field Calculator DOFMaster for Mobile Devices On-line Depth of Field Table Hyperfocal Distance Chart Articles FAQ Recommended Books Support Contact Links Home As an Amazon Associate I earn from qualifying purchases.	contents <- previous page next page -> converting airspeed (in knots) to feet is 1.7 (kts × 1.7 = ft/sec). For example, when the airspeed is 125 knots, the ground speed, in feet, is 212.5 feet per second (125 × 1.7 = 212.5). Head winds and tail winds must also be considered. When head winds are present, you should subtract the head wind from the airspeed. Tail winds should be added to the airspeed. For example, when the aircraft is flying north at 125 knots and the wind is blowing from the north at 10 mph, then the corrected airspeed is 115 knots (125 - 10= 115). When the air craft is flying south, then the corrected airspeed is 135 knots (125 + 10 = 135). The corrected airspeed must be used to find the ground speed, in feet. For the time interval between exposures, the following formula should be used: T= D S Where T = Time in seconds D = Ground-gained forward S = Ground speed in feet per second NOTE: When the interval between exposures can be accomplished in full seconds only, the tenths of a second should be dropped. By doing so, slightly more than the required 60-percent forward overlap is provided. This can be advantageous. SCALE OF THE FINISHED MOSAIC MAP The scale of the finished mosaic map is determined by using the following formula: F S= 12A Where S= Scale F = Lens focal length A = Altitude The answer derived by using this formula gives a representative fraction (RF) in like-units. Notice that you must convert the altitude to inches, since the lens focal length is normally in inches. For example, you used a 10-inch focal-length lens for a mapping mission flown at 5,000 feet. You can determine the scale of the finished mosaic as follows: S= 10 12 × 5,000 1 S= 6,000 The scale of the finished mosaic is 1/6,000 (1:6,000). To reinforce the mission planning procedures, you can use the following example: You are assigned to assist in the mission calculations required for a recon mapping mission. You are briefed on the mission and the following information is provided: Area to be mapped is 10 nautical miles east and west by 20 nautical miles north and south. Forward overlap required is 60 percent. Side lap required is 40 percent. Lens focal length is 12 inches. Negative size is 9 × 9 inches. True airspeed of aircraft is 140 knots. The wind is from the north at 15 knots. The scale of the chart used to plan and fly the mission is 1/50,000 (1:50,000). The required scale is 1/12,000 (1: 12,000). A graphic scale representing 3,000 feet is required on the printed mosaic map. 1. Determine the altitude. The first step in this problem is to determine the altitude at which the aircraft must fly to obtain the required scale of 1/12,000. The IFGA formula used to determine the altitude is as follows: I = G orA=FG F A I Since G (ground coverage) is not known, you must substitute the required scale (1/12,000) for it. At a required scale of 1/12,000, each unit of I (on the film plane) records 12,000 units of G. Since A is measured in feet, you must divide your answer by 12 to get the units in feet. A= 12 × 12,000 = 144,000 =144,000 1 1 Divide by 12 to get altitude units in feet 4-24 contents Advanced Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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