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Geomatics > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

What is GPS

A

Global positioning systems

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2
Q

What is geomatics

A

Geographical analysis using computers, tying data with a particular place

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3
Q

What is the base before we split it into sections

A

Reality

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4
Q

What data can we add to gis maps!

A

Data labels and values

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5
Q

What is remote sensing?

A

Observing a particular feature from a distance

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6
Q

What is an example of remote sensing

A

Satellite data

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7
Q

Why is remote sensing seeing a rise in popularity

A

Drones and technology is becoming cheaper so starting to get rolled out on a larger scale

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8
Q

Who can generate their own remote sensing data

A

Anyone

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9
Q

What is the principle to gis

A

Network of orbiting stallites

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10
Q

What is the issue with old aciol maps

A

All the information is in one place/document hard to distinguish the data

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11
Q

What is the desire of change from gis

A

The desire to have more than one theme

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12
Q

Who discovered the cause of a cholera outbreak in London using rudimentary GIS

A

Jon Snow

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13
Q

What are the main GPS systems in use today?

A

NAVSTAR USA and Glonass Russia, also Galileo Europe

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14
Q

How many satellites are run by nav star

A

24, each with 12 hour orbit

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15
Q

How does a GPS find your location

A

Triagulates data from 3 points

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16
Q

How manny satellites are needed to calculate altitude

A

4

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17
Q

Is every GPS position 100% accurate

A

No

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18
Q

What is the standard error range for GPS location

A
    • 25m 95% of the time
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19
Q

What measures the accuracy of a GPS fix

A

Dilution of precision

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20
Q

What will some GPS systems do while you are collecting data

A

Give a constant DOP reading

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21
Q

What causes delays through the atmosphere

A

Ionisation as it passes through the atmospheres, some have a built in counter delay but this may not be accurate

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22
Q

What is signal multi path?

A

Multiple signals from the state lites which is bouncing of buildings,
No way of accounting for this apart from making sure you can see as many satellites as possible and move into an open space

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23
Q

What is a receiver clock error?

A

Clocks on phones may be out compared with the atomic clock, meaning any time differences would screw up data

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24
Q

What are orbital errors

A

Satellite orbit can get out of sync so data might be screwed

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25
Q

Why might people manually turn down or distort satellite signal,

A

Selective availability, US used it to stop enemies using their satellites or finding out about military bases ect, terminated in 2000 which improved civilian reception

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26
Q

How can we improve gps accuracy?

A

Use systems such as differential GPS, uses 2 receivers rather than just one

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27
Q

How does differential GPS work

A

Error and position should be accurate for both receivers, if they are not you subtract the error for our fixed base station from GPS receiver

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28
Q

What is vector data

A

The simplest forms of data, points lines polygons and surfaces

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29
Q

What is topology

A

How different data fit together and overlap

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30
Q

What does GIS use

A

Spatial data

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31
Q

What is the most basic form of spatial data?

A

The point, position lat long ect

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32
Q

What separates out data in gis

A

IDs

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33
Q

What is data in a single table in gis called

A

A flat file

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34
Q

What is the negative with a flat file

A

Very useful but very simple

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35
Q

What can points be turned into

A

Lines or shapes

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36
Q

How does heywood describe topology?

A

How spatial data is related to each other based on what it’s next to what is within bits of data

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37
Q

What are the 3 layers to. Topology

A

Adjacency, containment and connectivity

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38
Q

What is the goal in showing topology data?

A

Most amount of information with limited amount of data

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39
Q

Why else can we show in data points

A

Size of the data points could show size of the city or place

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40
Q

In line data what is each circle or point called?

A

A node, the line is the link

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41
Q

What is the valency of the node

A

The number of points at the node, a crisis road would be 4 valent

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42
Q

What are the 2 different types of data associated with polyline

A

Link data, one way streets, number of motorway lanes l, attaching data to individual points,
Node data, where roads meet eg roundabout crossroad

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43
Q

What are polyline networks

A

Say what is flowing into what, requires good attribute data, data about road networks, Behind satellite data on gps

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44
Q

What is polygon data

A

Lines connected together to make a shape

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45
Q

Why can polygon data be used for?

