Proposals for “DAICHI 2”
SAR Data Utilization

3rd edition
Japan Aerospace Exploration Agency

宇宙航空研究開発機構

Japan Aerospace Exploration Agency

The Earth Needs
a Health Check
The Earth is changing in ways that are visible only
from space.
Japan’s world-class L-band radar satellite keeps its
eye on our Earth out for even the slightest symptoms
caused by constant changes such as land
deformation and environmental destruction.

Introductionof new applications for the analysis and processing of data, as well as the discovery of new ways

The Advanced Land Observing Satellite 2(ALOS-2, also known as “DAICHI-2”) was
launched in May 2014 as the successor satellite
to “DAICHI” (ALOS), and is used for a range of
purposes including capturing information about
disaster conditions, agriculture, forestry and fishery, marine observation, and resource exploration.
In particular, Japan has built up a wealth oftechnological know-how ahead of the world in
the field of the L-band Synthetic Aperture Radar(L-band SAR) mounted on ALOS-2, which is contributing to resolving issues in various sectors.
This book introduces the uses of satellite data
to everyone in the industrial, academic, and administrative sectors, with a focus on solutions
that are enabled by ALOS-2. It was producedwith the objective of facilitating the developmentof using satellite data.
Therefore, this book introduces first the special features of ALOS-2, SAR data analysis andthe latest research findings, and real-life examples with “Solution Proposal”.
ALOS-2 data can be used in combination withthe archive of data collected by ALOS. There isunlimited potential in satellite data, as new information waits to be discovered by being combined with other satellite data and ground data,
for example.
For all of you reading this book, we sincerely
hope that you sense the potential for applicationof ALOS-2.
And should you come up with an idea for solving a challenge using satellite data, do not hesitate to contact JAXA. Our contact details can befound at the back of this book.

Background photo: Mount Fuji observed by ALOS-2/PALSAR-2©JAXA

Contents
Introduction

What ALOS-2 Is Capable Of

About ALOS-2 and PALSAR-2 (Basic Level)

4

Overview of ALOS-2
Differences Between SAR Images and an Optical Images
SAR Imaging Principle
Characteristics of L-Band SAR

Information Available Regardless of Day or Night, Weather Conditions

6

Three Characteristics of ALOS-2
The Observation Mode and Each Resolution/Observation Swath
Spotlight Mode
Stripmap Mode
ScanSAR Mode

Case Studies of Recent ALOS-2 Observations, and Future Potential

8

Observation carried out on 1 December 2017 Results of the observation of Mount Agung, Indonesia
Observation carried out from 8-12 September 2017 Results of the observation of hurricane damage along the
Caribbean Coast
Observation carried out on 9 May 2016 Results of the observation of wildfires in Canada
Observation carried out on 10 September 2015 Results of the observation of torrential rains caused by Typhoon No. 18 in Ibaraki Prefecture

ALOS-4		

11

Solution case study: Disasters

Capturing information about the situation to speed up disaster measures

12

Capturing Displacement Information Just Before a Volcanic Eruption And Using it for Decision- Making on
Safety Measures
User Interview

Capturing Changes in a Volcano Through Interferometry using ALOS-2 Data

Estimating Earthquake Damage Based on Land Deformation
Landslides on Izu-Oshima
Providing Information About Disasters Around the World Through International Cooperation
Using Satellite Images in Local Governments’ Disaster Prevention Plans

Solution case study: Civil Engineering

Protecting Cities from Land Deformation

16

Land Subsidence Monitoring Work With Greater Precision, and at Lower Costs
User Interview

Reducing Cost and Labor in Leveling Work Through the Use of SAR Images Observed by ALOS-2

Reducing the cost of river maintenance and management through SAR images and analysis
User Interview

Toward building an embankment maintenance and management system

Capturing Information on Long-Term Crustal Movements to Contribute to Earthquake Prediction Research
Utilizing for Maintenance, Inspection, and Management of Roads and Rails
Utilizing for the Management of Bridges
Managing Huge Structures

