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COMP228 > Context and Sensors > Flashcards

Context and Sensors Flashcards

1
Q

What are accelerometers?

A
  • a device that measures the vibration, or acceleration of motion of a structure
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2
Q

What is a Gyroscope?

A
  • Measures and maintains orientation based on the principles of conservation of angular momentum
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3
Q

What are Gyroscopes in IPhone used for?

A
  • for games to provide rotational information and supplement accelerometers
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4
Q

How does a gyroscope in a phone work?

A

When the user rotates their phone, a mass gets displaced, so it can tell the phone has been rotated

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5
Q

What are solid state hall effect sensors used for?

A
  • most commonly used in mobile devices for orientation and magnetometers
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6
Q

What are solid state hall effect sensors?

A
  • sensors that produce a voltage proportional to the applied magnetic field, can sense polarity
  • the movement of electrons is curved when a magnetic field is perpendicular to the direction of the charge through a conductor
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7
Q

What can orientation be used to determine?

A

The direction the phone is pointing in
- can be used for compass app, rotation in maps, or determine orientation of the camera

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8
Q

What are touch screens?

A
  • A display that detects the presence and location of a touch on the display
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9
Q

What techniques can be used for picking up touches on a touch screen

A
  • Surface acoustic wave
  • infrared arrays: measures the infrared being broken
  • Strain Gauge configurations: measure the bend of the screen so can measure strength of press
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10
Q

What is captive touch screen?

A
  • electrostatic-based design (insulator is coated with a transparent conductor, humans are conductive, touch with a finger creates a distortion in the electromagnetic field)
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11
Q

How does multi-touch work?

A
  • it registers two or more fingers simultaneously on the screen
  • fingers generate gestures that can be converted into actions
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12
Q

What is Voice Input / Automatic Speech Recognition?

A
  • converts spoken word into text or commands
  • most use internet based processing, i.e. the recording is sent to a server to process
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13
Q

How can using siri be improved?

A
  • By training: user can give typical input of saying “Hey Siri”
  • then in new instances of saying “Hey Siri”, input is compared to stored examples
  • speech patterns (digital representation) tends to be unique to individual speakers
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14
Q

What does speech recognition of complex sentences require?

A
  • lots of processing power
  • machine learning tasks have improved processing power in devices as originally complex sentences had to be processed in the cloud
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15
Q

What are context aware systems?

A

Systems that can sense and react based on their environment

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16
Q

Give an example of a context aware system?

A

-A travel guide offering information based on current location
-A weather app giving information about weather based on location

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17
Q

What are the 3 categories human factors related to context and be structured into?

A
  • information on the user (habits, emotional state, biophysiological conditions)
  • the users social environment (co-location of others/ social interaction / group dynamics)
  • the users tasks (spontaneous activity / general goals / engaged tasks)
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18
Q

What are the 3 categories context related to the physical environment is structured into?

A
  • Location (absolute/relative (distance relative to some object - a telephone pole) position)
  • infrastructure (surrounding resources available for computation, communication (e.g. proximity to a printer))
  • physical conditions (noise, light levels (automatic adjustment of screen brightness), temperature, air quality)
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19
Q

What are the classifications of context aware systems?

A
  • proactive triggering (performing interaction based on environmental perceptions)
  • streamlining interaction (reducing irrelevant information - travel guide for current location)
  • memories for past events (contextual retrieval based on spacial cues - photos last time you were here)
  • reminders for future contexts (tagging details relating to current context for future access)
  • optimising patters of behaviour (changing interface based on situation)
  • sharing experiences (social networking based on shared concepts)
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20
Q

What is the difference between passive and active context aware systems?

A
  • in passive CA the device alerts the user of a change in context and asks them to make a decision - such as low battery, put on low battery mode?
  • in active CA the device automatically changes something due to a change in context - such as degrading playback quality of video if network connection degrades
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21
Q

What is context creation?

A

sensor data can create new contexts
- this sensor data is raw and may need to be processes

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22
Q

What are some challenges in Context Awareness

A
  • Environmental cues may be inaccurate or erroneous (a dark tunnel can make phone turn to dark mode as it thinks it’s night)
  • user context may be incorrectly determined or predicted or ambiguous
  • lack of alignment with cues and internal representation of context (fitbit detecting steps when on a bike)
  • the use of context may reduce user privacy (know users location)
  • aware of context shifts/changes in application may overload use (too many alerts)
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23
Q

What is spacial awareness?

