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DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
SnowWatch
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
Roman Fedorov: [email protected]
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
UGC
2
Media User Generated Content (UGC) publicly available on the Web is reaching unprecedented size nowadays:• Facebook ~ 350 MM daily photo uploads• Flickr ~ 8.000 MM photographs with 3.5 MM daily
uploads• Panoramio reached ~ 75 MM geo-tagged photograph
It contains an enormous amount of latent implicit knowledge, the challenge is to extract it.
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Introduction
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring 3
• Challenge: transform geolocated and timestamped public images depicting natural scenarios into virtual environmental monitoring stations.
• Complement existing measurements.
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Project
4
SnowWatch aims at:• improving snow analysis and water management through
the acquisition and analysis of public media content depicting alpine mountains
• Creating alpine snow media dataset with open contribution of new media and access to processed media and its results for any environmental researchers
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Content Providers
SnowWatch Engine
SnowWatch Architecture
User Photos
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Flickr Photos
Content Consumers
Webcams
API Media Storage
Get Image Orientation, Identify Mountain Peaks
Get Image Snow Pixel-level classification
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Flickr Photographs Crawling
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Does an image contain a clear a mountain slope view?
- Heavily depends on thephotograph shooting point altitude
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Flickr Crawling Implementation
7
SVM Image Content-based Classifier:� Bag of Visual Words / Fisher Vector� SIFT/SSIM/GIST/HOG2x2 Descriptors� Spatial Histogram, Vertical Bands
Manually annotated 1658 samples (~70%) for training and validation and 710 samples (~30%) for testing.
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Webcam Images Aggregation
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Identified ~2.000 webcams depicting mountains in Alpine regions.Each webcam produces an image every 1’ – 15’.• 67% of the images are not suitable due to bad weather• More than 50.000 images and 6 GB of data acquired dailyThrough the extraction of the edges we can compute the percentage of the skyline clearly visible, and discard all images with visibility lower than a certain threshold, obtaining the following ROC curve varying the threshold:
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Webcam Images Aggregation
9
Remaining small moving obstacles (such as low clouds, persons, vehicles) and varying illumination conditions are managed through the median aggregation of all daily images
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Photo Peak Identification
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An orientation of a geo-tagged photograph is needed.
Given a Digital Elevation Model (a 3D terrain model) we can simulate the terrain silhouettes that should be seen from the photographer point of view.
Steps� Panorama� Scale� Edges� Filter� Match
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Photo Panorama
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Steps� Panorama� Scale� Edges� Filter� Match
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Photo Scaling
12
Photo must be scaled properly, so the mountains have the same pixel dimension on the photograph and on the panorama.This can be obtained by calculating the Field Of View (FOV) of the photo:
Steps� Panorama� Scale� Edges� Filter� Match
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Photo Edge Extraction
13
Steps� Panorama� Scale� Edges� Filter� Match
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Photo Edge Filtering
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Too many edges on the image that do not belong to a terrain contour!• Skyline detection algorithm is employed, and all the edge
pixels above the skyline are removed, being considered obstacles or clouds.
• Weighting mechanism is applied, which assigns decreasing weights to the edge pixels as the distance from the skyline increases.
Steps� Panorama� Scale� Edges� Filter� Match
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Photo Alignment
15
Find the best overlap maximizing the vector cross correlation score:
Steps� Panorama� Scale� Edges� Filter� Match
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Photo Peak Alignment
16
A global overlap between the photo and the panorama is often not enough, a neighborhood vector cross correlation adjustment is applied to each identified peak:
Steps� Panorama� Scale� Edges� Filter� Match� Local Match
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Photo Peak Identification
17
Fraction of photographs with orientation correctly identified
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Snow Pixels Classification
18
Classifying each pixel as snow covered/terrain is much more than simply checking bright/dark pixels:
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Snow Pixels Classification
19
SnowGround GroundGroundSnow Snow Snow
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Snow Pixels Classification
20
Random Forest Classifier that considers pixel and pixel neighbors color, global and local intensity of the image.Trained on 59 manuallylabeled images(~ 7 Million pixels),outperform currentmethods:
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Environmental Impact Evaluation
21
Environmental consistency evaluation of extracted snow cover indexes.� No direct ground truth, how do we
evaluate it?� Practical utility w.r.t. an environmental
model
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Environmental Impact Evaluation
22
Use case: Como Lake water managementFlooding vs Irrigation trend, what is the best solution?
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
SnowWatch 2°°°° year
23
If the physical snow estimations provided by ARPA (Italian EPA) are not available, Adding Virtual Snow Measures improves the performance by ~100%!
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
SnowWatch 2°°°° year
24
With some irrigation <-> flooding target solutions, using SnowWatch virtual measurements is even better than using ARPA snow estimation!
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring
DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA
Current and Future Work
25
Current:• MountainWatch: real time augmented reality mobile
application• Expand tests on environmental impact
Future:• Expand area of interest and content providers• Orthophotos and new snow indexes
Applying Computer Vision Techniques to Public Web Images for Environmental Monitoring