Solution case study: Forests

Forests are Our Responsibility to Future Generations
Observing Forests for Optimum Thinning
The Potential of JJ-FAST A New Forest Monitoring System that Uses ALOS-2

22

Solution case study: Oceans

Observing Boundless Oceans from Boundless Space

24

Improving Observation Frequency with ALOS-2 Monitoring Sea Ice to Prevent Accidents at Sea
User Interview

With ALOS-2— Possible to Observe Sea Ice without Being Affected by Weather Conditions

Using Observations of Ocean Wind for Optimum Location for Wind Farms
Providing Navigation Services, and Safety and Security for the Fishery Industry
Understanding Marine Pollution, and Formulating Countermeasures

Solution case study: Energy

Exploring Energy Resources

28

Tracking Down Clues of Undersea Resources

Solution case study: Agriculture

Securing Food Sources in the Future

29

Monitoring Rice-Paddy Acreage with High Accuracy

Image processing products

Learn About Image Analysis (Advanced Level)

30

What is a Polarized Wave?
PolSAR (Polarimetric Decomposition)
D-InSAR (Differential Interferometric SAR)
SBAS-InSAR (Small Baseline Subset Interferometric SAR)
PS-InSAR (Permanent Scatters Interferometric SAR)PolInSAR (Multi-Polarization Interferometric SAR)

New Analysis Methods and Products

32

From Monochrome to Color—Bringing the Earth’s Expressions Back to Life
Comparing Past and Present Conditions Using Archival Images Accumulated by ALOS
Processing Level Definitions for PALSAR-2 Standard Products
List of Data Sizes for Each Product (Gigabyte)

Data processing software

I Want to View and Use Satellite Images!

34

JAXA Let’s SAR
ALOS2 Viewer
PolSAR-Pro
MultiSpecNEST (Next ESA SAR Toolbox)
ASF MapReady

Ground system and observation operation

36

FAQ

38

Solution case study: Design and Art

Satellite Imagery in These Wonderful Products!

40

DesignArt Created from SAR Data
Cover Image
Top left: Forest fires in Canada (see p.9)
Bottom left: Sea ice in the Sea of Okhotsk (see p.24)
Top right: Torrential rains in Ibaraki Prefecture (see p.10)
Bottom right: Volcanic eruption in Bali, Indonesia (see p.8)
Background Image: Mt. Fuji (Observed by ALOS/AVNIR-2)©JAXA

What ALOS-2 Is Capable Of

About ALOS-2 and PALSAR-2 (Basic Level)
Overview of ALOS-2
ALOS-2 is the successor to the Advanced Land Observing
Satellite (ALOS).
The SAR mounted on ALOS-2 is the “Phased Array type

Design life

5 years (target: 7 years)

Launch date

24 May 2014

Launch vehicle

H-IIA launch vehicle No. 24

Launch site

Tanegashima Space Center

Orbit (altitude)

628 km (on the equator)

Orbit period

Approx. 100 min

Repeat cycle

14 daysSatellite mass

Approx. 2,100 kg

L-band Synthetic Aperture Radar” (PALSAR-2), a high-performance microwave sensor. It improves performance in aspects
such as resolution and regions that can be observed, and makes
it possible to provide information more accurately and swiftly.

Data relay antenna

7.2m

PALSAR-2
2.7m

Satellite size (on orbit)

10.0m

3.0m

Solar array paddle

Approx. 10.0 m × 16.5 m × 3.7 m

Mission data transmission

Direct transmission,and via data relay satellite

PALSAR-2 (Frequency)

L-band (1.2 GHz band)

ALOS-2 also carries Space-based Automatic Identification System Experiment
2 (SPAISE-2), and Compact Infrared Camera (CIRC) as technology demonstration missions.