A

(referred to as location-aware systems)
- services can be related spacially - displayed in terms of proximity on a list

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24
Q

Examples of Spatially Aware Applications

A
  • navigation (find next train home requires current location, home location and time table)
  • context change (route is congested, take another road)
  • query location context - tell me about the building i’m in
  • personal emergency - my car has broken down
  • location/time based offers - special offer on nearby restaurant
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25
Q

What is asset tracking?

A

-Why does this process take so long - can optimise product flow
- public - how long before next bus arrives at stop
- personal - car has been stolen, can it be tracked
- location tagging: where was this photo taken
- location/time synchronisation (users can share/synchronise their context to arrange meetings)

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26
Q

What is location acquisition?

A
  • triangulation (based on angulation given two or more fixed points)
  • lateration (determines distance from fixed points - determine eta)
  • proximity (recognising RFID tags)
  • scene analysis (image recognition of places - not used often, not scalable)
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27
Q

How does triangulation work?

A
  • uses pythagoras’ theorem
  • measures location of a point by measuring the angles to it from known points
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28
Q

How does Lateration - by Attenuation work?

A
  • determines distance based on known transmitter strength
  • If you have a lot of WLAN’s close by then you can get data from multiple of these extra points to improve the accuracy.
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29
Q

How does Global Positioning System work?

A
  • positioning based on satellites in medium earth orbit that can pick you up
  • Knowing where the satellite is exactly positioned is crucial in calculating your device’s location
  • each satellite beams a laser to earth
  • if you’re picked up by at least 4 lasers you can get a location
  • still uses trilateration to determine your position, with the satellites positions
30
Q

How can we get a more accurate location position using global positioning system

A
  • the more satellites that pick up your device, the more accurate
    your location will be determined
31
Q

How does assisted GPS work?

A

-dependent upon network carrier as well as satellites
- network carriers can use timing information
- cell towers have fixed positions so their known locations can be used to determine where you are

32
Q

What is Mobile Phone Localisation

A

Determines the location of a phone based on power levels of signals and antenna patterns from cell towers

33
Q

Why is Mobile Phone Localisation worse in rural areas?

A
  • In rural areas, the precision is a lot worse as there are fewer cell towers and these are spread further apart.
34
Q

Three approaches to mobile phone localisation

A
  • Network Based
  • Handset Based
  • Hybrid Systems
35
Q

What is network based mobile phone localisation

A
  • provider identifies location of the handset by knowing which cell tower your phone is communicating with, this gives us information about how far away you are from cell tower, trilateration can be used for more accuracy.
  • Relies on the Provider’s network to (non-intrusively) identify the location of the handset.
36
Q

What is Handset based mobile phone localisation

A
  • This relies on your device determining your position using various methods, this may be GPS, or using cell towers and this information is then sent back to the service provider
  • Relies on applications running on phone itself to determine position using various methods
  • These are then processed, and sent to the receiver
37
Q

What is Hybrid based mobile phone localisation

A
  • Hybrid systems use both things in order to achieve the most accuracy
  • Combines both network and handset-determined positioning to get the best accuracy
  • May vary the mechanism used depending on local conditions and available signals
38
Q

When is GPS used for iphone location services?

A
  • used whenever possible
    however can be inaccurate indoors because signal is easily absorbed or reflected by buildings or due to urban canyons (e.g. in big cities such as London, with many tall buildings that most likely have metal structures that the signal can’t pass through)
39
Q

What is Skyhook’s WiFi Positioning System?

A

If you can’t see GPS use this because there’s such a large amount of wifi networks in very urban spaces, if you know wifi networks are going to be in the vicinity and how strong the signals are, you can figure out your location.
This relies on a large database of known WiFi access points.
The MAC address and Received Signal Strength is used from each detected Wifi Point to generate an approximate location through trilateration
Good accuracy, but dependent on high density of Wifi access points
Prone to error if Access Points are moved (e.g. consumers change addresses!)

40
Q

How does proximity analysis work?

A
  • makes use of short-range transceivers at fixed positions - attached to things like RFID tags and bluetooth
  • used for asset tracking
  • not usually about finding an absolute location for you but more about how far away you are from some object of interest
41
Q

How does scene analysis work?

