1
00:00:01,870 --> 00:00:03,640
- [Instructor] Hi, welcome to week two

2
00:00:03,640 --> 00:00:05,570
of Remote Sensing Foundations.

3
00:00:05,570 --> 00:00:07,510
This week we will talk
about sensors on the ground

4
00:00:07,510 --> 00:00:08,970
and in the sky.

5
00:00:08,970 --> 00:00:10,250
At the end of this week

6
00:00:10,250 --> 00:00:12,320
I hope you'll be able
to describe some types

7
00:00:12,320 --> 00:00:13,800
of remote sensing imagery

8
00:00:13,800 --> 00:00:16,810
and how they differ in spatial
and temporal dimensions,

9
00:00:16,810 --> 00:00:19,020
access and understand how to query

10
00:00:19,020 --> 00:00:21,600
the Earth Engine catalog of data,

11
00:00:21,600 --> 00:00:24,920
including, finding an
understanding about metadata

12
00:00:24,920 --> 00:00:26,910
for a data set of interest,

13
00:00:26,910 --> 00:00:29,630
and also know how to
draw points and polygons

14
00:00:29,630 --> 00:00:32,130
to map a place of interest
in Google Earth Engine.

15
00:00:34,490 --> 00:00:36,600
This semester we have
the unique opportunity

16
00:00:36,600 --> 00:00:40,080
to use a working draft of a new
Google Earth Engine textbook

17
00:00:40,080 --> 00:00:41,700
called "Cloud-Based Remote Sensing

18
00:00:41,700 --> 00:00:43,480
with Google Earth Engine."

19
00:00:43,480 --> 00:00:45,550
Because I am an author
of a chapter in this book

20
00:00:45,550 --> 00:00:47,310
the editors of the book
have given us permission

21
00:00:47,310 --> 00:00:49,960
to test drive the chapters and tutorials.

22
00:00:49,960 --> 00:00:51,720
I will be assigning
some readings from here

23
00:00:51,720 --> 00:00:53,190
and I would like you to follow along

24
00:00:53,190 --> 00:00:54,380
with the code tutorials,

25
00:00:54,380 --> 00:00:57,333
especially as we get underway
in using Google Earth Engine.

26
00:00:58,430 --> 00:01:01,990
Please don't be intimidated
by the amount of reading

27
00:01:01,990 --> 00:01:04,210
that it appears that I am assigning.

28
00:01:04,210 --> 00:01:06,850
I can assure you that
it's not that much text.

29
00:01:06,850 --> 00:01:09,840
Really what takes up a lot
of space on all these pages

30
00:01:09,840 --> 00:01:11,670
are the tutorials themselves

31
00:01:11,670 --> 00:01:15,867
because they are shown
in big blocks of visuals

32
00:01:17,670 --> 00:01:20,230
and include the code
that you will be entering

33
00:01:20,230 --> 00:01:23,350
in your code editor in
Google Earth Engine.

34
00:01:23,350 --> 00:01:26,220
This week, we will be taking a look at

35
00:01:26,220 --> 00:01:29,230
F1 Programming and Remote Sensing Basics,

36
00:01:29,230 --> 00:01:31,770
and specifically at chapter F1.0,

37
00:01:31,770 --> 00:01:34,500
JavaScript and the Earth Engine API,

38
00:01:34,500 --> 00:01:37,663
and also F1.1, Exploring Images.

39
00:01:39,120 --> 00:01:41,410
I'm confident that the amount of reading

40
00:01:41,410 --> 00:01:45,080
that has been assigned in this
week will not take too long

41
00:01:45,080 --> 00:01:48,560
and hopefully you will
gain a good understanding

42
00:01:48,560 --> 00:01:52,530
of how to work with Google
Earth Engine Code Editor

43
00:01:52,530 --> 00:01:54,560
and how to go about searching

44
00:01:54,560 --> 00:01:59,303
through the catalog of
images that Earth Engine has.

45
00:02:01,290 --> 00:02:02,950
By way of a little review,

46
00:02:02,950 --> 00:02:05,350
last week we touched
briefly on particle energy

47
00:02:05,350 --> 00:02:06,620
and how it can be organized

48
00:02:06,620 --> 00:02:09,530
and understood in terms of
the electromagnetic spectrum,

49
00:02:09,530 --> 00:02:10,920
which is the entire distribution

50
00:02:10,920 --> 00:02:14,110
of electromagnetic radiation
according to the wide range

51
00:02:14,110 --> 00:02:17,060
of frequencies, wavelengths,
and photon energies.

52
00:02:17,060 --> 00:02:20,640
The top left figure helps us
understand that what we measure

53
00:02:20,640 --> 00:02:22,780
and with remote sensing is energy

54
00:02:22,780 --> 00:02:25,620
and how energy transmits from a surface.

55
00:02:25,620 --> 00:02:27,980
We understand that the
main source of radiation

56
00:02:27,980 --> 00:02:30,680
that is incident on our
planet comes from the sun,

57
00:02:30,680 --> 00:02:33,700
which emits a broad spectrum
of electromagnetic energy

58
00:02:33,700 --> 00:02:37,030
from long wave microwave
to short wave ultraviolet.

59
00:02:37,030 --> 00:02:39,220
How we measure the sun's radiation depends

60
00:02:39,220 --> 00:02:41,030
on what sensor we use

61
00:02:41,030 --> 00:02:43,180
and on how the radiative energy behaves

62
00:02:43,180 --> 00:02:44,640
as it moves through our atmosphere

63
00:02:44,640 --> 00:02:47,140
to the surface of interest
and back to the sensor.