Differences Between SAR Images and Optical Images
There are two main types of sensors (observation instrument)

to observe day and night regardless of weather conditions. Hence,in the ALOS series—an optical sensor and Synthetic Aperture Ra-

because SAR penetrates clouds, the earth surface covered bydar (SAR). The optical sensor observes visible light, while the SAR

clouds is captured on the SAR image, even though the same areaemits microwaves and receives the backscatter of the microwave

is covered by clouds on the optical image.

from the surface of the Earth. A key feature of the SAR is its ability

SAR

Optics
Optical satellite

SAR satellite

Receive Backscatter

Incident radiation

Transmit
Microwaves

Reflected radiation(Top left) Observation Image of SAR
satellite(Bottom left) SAR image

4

©JAXA

©JAXA

What ALOS-2 Is Capable Of

SAR Imaging Principle
SAR transmits the pulse signals to the target, and obtains

As shown in the figure, when the pulse signals are transmitted

information about the conditions of the surface depending on the

onto a rough surface, it appears bright, because the backscatter isstrength of receiving signals. This reflection component is calledstrong by scattering on the surface.

“backscatter.” The target that has strong backscatter appears
bright on SAR image.

On the other hand, the backscatter is small on a smooth surface such as water surface because most waves are forward scattered. The target appears dark on the image.

Backscatter
Transmit
Microwaves

Surfacescatter

Taransmit
Microwaves

Roughness: Rough surface

Backscatter (strong)

ForwardscatterRoughness: Smooth surface

Backscatter (moderately)

Grassland

Backscatter (weak)

Lake Surface

Forest©JAXA, METI, analyzed by JAXA

Characteristics of L-Band SAR
Today the three wavelength bands, X-band, C-band, andL-band are used for observations by SAR satellite.
X-band and C-band microwaves with a short wavelength aresuitable to observe detailed structures. For example, the signal has
the capability to detect slight unevenness on the earth surface, andto be reflected from detailed structures such as ripples on water
surfaces and foliage in forests.
On the other hand, L-band microwaves with the a long wavelength penetrate detailed structures. For example, the signal penetrates the foliage of trees easily, and is therefore able to observe
the shape of ground surfaces.
L-band SAR is Japanese advanced technology. It is extremely
useful for observing surfaces in vegetated area and steep terrain,including Japan.
5What ALOS-2 Is Capable Of

Information Available Regardless of Day or Night,
Weather Conditions
Three Characteristics of ALOS-2

Observation of Wide Areas on the Earth
The PALSAR-2 antenna is fixed to the nadir direction of thesatellite. Because ALOS-2 satellite body can tilt right and left toobserve on both sides, it is possible to expand its observation
range to 2,320 km almost three times greater than DAICHI’s. ScanSAR Mode was able to achieve 490km swath wider than 350km
observed by ALOS/PALSAR. ALOS-2 has another advantage tosecure observation time of 48 minutes during approximately 100
minutes to circle the Earth once.

High-resolution Observation Regardless of
Day or Night, Weather Conditions
The greatest characteristic of Synthetic Aperture Radar (SAR)
is its ability to observe the Earth’s surface day and night, regardlessof weather conditions. PALSAR-2 also has Spotlight Mode toachieve the resolution of 1m × 3m, allowing it to carry out observa-

Continuous
imaging time:

48 minSwath width:

490km

tions at a higher resolution as compared to ALOS. Another characteristic is its ability to maintain a broader swath width even at highresolution. The swath width is 25km at a resolution of 1m × 3m,
and 50km at a resolution of 3m.

Disaster Response by Emergency Observation
When natural disasters occur, immediate response is required. ALOS-2 realizes emergency observation by left-and-rightlooking capability, the significant reduction in revisit time (to target quickly on the location to be observed) and improved datatransmission ability. In the case thatthe emergency observation for natural disaster is required in Japan, images of the disaster area can be obtained in as little as two hours or in 12hours at the longest.

