Instructor: Dr. Ashton Southard Email: [email protected] Office: 212 Pryale Hall.
2019 NYSAPLS Conf> · 2019-01-18 · 2019 NYSAPLS Conf> Fundamentals of Photogrammetry for Land...
Transcript of 2019 NYSAPLS Conf> · 2019-01-18 · 2019 NYSAPLS Conf> Fundamentals of Photogrammetry for Land...
2019 NYSAPLS Conf>
Fundamentals of Photogrammetry for
Land Surveyors
George Southard
GSKS Associates LLC
George Southard:
Master’s Degree in Photogrammetry and Cartography
40 years working in the mapping industry
Owner – GSKS Associates LLC
“Consulting for the Geomatics Profession”
Introduction
data processing
using the science of
Photogrammetry
Remote Photogrammetry
”The science or art of obtaining reliable
measurements by means of photographs.”
”Photogrammetry is the art, science, and
technology of obtaining reliable information
about physical objects and the environment
through the processes of recording, measuring,
and interpreting photographic images.”
(ASPRS, 1980)
Definitions:
Analog Photogrammetry
Using optical/mechanical/electrical instruments, to perform measurements from images printed on paper, film or glass, thus creating stereographic views of the image space for the purpose of 3D measurements.
Analytical Photogrammetry
Using equipment similar to those used in analog photogrammetry but which have computer/electronic components added for more efficient measurement of photographic images. Computer software programs are also a key element in these operations.
Digital or Softcopy Photogrammetry
The performance of photogrammetric operations using digital rather than hardcopy images. This work is accomplished primarily using computer, monitors, and a specially designed mouse along with sophisticated software.
Definitions:
• Photogrammerty• The Science of making maps from stereo imagery
o Stereo (3D) Imaging
o Ground Control (reference points, GPS, GNSS)
o Aero-Triangulation (georeferencing)
o Stereo Compilation
o Topographic Mapping
o Planimetric Mapping
o 3D Point Clouds
o Orthophotography
Key Technologies and Terms
History
Origins of Remote Sensing
First photographs taken in 1839
Remote sensing began withaerial photography
A brief history of Photogrammetry
1858 Gasper Felix Tournachon "Nadar" takes photograph of village of Petit Bicetre in France from
a balloon.
Paris by Nadar, circa 1858
A brief history of Photogrammetry
City of Boston by Black and King (1860), from hot air balloon
A brief history of Photogrammetry
A brief history of Photogrammetry
Major developments in aerial photography – WW1
A brief history of Photogrammetry
After the war the technology was in place to begin large scale aerial surveys
A brief history of Photogrammetry
Foundational Principles
Photogrammetric Fundamentals
First Assumption: the photo image is a flat planar surface
Second Assumption: There are planar distortions in all photo images:
- Distortions come from two sources
1) the camera platten for film or the CCD platten for
digital images
2) the camera lens(s)
Photogrammetric Fundamentals
Known constants and variables…..
Photo Orientation
Six positions of orientation are needed to georeference each photo
Ω Omega – Yaw Φ Phi – Pitch Κ Kappa - Roll
x – Longitude y – Latitude Z - Elevation
•Over lap about 60%
Aerial Photography -Stereo pair
•Over lap about 60%
Precisely controlled image capture…..
Types of Photogrametry
Photogrammetric Types from Applications Point of
View (d is distance from camera to object)
▪ Close Range Photogrammetry d<50 m
▪ Aerial Photogrammetry 50m>d<15km
▪ Space Photogrammetry d = 300 km+
Photogrammetric Types
Close Range (terrestrial) Photogrammetry
Close Range (terrestrial) Photogrammetry
Aerial Photogrammetry
Space Photogrammetry
❖ Extraterrestrial pictures taken from space-based cameras
Photogrametric Imagery
Types of Images
• Panchromatic, Black & White, Grayscale
• Color - Red Green Blue (RGB)
• Multispectral (RGB + Infrared)
• Hyperspectral
Introduction
Sensitive to
light in the
400-680nm
range
Panchromatic Image
Black and white Image
Grayscale Image
False Color composite image
True Color composite image
Types of photographs (categorized by tilt)
• Vertical - camera axis as nearly vertical as Possible
• Oblique - camera axis intentionally tilted• Low Oblique
• High Oblique
Types of photographs (categorized by tilt)
Vertical - Aerial Photo
❖ Mainly used for mapping
Low oblique (no horizon)
❖Seldom used for mapping
Low Oblique – Aerial Photo
• Horizon line in the
photo
• Typically used for
3D city modeling
High Oblique – Aerial Photo
• Maps are based on parallel projection while photo has central projection
• Maps have a unique scale. Photo scale varies depending on terrain relief and degree of radial distortion
Characteristic of a Map vs a Photo
Aerial images are not maps!
Image Acquisition for photogrammetric mapping
Image Acquisition
Precisely controlled image capture…..
Precisely controlled image capture…..