64
00:02:48,320 --> 00:02:51,680
All the types of radiation,
or energy, coming from the sun

65
00:02:51,680 --> 00:02:55,590
composed of what is in
the visible range of light

66
00:02:55,590 --> 00:02:57,850
and outside of what the human eye can see

67
00:02:57,850 --> 00:02:59,470
has the potential to be absorbed,

68
00:02:59,470 --> 00:03:01,510
scattered, reflected, transmitted,

69
00:03:01,510 --> 00:03:02,820
and also emitted

70
00:03:02,820 --> 00:03:05,430
as it travels from the
source to the sensor.

71
00:03:05,430 --> 00:03:07,800
Satellites measure what travels back

72
00:03:07,800 --> 00:03:10,180
from the source to the sensor,

73
00:03:10,180 --> 00:03:13,430
and these images must then
be processed with algorithms

74
00:03:13,430 --> 00:03:15,723
that account for the
atmospheric conditions.

75
00:03:16,960 --> 00:03:19,110
We can use the spectral signatures

76
00:03:19,110 --> 00:03:20,840
of how different surfaces absorbed

77
00:03:20,840 --> 00:03:25,030
and reflect different wavelengths
of energy to interpret

78
00:03:25,030 --> 00:03:27,920
what we are seeing on
the ground from space.

79
00:03:27,920 --> 00:03:31,140
Finally, the type of sensor
that we use to determine

80
00:03:31,140 --> 00:03:33,810
what, when and how we
detect spectral signatures

81
00:03:33,810 --> 00:03:35,063
on the Earth's surface.

82
00:03:36,800 --> 00:03:40,533
Active sensors use an
artificial source of energy.

83
00:03:41,530 --> 00:03:44,160
The satellite itself can
send a pulse of energy

84
00:03:44,160 --> 00:03:47,810
which can interact with a target surface.

85
00:03:47,810 --> 00:03:50,800
Essentially humans can control
the nature, wavelength,

86
00:03:50,800 --> 00:03:53,890
power, and duration of the source energy.

87
00:03:53,890 --> 00:03:57,080
An example of an active
sensor type is called LIDAR,

88
00:03:57,080 --> 00:03:59,160
or Light Detection and Ranging.

89
00:03:59,160 --> 00:04:01,610
These sensors send out
a pulse of laser light

90
00:04:01,610 --> 00:04:04,390
and record the reflectance
back to the instrument.

91
00:04:04,390 --> 00:04:07,040
We can then use data to
construct height profiles

92
00:04:07,040 --> 00:04:10,750
of forest canopy, ice and
other surface features.

93
00:04:10,750 --> 00:04:12,230
Passive sensors on the other hand,

94
00:04:12,230 --> 00:04:14,560
record the natural
energy that is reflected

95
00:04:14,560 --> 00:04:17,440
or emitted from the Earth's surface.

96
00:04:17,440 --> 00:04:19,900
Landsat is a well known
example of a passive sensor

97
00:04:19,900 --> 00:04:22,860
that has mapped the Earth's
surface for over 40 years.

98
00:04:22,860 --> 00:04:25,370
The downside of passive sensors

99
00:04:25,370 --> 00:04:27,350
is that they typically only measure

100
00:04:27,350 --> 00:04:29,493
during the daytime and in good weather.

101
00:04:31,790 --> 00:04:34,620
Remote sensing is a tool
that is particularly helpful

102
00:04:34,620 --> 00:04:37,570
to characterize the Earth's
biophysical environment,

103
00:04:37,570 --> 00:04:40,900
including variables related
to habitat, climate change,

104
00:04:40,900 --> 00:04:43,570
and human modification of VR systems,

105
00:04:43,570 --> 00:04:45,543
as well as vegetation,
composition, function,

106
00:04:45,543 --> 00:04:48,440
phenology, physiology, and morphology.

107
00:04:48,440 --> 00:04:50,740
These observations require integration

108
00:04:50,740 --> 00:04:53,820
with the biological understanding gained

109
00:04:53,820 --> 00:04:57,230
from the vast advances in
biological methods and tools

110
00:04:57,230 --> 00:04:59,440
for observing the many dimensions

111
00:04:59,440 --> 00:05:01,500
of life above and below ground.

112
00:05:01,500 --> 00:05:03,530
Here, we can see an example

113
00:05:03,530 --> 00:05:07,120
remote sensing data layer
shown at a spatial grain

114
00:05:07,120 --> 00:05:10,231
of one kilometer and
extent of 40 kilometers,

115
00:05:10,231 --> 00:05:14,180
from left to right on the
top left side of the figure.

116
00:05:14,180 --> 00:05:16,460
The environment, function, phonology,

117
00:05:16,460 --> 00:05:18,340
physiology and morphology.

118
00:05:18,340 --> 00:05:21,630
We can also think of
the temporal variations

119
00:05:21,630 --> 00:05:23,710
as shown across the top right,

120
00:05:23,710 --> 00:05:27,553
from hourly and daily to
seasonal, annual and decadal.

121
00:05:31,450 --> 00:05:34,160
Finally, I wanted to show
you this interesting figure

122
00:05:34,160 --> 00:05:38,090
from Levizzani and Cattani from 2019.