Yellow band: ScanSAR Mode (Swath width: 490km)
Red band: ScanSAR Mode (Swath width: 350km)
Green band: Stripmap (10m) Mode (Swath width: 70km)
Pink band: Stripmap (3m/6m) Mode (Swath width: 50km)

6

ScanSAR Mode Observation Area
(Maximum)What ALOS-2 Is Capable Of

The Observation Mode and Each Resolution/Observation Swath
ALOS-2 has three observation modes.
We can choose Spotlight Mode with the resolution of 1m × 3m

Observation mode

Resolution

Swath

Spotlight

1m
（Az）
×
3m
（Rg）

25km
（Az）
×
25km
（Rg）

3m

50km

6m

50km

10m

70km

100m

350km

60m

490km

for the most detailed observation. And also Stripmap Mode with theresolution of 3 – 10m (swath width of 50 – 70km), and ScanSAR
Mode to cover a wide area in just one observation (resolution of 60– 100m, swath width of 350 – 490km) are operated. It is possible torealize the optimal observation by selecting the most appropriate
observation mode that corresponds with your objectives.

Satellite Progress
Direction

8°25km × 25km

8°

ScanSAR

350km

Non Observation
Area:

50 or 70km

Approx. 80km
Observation Area:

Approx. 1160km

Stripmap

70°

ScanSAR Mode
Swath: 350km
Stripmap Mode
Swath: 50km or 70km

Spotlight Mode
Swath: 25km
New observation mode*“Az” means azimuth direction (Satellite progress direction). “Rg” means range direction (radio wave irradiation).

Observation modeand range

Spotlight Mode
Spotlight Mode, which was not available on ALOS, was added
as a new function. This mode makes it possible to obtain better
quality images at the high resolution of 1m × 3m. Spotlight Modeenables to increase the illumination time with electronic beamsteering in the direction of the azimuth away from nadir. As a result,
it is now possible to capture the Earth’s surface in more detail.

Image captured using Spotlight Mode(around Maihama Station)(Observation by ALOS-2/PALSAR-2)©JAXA

Stripmap Mode
Incorporating the dual-beam system into PALSAR-2 makes it
possible to maintain a high resolution and wide swath width inStripmap Mode. While realizing the resolution of 3m – 10m, it also
ensures a wide swath width extending from 50 – 70km.

Image captured using Stripmap Mode
(Tokyo, Chiba area)(Observation by ALOS/PALSAR)©JAXA, METI

Image captured using ScanSAR
Mode (Kanto region)(Observation by ALOS/PALSAR)©JAXA, METIScanSAR Mode
It is possible to capture images up to 490 km swath with ALOS2. Compare d to other Earth observation satellites, it can capture
images over an extremely wide area.
In addition, it can carry out continuous observations up to 48
minutes, going about halfway around the Earth in a single observation. Improved instruments allow continuous monitoring andgreatly expanding the observable range.

7

What ALOS-2 Is Capable Of

Case Studies of Recent ALOS-2
Observations, and Future Potential
Following on from its predecessor ALOS, ALOS-2, launched in May 2014, provides data as well as emergency observation services accompanying disaster monitoring in Japan and countries around the world. There are also plans tolaunch its successor satellite, ALOS-4, in 2020. Here, we will feature some of the exceptional case studies fromamong the recent observations carried out by ALOS-2 (as of November 2017). We hope that these case studies will
help you learn more about some of the observation results that can be obtained only through the use of an L-bandsynthetic aperture radar (PALSAR-2), and that you will use these as hints for problem-solving and business development going forward.

Observation carried out on 1 December 2017 Results of the observation of Mount Agung, Indonesia
On 21 November 2017, Mount Agung on the island of Bali, In-found that although crustal deformation was not observed arounddonesia, erupted for the first time in 54 years. JAXA conducted an

Mount Agung, surface change had occurred on the south side ofobservation through the L-band synthetic aperture radar (PAL-

the crater, including the deposition of volcanic ash and ejecta.

SAR-2) mounted on ALOS-2 on 1 December at 1:38 a.m. (Japan

Through Sentinel Asia, information was provided to the relevanttime), and obtained images of the emergence of lava from the cra-institutions and authorities at the local site. This is an example

ter of the volcano.

where the ability of ALOS-2 to observe ground surfaces evenduring night time or under cloudy conditions or fumes was utilized.