• Photos taken in parallel flight strips
Image Acquisition
• Each successive photograph overlap previous photo
Image Acquisition
Ground Control
Types of Ground Control Points
Types of Stereo Model control layout
Full Stereo Model
Control
Stereo Model Control for
Aero-triangulation
Types of Stereo Model control layout
Full Stereo Model Control – with Aero-triangulation
Ground Control Point Planning
Aero-Triangulation - (georeferencing all images for a unified
block of ground control positions and tie points)
Types of Stereo Model control layout
Photogrammetric Instruments
• MULTIPLEX MODEL SKETCH
Direct Optical Projection Stereo plotters
Kelsh – Optical/ Mechanical Stereoplotter
1930s to 1970s
Direct Optical Projection Stereo plotters
Wild Heerbrugg A8–Analogue Optical Mechanical Stereoplotter
1960s to 1980s
Direct Optical Projection Stereo plotters
• Wild BC2 analytical stereo-plotter.
Analytical Optical/Electronic Stereoplotter
1980s – 1990s
Direct Optical Projection Stereo plotters
Digital Softcopy Stereoplotter
1990s - Present
Softcopy (digital) Stereo plotters
Wild C2 - 1927
Wild RC5 - 1944
Wild RC30 & Zeiss TOP15 – 1980s
3D Aerial Film Cameras
Large Format
Medium Format
Small Format
RGB and IR≥200 MP
RGB or IR60 - 100 MP
RGB or IR10 – 20 MP
Imaging Cameras for Manned Aircraft
High Quality Photogrammetric Mapping – Calibrated Lens Distortion, Mid-
Exposure Pulse, Fixed Focal Length
Medium Quality – Photogrammetric Mapping, Lens characterization, no MEP
Imaging only, no photogrammetric mapping, no lens correction
Imaging Cameras for Unmanned Aircraft
Canon S100
12 MP
Horizontal RMSE =
6.4 cm
Vertical RMSE =
14.0 cm
Sony NEX-5
16 MP
Horizontal RMSE =
1.3 cm
Vertical RMSE =
1.9 cm
Does camera choice effect accuracy?
Camera Sensor Dimensions
(mm)
Rows x Columns (pixels) Pixel Area (μm2)
Canon S100 7.5 x 5.5 4000 x 3000 (12MP) 3.4
NEX-5R 23.4 x 15.6 4912 x 3264 (16MP) 28.8
The light collected is proportional to the sensor pixel area. Note
that the NEX has 8 ½ times the area of the Canon – this is a huge
difference!
Photon noise varies as the square root of the image signal, so
collecting more light results in proportionally less noise, i.e. a
higher signal-to-noise ratio is achieved.
Higher signal-to-noise means more sensitivity to low-light
situations, and broader dynamic range.
Sensor Size vs. image noise
Significant
Noise
Poor Conformance
Noise from Cannon S100 images
Image Noise
Noise from NEX-5R Images
Low
Noise
High Conformance
Image Noise
Focal length is highly
correlated with vertical scale
and accuracy
Precise focal length cannot be
established for zoom lenses,
even if the zoom feature is
disabled.
Focal length calibration
• Consumer cameras do not have a Mid-Exposure Pulse
(MEP)o Real Time Kinematic GNSS
o One must know the exact correlation of each photo center to the GNSS position at
time of exposure
o Common practice is to use the camera flash signal to create a MEP with
modifications to the electronic circuitry
• Consumer cameras do not offer stock fixed focus lens
optionso Requires special lenses (which are expensive or not available for many consumer
cameras.)
Other Issues….
• Airborne LIDAR: Manned Aircraft
Wide Area Mapping500-800 kHz pulse
rate
Corridor Mapping200-500 kHz pulse
rate
OR
3D LIDAR Scanning
Image Processing
o Ground Control (reference points, GPS, GNSS)
o Aero-Triangulation - (georeferencing all images a unified block and tying the block to ground control positions)
o Stereo Compilation – (3D extraction of information from the georeferenced block of imagery)
o Topographic Mapping
o Orthophotography
o Planimetric Mapping
Photogrammetric Image Processing
Contour/topographic map
Photogrammetric Image Processing
Topographic Map with Planimetric Features
Photogrammetric Image Processing
o Orthophotography
Vertical Photo Mosaic DTM/DSM (3D-view)
Photogrammetric Image Processing
Orthophotography
3D Ortho Mosaic
Photogrammetric Image Processing
UAS Survey GNSS Survey Comments
Area 1.5 km2 1.5 km2
Ground control setup &
measurement
1 ¼ hr --- Ground control not required
for all applications
Setup time 15 min 15 min (per day)
Survey time 45 min 30 ½ hr (4 days)
Tear-down time 15 min 15 min (per day)
Data processing time 4 hrs
(2.80 GHz Intel Core i7,
16 GB RAM)
--- Data can be processed
overnight
Total time 6 hr 30 min 32 hr 30 min 5x faster than GNSS
Measurement sampling Distance 3.8 cm (at 120 m flight
altitude)
15 m Minimum sampling size is 2.4
cm
Horizontal accuracy 2 cm 1 cm
Vertical accuracy 4 cm 2 cm
Land Survey vs. UAS Survey Example
Surface model generated from UAS
survey (± 300,000 measurements)
Surface model generated from GNSS
survey (±1,000 measurements)
Topographic Survey Comparison
Questions