A
  • Relies on the abstraction of image markers from terrain scenes
  • These are then cross-correlated from a database of known markers * E.g. church spires, canals, railway lines etc
  • Can be used for absolute positioning, but requires significant image information on unique buildings
  • Requires big database of information that can be searched and the details matched to that database entry, which will have the rough location linked to that entry
  • Not as accurate if you’re in a place with a lot of similar looking buildings.
42
Q

What are the 4 techniques for indoor location positioning?

A
  • magnetic positioning, visual markers, wifi/bluetooth, intertial measurements
43
Q

How does magnetic positioning work to determine location?

A
  • buildings almost certainly have metal infrastructures, which cause local variations in the earth’s magnetic field and can be sensed by your mobile because it has a magnetometer in it
  • A magnetometer is a scientific instrument that measures the strength and direction of the magnetic field in the vicinity of the instrument.
44
Q

How does Wifi and bluetooth work to determine location?

A

Lots of internal information is provided by wifi access points and bluetooth beacons

45
Q

How does Inertial measurements work to determine location?

A

there’s a gyroscope and an accelerometer in your device and it knows the direction you’re moving in and how you’re moving. This information can be used with machine learning algorithms to figure out how you’ve moved with regards to where you originally were standing.

46
Q

How does Visual Markers/features work to determine location?

A

if you have buildings that have lots of signs in or iconic elements which could be recognised, this information could be used to give a location.
This is often used with other methods, as a confirmation

47
Q

How do we get IOS to provide us with our location?

A

Don’t have to know specifically which mechanism you’re using, you just have to request IOS to provide you with a location via framework known as Core Location

48
Q

What does the core location framework include?

A

A framework for providing details about:
Location, in terms of
* latitude, longitude, altitude
* horizontal accuracy (latitude/longitude radius)
* vertical accuracy (altitude)

Heading, in terms of
* heading (degrees from magnetic or true north)
* heading accuracy

Regions
* Uses a three tiered approach
* The more accurate the approach, the more power it consumes

49
Q

What is the Core Location Manager?

A
  • a delegate protocol and what your view controller does is respond to location events
  • You create a function called Location manager didUpdateLocations and that receives messages and is called by the core location framework every time the user moves
    -object responsible for managing locations, and generating notifications of location change
50
Q

What is desired accuracy?

A
  • the appropriate level of accuracy (of our location) to return as there are multiple levels we can choose from and this affects the technology you use (and processing power required)
51
Q

What is augmented reality?

A

an enhanced version of reality
* How? - due to some technology-generated material
* AR objects are overlaid onto an image of reality (obtained from the device’s camera)
* Augmented material usually appears to be part of environment in which it is emplaced
* Size, position and effects of light and shadow are often (nearly) realistic and appropriate

52
Q

What are AR Challenges?

A

There are several technological challenges:
* Live video is required to project the graphics onto - app needs to display in real time what the user is looking at, and add the “augmented images” onto that video
* Positioning information required, to determine relative location of other artefacts that may be annotated
* Image analysis is required to identify cues to overlay graphics

53
Q

What are some of the outcomes of AR?

A
  • Using Augmented Reality apps in real world (on the go) scenarios can be hazardous!
  • Users can be lured into relying on the app to provide that awareness of their environment
  • However, this can restrict full awareness, or become fixated on details, and thus act in a dangerous, or unexpected way * e.g. loss of peripheral vision etc
54
Q

What are the features the ARKit package can provide?

A
  • Tracking - knowing where your device is pointing, it uses camera images and motion data and precise view of how it’s located and orientated.
  • Scene understanding - Determine property of the environment around the device. This provides: Plane Detection / Hit Testing / Light Estimation
  • looking at the environment of what you’re seeing through the camera. If you’re going to place an AR object in that area, you need to know where there are flat surfaces, etc…
    Plane detection, detects a table or a floor
    Hit testing which looks at whether your virtual object and the real objects are intercepting in some way
    Good AR pays attending to light interception, so the lighting and shadows in the room so it can mimic this.
  • Rendering - easy integration into any renderer
    Having figured out what you’re pointing at and what lighting is and where to place your object etc… you’ve then got to actually draw this AR object into the video stream.
55
Q

What is the difference between AR Passive vs Active Sensing

A
  • passive: camera and orientation
  • active: device can project patter of infra-red dots/lines and calculate the location of objects
56
Q

What are discovery architectures?