Through an interference SAR analysis (interferometry), it was

The figure above shows the PALSAR-2 observation area on 1 December 2017 (Redtriangle on the top right of the figure: Location of Mount Agung; Black frame: Observation
range). The color composition is as follows: HH polarization data observed through the
ALOS-2 Stripmap 10m mode (dual polarization) in red, HV polarization in green, and HHpolarization/HV polarization ratio in blue. The areas in blue and black show water and bareground respectively, areas in green denote vegetation, and the localized areas in brightgreen and purple show town and urban areas.

8

The figure above is a differential interference image obtained by subjecting ALOS-2 image
data for two periods, before and after the eruption of Mount Agung, to interference
processing (interferometry). Through interference processing, it is possible to obtain the
degree of variation in cases where crustal deformation (uplift or subsidence, etc.) has
occurred alongside the eruption. In this observation, no significant variations exceeding thedetection limit of interference processing were observed, and the event did not result in aserious disaster.

What ALOS-2 Is Capable Of

Observation carried out from 8-12 September 2017
Results of the observation of hurricane damage along the Caribbean Coast
A number of hurricanes passed by the Caribbean Coast from

September detected a location in the Dominican Republic that was

the end of August 2017, and caused serious damage to the region.

very likely to be flooded. Based on observation images dated 12

ALOS-2 carried out emergency observations, and provided theSeptember, locations on the west coast of Florida, the United

data to the relevant organizations. Observation images dated 8

States were identified as places that were very likely to be flooded.

The figures above show data of observations carried out on the northern part of the
Dominican Republic on 8 September 2017, using Stripmap mode (Resolution: 10m;
Observation width: 70km). Based on image processing, the area in blue is inferred to be aflooded region. Through this observation, we can see that much flood damage has been
incurred along the inland areas, rather than along the coastal regions.

Observation carried out on 9 May 2016 Results of the observation of wildfires in Canada
With regard to the wildfire that occurred near Fort McMurray inwhich is capable of analyzing changes in the situation of theAlberta, Canada, on 1 May 2016, JAXA carried out an observation

ground surface, the observation was able to capture the majority ofthrough ALOS-2 on 9 May 2016 at the request of the International

the areas affected by the wildfire.

Disasters Charter. Using the 4 polarization mode (full polarimetry),

Source: ALOS Research and Application Project of EORC, JAXA website
While forests usually appear in green, the areas affected by this wildfire have changed to a
reddish or orange color. This indicates that the branches and leaves of the trees have been
destroyed by the fire, leaving only the trunks. It is possible to infer that this is because thedominant reflection from the leaves and branches (green) has become a dominant reflection

from the trunks (red).
The smooth ground surfaces (water surfaces) such as rivers, lakes, and runways arepresented in black, while towns and urban areas are shown in bright pink or yellow-green.

9What ALOS-2 Is Capable Of

Observation carried out on 10 September 2015
Results of the observation of torrential rains caused by Typhoon No. 18 in Ibaraki Prefecture
From 9 to 10 September 2015, torrential rains occurred due toand Tourism (MLIT), JAXA carried out an emergency observation

Typhoon No. 18, and river flooding as well as landslides and otherthrough PALSAR-2 mounted on ALOS-2 at 11:43 a.m. on 10 Sep-

sediment-related disasters struck various regions, particularly intember. The data from this observation was provided to organiza-

Tochigi and Ibaraki Prefectures.

tions involved in disaster prevention, including MLIT. The observation allowed to clarify multiple regions that were considered to be

At the request of the Ministry of Land, Infrastructure, Transport

flooded regions.

Figure 1: Observation image of the area near Joso City

Figure 1 shows an observation image of thearea near Joso City. Kinugawa River flows
near the center of the image, and the section
where the river width has expanded is shownin dark blue along the river. The area in evendarker blue east of the river is highly likely to
be flooded (area within the yellow circle in the
figure). Figure 2 is an image of the area near
Chikusei City. The area shown in dark blue inthe yellow-framed section is likely to be aflooded region.
Both Figures 1 and 2 were obtained using
Stripmap mode (3m resolution) of ALOS-2 at
the time of the disaster. These weresuperimposed with images obtained under thesame conditions on 13 August of the same
year, before the flood, subjected to color
synthesis, and analyzed. (These changes
include changes in the agricultural land as aresult of the harvesting of rice and otherfactors, and it is important to note that not all
the changes are related to the disaster.)Figure 2: Observation image of the area near Chikusei City

