Flight Planning (photogrammetry) 443469
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Flight Planning Presented by-
Praveen Meena 14520012 Geomatics engineering, M.Tech 1st year
What is flight planning ?
It is one of the three basic phases of planning for a photogrammetric project.
Three phases of planning a photogrammetric project are:1. development of a flight plan. 2. planning the ground control and executing necessary field surveys- for accuracy requirement of the project. 3. estimation the cost involved in the project.
To produce a map of the desired accuracy.
Finding out the best fit flight lines and camera exposure stations to cover the project area with minimum number of models, flight lines and camera exposure stations.
Basic elements in flight planning:
The flying height above a datum.
The ground distance between successive exposures.
The ground spacing between the flight lines.
Why we need flight planning in photogrammetry?
To ensure coverage of the area to be mapped at the required scale with no gaps, and provide stereo models by an efficient design.
A flight plan will determine the spacing between successive photographs, location of flight lines and other details.
This entails the preparation of detailed instructions for the plane-camera crew regarding the location of the pictures, the flight strips, and the area to be flown.
This is also important for a safety flight , reducing aerial survey operational costs, and speeding up the preparation and execution of the photo missions and flight.
Flight planning or flight design depends on the following factors:
The intended use of the photography: Mosaic, land-use study etc. Map compilation using stereo plotting equipment.
The exact boundaries of the project.
The nature, extent, and location of existing control.
The type of terrain.
Factors for plannig the flight map:
Purpose of the photography
The ground distance between successive exposures
Ground spacing of between the flight lines
Flying height above a datum , usually sea level
Photographic scale
Allowable scale variation
Relief displacement
Photographic Tilt
Crab and drift
Direction or orientation of the topography or terrain
Steps for flight planning:
Determining of the project requirements.
Considering the requirements of the project , project area, photo scale, end lap, side lap, direction of strips, coordinate system, camera type, and film type are determined.
According to these data, base distance between two exposure stations along flight line and the distance between two adjacent flight strips are calculated.
The flight height is calculated for each strip by checking the terrain height of related strip.
After that, coordinates of exposure stations are obtained.
Purpose of the photography:
Wide or normal camera types are selected according to characteristics of the project area.
Wide length cameras (f= 152mm) are preferred for the area that is smooth.
In order to obtain a favorable base height ratio that enhances vertical accuracy.
Super-wide angle (f=88mm) camera:- if the topography is very flat.
Normal lens (f=210mm) cameras are preferred for the area that is hilly or urban area. eg. Forest area..
It will also determine the %age of overlap and sidelap.
Photo scale:Varies with the project. Scale =
𝑓𝑜𝑐𝑎𝑙 𝑙𝑒𝑛𝑔𝑡 𝑓𝑙𝑦𝑖𝑛𝑔 𝑒𝑖𝑔𝑡
=
𝑓 𝐻−
It affects the map accuracy and area configuration.
Longer the f, the larger the scale, assuming a constant flight height.
The scale of a vertical aerial photograph is inversely proportional to the quantity (H-h), i.e. high altitude photographs are normally small scale.
Scale not only differs from photograph to photograph and strip to strip but also the average scale can differ somewhat from what is intended.
Photo scale is selected depending on the project purposes, such as the desired accuracy of final product, purpose of use etc.
The smallest possible photo scale is selected because of reducing the number of models.
End lap and side lap:
Overlap :- the overlap in the along the line of sight is called forward overlap, or simply overlap.
In order to obtain stereo model, end lap is assumed to be 60 %.
To cover the project area completely with stereo models along the strips, side lap is assumed to be 30 % of the width of the photograph.
if the terrain is fairly rugged, both overlap and sidelap should be increased.
Allowable scale variation:
Scale variation in a photograph or between photographs is caused by variation in the ground elevation, by a variation in flying height, or by both.
Variations caused by difference in ground elevation and flying height.
Longer focal length reduces the scale variation.
Flying height:
Height above the datum.
Factors affecting the flying height: Desired scale, relief displacement, and relief. Precision of scale used Greater precision, greater possible flying height, and that will
also increase the ground coverage per photography four times.
More the flying height, greater the area covered, and thus less ground control and fewer photos required.
