Ariel Photogrametry Flashcards
What are the advantages of classic photogrammetry?(5)
- Contactless Measurements
- Large range of sizes
- Short time of Observation
- 3-D analysis
- Extensive Documentation
What are the cons of classic photogrammetry?(3)
- Sufficient Illumination required
- Sufficient Visibility Required
- Expensive Technology
What are the 3 types of data acquisition?
Terrestrial, Aerial, and Satellite
What are the four types of images?
- Single Image (Orth projection)
- Image Pair (Stereo Triangulation)
- Image Block (Block Triangulation)
- Image Sequences (Movement)
What are the three technology levels of Photogrammetry?
Analog, Analytical, and Digital
What is a necessity for ortho image generation?
A surface model
What are Vector Products / Orthophoto useful for?
Map updates and plotting of sealed areas
What is DTM and what is it useful for?
Digital Terrain Model, useful for wire frame representation, 3d Visualization and height variation
What is the pinhole camera defined by?
Interior orientation
- Calibrated Focal Length
- Perspective center
What are three important features of working of pinhole camera?
- Image rays are straight lines
- Perspective center as point
- Image points in a plane
What are some model errors for pinhole cameras (5)?
- Distortion
- Blurring caused by diffraction
- Lens errors
- spherical aberration
- chromatic aberration
- Blurring caused by motion
- Filter / Color
What is the Formula for ground sampling distance?
GSD = \delta Pix’ h_g/c’ = \delta pix m_b
where \delta Pix’ = size of pixel on sensor
h_g = height above ground
c’ = chamber constant
What is formula for Image scale M_b?
M_b = c’ / h_g
What is formula for image scale figure m_b?
m_b = 1/ M_b = h_g/c’
where M_b = image scale
h_g = height above ground
c’ =chamber constant
How much larger is minimum recognition size usually?
4 - 5 times the GSD
What is the formula for swath width?
S = s’ h_g/c = s’m_b
What is the formula for position error?
delta r = delta h tan alpha = delta h r’/c’
How do you reduce radial displacement?
Bigger calibrated focal length
What are direct geo-references?(6)
- Directly measuring position and altitude
- GNNS Global Navigation Satellite Systems
- Inertial Measurement Units IMU
- Star Tracker
- Position is fixed in parallel data acquisition
- Synchronization Necessary
What are Indirect Geo References? (5)
- Computing absolute position from image data
- Spatial Resection / Bundle Block adjustment
- Needed are known points and Ground Control Points
- Position is computed in post-processing
- Sufficient amounts of known points neccessary
What is photogrammetry?
The science of obtaining reliable information about the earth and its environment using non-contact sensors.
What are analog ariel images useful for?
Updating building footprints
What is GSD useful for?
For getting an estimation of the resolution of the system
What is swath width important for?
Satellites