10

ALOS-4

ALOS-4

From Capturing Information after the Event, to the Early Detection of Abnormalities
The launch of ALOS-4, positioned as the successor to ALOS-2, has beenscheduled for FY2020 (*). This successor satellite is mounted with an L-bandsynthetic aperture radar like the ALOS-2, and also maintains the orbital
altitude (628km) and recurrent period (14 days) of the ALOS-2. By retaining
these features, it is able to maintain data continuity while development isongoing, providing users with even greater convenience than before.
The greatest change from ALOS-2 is the significant increase inobservation width.
For example, in Stripmap mode, the observation width at a resolution of
3m increases from 50km for ALOS-2 to 200km for ALOS-4. Until now,
observation of the entire land mass of Japan by ALOS-2 using the samemode could only be carried out about four times a year; with the ALOS-4,
however, it can now be carried out about 20 times a year. This significant

Comparison of the observation width of ALOS-2 and ALOS-4. It is extended by close
to 4 times.

increase in observation frequency makes it possible to carry out long-term
observation of crustal deformation and other phenomena at greater precision,and is expected to contribute to the early detection of abnormalities and theformulation of countermeasures.
To bring about the realization of the expansion in observation width,
digital beamforming (DBF) technology will be introduced into the ALOS-4.
This technology enables an increase in observation width without incurring
any decline in sensitivity. While this technology is already being used infields such as mobile phone communication, Japan has taken a step ahead of
the world in applying this technology to observation satellites.
In other aspects, the ship Automatic Identification Systems (AIS)

The range expands significantly with one observation in Stripmap mode.

receiver also performs better than the one mounted on the ALOS-2, and is
expected to produce an improvement in ship detection rate over waters thatare overcrowded with ships. By carrying out observation in tandem with thesynthetic aperture radar, it is expected to contribute further to marine
monitoring.
ALOS-2, which continues to carry out observations smoothly at present,
should also continue to play an important role going forward. ALOS-4 will
get off to a flying start as an even more reliable satellite, even as it inherits
the track record and capabilities of its predecessor.

*An observation satellite mounted with optical sensors is scheduled to be launched in FY2020 as ALOS-3.

Image of improved forest monitoring. It is possible to capture changes in greater
detail.

11

Solution case study: Disasters

Disasters

SO L U T I O N

Capturing information about the situation to speed up disaster measures
Earth observation satellites providing a bird’s-eye view of the overall situation demonstrate their true value when grasping thesituation of wide disaster hit areas immediately.
Because ALOS-2 can carry out observations even in rainy weather and at night, ALOS-2 can be used as a means for understanding
the situation in the event of a disaster.

Capturing Displacement Information Just Before a Volcanic Eruption
And Using it for Decision-Making on Safety Measures
In June 2015, Mt. Hakone in Kanagawa Prefecture erupted for the first time

images obtained in that observation, as well as SAR images obtained in observationsin the history of its observation. The signs of a potential eruption began to emerge

carried out in October 2014 before the occurrence of this event, an interferometry

in around April the same year, when it was confirmed that the mountain itself had(refer to p.31) was conducted, and it was found that an uplift was emerging within

begun expanding marginally. Eruption activity intensified at the start of May, andan approximately 200m-diameter range centered around Owakudani. This locationa part of the Owakudani area, which is visited by many tourists, had to be closed

corresponded perfectly with the location of a hot spring supply facility where

off. Earthquake activity dampened after peaking on 15 May, but crustal deformation

abnormal fumarole activity had been confirmed four days before the emergency

continued thereafter. On 29 June, the situation escalated into a steam eruption,observation. Based on these results, a decision was made to shut off Owakudani

although it was a very small-scale one. After a magma eruption about 3,000 years

completely with effect from the afternoon of 8 May, making it off-limits even toago, Mt. Hakone has not had any records of eruptions in recent history except for

local personnel. At the end of June, a steam eruption occurred very close to thesigns of a steam eruption around the 12th to 13th century, which were revealed

area of uplift observed by ALOS-2.

