Eye tracking: From eye movements recordings to the ...

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Eye tracking: From eye movements recordings to the analysis metrics and visualizations Vassilios Krassanakis

Dr. Engineer NTUA Dipl. Rural & Surveying Engineer NTUA [email protected] https://sites.google.com/site/vassilioskrassanakis/

National and Kapodistrian University of Athens 7 March 2016 Dr. Vassilios Krassanakis, 7 March 2016

1

Contents ¡  Eye

tracking systems

¡  Eye

movements recordings

¡  Fixation

identification algorithms

¡  Data

quality check processes

¡  Main

and derived metrics

¡  Visualization ¡  Analysis

software

¡  Research Dr. Vassilios Krassanakis, 7 March 2016

techniques

studies examples 2

Eye tracking The methodology of eye movements monitoring. Eye tracking techniques measure: ¡  the

position of the eye relative to the head.

¡  the

orientation of the eye in space (“point of regard”).

(Duchowski, 2007; Young & Sheena, 1975) Dr. Vassilios Krassanakis, 7 March 2016

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Eye tracking techniques ¡  Electro-OculoGraphy ¡  Scleral

(EOG)

contact lens – search coil

¡  Photo-Oculography

Oculography (VOG)

(POG) & Video-

¡  Video-Based

techniques based on pupil and corneal reflection.

Dr. Vassilios Krassanakis, 7 March 2016

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Electro-OculoGraphy (EOG)

(Source: http://www.cesti.gov.vn/images/cesti/ stinfo/Nam%202013/So7/0713_SNTT_Eye %20tracking_nhien%20_H07.jpg) Dr. Vassilios Krassanakis, 7 March 2016

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Scleral contact lens – search coil

(Duchowski, 2007 - Pictures: Skalar Medical, Delft, Netherlands) Dr. Vassilios Krassanakis, 7 March 2016

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Video-Oculography (VOG)

(Strupp, Kremmyda, Adamczyk, Böttcher, Muth, Yip, & Bremova, 2014) Dr. Vassilios Krassanakis, 7 March 2016

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Pupil & corneal reflection

(Source: http://apps.usd.edu/coglab/schieber/eyetracking/ets/ets-calibration.html) Dr. Vassilios Krassanakis, 7 March 2016

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Pupil & corneal reflection detection

(Source: http://users.ntua.gr/bnakos/Eye_Tracking_Eng.html) Dr. Vassilios Krassanakis, 7 March 2016

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Eye tracker system’s operation: A prototype diagram

(Source: http://users.ntua.gr/bnakos/Eye_Tracking_Eng.html)

Dr. Vassilios Krassanakis, 7 March 2016

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Head mounted eye tracking device

(Source: http://www.asleyetracking.com/Site/Portals/0/DSC_0065%20(rotated).JPG) Dr. Vassilios Krassanakis, 7 March 2016

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Head stabilization with chin rest

(Pfeiffer, Latoschik, & Wachsmuth, 2008) Dr. Vassilios Krassanakis, 7 March 2016

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An example of modern eye tracking device

(Source: http://www.tobiipro.com/siteassets/tobii-pro/products/product-commerce-images/ tobiipro_tx300_eye_tracker_front_2_1.jpg) Dr. Vassilios Krassanakis, 7 March 2016

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Eye tracking glasses

(Source: http://mms.businesswire.com/media/20141219005468/en/446323/5/15405230130_34a80b5bec_o.jpg)

Dr. Vassilios Krassanakis, 7 March 2016

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Portable & low cost eye trackers

(Source: https://theeyetribe.com/wp-content/uploads/2013/09/blogpost3.jpg)

Dr. Vassilios Krassanakis, 7 March 2016

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Eye tracking applications psychology landscape perception

graphical user interface evaluation

computer vision

sports vision

medical research

neuroscience

text reading

Eye tracking

web page reading

cartography

advertising

driving behavior art perception

Dr. Vassilios Krassanakis, 7 March 2016

human computer interaction

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Steps of a typical eye tracking experiment research question experimental design eye movements recording

eye movements analysis results

Dr. Vassilios Krassanakis, 7 March 2016

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Eye movements recordings ¡  Recordings

of the spatiotemporal coordinates (x,y,t) produced during visual scene* reading process.