123
00:05:38,090 --> 00:05:39,240
This figure depicts many

124
00:05:39,240 --> 00:05:42,400
but perhaps not even all of the tools

125
00:05:42,400 --> 00:05:45,193
that we humans utilize to
remotely sense our world.

126
00:05:46,510 --> 00:05:48,710
Though we will not delve into each

127
00:05:48,710 --> 00:05:49,920
and every one of these tools,

128
00:05:49,920 --> 00:05:51,360
I wanted to put this here

129
00:05:51,360 --> 00:05:53,930
to show you how many
remote sensing data tools

130
00:05:53,930 --> 00:05:56,760
we use on a daily basis
without much deep thought

131
00:05:56,760 --> 00:05:59,960
about how they are
measured, what they measure

132
00:05:59,960 --> 00:06:02,780
and how it can be used in conjunction

133
00:06:02,780 --> 00:06:04,180
with other data sets,

134
00:06:04,180 --> 00:06:05,410
either directly measured

135
00:06:05,410 --> 00:06:07,780
or derived to gain a deeper understanding

136
00:06:07,780 --> 00:06:09,520
of the world in which we live.

137
00:06:09,520 --> 00:06:11,710
I wanted to put these
last two figures in here

138
00:06:11,710 --> 00:06:13,270
to hopefully spark your interest

139
00:06:13,270 --> 00:06:15,810
and perhaps plant a seed in your thinking

140
00:06:15,810 --> 00:06:18,660
about what you might wanna
do your semester project on

141
00:06:18,660 --> 00:06:20,640
because literally the sky, or technically,

142
00:06:20,640 --> 00:06:22,090
beyond the sky, is the limit.

143
00:06:25,220 --> 00:06:27,580
There are many types of sensors out there.

144
00:06:27,580 --> 00:06:31,300
Here is one example of a
satellite series of sensors.

145
00:06:31,300 --> 00:06:32,910
Beginning in the mid 1960s,

146
00:06:32,910 --> 00:06:34,980
the US began an effort to develop

147
00:06:34,980 --> 00:06:38,370
and launch the first civilian
earth observation satellite.

148
00:06:38,370 --> 00:06:41,220
This is when the Earth
Resources Technology Satellite,

149
00:06:41,220 --> 00:06:43,230
or Landsat, was born.

150
00:06:43,230 --> 00:06:46,440
There have been eight
Landsat missions to date

151
00:06:46,440 --> 00:06:48,470
with the first beginning in 1972

152
00:06:48,470 --> 00:06:50,460
with the launch of Landsat 1.

153
00:06:50,460 --> 00:06:54,240
Currently Landsat 7 and
8 are still operating.

154
00:06:54,240 --> 00:06:59,240
Landsat 7 was launched in 1999
and 8 was launched in 2013.

155
00:06:59,670 --> 00:07:02,330
There's also a Landsat 9 mission planned

156
00:07:02,330 --> 00:07:05,263
for launch later this
year or early next year.

157
00:07:10,210 --> 00:07:12,160
The Landsat mission example provides us

158
00:07:12,160 --> 00:07:13,710
with a good opportunity to talk about

159
00:07:13,710 --> 00:07:15,253
a number of different sensors.

160
00:07:17,520 --> 00:07:19,410
Landsat missions have different sensors

161
00:07:19,410 --> 00:07:21,280
which measure in slightly
different regions

162
00:07:21,280 --> 00:07:23,310
of the electromagnetic spectrum.

163
00:07:23,310 --> 00:07:24,520
Do you remember from last week

164
00:07:24,520 --> 00:07:26,790
whether the Landsat
satellites contain active

165
00:07:26,790 --> 00:07:27,973
or passive sensors?

166
00:07:29,270 --> 00:07:31,460
Okay, so Landsats 1, 2, and 3

167
00:07:31,460 --> 00:07:33,720
had a multi-spectral scanner aboard.

168
00:07:33,720 --> 00:07:35,120
If you remember from last week

169
00:07:35,120 --> 00:07:38,100
a multi spectral scanner
is a passive sensor

170
00:07:38,100 --> 00:07:40,940
that distinguishes and measures
a range of spectral bands.

171
00:07:40,940 --> 00:07:44,603
Landsats 4 and 5 contain
a thematic mapper.

172
00:07:45,561 --> 00:07:48,500
This is a related sensor type

173
00:07:48,500 --> 00:07:50,390
but includes more spectral bands,

174
00:07:50,390 --> 00:07:52,970
including the NIR infrared
and the short wave infrared,

175
00:07:52,970 --> 00:07:53,920
also known as SWIR.

176
00:07:56,410 --> 00:07:59,080
Landsat 7 senses an additional band.

177
00:07:59,080 --> 00:08:03,403
So it was named ETM+, or the
Enhanced Thematic Mapper Plus.

178
00:08:05,030 --> 00:08:06,940
Landsat 8 has ETM+

179
00:08:06,940 --> 00:08:10,670
but also contains the addition
of a Thermal Infrared Sensor.

180
00:08:10,670 --> 00:08:13,200
It measures 11 bands overall.

181
00:08:13,200 --> 00:08:15,190
If you look at the figure
at the bottom right,

182
00:08:15,190 --> 00:08:17,530
you can get a sense of
where each Landsat measures

183
00:08:17,530 --> 00:08:19,543
across the spectrum of wavelengths.