through a geological survey.
The capturing of the displacement at the location where the steam eruption
SAR images observed by ALOS-2 were used to obtain information about theoccurred immediately prior to the eruption, through a satellite observation, is

situation leading up to this eruption. On 6 May, the Japan Meteorological Agency

considered to be the first such case in the world. ALOS-2 had demonstrated how

announced a level 2 volcanic alert for Mt. Hakone. In response, an emergency

significant a role SAR images can play in volcano monitoring.

observation was carried out by ALOS-2 the next day, on 7 May. Using the SAR

Changes to Owakudani observed by ALOS-2/PALSAR-2(Descending orbit, observation from the right)*Results of analysis using the SAR interferometry analysis
tool (RINC) developed by the National Research Institute for
Earth Science and Disaster Resilience.

2014/10/09

5/7

2 weeks

5/21

7 months

2 weeks

6/4

2 weeks

6/18

2 weeks

7/2

2 weeks

7/16

Volume of displacement in the directionof the satellite’s line of sight

12

Occurrenceofphreatic eruptions

6 weeks

Angle of incidence near Owakudani: 42.8°
Volume of displacement calculated by taking the point 200m in the
N60E direction from the area near No. 39 I as the stationary point

8/27

Interferometry by ALOS-2/PALSAR-2 after
9 October 2014. The presence of an uplift
about 6cm high, at maximum, was verified.

Solution caseUser
study:
interview
Disasters

Capturing Changes in a Volcano
Through Interferometry using ALOS-2 Data
During the volcanic eruption at Mt. Hakone in Kanagawa
Prefecture that struck in June 2015, SAR images from ALOS-2
successfully observed the unusual events that occurred
beforehand. How did it succeed in doing that, and what possibilities for ALOS-2 did it present? We spoke to the researcher
who carried out the data analysis.

U S ER
INTERVIEW

Dr.Ryosuke DokeHot Springs Research Institute of Kanagawa
Prefecture—— How were observations by ALOS-2 utilized?
Once SAR images of the observation carried out on 7 May were available, weused these images, as well as SAR images observed in October 2014 prior to
the eruption, to carry out an interferometry immediately. As a result, it was
confirmed that an uplift was emerging at a range of about 200m centered—— Could you give us an overview of the Hot Springs Researcharound Owakudani, and we also found out that its core corresponded with theInstitute of Kanagawa Prefecture?

location of the hot spring supply facility where abnormal fumarole activity oc-

The Hot Springs Research Institute of Kanagawa Prefecture is a research institute that conducts research in fields such as hot springs, groundwater, geology, earthquakes, and volcanoes. The primary aim of conducting research on
hot springs and groundwater is to conserve and protect resources, while thatof research on earthquakes and volcanoes is to ensure the safety and securityof the citizens of the prefecture. From that perspective, Mt. Hakone is an important research subject for the institute.

—— How is the observation of Mt. Hakone usually carried out?
There are multiple GPS observation points at Mt. Hakone and its surroundings.
If any unusual events occur underground, the ground will move, and based on

curred on 3 May.
Based on these results, we were able to ascertain that the abnormal fumarole
activity was related to the ground displacement, and a decision was made to
shut off Owakudani completely with effect from the afternoon of 8 May, making it off-limits even to the parties concerned. At a meeting held on 11 May, it
was decided that the complete prohibition of entry would be returned to astatus of allowing conditional entry. In making that decision, the analysis results of the observation carried out from the skies in the west on 10 May (adifferent observation from the emergency observation carried out on 7 May
from the skies in the east) were also taken into consideration in the review.

that change in positional information, we will be able to know what the crustal—— The unique advantages offered by SAR images became clear

displacement is. However, due to the distribution of the observation points,

in this event, didn’t they?

