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Topic 2. Orientation of Single Aerial
Photographs and Images
Division of Geodetic Engineering College of Engineering and Information Technology Caraga State University
GE 119 – PHOTOGRAMMETRY 2
Instructor: Engr. Jojene R. Santillan jrsantillan@carsu.edu.ph santillan.jr3@gmail.com
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 2
Outline
• Background and Principles behind the orientation of Aerial Photographs and Images
• Interior Orientation of Aerial Photographs and Images
• Exterior Orientation of Aerial Photographs and Images
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 3
Intended Learning Outcomes
• After this lecture and hands-on exercises, the students must have:
– Understood the mathematical concepts behind the orientation of single aerial photographs
– Performed orientation of single digital aerial photographs using digital photogrammetric software
– Explained the processes involved in the orientation of single aerial photographs.
4 Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES
BACKGROUND AND PRINCIPLES BEHIND THE ORIENTATION OF AERIAL PHOTOGRAPHS AND IMAGES
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 5
Recall: A Typical Workflow in Photogrammetry
Generally: • Begins with the
capture of the images
• Calculation of the orientation parameters of all images that will be used
• Measure co-ordinates • Create several image
products • Use of results in
cartographic or GIS software
Source: Linder, W., 2016. Digital Photogrammetry – A Practical Course, Springer-Verlag Berlin Heidelberg, Germany.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 6
The Orientation Process in Photogrammetry
Orientation the process of
establishing the relation between two coordinate systems of an aerial photograph or image
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 7
Recall: Geometry of a Vertical Aerial Photograph
Aerial Photograph
Source: Lillesand et al 2004, Remote Sensing and Image Interpretation Fifth Edition, Wiiley.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 8
Photo-coordinate System = “Camera-internal coordinate System”
Aerial Photograph
• Each point in the aerial photograph can be located through the use of the “photo-coordinate system”
• This “photo-coordinate system” is defined based on the geometric properties of the camera system
• The photo-coordinate system’s origin is defined by the use of fiducial marks
• This coordinate system can be referred to as “camera-internal coordinate system”
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 9
Camera Internal Coordinate System
Aerial Photograph
x
y
Fiducial marks p
Object p’s location in the photo can be defined as (xp, yp)
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 10
Image Coordinate System of Digital Aerial Photographs or Images
• Aside from the “camera-internal coordinate system”, objects can also be located based on their pixel row and column numbers in a digital aerial photograph or image
• The pixel row and column numbers refers to the “image coordinate system” or more appropriately, “pixel coordinate system” denoted by the X‟ and Y‟ axes.
Aerial Photograph
x
y
p
X'
Y‟
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 11
Recall: Digital Image Characteristics
• Digital Image = a matrix of Digital Number (DN) values
• Each DN is located at a specific row and column in the matrix
• Pixel: - the smallest unit of an
image. - image pixels are normally
square and represent a certain area on an image (e.g., the ground segment within the sensor’s IFOV)
- Each pixel has DN value associated with it.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 12
Image/Raster/Pixel Coordinate System
• x‟-axis = column number
• y‟-axis = row number; also called “line number”
• A pixel’s location can be identified by its (column, row) value
• The (1,1) axis is on the upper leftmost part of the images
• Cell height and cell width = depends on the image’s spatial resolution
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 13
In addition to (x,y) and (X‟, Y‟) coordinates…
• Objects in aerial photograph also have actual ground coordinates (X,Y, Z)!
• That means an object can be located in an aerial photo or image in terms of 3 coordinate systems!
Aerial Photograph
x
y
p
X'
Y‟
X
Y
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 14
• Ground coordinate system in 3D
X
Y
Z
Source: Lillesand et al 2004, Remote Sensing and Image Interpretation Fifth Edition, Wiiley.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 15
• In aerial photogrammetry, we are interested in getting 3D spatial location of objects in aerial photographs in terms of their true ground coordinates
• The question now is, how do we obtain the 3D ground coordinates of objects from the aerial photograph?
• Or…How will we get the „true ground coordinates” from the aerial photograph given that we know the “camera-internal coordinates” of the objects?
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 16
• The answer: we need to find the relation between the three (3) coordinate systems (CS):
• The camera-internal coordinate system
• The pixel coordinate system
• The ground coordinate system
To find the relations, we apply the process of “ORIENTATION”
Camera-Internal CS
Pixel CS Ground CS
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 17
For single aerial photographs, there are 2 kinds of orientation procedures:
• Interior Orientation – establishing the relation between the
camera-internal co-ordinate system and the pixel co-ordinate system
• Exterior Orientation – establishing the relation between the pixel
co-ordinate system and the ground coordinate system
18 Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES
INTERIOR ORIENTATION OF AERIAL PHOTOGRAPHS AND IMAGES
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 19
Interior Orientation
• establishing the relation between the camera-internal co-ordinate system and the pixel co-ordinate system
Camera-Internal CS
x
y
p
Pixel CS
p
X'
Y‟
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 20
Output of Interior Orientation
• After doing an interior orientation, we would be able to determine the following:
– The pixel coordinates of each and all objects in the photograph/image
– The size of each pixel in the photograph in terms of “mm”.