184
00:08:24,030 --> 00:08:25,980
In order to understand

185
00:08:25,980 --> 00:08:27,960
what different satellite
sensors can measure

186
00:08:27,960 --> 00:08:30,880
we must understand what
resolution they operate at.

187
00:08:30,880 --> 00:08:32,520
There are a number of
different resolutions

188
00:08:32,520 --> 00:08:34,040
that we must consider.

189
00:08:34,040 --> 00:08:36,170
First, the spatial resolution of a sensor

190
00:08:36,170 --> 00:08:37,890
is essentially the size of a pixel

191
00:08:37,890 --> 00:08:40,290
when that sensor's data is mapped.

192
00:08:40,290 --> 00:08:42,600
It is a size of the smallest area

193
00:08:42,600 --> 00:08:46,000
that can be separately recorded
as an entity on an image.

194
00:08:46,000 --> 00:08:48,160
It is also the distance between patterns

195
00:08:48,160 --> 00:08:50,070
or objects in an image

196
00:08:50,070 --> 00:08:52,190
that can be separated from each other.

197
00:08:52,190 --> 00:08:54,670
Spatial resolution is
often expressed in meters

198
00:08:54,670 --> 00:08:56,120
but can be expressed in finer

199
00:08:56,120 --> 00:08:57,720
or coarser measurements as well.

200
00:08:58,940 --> 00:09:00,130
At the bottom right

201
00:09:00,130 --> 00:09:03,160
the resolution of a Landsat
image is around 30 meters.

202
00:09:03,160 --> 00:09:05,980
At 30 meter resolution,
two adjacent objects,

203
00:09:05,980 --> 00:09:09,300
30 meters long or wide can
be separated or distinguished

204
00:09:09,300 --> 00:09:10,203
by the human eye.

205
00:09:11,100 --> 00:09:14,480
On the bottom left, we
see a coarser MODIS image

206
00:09:14,480 --> 00:09:16,280
of the same region of interest.

207
00:09:16,280 --> 00:09:18,600
Here the pixel size is 250 meters.

208
00:09:18,600 --> 00:09:20,020
And so it's harder to distinguish

209
00:09:20,020 --> 00:09:21,633
individual building structures.

210
00:09:24,570 --> 00:09:27,830
Temporal resolution is also
known as the revisit period

211
00:09:27,830 --> 00:09:29,420
or the length of time for a satellite

212
00:09:29,420 --> 00:09:31,830
to complete an entire orbit cycle.

213
00:09:31,830 --> 00:09:34,630
It's basically the time it
takes for a satellite to return

214
00:09:34,630 --> 00:09:37,790
to approximately the
same location in space.

215
00:09:37,790 --> 00:09:41,700
For instance, for Landsat,
this is a 16 day period.

216
00:09:41,700 --> 00:09:43,630
Revisit periods are dependent

217
00:09:43,630 --> 00:09:45,470
on the orbital speed of the satellite,

218
00:09:45,470 --> 00:09:46,850
as well as the type of orbit

219
00:09:46,850 --> 00:09:49,780
and what the global coverage
of the instrument is.

220
00:09:49,780 --> 00:09:51,580
Some sensors, like currently

221
00:09:51,580 --> 00:09:53,490
the ones aboard the
International Space Station

222
00:09:53,490 --> 00:09:54,440
for instance,

223
00:09:54,440 --> 00:09:56,070
do not measure the entire planet

224
00:09:56,070 --> 00:09:57,500
because of the orbit path

225
00:09:57,500 --> 00:09:59,703
that the International
Space Station takes.

226
00:10:00,650 --> 00:10:03,560
On the triptic at the bottom of the slide,

227
00:10:03,560 --> 00:10:06,290
you can see a number of
different Landsat images

228
00:10:06,290 --> 00:10:11,080
that were recorded in 1973, 2000 and 2006.

229
00:10:11,080 --> 00:10:12,330
This is from a study

230
00:10:12,330 --> 00:10:14,893
that's showing the
urbanization of a desert city.

231
00:10:18,880 --> 00:10:21,960
Spectral resolution indicates
the sensitivity of a sensor

232
00:10:21,960 --> 00:10:24,370
to distinguish a range of frequencies.

233
00:10:24,370 --> 00:10:27,630
It is the ability of a sensor
to define wavelength intervals

234
00:10:27,630 --> 00:10:30,010
which corresponds to the
number of spectral bands

235
00:10:30,010 --> 00:10:31,300
which are measured.

236
00:10:31,300 --> 00:10:33,010
For instance, the bottom right

237
00:10:34,330 --> 00:10:37,110
are some examples of spectral resolutions.

238
00:10:37,110 --> 00:10:39,880
What is called the
panchromatic measures one band

239
00:10:39,880 --> 00:10:42,362
and is typically displayed
in black and white.

240
00:10:42,362 --> 00:10:45,810
Multispectral, which measures
four or greater bands,

241
00:10:45,810 --> 00:10:48,600
and typically includes the
visible in the infrared spectrum.

242
00:10:48,600 --> 00:10:50,380
And finally, there's the hyperspectral,

243
00:10:50,380 --> 00:10:52,020
which measures hundreds of bands

244
00:10:52,020 --> 00:10:54,013
across a broader wavelength spectrum.

245
00:10:58,820 --> 00:11:01,470
Okay, so with this knowledge
we can move forward

246
00:11:01,470 --> 00:11:04,380
and delve a little bit deeper
into Google Earth Engine.