¡  Recordings

peripheral).

¡  High

of the central vision (not

frequency recordings (30-2000Hz).

*visual scene: a scene provided on a computer monitor, an image projected to a surface, real world or virtual reality Dr. Vassilios Krassanakis, 7 March 2016

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Eye tracking data as a (simple) trace Red crosses correspond to records

Dr. Vassilios Krassanakis, 7 March 2016

(Krassanakis, 2009; Krassanakis, Filippakopoulou, & Nakos, 2011a; 20011b)

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Eye tracking data: A complicated trace 1/3

Observation of 9 fixed points on a computer monitor

(Krassanakis, Filippakopoulou, & Nakos, 2014) Dr. Vassilios Krassanakis, 7 March 2016

(Krassanakis, 2009) 20

Eye tracking data: A complicated trace 2/3

(Krassanakis, Filippakopoulou, & Nakos, 2014) Dr. Vassilios Krassanakis, 7 March 2016

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Eye tracking data: A complicated trace 3/3

5 targets





(Krassanakis, 2014) Dr. Vassilios Krassanakis, 7 March 2016

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Eye tracking data as ASCII files: Raw data ¡ 

Time

¡ 

Horizontal coordinate

¡ 

Vertical coordinate

¡ 

Delta time

¡ 

Pupil Width

¡ 

Pupil Aspect

¡ 

Torsion

¡ 



Dr. Vassilios Krassanakis, 7 March 2016

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Eye movement analysis Quantitative ¡  Analysis

of eye movements recordings in fundamental and derived metrics.

¡  Fundamental

Saccades

¡  Main

metrics: Fixations &

derived metric: Scanpath

Qualitative ¡  Eye Dr. Vassilios Krassanakis, 7 March 2016

movements visualizations 24

Fixation detection: the critical process of analysis time horizontal coordinate

fixations

vertical coordinate

raw data x1, y1, t1 x2, y2, t2 . . xn, yn, tn

fixations list a 1, b 1, d 1 a 2, b 2, d 2 . . a k, b k, d k

x, y, a, b: coordinates, ti: passing time, di: fixation duration Dr. Vassilios Krassanakis, 7 March 2016

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Basic eye movement analysis in simple steps

raw data

point cloud clustering

scanpath modeling fixation

saccade (Krassanakis, 2014) Dr. Vassilios Krassanakis, 7 March 2016

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Events of a typical fixation

(Goldberg & Kotval, 1999)

Dr. Vassilios Krassanakis, 7 March 2016

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Mean fixation duration and saccade length Task

Mean fixation duration in ms

Mean saccade size in degrees

Silent reading

225

2 (about 8 letters)

Oral reading

275

1.5 (about 6 letters)

Visual search

275

3

Scene perception

330

4

Music reading

375

1

Typing

400

1 (about 4 letters)

(Ryaner, 1998) Dr. Vassilios Krassanakis, 7 March 2016

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Fixation clustering 1/2 Note: Eyes are relative stationary during a fixation event Cluster definition: an example

(Goldberg & Kotval, 1999) Dr. Vassilios Krassanakis, 7 March 2016

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Fixation clustering 2/2 Spatial and temporal constraints are required.