A

Representing postcodes countries

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46
Q

What are the types of construction of polygon data

A

Island eg woods, adjacent eg countries and nested eg contour lines

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47
Q

What can be shown as an individual surface

A

Elevation, rainfall, temperature, population ect

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48
Q

What are the main advantages of vector data

A

Data is compact, effecient, well suited for map output, resolution can be independent of detail

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49
Q

What are the problems with vector data

A

When would you use a specific point/polygon, what one user requires will be different to the other

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50
Q

What is raster data

A

A grid of numbers, can show different sorts of data, especially spatially continuous

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51
Q

What do analysis on rasters create

A

Secondary products or derivatives

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52
Q

What is each imagine made up of

A

A series of numbers

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53
Q

What determines raster quality

A

Resolution

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54
Q

Where is raster data normally displayed

A

Behind other data normally to an extent transparent

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55
Q

What is the negative with raster data

A

Can skew specific points

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56
Q

What happens when we convert from raster and vector vice versa

A

Start to loose information

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57
Q

What is raster good at showing

A

High spatial variability l, simple data structure, overlay options are straight forward

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58
Q

What are dtms

A

Digital terrain models

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59
Q

What is the main place where dtms come from

A

Satellites

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60
Q

Why derivatives can we make from dtm

A

Steepness of slope, which way it’s facing

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61
Q

What can we get if we draw a line over height raster data?

A

Graph of altitude

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62
Q

What is TIN

A

Triangular irregular network, good for visualisation

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63
Q

When were data based developed

A

1950’s and 60 by ibm in response to the amount if data that is needed to be stored

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64
Q

What is a database?

A

A collection of data usually stored as single or multiple files

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65
Q

What is a DBMS

A

Database management system, a set of computer programs for organising information at the core of which is a database

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66
Q

What does the database allow us to do

A

Access files from and small space while having lots of storage space

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67
Q

What is at the heart of any gis program

A

DBMS

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68
Q

What is the main advantage of a database

A

The data that we are storing is physically separate to what we are doing with it

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69
Q

By changing the information on screen what are we not doing to the underlying database

A

Changing it, remains static, altering the way that we are viewing the database

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70
Q

What is the user advantage of a database

A

The user does not need to know how the data is stored

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71
Q

By altering the underlying data base what does this do to the overall map

A

Changes it for us

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72
Q

What is the cost advantage with databases

A

Reduced software development costs

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73
Q

Is the database secure

A

Yes

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74
Q

Can the data base be views singularly or multiple times

A

Multiple

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75
Q

What are the main advantages of databases?

A

Reduced data redundancy, enables maintenance in data quality and integrity,
Data self documented, consistent

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76
Q

What is data redundancy

A

How the data is used, in data bases we can use data that can be used in multiple projects

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77
Q

What is attribute data

A

Geographic information such as spatial location at that point

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78
Q

What sort of attribute data can be associated with roads

A

Classification, width, flow

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79
Q

What sort of attribute data can be associated with soils

A

Colour, texture organic matter ect

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80
Q

What sort of attribute data can be associated with weather

A

Temperature, precipitation, wind ect

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81
Q

What sort of attribute data can be associated with rivers

A

Discharge,

Velocity, width ect

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82
Q

What is attribute data also referred as

A

Aspatial data, constraints with the geographic coordinates

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83
Q

What do we need to do with aspatial and spatial coordinates

A

Combine them within a database

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84
Q

What is floating point data

A

Decimals

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85
Q

What are integers

A

Nominal ordinal or interval

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86
Q

What is a domain

A

Set to controls the range, eg temperature -50 to +50 degrees

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87
Q

What is another name for records

A

Tuples

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88
Q

Why are non data components

A

Operations, user function- Data language, used to describe data base contents-query language Standard language used to edit

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89
Q

What is the most simple data model?

A

A flat file

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90
Q

What are the negatives to a flat file

A

Very simplistic cannot deal with relationships between objects

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91
Q

What happens if two sets of data a stored seperatly in a shape file

A

Cannot tell us how they interlinked

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92
Q

What is a relational data model

A

Use the IPs to create linkages between the data files

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93
Q

Why do data based sometimes cause issues

A

Not designed for GIS

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94
Q

With gis data what happens with the files

A

All linked together which makes the gis data

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95
Q

What is a shp file

A

Tells us of the geometry of the file

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96
Q

How many files do shapfiles have at least

A

3

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97
Q

What is a DBF file

A

Attribute data

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98
Q

What is a sbx file

A

Index of the feature of geography

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99
Q

What are GRID files

A

Raster data

100
Q

What is a grid file made up of

A

Aux file and adf file

101
Q

What is arccatalog

A

Seperate software to arcmap, took for exploring and managing data

102
Q

What does arc catalog look at?