247
00:11:04,380 --> 00:11:07,480
Today, I'd like to show you
about how to search for images

248
00:11:07,480 --> 00:11:10,890
and also how to draw a shape
around a region of interest.

249
00:11:10,890 --> 00:11:12,600
Here I'm just showing a screenshot

250
00:11:13,574 --> 00:11:16,210
of the opening page of Google Earth Engine

251
00:11:16,210 --> 00:11:17,860
when you sign it to your account.

252
00:11:20,880 --> 00:11:24,450
First, let's learn how to
access the Earth Engine catalog.

253
00:11:24,450 --> 00:11:26,610
When you open Google Earth Engine,

254
00:11:26,610 --> 00:11:28,700
you'll see that there is a search box

255
00:11:28,700 --> 00:11:30,580
at the top near the Earth Engine icon.

256
00:11:30,580 --> 00:11:33,200
If you click on that box,

257
00:11:33,200 --> 00:11:36,430
a dropdown will come up that
shows Browse data catalog,

258
00:11:36,430 --> 00:11:38,113
also Suggest a new data set.

259
00:11:38,980 --> 00:11:40,630
If you click on Browse data catalog,

260
00:11:40,630 --> 00:11:44,890
it'll take you to a webpage
that shows the entirety

261
00:11:44,890 --> 00:11:47,070
of the Earth Engine catalog,

262
00:11:47,070 --> 00:11:49,900
indexed and searchable there as well.

263
00:11:49,900 --> 00:11:51,570
You can also suggest a new data set.

264
00:11:51,570 --> 00:11:53,250
So if you're searching for a data set

265
00:11:53,250 --> 00:11:54,083
and you can't find it,

266
00:11:54,083 --> 00:11:56,360
and you really wanna work with
it in Google Earth Engine,

267
00:11:56,360 --> 00:11:58,770
you can also put in an inquiry

268
00:11:58,770 --> 00:12:01,193
to please upload that data set as well.

269
00:12:02,080 --> 00:12:03,880
Another thing I wanna point out here

270
00:12:03,880 --> 00:12:06,850
is if you look to the bottom
right you'll see two boxes,

271
00:12:06,850 --> 00:12:09,010
one for map and one for satellite.

272
00:12:09,010 --> 00:12:11,300
Right now I have map clicked.

273
00:12:11,300 --> 00:12:13,060
On the next page I'll show
you what it looks like

274
00:12:13,060 --> 00:12:14,963
if you click the satellite instead.

275
00:12:16,490 --> 00:12:20,570
Okay, so if I wanna search for
Landsat image for instance,

276
00:12:20,570 --> 00:12:23,130
I can just type the word
Landsat up in the search box.

277
00:12:23,130 --> 00:12:24,270
And by the way, you can see

278
00:12:24,270 --> 00:12:26,790
that this is what the
satellite option looks like.

279
00:12:26,790 --> 00:12:30,920
It is a Google Earth Engine
satellite image that is,

280
00:12:30,920 --> 00:12:34,290
I believe Landsat, and it
pretty much at this point

281
00:12:34,290 --> 00:12:39,290
looks the same as if you were
to open Google Earth as well.

282
00:12:39,490 --> 00:12:40,870
So back to Landsat.

283
00:12:40,870 --> 00:12:42,150
I typed the word Landsat in

284
00:12:42,150 --> 00:12:45,050
and what comes up are place
names, rosters, and tables,

285
00:12:45,050 --> 00:12:47,340
all that contain the word Landsat.

286
00:12:47,340 --> 00:12:51,290
Since I'm interested in the
Landsat satellite image,

287
00:12:51,290 --> 00:12:54,053
I'm gonna be most interested
in those roster data sets.

288
00:12:55,060 --> 00:12:58,110
So if I click enter
what comes up is a popup

289
00:12:59,290 --> 00:13:02,530
that shows all of these
different Landsat options.

290
00:13:02,530 --> 00:13:04,500
For purposes of this example,

291
00:13:04,500 --> 00:13:05,780
I'm gonna go ahead and click on

292
00:13:05,780 --> 00:13:10,223
the USGS Landsat 7 Surface
Reflectance Tier 2 data set.

293
00:13:11,200 --> 00:13:13,760
When I do that, another popup comes up

294
00:13:13,760 --> 00:13:15,290
and what I see this time

295
00:13:15,290 --> 00:13:17,920
is a description of the Landsat 7 data set

296
00:13:17,920 --> 00:13:21,060
as it exists in Google Earth Engine.

297
00:13:21,060 --> 00:13:24,950
If you can see right below
the icon on the left side

298
00:13:24,950 --> 00:13:26,493
under data availability,

299
00:13:27,350 --> 00:13:32,350
this image is available
from the date 5/28, 1999,

300
00:13:32,620 --> 00:13:35,100
May 28th, 1999.

301
00:13:35,100 --> 00:13:38,660
If there was an end date for this data set

302
00:13:38,660 --> 00:13:40,240
then there would be an
end date up there as well.

303
00:13:40,240 --> 00:13:42,640
But as we know, Landsat
7 is still an operation

304
00:13:42,640 --> 00:13:43,880
so there is no end date.

305
00:13:43,880 --> 00:13:45,950
And the data set gets uploaded

306
00:13:45,950 --> 00:13:50,483
as it is processed by Landsat
and the folks at USGS.