– The dimension of the photograph/image in terms of number of rows and columns
But how do we do an “Interior Orientation”?
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 21
Consider this aerial photograph:
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 22
Aerial photographs are provided along with the following information: 1. Fiducial marks 2. Camera-internal coordinates of each fiducial marks (usually
provided in the camera calibration certificate)
FIDUCIAL MARKS 1
2
3
4
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 23
The camera-internal coordinates of each fiducial marks are known based on film format size and the calibration of the camera used.
1
2
3
4 FM4 = (0 mm, 113 mm)
FM1 = (113 mm, 0 mm)
FM2 = (0 mm, -113 mm)
FM3= (-113 mm, 0 mm)
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 24
To transform the camera-internal coordinates into pixel coordinates, a
two-dimensional (2D) transformation method called “AFFINE
TRANSFORMATION” is used.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 25
Affine Transformation Equation
• If (x,y) is the camera-internal coordinates of an object in an aerial photograph, we wish to find its corresponding pixel coordinates (X’, Y’)
• Using Affine Transformation, the pixel coordinates can be determined as:
X‟ = a0 + a1x + a2y
Y‟ = b0 + b1x + b2y
• Note: a0, a1, a2, b0, b1 and b2 are called the „affine transformation parameters‟
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 26
Affine Transformation
• Using Affine Transformation, the pixel coordinates can be determined as:
X‟ = a0 + a1x + a2y
Y‟ = b0 + b1x + b2y
• How do we determine the values of the „affine transformation parameters‟?
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 27
We can relate (X‟, Y‟) to (x, y) by:
• Using the camera-internal coordinates of the fiducial marks as the (x,y) values
• How about (X‟, Y‟)? – Using a computer software, we need to find the
fiducial marks in the digital aerial photograph and determine its row and column values (i.e., their X’ and Y’ coordinates)
• To find the parameter values, a minimum of three (3) fiducial marks are required
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 28
We can then create a table like this:
Fiducial Mark
Camera-Internal Coordinates
Pixel Coordinates
x (mm)
y (mm)
X Y
1 113 0 2699 1363
2 0 -113 1369 2699
3 -113 0 28 1373
4 0 113 1358 37
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 29
We can then set-up the affine transformation equations: • For X’s:
– FM1: 2699 = a0 + a1(113) + a2(0)
– FM2: 1369 = a0 + a1(0) + a2(-113)
– FM3: 28 = a0 + a1(-113) + a2(0)
– FM4: 1358 = a0 + a1(0) + a2(113)
• For Y’s:
– FM1: 1363 = b0 + b1(113) + b2(0)
– FM2: 2699 = b0 + b1(0) + b2(-113)
– FM3: 1373 = b0 + b1(-113) + b2(0)
– FM4: 37 = b0 + b1(0) + b2(113)
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 30
Updating the equations:
• For X’s:
– FM1: 2699 = a0 + 113a1
– FM2: 1369 = a0 - 113a2
– FM3: 28 = a0 - 113a1
– FM4: 1358 = a0 + 113a2
• For Y’s:
– FM1: 1363 = b0 + 113b1
– FM2: 2699 = b0 - 113b2
– FM3: 1373 = b0 + 113b1
– FM4: 37 = b0 + 113b2
• If we use only 3 FM, we can easily compute for the values of a0, a1, a2, b0, b1, and b2
(i.e., number of equations = number
of unknowns)
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 31
• For X’s:
– FM1: 2699 = a0 + 113a1
– FM2: 1369 = a0 - 113a2
– FM3: 28 = a0 - 113a1
– FM4: 1358 = a0 + 113a2
• For Y’s:
– FM1: 1363 = b0 + 113b1
– FM2: 2699 = b0 - 113b2
– FM3: 1373 = b0 + 113b1
– FM4: 37 = b0 + 113b2
• If we use all the FMs, number of equations > number of unknown (redundancy of 2
equations)
• To determine the parameter values, LEAST SQUARES ESTIMATION IS USED!
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 32
After estimating the best values of a0, a1, … • The transformation equations:
X‟ = a0 + a1x + a2y
Y‟ = b0 + b1x + b2y
are used to easily convert (x,y) to (X‟, Y‟), and vice versa.