A

Not individual pieces of data but groups of files

103
Q

What is meta data?

A

Data which tells us about the data itself

104
Q

Give an example of the way that a library would use meta data?

A

Authors, Titles, ISBN numbers. Subject

105
Q

Who attempted to standardise meta data?

A

Federal geographic saga committee,

But deemed too complicated

106
Q

What standards are now used for meta data

A

Light meta data,

107
Q

What is the description of light meta data

A

Title, keywords, abstract purpose

108
Q

What is spatial data within meta data

A

Bounding coordinates

109
Q

What examples of attribute meta data is there

A

What other data in the database

110
Q

Where do most of our data sources come from

A

The internet, vector data, digital models, satellite imigary

111
Q

How could you collect your own data?

A

Ground surveys

112
Q

What are some steps between data capture and gis data base

A

Editing, re projection, generalisation, edge matching, layering

113
Q

What often shapes a GIS project

A

The data available

114
Q

What is the name given to the place where data is stored on the internet

A

Geo libraries

115
Q

What does data sometimes come in

A

A raw format, conversion into esri, processing within arccatelog

116
Q

What are governments currently doing with data?

A

Trying to make it more accessible

117
Q

What is arc gis online

A

Ads base maps and other things within gis, individual pieces of raster data, hosted by ESRI

118
Q

What compromise might we make in free online data

A

Lower resolution data, data only part processed

119
Q

What data that can be obtained online can show the whole world

A

Raw satellite data

120
Q

What is the advantage of satellite data

A

Can show remote places not often looked at

121
Q

Where does most free satellite data come from

A

USGS/NASA or Glovis

122
Q

What is the first processing you will need to do with satellite data

A

Unzip uncompressed it

123
Q

What will you have to do to satellite data

A

Reproject it

124
Q

What are the key features of digimap

A

Higher resolution maps are available, some data is vector so can be manipulated online

125
Q

Give an example of vector data

A

Strategi, meridian, vectormap, mastermap

126
Q

What resolution are landranger maps

A

1:50000

127
Q

What is NTF

A

Neutral transfer format, more of a raw format

128
Q

How do we use NTF

A

Need to convert it

129
Q

What does DTM come in

A

ASCII

130
Q

What is Photogrammetry?

A

Used aerial photographs, method of remote sensing , dates back to ww2 use

131
Q

What is photogrammetry good for

A

Assessing changes over time, can create 3s images,

Wide area views, high spatial resolution

132
Q

What is the negatives with photogrammetry

A

Difficult to find online,

No spatial referencing, scale varies across the image

133
Q

How would you fix photogrammetry in terms of spatial referencing

A

Would need some geo referencing

134
Q

In terms of the plane, what impact does altitude have

A

Different heights effects scales of the image

135
Q

What is it called where we create 3D images from Ariel 2d photos

A

Stereo imaging

136
Q

What has enabled the increase of stereo imaging

A

Increased availability of drones ect

137
Q

What are the features of digitising other peoples maps

A

Quite easy but time consuming

138
Q

What are the two main processes to digitisation of maps

A

Manual and automatic

139
Q

What are the two modes of manual digitisers

A

Point mode, lines are generalised as a series of points from the user, stream mode, liners are generalised using a series of points set at time intervals

140
Q

What are sources of error

In manual digitising

A

Shaky hands, elements wrongly perceived, line thickness, generalisation

141
Q

What do we use in automatic digitisation

A

A scanner

142
Q

What are the sources of error for automatic data

A

Same as manual plus, optical distortion, scanning unwanted info, still slow, could be poor resolution

143
Q

What is remote sensing

A

Capturing data remotely, eg satellites

144
Q

What is the main type of remote sensing

A

Satellite remote sensing

145
Q

How does satellite remote sensing work

A

Radiation is dense by satellite that is emitted from the surface

146
Q

What bodies emit radiation

A

Anything that is warmer than -273 Celsius

147
Q

What does most remote sensing focus on

A

Electromagnetic radiation

148
Q

Why might we want to use different wave lengths and sensors

A

Because they can detect and show us a different image

149
Q

If some thing is blue what is happening

A

Blue light is reflected all other colours are absorbed

150
Q

Why is looking beyond the visible range useful

A

Doing detection of what is going on at he earths surface

151
Q

How can electromagnetic sensing help for identifying objects

A

Thing in pictures that look the same can be differentiated using EM

152
Q

What do all satellites have on board

A

A range of sensors

153
Q

What can certain satellites do with detecting gravity

A

Look at changes in ground water (grace)