(Goldberg & Kotval, 1999)

Dr. Vassilios Krassanakis, 7 March 2016

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Detecting fixations in eye tracking protocols 1/3

raw data visual trace

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Detecting fixations in eye tracking protocols 2/3

cluster 1

Dr. Vassilios Krassanakis, 7 March 2016

cluster 2

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Detecting fixations in eye tracking protocols 3/3

saccade 1 fixation 2

fixation 1

radius represents the duration of the fixation

Dr. Vassilios Krassanakis, 7 March 2016

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Fixation detection algorithms ¡  Velocity-Based

Algorithms

¡  Dispersion-Based

¡  Area-Based

Algorithms

Algorithms

(Salvucci & Goldberg, 2000)

Dr. Vassilios Krassanakis, 7 March 2016

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A comparison among fixation identification methods (subcategories are also presented)

(Salvucci & Goldberg, 2000)

Dr. Vassilios Krassanakis, 7 March 2016

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EyeMMV’s algorithm: an example of fixation detection process ¡  Based

on two spatial parameters (t1,t2) and one temporal parameter that corresponds to the minimum duration.

Example: 5 records distribution

raw data: (x1, y1, pt1), (x2, y2, pt2), (x3, y3, pt3), (x4, y4, pt4), (x5, y5, pt5) x: horizontal coordinate, y: vertical coordinate, pt: passing time Dr. Vassilios Krassanakis, 7 March 2016

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EyeMMV’s algorithm: spatial parameter t1

d1, d2, d3, d4 < t1 d: Euclidean distances

Ft1 represents the mean point of the cluster Dr. Vassilios Krassanakis, 7 March 2016

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EyeMMV’s algorithm: spatial parameter t2 check records’ distances from mean point according to t2 parameter

Ft1 represents the mean point of the cluster Dr. Vassilios Krassanakis, 7 March 2016

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EyeMMV’s algorithm: fixation center after t1& t2

Ft2 represents the mean point of the new cluster which corresponds to fixation’s center

Dr. Vassilios Krassanakis, 7 March 2016

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EyeMMV’s algorithm: minimum duration parameter Suppose (example) 7 fixation points after the implementation of the spatial parameters. fixation list (after t1,t2) x1, y1, d1 x2, y2, d2 x3, y3, d3 x4, y4, d4 x5, y5, d5 x6, y6, d6 x7, y7, d7

d1, d2, d4, d5, d7 > minimum duration d3, d6 < minimum duration

final list x 1, y1, d 1 x 2, y2, d 2 x 4, y4, d 4 x 5, y5, d 5 x 7, y7, d 7

x: horizontal coordinate, y: vertical coordinate, d: fixation duration Dr. Vassilios Krassanakis, 7 March 2016

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The importance of fixation analysis ¡  Fixation

analysis affects directly next step analysis (computation of derived metrics, visualizations etc.).

¡  Fixation

parameters are depended on the procedure of the experimentation (e.g. task-specific or free viewing conditions etc.). Adaptations are needed.

¡  The

knowledge of raw data recording quality is also required.

Dr. Vassilios Krassanakis, 7 March 2016

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Comparing different setups

(Ooms, Dupont, Lapon, & Popelka, 2015) Dr. Vassilios Krassanakis, 7 March 2016

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Calibration check procedures 1/2

(Krassanakis, 2009) Dr. Vassilios Krassanakis, 7 March 2016

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Calibration check procedures 2/2 Based on fuzzy c-means clustering

(Krassanakis, 2014)

Dr. Vassilios Krassanakis, 7 March 2016

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Noise measurement in eye tracking data 1/2

Based on artificial eyes’ measurements.

(Krassanakis, 2014; Krassanakis, Filippakopoulou, & Nakos, 2016)

Dr. Vassilios Krassanakis, 7 March 2016

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Noise measurement in eye tracking data 2/2

Reporting spatial and temporal noise for each eye (for binocular systems)

(Krassanakis, 2014; Krassanakis, Filippakopoulou, & Nakos, 2016) Dr. Vassilios Krassanakis, 7 March 2016

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Main and derived metrics ü coordinates ü durations Fixations ü start/end time ü total number ü mean duration ü time to first fixation ü list of repeat fixations ü total duration

Saccades

Scan path

ü total number ü saccade list ü start/end fixation point ü duration ü amplitude ü direction angle