33 Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES
EXTERIOR ORIENTATION OF AERIAL PHOTOGRAPHS AND IMAGES
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 34
• establishing the relation between the pixel (or image) co-ordinate system and the ground coordinate system
X
Y
Z
Exterior Orientation
Source: Lillesand et al 2004, Remote Sensing and Image Interpretation Fifth Edition, Wiiley.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 35
Exterior Orientation
• When we do exterior orientation, we define the geometric relationship between an object and its image.
• Once we have done exterior orientation, it becomes possible to reconstruct the spatial position of an object from its image.
• Exterior orientation is based on the condition of collinearity
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 36
The Collinearity Condition
• Collinearity is the condition in which:
– the exposure station of any photograph (or image),
– any object point in the ground coordinate system, and
– its photographic image
all lie on a straight line.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 37
The Collinearity Condition
• Collinearity is the condition in which:
– the exposure station (L) of any photograph (or image),
– any object point (P) in the ground coordinate system, and
– its photographic image (p)
all lie on a straight line.
Ground
Photo/Image
Source: Lillesand et al 2004, Remote Sensing and Image Interpretation Fifth Edition, Wiiley.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 38
The Collinearity Condition
• The collinearity condition holds irrespective of the angular tilt of the photograph.
• The possible angular rotations from that of an equivalent vertical photograph are:
– ω (“pitch”)
– φ (“roll”)
– К (“yaw”)
Ground
Photo/Image
Source: Lillesand et al 2004, Remote Sensing and Image Interpretation Fifth Edition, Wiiley.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 39
ω, φ, К ….
Source: http://howthingsfly.si.edu/sites/default/files/image-large/Roll,-Yaw,-Pitch_lg_0.jpg
Source: http://doc.aldebaran.com/2-1/_images/rollPitchYaw.png
Source: https://www.novatel.com/assets/Web-Phase-2-2012/Solution-Pages/AttitudePlane.png
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 40
The Collinearity Equations
• The collinearity equations are the equations that express the collinearity condition
• They describe the relationships among pixel/image coordinates, ground coordinates, the exposure station position, and angular orientation of a photograph/image.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 41
The Collinearity Equations
• The equations are non-linear
• Contain 9 unknowns:
– The exposure station position (XL, YL, ZL)
– The three rotation angles (ω, φ, К) which are embedded in the m coefficients
– The object point coordinates (XP,YP,ZP)
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 42
The Collinearity Equations
• The parameters (XL, YL, ZL) and (ω, φ, К) are commonly
referred to as the “Exterior Orientation Parameters”
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 43
The Collinearity Equations
• The “m” coefficients are elements of a 3x3 rotation matrix
cos φ cos κ −cos φ sin κ sin φ cos ω sin κ + sin ω sin φ cos κ cos ω cos κ − sin ω sin φ sin κ −sin ω cos φ sin ω sin κ − cos ω sin φ cos κ sin ω cos κ + cos ω sin φ sin κ cos ω cos φ
m =
• m is obtained by getting the product of matrices of rotation around the first (ω), second (φ) and third (κ) axis (i.e., m = R3*R2*R1)
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 44
m values
• m11 = cos φ cos κ • m21 = cos ω sin κ + sin ω sin φ cos κ • m31 = sin ω sin κ − cos ω sin φ cos κ • m12 = −cos φ sin κ • m22 = cos ω cos κ − sin ω sin φ sin κ • m32 = sin ω cos κ + cos ω sin φ sin κ • m13 = sin φ • m23 = −sin ω cos φ • m33 = cos ω cos φ
cos φ cos κ −cos φ sin κ sin φ cos ω sin κ + sin ω sin φ cos κ cos ω cos κ − sin ω sin φ sin κ −sin ω cos φ sin ω sin κ − cos ω sin φ cos κ sin ω cos κ + cos ω sin φ sin κ cos ω cos φ
m = cos φ cos κ −cos φ sin κ sin φ cos ω sin κ + sin ω sin φ cos κ cos ω cos κ − sin ω sin φ sin κ −sin ω cos φ sin ω sin κ − cos ω sin φ cos κ sin ω cos κ + cos ω sin φ sin κ cos ω cos φ
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 45
The Collinearity Equations
• The collinearity equations are “at the heart” of softcopy (e.g, digital) photogrammetric operations
• If the location of the exposure station is known as well as the angular rotations, then any position on the ground can be located in the photo or image.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 46
• Since there are 9 unknowns, how do we proceed with the exterior orientation?
