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Photogrammetry Fundamentals
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Photogrammetry Fundamentals
Photogrammetry Fundamentals
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1
Question
What is the introduction of photogrammetry about?
Answer
The introduction includes the establishment of model space and coordinate systems through stereopair orientation.
2
Question
What is model space in photogrammetry?
Answer
Model space is the virtual representation of space in 3D of objects on the ground.
3
Question
What is the model coordinate system?
Answer
The model coordinate system is the reference system established to determine the corresponding position of objects on the ground in the model space.
4
Question
What are the two coordinate systems involved in model space orientation?
Answer
The model space orientation involves the establishment of the relationship between the object's position and an identified standard reference frame.
5
Question
What do standard equations represent in photogrammetry?
Answer
Standard equations represent specific relationships, such as: 1. Linear: y = mx + b, 2. Quadratic: y = ax² + bx + c.
6
Question
What are parameters in the context of equations in photogrammetry?
Answer
Parameters are the coefficients in the equation, like m and b in the linear equation, and a, b, and c in the quadratic equation.
7
Question
When is interior orientation necessary?
Answer
Interior orientation is necessary only for analog photos that need to be digitally scanned.
8
Question
What is the purpose of exterior orientation in photogrammetry?
Answer
Exterior orientation is necessary only for images without corrected positioning and/or angular rotation values.
9
Question
What are Ground Control Points (GCPs)?
Answer
GCPs are special and specific point objects on the ground that are expected to be visible in photos, serving as reference points for model orientation.
10
Question
What is the collinearity principle?
Answer
The collinearity principle states that the exposure point L, point in the image p, and point on the ground P must all lie in a straight line.
11
Question
What is the general requirement for determining exterior orientation parameters?
Answer
At least 3 well-distributed points forming a triangle are required to determine the exterior orientation parameters XL, YL, ZL.
12
Question
What is the mathematical expression for the collinearity condition?
Answer
The mathematical expression of the collinearity condition relates the image/photo coordinates, ground coordinates, and exposure points.
13
Question
What happens after exterior orientation in a single photo?
Answer
After exterior orientation, the exposure station ground coordinates XL, YL, ZL and attitude of the single photo are determined.
14
Question
What is the objective of photogrammetry?
Answer
The objective of photogrammetry is to determine the ground coordinates of the points of objects in the photo or the coordinates Xp, Yp, Zp.
15
Question
How many GCPs are required for exterior orientation?
Answer
At least 3 GCPs are required for exterior orientation in a single image.
16
Question
What is stereopair orientation?
Answer
Stereopair orientation refers to the process of determining ground coordinates in a single photo, requiring two photos with known exterior orientation parameters.
17
Question
What is the purpose of using two photos in stereopair orientation?
Answer
Using two photos in stereopair orientation allows for the creation of a model coordinate system for accurate ground coordinate determination.
18
Question
What happens during the creation of model space?
Answer
The creation of model space occurs after stereopair orientation, establishing a single space known as model space.
19
Question
What are the two methods of stereopair orientation?
Answer
The two methods of stereopair orientation are dependent relative orientation and independent relative orientation.
20
Question
What does direct orientation establish?
Answer
Direct orientation establishes the model coordinate system identical with the ground system.
21
Question
What is the significance of control points in photogrammetry?
Answer
Control points are points with known coordinates that serve as references for accurate measurements and orientation.
22
Question
What does the correction for lens distortion involve?
Answer
Correction for lens distortion involves accounting for symmetric radial and decentering distortion parameters in camera calibration.
23
Question
What is the purpose of photogrammetric scanners?
Answer
Photogrammetric scanners are used to convert photographs from analog form to digital form, quantifying gray levels.
24
Question
What are the major sources of errors in photogrammetry?
Answer
Major sources of errors include film distortions, CCD array distortions, failure of photo coordinate axes to intersect at the principal point, and lens distortions.
25
Question
How is the distance between two points determined in photogrammetry?
Answer
The distances between two points can be determined using the distance formula.
26
Question
What is the importance of the principal point in camera calibration?
Answer
The principal point is the reference point about which lens distortions are most symmetric and is crucial for accurate calibration.
27
Question
What are the steps in a typical workflow in photogrammetry?
Answer
1. Capture of images, 2. Calculation of orientation parameters, 3. Measure coordinates, 4. Create image products, 5. Use results in cartographic or GIS software.
28
Question
Why is it impractical to establish a high number of GCPs?
Answer
Establishing a high number of GCPs can be impractical and expensive, especially as the number of images and strips increases.
29
Question
What do we need for 3D information extraction after determining exterior orientation parameters?
Answer
We need both images for 3D information extraction through space intersection, manual measurement, and generating DEM.
30
Question
What are connection points or tie points in photogrammetry?
Answer
Connection points or tie points are points measured in the images that connect the images together for accurate orientation.