𝑓𝑙𝑦𝑖𝑛𝑔 𝑒𝑖𝑔𝑡 𝑐𝑜𝑛𝑡𝑜𝑢𝑟 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙
C-factor =
( precision factor)
from which,
Flying height = (contour interval) X (C- factor) WHY CONTOUR INTERVAL ? Because vertical accuracy in a topographic map is the liming factor in photogrammetry.
The C factor is understood to be that value which will produce photography satisfactory to obtain the desired vertical accuracy In the map. C factor take ib values anywhere from 750 to 2500 ( mostly 2200) For a given system, its value will depend on the conditions surrounding the entire map-compilation operation.
Relief displacement:
It affects the construction of mosaics.
it is a characteristic of aerial images over varied terrain.
Objects that rises above the surface lean away from the principal point.
Objects extending below the surface lean towards the principal point.
Relief displacement increases with the height of the object and/or distance from the principal point.
It will decrease as the flying height is increased.
Also, to maintain a certain scale as the flight height is increased, the focal length must be increased.
𝑓 𝑟 = 𝐻−ℎ 𝑅
𝑓 𝑟′ = 𝐻 𝑅 𝑟=
𝑅𝑓 𝑅𝑓 and 𝑟′ = 𝐻ℎ 𝐻
𝑟(𝐻 − ℎ) 𝑟′𝐻 𝑅= and R = 𝑓 𝑓 𝑅𝑓
Relief distortion 𝑑 = 𝑟 − 𝑟 ′ = 𝐻− −
𝑑=𝑟−
𝑟′
=
𝑟 𝐻
=
𝑅𝑓 𝐻
𝑅𝑓
= 𝐻(𝐻−)
𝑟 ′ 𝐻−
RD is radial from nadir point regardless of unintentional or accidental tilt of the camera. This is a fundamental concept of photography.
The effect of tilt:Two component:1. the amount in the direction of flight, called y-tilt, or angle .
2. the amount in the direction of the flight line, called x-tilt or angle . •
y tilt will cause increase or decrease in overlap between successive photographs.
•
X tilt will cause the sidelap to increase on one side of the flight line and to decrease on the opposite side.
Causes of tilt
The absence of stable horizontal reference plane during flight.
Human error in holding the camera in the only available reference plane.
Air turbulence.
The effect of y tilt on overlap must be allowed for by decreasing the computed exposure interval slightly to produce a slight increase in the theoretically desired overlap
The effect of x tilt on sidelap must be allowed for by decreasing the computed spacing between flight lines slightly to produce a slight increase in the desired sidelap.
Crab crab is the angle formed between the flight line and the edges of the photograph in the direction of flight.
it will reduce the effective width of coverage of the photography .
it is caused by not having the focal plane of the camera squared with the direction of flight at the instant of exposure.
It can be corrected by the rotation of camera about the vertical axis of the camera mount.
Drift
It is caused by the failure of the aircraft to stay on the predetermined flight line.
It will cause in loss of sidelap on the side
opposite the direction of drift.
It will cause gapping in between adjacent flight lines.
Computation of flight plan:Data required to compute different quantities for flight planning of an area are:
1. focal length of the camera lens
2. flying height above a stated datum.
3. Size of photograph.
4. Size of area to be photographed.
5. Position of the outer flight lines with respect to the boundary of the area.
6. Overlap.
7. Sidelap.
8. Scale of flight map.
9. Ground speed of aircraft.
An area that is 15 miles long in the north south direction, and 8.5 miles wide in the east west direction is to be photographed with a lens having a 12-in. focal length for the purpose of constructing a mosaic. The photograph size is 9 by 9 in. The average scale is to be 1:12,000 effective at an average elevation of 700 ft above sea level. Overlap is to be at least 60% and sidelap is to be at least 35%. An intervalometer will be used to control the interval between exposures. The ground speed of the aircraft will be maintained at 150 mph. The flight lines are to be laid out in a north south direction on an existing map having an scale of 1:62,500. The two outer flight lines are to coincide with the east and west boundaries of the area. Determine the data for the fight plan. Problem:-
FIG. Calculation of flight plan
Flying height:we know that i.e.
scale = focal length / flying height 1 𝑓𝑡 (𝐻−700) 𝑓𝑡
=
1 12000
So, H= 12,700 ft above sea level.