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 47
Solving the Collinearity Equations to do Exterion Orientation
• 1st Approach:
– Use of combined GPS/GNSS and IMU during photo/image acquisition to determine the 6 exterior orientation parameters
• GPS/GNNS to determine (XL, YL, ZL)
• IMU or Inertial Measuring Unit to determine (ω, φ, К)
Source: http://www.mdpi.com/remotesensing/remotesensing-04-01519/article_deploy/html/images/remotesensing-04-01519f1-1024.png
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 48
Example Set-up to get the 6 orientation parameters using GPS and IMU
Source: http://www.mdpi.com/remotesensing/remotesensing-04-01519/article_deploy/html/images/remotesensing-04-01519f1-1024.png
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 49
Solving the Collinearity Equations to do Exterior Orientation
• 2nd Approach:
– Through the process of “space resection”
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 50
Space resection (or photo-resection)
• Similar to the “resection” method in Surveying
• Use of Ground Control Points (GCPs)
• In this process, known Ground Control Points are located in the image, and the image coordinates are determined
• This means, for each GCP we know the following variables of the collinearity equations: – XP, YP, ZP
– xp, yp
• We are left with the following unknowns: – XL, YL, ZL
– ω, φ, К (or the rotation matrix coefficients)
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 51
Space resection (or photo-resection)
• To determine the unknowns, we need to have at least three (3) GCPs to set-up 6 equations which can be solved simultaneously
– More than 3 GCPs are recommended when doing exterior orientation to allow redundancy and to get the best estimates of the exterior orientation parameters
– If more than 3 GCPs, then more than 6 equations can be formed and a least squares solutions for the unknown is performed • Digital photogrammetric software can do this
automatically
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 52
Using GCPs for Exterior Orientation
• In photogrammetry, a GCP is an object point which is represented in the images and from which the three-dimensional object (ground) coordinates (XP, YP, ZP) are known
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 53
Using GCPs for Exterior Orientation
• Using GCPs in exterior orientation means:
– We have to look for points in our image
– Then:
• Find these points for instance in a topographic map and get their coordinates out of the map (e.g., by manually measuring XP and YP, and interpolating the elevation between neighboring contours to get ZP)
• Or: Conduct GPS/GNSS survey to obtain the 3D coordinates of the GCPs
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 54
Using GCPs for Exterior Orientation
• For each image, we need at least 3 well-distributed GCPs
– Well-distributed means that the 3 GCPs should form a triangle, not a line
• Basic rule: “The more, the better” to get a stable over-determination of the exterior orientation parameters
– Will allow error checking (e.g., how good our selected GCPs are)
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 55
Two Kinds of GCPs used during Exterior Orientation
• Signalized (targeted) GCPs: – These GCPs are set-up on the
ground before taking the photos
– Example: • GCPs “signalized” using white
bars forming a cross with the point itself marked with a central “dot” or “square” – The bars are usually 1.2 x 0.2
m in size
– The dot is usually 0.2 m diameter
– However, dimensions will depend on the photo scale
Source: https://cdn-images-1.medium.com/max/1600/0*3FhWS4peJNBdupE4.
Source: http://old.grida.no/images/thumbs/3.png
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 56
Example of Signalized GCPs
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 57
Another Example of Signalized GCPs
Source: https://pbs.twimg.com/media/C7rEUfwVMAEnvg-.jpg
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 58
Appearance of a “Signalized” GCP in an Image
Source: http://slideplayer.com/slide/2520727/9/images/15/GCP+Measurement+Signalized+GCP+/+ICP.jpg
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 59
Two Kinds of GCPs used during Exterior Orientation
• Natural GCPs – Real object (ground/terrain) points which we can
clearly identify in the image as well as in a topographic map (or in the field when we do GPS/GNSS survey)
– More commonly Used – Suggested Natural GCPs:
• Objects with rectangle corners (e.g., buildings) • Small circle-shaped points
– Important: • Natural GCPs must have 3D coordinates:
– Do not select GCPs whose elevation is difficult or not possible to determine (from a topo map or from GPS/GNSS survey)
» Example: Rooftops
• Prefer selecting GCPs that are on the ground.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 60
Examples of Natural GCPs
Source: Linder, W., 2016. Digital Photogrammetry – A Practical Course, Springer-Verlag Berlin Heidelberg, Germany.
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 61
Example GCP Data
Indicative Location of the GCPs in the photo
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 62
Remarks
• To experience how interior and exterior orientation works, a lab exercise will be given in the coming weeks (after the Prelim Exam)
Lecture Notes in GE 119: Photogrammetry 2 TOPIC 2. ORIENTATION OF SINGLE AERIAL PHOTOGRAPHS AND IMAGES 63
Further Reading
• Linder, W., 2016. Digital Photogrammetry – A Practical Course, Springer-Verlag Berlin Heidelberg, Germany.
• Lillesand et al 2004, Remote Sensing and Image Interpretation Fifth Edition, Wiiley.
(See Facebook page for the PDF link)