307
00:13:51,490 --> 00:13:53,970
You can also see that
there's a collection snippet

308
00:13:53,970 --> 00:13:55,810
with a little copy icon there.

309
00:13:55,810 --> 00:13:58,080
If you wanted to copy and paste

310
00:13:58,080 --> 00:14:02,520
this dataset directly into your script,

311
00:14:02,520 --> 00:14:04,610
you could do that as well

312
00:14:04,610 --> 00:14:06,960
but we'll talk about how
to do that more later.

313
00:14:08,488 --> 00:14:11,440
Up at the top, you can see four tabs.

314
00:14:11,440 --> 00:14:15,673
Description, Bands, Image
Properties and Terms of Use.

315
00:14:16,630 --> 00:14:19,640
These are all scrollable as well.

316
00:14:19,640 --> 00:14:24,350
So with Description, you can
read all about what the image

317
00:14:24,350 --> 00:14:27,640
or what the Landsat 7 sensor records

318
00:14:27,640 --> 00:14:31,650
and how long it's been up
and why it was put in place.

319
00:14:31,650 --> 00:14:33,830
Also data provider notes.

320
00:14:33,830 --> 00:14:35,740
If you then click on Bands,

321
00:14:35,740 --> 00:14:37,690
you'll get a list of the bands,

322
00:14:37,690 --> 00:14:40,270
what their description of each band is

323
00:14:40,270 --> 00:14:44,570
and also what wavelength
range they capture.

324
00:14:44,570 --> 00:14:46,980
This is very important for understanding

325
00:14:46,980 --> 00:14:51,000
how to work with these data sets.

326
00:14:51,000 --> 00:14:52,390
So we should always come

327
00:14:52,390 --> 00:14:53,960
and look at what bands are available

328
00:14:53,960 --> 00:14:56,000
because sometimes when you are working

329
00:14:56,000 --> 00:14:58,270
with the data set itself
in Google Earth Engine

330
00:14:58,270 --> 00:14:59,980
you'll be calling out the bands by name.

331
00:14:59,980 --> 00:15:01,740
So you'll need to know what they're named

332
00:15:01,740 --> 00:15:06,740
and also what their
description is to understand.

333
00:15:07,030 --> 00:15:08,960
You can also scroll down.

334
00:15:08,960 --> 00:15:13,313
So Landsat 7 has far
more than seven bands.

335
00:15:16,170 --> 00:15:17,620
Then if we look at Image Properties

336
00:15:17,620 --> 00:15:19,150
we get further descriptions

337
00:15:19,150 --> 00:15:22,410
of some of the properties
of the image that we see

338
00:15:22,410 --> 00:15:23,673
and how it was collected.

339
00:15:27,900 --> 00:15:30,680
Finally, I just wanna
point out that there's a

340
00:15:33,270 --> 00:15:35,930
tab open button at the top right there.

341
00:15:35,930 --> 00:15:38,020
So if you didn't find the information

342
00:15:38,020 --> 00:15:39,600
that you were looking
for with this pop up,

343
00:15:39,600 --> 00:15:41,260
you could also click that

344
00:15:41,260 --> 00:15:42,410
and it would take you directly

345
00:15:42,410 --> 00:15:45,050
to the Earth Engine data catalog page

346
00:15:45,050 --> 00:15:49,783
for USGS Landsat 7 Surface
Reflections Tier 2 data.

347
00:15:51,160 --> 00:15:53,310
And again, you can see that
the description, bands,

348
00:15:53,310 --> 00:15:54,840
image properties, terms of use,

349
00:15:54,840 --> 00:15:56,050
and some of the other information

350
00:15:56,050 --> 00:15:58,173
are all also on this webpage as well.

351
00:15:59,400 --> 00:16:01,093
But back to our popup.

352
00:16:02,440 --> 00:16:04,600
If you click Import,

353
00:16:04,600 --> 00:16:06,930
then what you'll have happen is

354
00:16:06,930 --> 00:16:08,930
the entire image
collection will be imported

355
00:16:08,930 --> 00:16:10,320
into your script.

356
00:16:10,320 --> 00:16:12,770
You can also rename this image collection

357
00:16:12,770 --> 00:16:17,170
and then below you can
start to work within it

358
00:16:17,170 --> 00:16:19,820
by coding different queries

359
00:16:19,820 --> 00:16:22,533
or filtering the data set as you wish.

360
00:16:29,840 --> 00:16:31,020
Okay, so of course

361
00:16:31,020 --> 00:16:33,640
Landsat is not the only
thing that you can search for

362
00:16:33,640 --> 00:16:35,560
in the Google Earth Engine catalog.

363
00:16:35,560 --> 00:16:38,430
And in fact, you don't
also have to know the name

364
00:16:38,430 --> 00:16:40,310
of a satellite that you're
interested in working with.

365
00:16:40,310 --> 00:16:44,040
Sometimes we wanna look at
data sets or place names.

366
00:16:44,040 --> 00:16:45,360
Here's just another example

367
00:16:45,360 --> 00:16:46,970
where I search for the name human

368
00:16:46,970 --> 00:16:49,120
because I wanted to
see what types of human

369
00:16:50,690 --> 00:16:53,410
interactive data sets were out there

370
00:16:53,410 --> 00:16:55,290
in the world of Google Earth Engine.

371
00:16:55,290 --> 00:16:59,373
So I came up with a global
human modification data set.