Ground distance between flying lines:the ground spacing, W=
5.85 𝑖𝑛.𝑋 12,000 12 𝑖𝑛./𝑓𝑡
= 5850 𝑓𝑡
Number of flight lines:Width of the area = 8.5 miles X 5280 ft/mile = 44,880 ft. Required number of flight lines = number of spacings + 1 =
44,880 𝑓𝑡 5850 𝑓𝑡
+1=9
Adjacent ground distance between flight lines:Wa =
44,880 𝑓𝑡 9−1
= 5610 𝑓𝑡
the sidelap will be slightly greater than 35%
Spacing of flight lines on flight map:-
Wm =
5610 𝑓𝑡 𝑋 62,500
12
𝑖𝑛 𝑓𝑡
= 1.08 𝑖𝑛
Ground distance between exposures:since 60% overlap is there, the net gain per photograph = 0.40 x 9 in. = 3.60 in. The corresponding ground distance is, B=
3.60 𝑋 12,000 12 𝑖𝑛.𝑓𝑡
= 3600 𝑓𝑡.
Exposure interval:Speed of aircraft = 150 mph =
150 𝑋 5280 𝑓𝑡 60 𝑋 60 𝑠
= 220 ft/s
The required exposure interval is,
I=
3600 𝑓𝑡 220 𝑓𝑡/𝑠
= 16.4 s
or 16 seconds
Adjusted ground distance between exposures:for the adjacent exposure interval, the ground distance is,
Ba= 220 ft/s X 16 s = 3520 ft
Number of photographs per unit flight line:total length of a flight line = 15 miles X 5280 ft/mile = 79,200 ft. lets make allowance for two extra exposures at each end of each strip, the number of photographs per flight lines is, 79,200 + 3520
4 = 26.5
Hence entire photography will require,
or 27 photos/flight line 9 X 27 = 243 photographs.
Hence,
Number of photographs required = 243 photographs
Flight lines spacing on map = 1.08 inch
Exposure interval = 16 seconds It will ensure the required overlap of 60 %.
THANK YOU
Praveen Meena 14520012 Geomatics engineering, M.Tech 1st year
What is flight planning ?
It is one of the three basic phases of planning for a photogrammetric project.
Three phases of planning a photogrammetric project are:1. development of a flight plan. 2. planning the ground control and executing necessary field surveys- for accuracy requirement of the project. 3. estimation the cost involved in the project.
To produce a map of the desired accuracy.
Finding out the best fit flight lines and camera exposure stations to cover the project area with minimum number of models, flight lines and camera exposure stations.
Basic elements in flight planning:
The flying height above a datum.
The ground distance between successive exposures.
The ground spacing between the flight lines.
Why we need flight planning in photogrammetry?
To ensure coverage of the area to be mapped at the required scale with no gaps, and provide stereo models by an efficient design.
A flight plan will determine the spacing between successive photographs, location of flight lines and other details.
This entails the preparation of detailed instructions for the plane-camera crew regarding the location of the pictures, the flight strips, and the area to be flown.
This is also important for a safety flight , reducing aerial survey operational costs, and speeding up the preparation and execution of the photo missions and flight.
Flight planning or flight design depends on the following factors:
The intended use of the photography: Mosaic, land-use study etc. Map compilation using stereo plotting equipment.
The exact boundaries of the project.
The nature, extent, and location of existing control.
The type of terrain.
Factors for plannig the flight map:
Purpose of the photography
The ground distance between successive exposures
Ground spacing of between the flight lines
Flying height above a datum , usually sea level
Photographic scale
Allowable scale variation
Relief displacement
Photographic Tilt
Crab and drift
Direction or orientation of the topography or terrain
Steps for flight planning:
Determining of the project requirements.
Considering the requirements of the project , project area, photo scale, end lap, side lap, direction of strips, coordinate system, camera type, and film type are determined.
According to these data, base distance between two exposure stations along flight line and the distance between two adjacent flight strips are calculated.
The flight height is calculated for each strip by checking the terrain height of related strip.
After that, coordinates of exposure stations are obtained.