A

They support the dynamic real-time discovery and use of services offered by other devices
- Particularly important if you need to access devices while you’re out and about and you’re unlikely to have access to install a device driver.

57
Q

What do discoverable devices have the ability to:

A

*make other devices aware of its own existence. Don’t have to know they exist in advance, as they can broadcast information about their availability.
* To do this it advertises what services it offers
* bluetooth for example is a LAN protocol that supports a number of different types of services, it works for headphones, medical devices, bluetooth printers
* There’s lots of bluetooth profiles that support specific features of these individual devices.
* bluetooth is just one of the many mechanisms used for connectivity
* dynamically search and use other services

Requires zero administration or very little administration on your part
Interaction with other devices in the environment fulfils some goal, you usually connect with them to achieve some purpose, like speakers or a scanner etc…

58
Q

How are context and service discovery linked?

A

Many existing services rely on determining location, then searching for services relevant to that location

59
Q

What is universal plug and play

A

uses established standard (TCP/IP, UDP, HTTP) for networking, communication and broadcast
- used for transferring data between your device and supporting devices

60
Q

What can any device that’s set up for Upnp do?

A

*dynamically join a network and obtain an IP address
*announce themselves and convey their capabilities upon request, so they can say I am available and can provide these services.
*learn about the presence and capabilities of other devices

61
Q

What is DLNA?

A

Digital Living Network Alliance supports discovery and sharing of content across a home network

62
Q

What are the 4 types of devices?

A

Digital media servers (DMS)
*Serve content to other devices over the network

Digital media players (DMP)
*Discover content from DMS and allow you to playback and control that content

Digital media controllers (DMC)
*Control media sent to a DMR

Digital media renderers (DMR)
*Render content that is controlled by a DMC

63
Q

What is Zenconf/bonjour and why did it replace PnP?

A
  • plug and play used too much network bandwidth and wasn’t secure
  • *A set of technologies that automatically creates a usable computer network
    *Based on TCP/IP
    *Does not require manual intervention or special config servers, you just put them in a space and they’ll find other devices that are available
64
Q

What are the three core technologies zenconf is built on?

A

*Automatic assignment of network addresses for networked devices
*Automatic distribution and resolution of computer hostnames
*Automatic location of network services, such as printing devices

65
Q

What is Apple’s bonjour

A
  • Apple’s version of zenconf
  • The way it cuts down on presenting with too much information all at once is to reduce it and give you a hierarchy of what’s most important to see.
66
Q

What are the different types of contexts?

A

*Utility Context
*Locale Context
*Informative Context
*Productivity Context
*Immersive Context

67
Q

Describe utility context

A

Short, simple task-based scenarios
*e.g. calculator, weather forecast, *User provides minimal info either by fetching relevant info from a server, or performing a simple calculation, the relevant info is presented to the user.

*provides “at a glance” information
*focuses on presenting only the relevant info unambiguously
*avoids clutter, use minimal design aesthetic, focus on the content in view, often with large fonts and sparse layout.

68
Q

Describe Productivity context

A

Assist with heavier, task-based services
*User is focussed on performing a task, rather than glancing or consuming information
*Similar to using a tool on a desktop *e.g. managing email, contacts, plans etc

Information presented in a group or hierarchy format:
*should think how the user thinks about information
*order and priority of tasks, etc
*e.g. mail apps focus on inbox as a top priority item
*yet sending email is still important
* you’re presented with the most obvious default view

69
Q

Describe Locale context

A

Prominent due to location-based services.
Provides info given the user’s position
*tourist guides, location-based social networks, finder apps

Normally, a map is presented with the location of items plotted.
*Ordering is based on proximity
*Location of the user is important, and should be emphasised

70
Q

Describe Informative context

A

Goal is to provide info such as a news site
*User wants to read or browse, but not necessarily interact
*Used during brief idle times such as waiting for public transport
*Need to provide the option to bookmark or save story to read later, or flag favourites
-Aim to avoid having the user enter complex or lengthy data

71
Q

Describe Immersive context

A

COMP228 (4 decks)

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