372
00:17:01,960 --> 00:17:03,190
Once again if I click on that

373
00:17:03,190 --> 00:17:05,540
I'll get a description
of what it is I'm seeing.

374
00:17:05,540 --> 00:17:07,440
So a lot of these data sets have been

375
00:17:08,330 --> 00:17:11,390
calculated from satellite imagery

376
00:17:11,390 --> 00:17:13,280
and processed by other people.

377
00:17:13,280 --> 00:17:15,050
These data sets were developed

378
00:17:15,050 --> 00:17:16,360
and then they were uploaded

379
00:17:16,360 --> 00:17:18,607
and then shared freely
on Google Earth Engine.

380
00:17:18,607 --> 00:17:20,230
And so now we can download them

381
00:17:20,230 --> 00:17:21,930
and use them ourselves if we want.

382
00:17:22,840 --> 00:17:25,990
So here's a description of what this

383
00:17:25,990 --> 00:17:28,880
global human modification data set is.

384
00:17:28,880 --> 00:17:30,310
Also what the bands are.

385
00:17:30,310 --> 00:17:31,980
So here's an example of a data set

386
00:17:31,980 --> 00:17:33,610
that only contains one band

387
00:17:33,610 --> 00:17:37,630
and it tells us what the
resolution of the data set is,

388
00:17:37,630 --> 00:17:38,983
which is a thousand meters.

389
00:17:40,910 --> 00:17:43,280
And then finally, it also
will tell you how to cite it.

390
00:17:43,280 --> 00:17:45,780
So if you're ever working with a data set

391
00:17:45,780 --> 00:17:47,570
that somebody else produced

392
00:17:47,570 --> 00:17:49,090
and you're furthering that data set

393
00:17:49,090 --> 00:17:50,440
then you want to publish it.

394
00:17:50,440 --> 00:17:52,070
This is where you're gonna
find that information

395
00:17:52,070 --> 00:17:54,253
on how to cite what you worked with.

396
00:17:56,740 --> 00:17:58,800
Okay, so now let's learn how to draw

397
00:17:59,830 --> 00:18:02,773
boxes and polygons around
regions of interest.

398
00:18:03,650 --> 00:18:05,610
Here I've gone on my script page

399
00:18:05,610 --> 00:18:08,760
and I've used the scroll
features on the map

400
00:18:08,760 --> 00:18:10,980
to be able to navigate around the globe.

401
00:18:10,980 --> 00:18:12,720
And I've taken myself to an area

402
00:18:12,720 --> 00:18:15,390
in the east coast of
Madagascar that I know well.

403
00:18:15,390 --> 00:18:17,640
It's actually where I did my PhD research

404
00:18:17,640 --> 00:18:19,150
and I loved working in the forest there.

405
00:18:19,150 --> 00:18:21,280
So I'm gonna draw a region of interest

406
00:18:21,280 --> 00:18:24,320
right around the area that
I did my PhD research in.

407
00:18:24,320 --> 00:18:26,330
One of the things that
you'll notice from this map,

408
00:18:26,330 --> 00:18:28,870
which is Landsat based,

409
00:18:28,870 --> 00:18:31,900
is that there are dark green
areas and light green areas.

410
00:18:31,900 --> 00:18:36,900
Dark green areas here actually
indicate primary rainforest.

411
00:18:37,530 --> 00:18:40,890
Whereas the lighter green
areas are the secondary forest

412
00:18:40,890 --> 00:18:43,150
or other types of vegetation

413
00:18:43,150 --> 00:18:46,500
but I'm interested in looking
at a primary rainforest.

414
00:18:46,500 --> 00:18:49,350
And so I'm going to first go over

415
00:18:49,350 --> 00:18:53,710
and click on the geometry icons

416
00:18:53,710 --> 00:18:56,660
down at the upper right of the map.

417
00:18:56,660 --> 00:18:58,920
If I click on that box,

418
00:18:58,920 --> 00:19:01,970
what will pop up will be a geometry pop up

419
00:19:01,970 --> 00:19:06,010
that now I have the
capability to draw a box,

420
00:19:06,010 --> 00:19:09,353
just by clicking and dragging
my mouse directly on the map.

421
00:19:10,640 --> 00:19:12,630
So I've drawn a box around an area.

422
00:19:12,630 --> 00:19:14,650
This is called Betampona.

423
00:19:14,650 --> 00:19:16,110
I've drawn a box around Betampona

424
00:19:16,110 --> 00:19:20,440
because I want to perhaps look
at a stack of Landsat images

425
00:19:20,440 --> 00:19:24,020
or maybe perhaps look at change
around this particular area.

426
00:19:24,020 --> 00:19:27,253
So I'm only gonna be doing
that around that area.

427
00:19:28,770 --> 00:19:31,930
If I wanted to draw a
polygon, though, for instance,

428
00:19:31,930 --> 00:19:36,000
maybe I wanna look at the area
around a city that's nearby,

429
00:19:36,000 --> 00:19:37,380
the city of Toamasina.

430
00:19:37,380 --> 00:19:40,020
If I wanted to look at something maybe,

431
00:19:40,020 --> 00:19:43,320
urban modification or human
modification around this area,

432
00:19:43,320 --> 00:19:47,500
maybe I would draw myself a
different type of geometry.

433
00:19:47,500 --> 00:19:49,060
So I'm gonna draw a polygon.