Purpose of the photography:
Wide or normal camera types are selected according to characteristics of the project area.
Wide length cameras (f= 152mm) are preferred for the area that is smooth.
In order to obtain a favorable base height ratio that enhances vertical accuracy.
Super-wide angle (f=88mm) camera:- if the topography is very flat.
Normal lens (f=210mm) cameras are preferred for the area that is hilly or urban area. eg. Forest area..
It will also determine the %age of overlap and sidelap.
Photo scale:Varies with the project. Scale =
𝑓𝑜𝑐𝑎𝑙 𝑙𝑒𝑛𝑔𝑡 𝑓𝑙𝑦𝑖𝑛𝑔 𝑒𝑖𝑔𝑡
=
𝑓 𝐻−
It affects the map accuracy and area configuration.
Longer the f, the larger the scale, assuming a constant flight height.
The scale of a vertical aerial photograph is inversely proportional to the quantity (H-h), i.e. high altitude photographs are normally small scale.
Scale not only differs from photograph to photograph and strip to strip but also the average scale can differ somewhat from what is intended.
Photo scale is selected depending on the project purposes, such as the desired accuracy of final product, purpose of use etc.
The smallest possible photo scale is selected because of reducing the number of models.
End lap and side lap:
Overlap :- the overlap in the along the line of sight is called forward overlap, or simply overlap.
In order to obtain stereo model, end lap is assumed to be 60 %.
To cover the project area completely with stereo models along the strips, side lap is assumed to be 30 % of the width of the photograph.
if the terrain is fairly rugged, both overlap and sidelap should be increased.
Allowable scale variation:
Scale variation in a photograph or between photographs is caused by variation in the ground elevation, by a variation in flying height, or by both.
Variations caused by difference in ground elevation and flying height.
Longer focal length reduces the scale variation.
Flying height:
Height above the datum.
Factors affecting the flying height: Desired scale, relief displacement, and relief. Precision of scale used Greater precision, greater possible flying height, and that will
also increase the ground coverage per photography four times.
More the flying height, greater the area covered, and thus less ground control and fewer photos required.
𝑓𝑙𝑦𝑖𝑛𝑔 𝑒𝑖𝑔𝑡 𝑐𝑜𝑛𝑡𝑜𝑢𝑟 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙
C-factor =
( precision factor)
from which,
Flying height = (contour interval) X (C- factor) WHY CONTOUR INTERVAL ? Because vertical accuracy in a topographic map is the liming factor in photogrammetry.
The C factor is understood to be that value which will produce photography satisfactory to obtain the desired vertical accuracy In the map. C factor take ib values anywhere from 750 to 2500 ( mostly 2200) For a given system, its value will depend on the conditions surrounding the entire map-compilation operation.
Relief displacement:
It affects the construction of mosaics.
it is a characteristic of aerial images over varied terrain.
Objects that rises above the surface lean away from the principal point.
Objects extending below the surface lean towards the principal point.
Relief displacement increases with the height of the object and/or distance from the principal point.
It will decrease as the flying height is increased.
Also, to maintain a certain scale as the flight height is increased, the focal length must be increased.
𝑓 𝑟 = 𝐻−ℎ 𝑅
𝑓 𝑟′ = 𝐻 𝑅 𝑟=
𝑅𝑓 𝑅𝑓 and 𝑟′ = 𝐻ℎ 𝐻
𝑟(𝐻 − ℎ) 𝑟′𝐻 𝑅= and R = 𝑓 𝑓 𝑅𝑓
Relief distortion 𝑑 = 𝑟 − 𝑟 ′ = 𝐻− −
𝑑=𝑟−
𝑟′
=
𝑟 𝐻
=
𝑅𝑓 𝐻
𝑅𝑓
= 𝐻(𝐻−)
𝑟 ′ 𝐻−
RD is radial from nadir point regardless of unintentional or accidental tilt of the camera. This is a fundamental concept of photography.
The effect of tilt:Two component:1. the amount in the direction of flight, called y-tilt, or angle .
2. the amount in the direction of the flight line, called x-tilt or angle . •
y tilt will cause increase or decrease in overlap between successive photographs.
•
X tilt will cause the sidelap to increase on one side of the flight line and to decrease on the opposite side.