154
Q

What are the most commonly used satellites

A

Polar orbiting- Landsat, AVHRR, MODIS, Geostationary- Meteosat and GOES

155
Q

What satellite uses vegetation in the visible and inferred spectrum

A

MODIS

156
Q

If statellites do not take images what do they do

A

They build up raster data via a swath width

157
Q

What varies between satellites

A

Resolution size

158
Q

Which satellite uses a much smaller pixel size

A

SPOT

159
Q

What size pixels do lansat use

A

30meters

160
Q

What is the typical Rasta range for an 8 bit system

A

0-255

161
Q

How many TM bands does the new Landsat have

A

13

162
Q

What can penetrate cloud cover with satellites

A

Infra red

163
Q

How can we use stallities to create more detailed images

A

Combining satellite bands

164
Q

Why can Landsat sometimes be bad for GIS

A

Can’t distinguish between some land features

165
Q

How are DTMs created

A

Remote sensing techniques

166
Q

What do DTMs create o

A

Very high resolution data sets

167
Q

How do DTMs collect data?

A

Space craft or upper orbit aircraft, side looking camera sends pulses which bounces back

168
Q

What are the advantages to remote sensing

A

Unlimited rescources with good spatial resolution, observations are unbiased

169
Q

What are the disadvantages to remote sensing

A

Expensive, does not produce measurements,

170
Q

Why is there loads of room for error in remote sensing

A

Complexity

171
Q

What are the two types of error with remote sensing

A

Radio metric and geometric

172
Q

What are radio metric errors

A

Anything that stops data reaching sensors, cloud and haze, could be problems with the sensor, could be problem with processed that calculates the image,

173
Q

What are atmospheric corrections

A

Making corrections for cloud and haze ect

174
Q

What eve lengths are less effected in haze

A

Long

175
Q

What are random sensor errors

A

Bit errors

176
Q

What are systematic radiometroc errors

A

Eg software malfunctions like corrector error Landsat

177
Q

Why was the Landsat systematic error

A

Lines needed to be pushed back into line, skew correction

178
Q

What are geometric errors

A

The problem with the shape of the earth is the problem

179
Q

What does geometric errors occur

A

Different heights of recording can create image distortion

180
Q

What do edges of remote sensing maps need to go though

A

Edge matching to create a transitions between the two

181
Q

Why is it easier to change raster data that has become distorted

A

Easier to squeeze and push the image around

182
Q

What is it harder to warp vector data

A

Hard to chew it while remaining solid topology

183
Q

What is georegistation

A

Series of control points, pick out points in image and slide it over with control points,
Adjusting a map to the geographic location of a known good map

184
Q

What is the negative with using landscapes for georegistration

A

The landscape can change over time eg rivers

185
Q

What are good control points

A

Trains tracks, City land marks, things that are fixed through time

186
Q

What is rubber sheeting

A

Adjust features in a non uniform manner

187
Q

How do we make a rubber sheeting more accurate

A

More ground control points,

Need to be spread out as well

188
Q

As a rule of thumb how should elements be digitised

A

In order of complexity m, points lines then polygons

189
Q

What do we need to do for manual editing

A

Generalise each element into a series of points, that line represents that street so you can then add attribute data such as the street

190
Q

What is automatic vectorisation

A

System finds lines automatically, digitises automatically

191
Q

What is quality

A

Factor used in GIS metadata,

9 key parameters

192
Q

What is accuracy

A

The ability to get the correct answer, when estimates value approaches it’s true value

193
Q

What is precision.