ü length ü duration ü saccades/fixations ratio ü spatial density ü transition matrix ü transition density * The list is not exhaustive. Here only the metrics supported by EyeMMV toolbox (Krassanakis et al., 2014) are presented. 47 Dr. Vassilios Krassanakis, 7 March 2016

Metrics example: scanpath duration & length

(Goldberg & Kotval, 1999) Dr. Vassilios Krassanakis, 7 March 2016

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Metrics example: scanpath spatial density

(Goldberg & Kotval, 1999) Dr. Vassilios Krassanakis, 7 March 2016

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Metrics example: scanpath transition density

(Goldberg & Kotval, 1999) Dr. Vassilios Krassanakis, 7 March 2016

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Visualizations of eye tracking data Raw data: ¡  Raw

data distribution: (x,y)

¡  Horizontal

and vertical coordinates along time: (x,t) & (y,t)

¡  Space-time-cube

visualization: (x,y,t)

Analyzed data: ¡  Scanpath

visualization

¡  Heatmap

visualization

¡  … Dr. Vassilios Krassanakis, 7 March 2016

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Raw data distribution

(Larsson, 2010) Dr. Vassilios Krassanakis, 7 March 2016

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Scanpath example

Dr. Vassilios Krassanakis, 7 March 2016

(Source: http://www.usability.de/assets/img/content/m-et-gazeplot.jpg)

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Multiple scanpaths

Dr. Vassilios Krassanakis, 7 March 2016

(Eraslan, Yesilada, & Harper, 2016)

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Heatmaps

(Source: http://www.neurotechnology.com/res/sentigaze-web-heatmap.jpg) Dr. Vassilios Krassanakis, 7 March 2016

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Heatmap construction

(Krassanakis, 2014) Dr. Vassilios Krassanakis, 7 March 2016

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Multiple scanpaths vs Heatmap

(Source: http://www.profitippliga.de/toreyetracking.jpg)

Dr. Vassilios Krassanakis, 7 March 2016

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Space time cube for video eye tracking data

(Blascheck, Kurzhals, Raschke, Burch, Weiskopf, & Ertl, 2014)

Dr. Vassilios Krassanakis, 7 March 2016

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Eye tracking analysis software ¡  Main

function: fixations/saccades identification (identification algorithms implementation)

¡  Analysis

metrics

¡  Eye

of eye tracking data in derived

tracking visualization techniques

¡  Regions

of Interest (ROIs) analysis

¡  …

Dr. Vassilios Krassanakis, 7 March 2016

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Freely available eye tracking tools ¡  ILAB ¡  Eyelink

¡  ITU

Toolbox

Gaze Tracker

¡  GazeAlyze

¡  iComp

¡  EHCA

Toolbox

¡  openEyes

¡  GazeParser

¡  eyePatterns

¡  EyeMMV

¡  iComponent

¡  ETRAN-R

¡  OGAMA

¡  …

toolbox

(modified after Krassanakis, Filippakopoulou, & Nakos, 2014) Dr. Vassilios Krassanakis, 7 March 2016

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Example 1: OGAMA ¡  Open

Gaze And Mouse Analyzer (Voßkühler, Nordmeier, Kuchinke, & Jacobs, 2008)

¡  Freeware,

C# .NET

¡  Graphical

User Interface (GUI)

¡  Several

modules (metrics, statistics, visualizations etc.)

¡  Fully

documented

¡  Supports

a lot of commercial and open source eye trackers.

¡  Supports

saliency calculations (based on Itti & Koch, 2001).