Causes of tilt
The absence of stable horizontal reference plane during flight.
Human error in holding the camera in the only available reference plane.
Air turbulence.
The effect of y tilt on overlap must be allowed for by decreasing the computed exposure interval slightly to produce a slight increase in the theoretically desired overlap
The effect of x tilt on sidelap must be allowed for by decreasing the computed spacing between flight lines slightly to produce a slight increase in the desired sidelap.
Crab crab is the angle formed between the flight line and the edges of the photograph in the direction of flight.
it will reduce the effective width of coverage of the photography .
it is caused by not having the focal plane of the camera squared with the direction of flight at the instant of exposure.
It can be corrected by the rotation of camera about the vertical axis of the camera mount.
Drift
It is caused by the failure of the aircraft to stay on the predetermined flight line.
It will cause in loss of sidelap on the side
opposite the direction of drift.
It will cause gapping in between adjacent flight lines.
Computation of flight plan:Data required to compute different quantities for flight planning of an area are:
1. focal length of the camera lens
2. flying height above a stated datum.
3. Size of photograph.
4. Size of area to be photographed.
5. Position of the outer flight lines with respect to the boundary of the area.
6. Overlap.
7. Sidelap.
8. Scale of flight map.
9. Ground speed of aircraft.
An area that is 15 miles long in the north south direction, and 8.5 miles wide in the east west direction is to be photographed with a lens having a 12-in. focal length for the purpose of constructing a mosaic. The photograph size is 9 by 9 in. The average scale is to be 1:12,000 effective at an average elevation of 700 ft above sea level. Overlap is to be at least 60% and sidelap is to be at least 35%. An intervalometer will be used to control the interval between exposures. The ground speed of the aircraft will be maintained at 150 mph. The flight lines are to be laid out in a north south direction on an existing map having an scale of 1:62,500. The two outer flight lines are to coincide with the east and west boundaries of the area. Determine the data for the fight plan. Problem:-
FIG. Calculation of flight plan
Flying height:we know that i.e.
scale = focal length / flying height 1 𝑓𝑡 (𝐻−700) 𝑓𝑡
=
1 12000
So, H= 12,700 ft above sea level.
Ground distance between flying lines:the ground spacing, W=
5.85 𝑖𝑛.𝑋 12,000 12 𝑖𝑛./𝑓𝑡
= 5850 𝑓𝑡
Number of flight lines:Width of the area = 8.5 miles X 5280 ft/mile = 44,880 ft. Required number of flight lines = number of spacings + 1 =
44,880 𝑓𝑡 5850 𝑓𝑡
+1=9
Adjacent ground distance between flight lines:Wa =
44,880 𝑓𝑡 9−1
= 5610 𝑓𝑡
the sidelap will be slightly greater than 35%
Spacing of flight lines on flight map:-
Wm =
5610 𝑓𝑡 𝑋 62,500
12
𝑖𝑛 𝑓𝑡
= 1.08 𝑖𝑛
Ground distance between exposures:since 60% overlap is there, the net gain per photograph = 0.40 x 9 in. = 3.60 in. The corresponding ground distance is, B=
3.60 𝑋 12,000 12 𝑖𝑛.𝑓𝑡
= 3600 𝑓𝑡.
Exposure interval:Speed of aircraft = 150 mph =
150 𝑋 5280 𝑓𝑡 60 𝑋 60 𝑠
= 220 ft/s
The required exposure interval is,
I=
3600 𝑓𝑡 220 𝑓𝑡/𝑠
= 16.4 s
or 16 seconds
Adjusted ground distance between exposures:for the adjacent exposure interval, the ground distance is,
Ba= 220 ft/s X 16 s = 3520 ft
Number of photographs per unit flight line:total length of a flight line = 15 miles X 5280 ft/mile = 79,200 ft. lets make allowance for two extra exposures at each end of each strip, the number of photographs per flight lines is, 79,200 + 3520
4 = 26.5
Hence entire photography will require,
or 27 photos/flight line 9 X 27 = 243 photographs.
Hence,
Number of photographs required = 243 photographs
Flight lines spacing on map = 1.08 inch
Exposure interval = 16 seconds It will ensure the required overlap of 60 %.
THANK YOU
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