434
00:19:49,060 --> 00:19:51,100
So I click on that polygon

435
00:19:51,100 --> 00:19:54,560
and what will pop up will
be the same scroll feature

436
00:19:54,560 --> 00:19:56,860
and option that I had with the box.

437
00:19:56,860 --> 00:19:58,460
But now when I click once,

438
00:19:58,460 --> 00:20:01,050
a little circle will pop
up and then I can drag

439
00:20:01,050 --> 00:20:04,750
and drop lines as if I'm drawing a shape.

440
00:20:04,750 --> 00:20:06,470
So I dragged and dropped the lines

441
00:20:06,470 --> 00:20:08,223
and drew them all over Toamasina.

442
00:20:09,120 --> 00:20:11,810
Finally, another way to draw geometry

443
00:20:11,810 --> 00:20:14,130
or to point out a place on a map

444
00:20:14,130 --> 00:20:18,680
is to click on the point,

445
00:20:18,680 --> 00:20:20,500
the place pointer.

446
00:20:20,500 --> 00:20:22,570
If I click on that, I
can drop one anywhere.

447
00:20:22,570 --> 00:20:23,690
So I think these features,

448
00:20:23,690 --> 00:20:25,810
this is similar to what you would see

449
00:20:25,810 --> 00:20:29,923
if you were working in Google Earth.

450
00:20:31,160 --> 00:20:32,740
Here, I've dropped it on Mahavelona,

451
00:20:32,740 --> 00:20:35,500
which is a well known vacation spot

452
00:20:35,500 --> 00:20:37,113
in the east coast of Madagascar.

453
00:20:38,120 --> 00:20:39,730
So those are three different ways

454
00:20:39,730 --> 00:20:43,690
that you can indicate a
region of interest on a map

455
00:20:43,690 --> 00:20:45,550
and you can actually go back

456
00:20:45,550 --> 00:20:50,550
and rename those areas just by
clicking once on the imports,

457
00:20:51,500 --> 00:20:53,020
under the imports, you can rename it.

458
00:20:53,020 --> 00:20:54,020
And when I renamed it

459
00:20:54,020 --> 00:20:57,350
I just called it red box,
green polygon and blue point.

460
00:20:57,350 --> 00:20:59,490
It'll automatically change below.

461
00:20:59,490 --> 00:21:02,390
You can also click those check boxes

462
00:21:02,390 --> 00:21:04,230
on and off on that map

463
00:21:04,230 --> 00:21:08,070
so that you can see those
boxes actually show up

464
00:21:08,070 --> 00:21:09,420
or not show up,

465
00:21:09,420 --> 00:21:11,240
which can come in handy
if you're drawing maps

466
00:21:11,240 --> 00:21:12,750
and you're trying to
check your work as you go.

467
00:21:12,750 --> 00:21:14,370
Sometimes you might not want those on

468
00:21:14,370 --> 00:21:17,060
but you wanna know where they are

469
00:21:17,060 --> 00:21:19,453
when you're trying to work with imagery.

470
00:21:25,390 --> 00:21:27,760
Okay, so now we have searched around

471
00:21:27,760 --> 00:21:30,010
in the Google Earth Engine
catalog a little bit

472
00:21:30,010 --> 00:21:34,020
and we've also learned
how to draw polygons,

473
00:21:34,020 --> 00:21:38,220
boxes and points for a region
of interest in the catalog.

474
00:21:38,220 --> 00:21:42,554
I definitely encourage you all
to play around a little bit

475
00:21:42,554 --> 00:21:44,500
in these blank scripts

476
00:21:44,500 --> 00:21:46,240
and kind of get to know the features

477
00:21:46,240 --> 00:21:48,340
that are available to you.

478
00:21:48,340 --> 00:21:51,140
Also, I highly suggest
that you mess around with

479
00:21:51,140 --> 00:21:53,010
the Earth Engine catalog.

480
00:21:53,010 --> 00:21:55,060
Just put in some
different words to search.

481
00:21:55,060 --> 00:21:56,660
See if you can come up with some data sets

482
00:21:56,660 --> 00:21:58,750
and just kind of see what's out there

483
00:21:58,750 --> 00:22:01,620
because that will be handy
for you for the future.

484
00:22:01,620 --> 00:22:03,960
Finally, for week two's assignment,

485
00:22:03,960 --> 00:22:05,840
I'd like you to read the first 34 pages

486
00:22:05,840 --> 00:22:07,010
and follow the tutorials

487
00:22:07,010 --> 00:22:08,540
in that "Cloud-Based Remote Sensing

488
00:22:08,540 --> 00:22:10,160
with Google Earth Engine" book.

489
00:22:10,160 --> 00:22:11,930
I promise that it's not a lot of reading.

490
00:22:11,930 --> 00:22:14,020
It is a lot of helpful tutorials

491
00:22:14,020 --> 00:22:19,020
and helpful JavaScript details
that will be really important

492
00:22:19,870 --> 00:22:22,700
for your future ability
to be able to accomplish

493
00:22:22,700 --> 00:22:25,220
what you need to do in
Google Earth Engine.

494
00:22:25,220 --> 00:22:27,620
Please do complete the
knowledge check as well.

495
00:22:27,620 --> 00:22:29,710
And finally, I'd like you to draw an ROI

496
00:22:29,710 --> 00:22:31,830
and talk about it on YellowDig.

497
00:22:31,830 --> 00:22:33,750
All right, well until next week,

498
00:22:33,750 --> 00:22:35,503
have a great one everyone, thanks.