Dr. Vassilios Krassanakis, 7 March 2016

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OGAMA: Stimulus design module

(Source: http://www.ogama.net) Dr. Vassilios Krassanakis, 7 March 2016

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OGAMA: Recording module

(Source: http://www.ogama.net) Dr. Vassilios Krassanakis, 7 March 2016

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OGAMA: Fixations module

(Source: http://www.ogama.net) Dr. Vassilios Krassanakis, 7 March 2016

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OGAMA: Statistics module

(Source: http://www.ogama.net) Dr. Vassilios Krassanakis, 7 March 2016

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OGAMA: Saliency module

(Source: http://www.ogama.net) Dr. Vassilios Krassanakis, 7 March 2016

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Example 2: EyeMMV toolbox ¡  Eye

Movements Metrics & Visualizations (Krassanakis, Filippakopoulou, & Nakos 2014)

¡  Open

source MATLAB code (under GPLv3)

¡  Complete

toolbox

post-experimental analysis

¡  Command

line toolbox (list of functions)

¡  Cross-platform

installed)

Dr. Vassilios Krassanakis, 7 March 2016

(where MATLAB is pre67

EyeMMV’s fixation identification algorithm: flowchart

Dr. Vassilios Krassanakis, 7 March 2016

(Krassanakis, 2014)

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EyeMMV toolbox: fixation detection report

(Krassanakis, 2013a) Dr. Vassilios Krassanakis, 7 March 2016

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EyeMMV toolbox: fixation/saccade metrics

(Krassanakis, 2013a) Dr. Vassilios Krassanakis, 7 March 2016

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EyeMMV toolbox: scanpath analysis

(Krassanakis, 2013a) Dr. Vassilios Krassanakis, 7 March 2016

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EyeMMV toolbox: visualizations

(Krassanakis, Filippakopoulou, & Nakos, 2014)

Dr. Vassilios Krassanakis, 7 March 2016

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EyeMMV toolbox: heatmap visualization and ROIs analysis

(Krassanakis, Filippakopoulou, & Nakos, 2014)

Dr. Vassilios Krassanakis, 7 March 2016

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Research studies: examples Experimentation in the field of map perception: ¡  Design

(visual and dynamic) variables

¡  Change

detection

¡  Post-detection ¡  Cartographic ¡  Modeling

Dr. Vassilios Krassanakis, 7 March 2016

reaction

generalization

map users gaze behavior 74

Research study 1 ¡  Examination

of the topological feature of hole as preattentive feature.

¡  Quantitative

tracking.

analysis based on eye

¡  Repeat

experimentation made by capturing Reaction Time (RT). targets

Dr. Vassilios Krassanakis, 7 March 2016

distractors

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Research study 1: Stimuli ¡  Cartographic

backgrounds

(Krassanakis, 2009; 2013b; Krassanakis, Filippakopoulou, & Nakos, 2011a; 2011b)

Dr. Vassilios Krassanakis, 7 March 2016

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Research study 1: Results 1/2 ¡  Based

on scanpaths examination

(Krassanakis, 2009, 2013b; Krassanakis, Filippakopoulou, & Nakos, 2011a, 2011b) Dr. Vassilios Krassanakis, 7 March 2016

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Research study 1: Results 2/2 ¡  Visual

search starts from previous location.

¡  More

complicated scanpath generated on map periphery.

¡  Fixations

correspond to point symbols locations.

¡  Saccades

correspond to the transitions through targets and distractors.

¡  In

case of target-absent trials, more complicated scanpath are observer (no special pattern).

Dr. Vassilios Krassanakis, 7 March 2016

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Research study 2 ¡  Preliminary

study

¡  Examination

of map readers reaction to the variables of duration and rate of change.

(Krassanakis, Lelli, Lokka, Filippakopoulou, & Nakos 2013a) Dr. Vassilios Krassanakis, 7 March 2016

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Research study 2: symbol detection

(Krassanakis, Lelli, Lokka, Filippakopoulou, & Nakos, 2013a) Dr. Vassilios Krassanakis, 7 March 2016

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Research study 2: Preliminary results

(Krassanakis, Lelli, Lokka, Filippakopoulou, & Nakos, 2013a; Krassanakis, 2013) Dr. Vassilios Krassanakis, 7 March 2016