A

How repeatable it is to get the correct answer, or defined, eg lots of decimal spaces

194
Q

What is bias in data quality

A

Is there systematic variation of data

195
Q

What is resolution in data quality

A

Resolution of raster data sheets

196
Q

What is completeness of data quality

A

Means the data set is complete both temporally and spatially

197
Q

What is data combatability

A

Consistent data scale and coordinate system

198
Q

What is data consistency

A

Did different people collect the same data or is it different, had biased been reduced

199
Q

What is applicability

A

Can the data set be used to solve the problem

200
Q

What is the process called where we remove errors

A

Data cleaning

201
Q

Which errors are easy to spot

A

Attribute data, spatial errors are harder to spot

202
Q

What are common spatial data errors

A

Missing entities, eg roads. Duplicate entries, mis locates entities, noise irrelevant data

203
Q

What are artifacts of digitisation

A

Undershoots or over shoots, wrongly placed nodes, loops

204
Q

What is a conceptual error

A

How we perceived what is being mapped

205
Q

What are source data errors

A

Maybe the original cartographer made and error and maybe we are just copying that

206
Q

What can happen by mismtake in data cleaning

A

Intentional gaps can be destroyed creating more errors

207
Q

What is the basic problem with converting the earth to maps

A

The world needs to be treated as a flat surface

208
Q

What is the most common projection for theUK

A

Mercator

209
Q

In a normal cyclindrical projection what becomes distorted

A

The poles become bigger and equator is smaller

210
Q

What is the main example of distortion on Mercator

A

Greenland vs Africa, look the same size but africa is 14x bigger

211
Q

Why was the Mercator often used

A

Made Europe and the uk look bigger

212
Q

What is azimuthal map projection

A

Put onto a circle, shape preserved in the middle well but not on the outsides

213
Q

What does azimuthal preserve

A

Distance

214
Q

Give an example of a map that preserves area

A

Werner projection

215
Q

What is conic projection

A

Displayed on a cone, scale is preserved but area and distance is distorted

216
Q

What map projection do sattelites use

A

Sinusoidal, preserves area storage shape

217
Q

What are the two main methods of spatial referencing

A

Geographic coordinate systems and rectangular coordinate systems

218
Q

What is the idea with rectangular coordinates

A

Map is made by projecting lines of lag and Long onto a flat surface, errors are smaller on smaller scale maps

219
Q

What is a graticule

A

Grid

220
Q

What is the projection that the British national grid is based on

A

Transverse Mercator

221
Q

How many grids in the British national grid

A

700x1300,

First divided into 100 squares

222
Q

How can lidar determine trees

A

Not all of the lidar rays will go through, sattelite then knows these are trees

223
Q

What is a surface o

A

A continuous variation is space of a 3rd dimensional terrain

224
Q

How can we display 3D surfaces in gis

A

Wire diagram which shows a developed terrain

225
Q

What can be draped over a wire grid on gis

A

An image

226
Q

What is surface analysis

A

Creating a new output from one or more input rasters

227
Q

What is constraint stretching

A

Increase or change the range fan raster image, enables more detail to be seen

228
Q

What is reclassification

A

Change cell value to isololate particular bands so we can see certain aspects more clearly

229
Q

What are neibourhood functions

A

Look at what’s close in raster and use it to influence data around it, can filter and smooth the data

230
Q

What are the two data types in neibourhood functions

A

Proximity and filtering

231
Q

Why is it hard to calculate distance across rasters

A

Depending on the pixel size and if you draw a line through the raster

232
Q

Why is neibourhood function useful

A

Can be used to filter data to make it more manageable, filer can be in size shape or function

233
Q

What are applications for neibourhood data

A

Smoothing of noisy data, image sharpening edge detection

234
Q

What are some DEm derivatives

A

Slope, aspect, hillshade

235
Q

What si aspect

A

Direction thy a slope faces

236
Q

What is a kernel

A

5 cells

237
Q

What are view sheds

A

Show what can be seen from distance, used for planning wind turbines

238
Q

What makes multiple raster analysis easier

A

Using from the same data, eg Landsat

239
Q

How can u make a composite imagine using bands

A

Combine 3 blue red green to make full colour

240
Q

What is surface draping

A

Name given when a surface is overlain by another Layer, eg satellite imagery, adds mid geographic detail, geology cities forests

241
Q

What are the 2 methods of satellite land classification

A

Unsupervised and supervised

242
Q

What is unsupervised classification

A

Compute does the work, you decide how many clusters, computer picks up and divids clusters

243
Q

What is supervised classification

A

Need to train the pc, use field work to identity pixels to teach the computer

244
Q

What is mapematics

A

Intergrating rasters together to create more detailed maps

245
Q

What is the most simple analysis with vector data

A

Measurement,

Uses phythagorus

246
Q

What is a querie

A

Can query aspatial data, ask questions about the attribute data, eg how many universities are in the West Midlands. Or add a scale within 50km

247
Q

What is buffering

A

Drawing a box around the area of interest to see what’s in that zone,

Geomatics (1 decks)

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