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Research study 3 ¡  Examination

of the minimum duration threshold required for the detection by the central vision of a moving point symbol on cartographic backgrounds

(Krassanakis, 2014; Krassanakis, Filippakopoulou, & Nakos, 2016) Dr. Vassilios Krassanakis, 7 March 2016

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Research study 3: Analysis approach Definition of statistical metrics based on fixations: ¡  Success

metric

¡  Duration

metric

¡  Duration

percentage metric

¡  Number

metric

¡  Number

percentage metric

¡  Time Dr. Vassilios Krassanakis, 7 March 2016

to first fixation metric 83

Research study 3: Results 1/2 Explanation of “overall visual reaction” through regression analysis

(Krassanakis, 2014; Krassanakis, Filippakopoulou, & Nakos, 2016) Dr. Vassilios Krassanakis, 7 March 2016

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Research study 3: Results 2/2 Duration threshold computation

(Krassanakis, 2014; Krassanakis, Filippakopoulou, & Nakos, 2016)

Dr. Vassilios Krassanakis, 7 March 2016

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Research study 4 ¡  Post-detection

examination

¡  Stimuli:

blank background and cartographic background

¡  Results

are compared (quantitatively) with the corresponded outcomes of saliency models implementation.

¡  Saliency

models: developed to predict human vision behavior and based on natural scenes’ tests.

Dr. Vassilios Krassanakis, 7 March 2016

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Research study 4: Results (Itti, Koch, & Niebur, 1998)

(Harel, Koch, & Perona, 2006)

(Hou, Harel, & Koch, 2012]

(Krassanakis, Lelli, Lokka, Filippakopoulou & Nakos 2013b) Dr. Vassilios Krassanakis, 7 March 2016

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Research study 5 ¡  Comparison

of critical points’ locations with fixation points.

Cartographic generalization: 1:k initial line

generalized line Dr. Vassilios Krassanakis, 7 March 2016

1:10k 88

Research study 5: stimuli

(Bargiota, 2013) Dr. Vassilios Krassanakis, 7 March 2016

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Research study 5: Results 1/2

(Bargiota, Mitropoulos, Krassanakis, & Nakos, 2013) Dr. Vassilios Krassanakis, 7 March 2016

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Research study 5: Results 2/2

Detection of critical points based on “LR method”(ALR Index) (Nakos & Mitropoulos, 2005)

(Bargiota, Mitropoulos, Krassanakis, & Nakos, 2013)

(Bargiota, 2013) Dr. Vassilios Krassanakis, 7 March 2016

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Research study 6 ¡  Introduction

of a new visualization method of eye tracking data based on polylines inferred from samples’ analysis.

Dr. Vassilios Krassanakis, 7 March 2016

(Karagiorgou, Krassanakis, Vescoukis, & Nakos, 2014)

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Research study 6: Results

(Karagiorgou, Krassanakis, Vescoukis, & Nakos, 2014) Dr. Vassilios Krassanakis, 7 March 2016

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Thank you

Dr. Vassilios Krassanakis, 7 March 2016

Dr. Vassilios Krassanakis

[email protected] https://sites.google.com/site/vassilioskrassanakis/

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References 1/3 Bargiota T. (2013). Measuring critical points along cartographic lines using eye movements (In Greek). Master Thesis, Master of Science Program in Geoinformatics, National Technical University of Athens. Bargiota T., Mitropoulos V., Krassanakis V., & Nakos B. (2013). Measuring locations of critical points along cartographic lines with eye movement analysis. Proceeding of the 26th International Cartographic Conference. Dresden, Germany. Blascheck, T., Kurzhals, K., Raschke, M., Burch, M., Weiskopf, D., & Ertl, T. (2014). State-of-the-art of visualization for eye tracking data. In: Proceedings of EuroVis (Vol. 2014). Duchowski, A. (2007). Eye tracking methodology: Theory and practice. London: Springer. Eraslan, S., Yesilada, Y., & Harper, S. (2016). Eye tracking scanpath analysis techniques on web pages: A survey, evaluation and comparison. Journal of Eye Movement Research 9(1):2, 1-19. Goldberg, J.H., & Kotval, X.P. (1999). Computer interface evaluation using eye movements: methods and constructs. International Journal of Industrial Ergonomics, 24(6), 631-645. Harel J., Koch C., & Perona P. (2006). Graph-Based Visual Saliency. In: Advances in neural in- formation processing systems, 545-552. Hou X., Harel J., & Koch C. (2012), Image Signature: Highlighting Sparse Salient Regions, IEEE Transactions on Pattern Analysis and Machine Intelligence, 34(1): 194-201. Itti L. Koch C., & Niebur E. (1998). A model of saliency-based visual attention for rapid scene analysis, IEEE Transactions on Pattern Analysis and Machine Intelligence, 20(11): 1254- 1259. Itti, L., & Koch, C. (2001). Computational modelling of visual attention. Nature reviews neuroscience, 2(3), 194-203. Karagiorgou S., Krassanakis V., Vescoukis V., & Nakos B. (2014), Experimenting with polylines on the visualization of eye tracking data from observations of cartographic lines, In: P. Kiefer, I. Giannopoulos, M. Raubal, A. Krüger (Eds.), Proceedings of the 2nd International Workshop on Eye Tracking for Spatial Research (co-located with the 8th International Conference on Geographic Information Science (GIScience 2014)), Vienna, Austria, 22-26, pp. 22-26. Dr. Vassilios Krassanakis, 7 March 2016

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References 2/3 Krassanakis V. (2014). Development of a methodology of eye movement analysis for the study of visual perception in animated maps (In Greek). Doctoral Dissertation, School of Rural and Surveying Engineering, National Technical University of Athens. Krassanakis V., (2013a). Using EyeMMV Toolbox for eye movement analysis in cartographic experiments, Workshop of International Cartographic Association, Eye Tracking: Why, When, and How?, Dresden, Germany. Krassanakis V., (2013b). Exploring the map reading process with eye movement analysis. In P. Kiefer, I. Giannopoulos, M. Raubal, & M. Hegarty, eds. Eye Tracking for Spatial Research, Proceedings of the 1st International Workshop (in conjunction with COSIT 2013). Scarborough, United Kingdom, pp. 2-7. Krassanakis V., Lelli A., Lokka I. E., Filippakopoulou V., & Nakos B. (2013b). Searching for salient locations in topographic maps. In T. Pfeiffer & K. Essig, eds. Proceedings of the First International Workshop on Solutions for Automatic Gaze Data Analysis 2013 (SAGA 2013). Bielefeld, Germany: Center of Excellence Cognitive Interaction Technology, pp. 41-44. Krassanakis V., Lelli A., Lokka I. E., Filippakopoulou V., & Nakos B., (2013a). Investigating dynamic variables with eye movement analysis. Proceeding of the 26th International Cartographic Conference. Dresden, Germany. Krassanakis, V. (2009). Recording the trace of visual search: a research method of the selectivity of hole as a basic shape characteristic (In Greek). Diploma Thesis, School of Rural and Surveying Engineering, National Technical University of Athens. Krassanakis, V., Filippakopoulou, V., & Nakos, B. (2011a). The influence of attributes of shape in map reading process. Proceedings of the 25th International Cartographic Conference. Paris, France. Krassanakis, V., Filippakopoulou, V., & Nakos, B. (2011b). An Application of Eye Tracking Methodology in Cartographic Research. Proceedings of the EyeTrackBehavior 2011 (Tobii). Frankfurt, Germany. Krassanakis, V., Filippakopoulou, V., & Nakos, B. (2014). EyeMMV toolbox: An eye movement post-analysis tool based on a two-step spatial dispersion threshold for fixation identification. Journal of Eye Movement Research, 7(1): 1, 1-10. Dr. Vassilios Krassanakis, 7 March 2016

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