what we learn through the GPS are changes at a relatively deep depth of about

This time, we learned that information obtained through interferometry of SAR

7 – 10km. As such, an inclinometer is also used to detect changes in theimages is highly effective in capturing ground movement. Even for phenomena

shallow areas. Measuring the incline of the ground using an inclinometer al-that we can actually observe, such as abnormal fumarole activity, it is notlows us to learn if the ground near the surface has swelled, or if any cracks

possible to find out what changes are actually occurring under the groundhave emerged.

based on the observation of that phenomenon alone. SAR images were theAfter the launch of ALOS-2 in 2014, we began using SAR images in addition to

only information source that provided quantitative indication of ground move-these methods. Coincidentally, an eruption occurred the year after that, andment at Owakudani. I believe we would not have been able to make the deci-

SAR images began to play an important role in the aftermath of that eruption.

sion to restrict entry on 8 May without the SAR images observed by ALOS-2.

—— During this eruption, an emergency observation was carried—— Will SAR images also be used in volcano monitoring whenout by ALOS-2 immediately before the eruption. Could you tell us

there are no eruptions?

the flow of events that led up to that?

Even now, observation data of Mt. Hakone by ALOS-2 is continuously accumu-

Around the beginning of April, observations showed that the distance between
the GPS observation points positioned on either side of the volcano was growing. This presented the possibility that the magma chamber deep underground
could be swelling. However, due to GPS observation errors, it was only at theend of April, when earthquake activity began, when we could say for certainthat this had happened. After that, abnormal fumarole activity occurred at oneof the hot spring supply facilities in Owakudani on 3 May. Then, in response to
the announcement of a level 2 volcanic alert issued by the Japan Meteorolog-

lated at a frequency of once every few months. Using the large volume of datacollected in this way to conduct a time-series analysis can help us to understand how the region has changed over a long period of time. Going forward, I
understand that there are plans to launch a successor satellite offering improvements in observation frequency. By continuing to build up this wealth ofdata, I hope that we will gain an ever more precise understanding of the events
that are actually occurring in a volcano, and continue to monitor such volcanic
activity.

ical agency on 6 May, an emergency observation was carried out by ALOS-2
the next day, on 7 May. Thereafter, we continued to carry out observation ac-

Hot Springs Research Institute of Kanagawa Prefecture

tivities under the same conditions once every two weeks.

WEB: http://www.onken.odawara.kanagawa.jp/ (Japanese Only)13

Solution case study: Disasters

Estimating Earthquake Damage Based on Land Deformation©JAXA, METI analyzed by JAXA©JAXA, METI analyzed by JAXA
Toward the satellite(uplift or westward)-11.8cm(shortening)

Away from the satellite(subsidence or eastward direction)
0Satellite-ground
Distance Change+11.8cm(lengthening)

Crustal movements in the Great East Japan Earthquake(Observation by ALOS/PALSAR in 2011)

The method to measure distances or movements on the Earth’s
surface by interfering with two SAR images taken of the same locationis referred to as “Interferometry”. The figures show images of thecrustal movements by the Great East Japan Earthquake, before theearthquake (3 March 2011) and after the earthquake (18 April 2011),
detected using the PALSAR mounted onto ALOS. The rainbow-colored
stripes show the changes in distance between the satellite and theEarth’s surface. Each cycle of color changes, from blue to green,
yellow, red, then back to blue, shows the Earth’s surface moving closer
to the satellite (uplift) by 11.8cm. The localized interference stripes in
the right figure are considered to show the crustal movements occurredby M7.0 Earthquake in Hamadori region of Fukushima Prefecture on
11 April 2011.
Even if an earthquake occurs, ALOS-2 is able to obtain data
everywhere around the world within two days. SAR pair images are able
to be provided within 14 days at the latest. If we are able to capture thesituation of crustal movements early, we can use these data to estimate thescale of damage and formulate recovery and reconstruction plans.

Landslides on Izu-Oshima
The left figure shows SAR imagery of Izu-Oshima obtained by
PALSAR-2 mounted on ALOS-2. The right figure shows the same location,
but is a bird’s-eye view presentation that uses elevation data obtained by
ALOS PRISM. Here, we can still see the scars of the large-scale landslides
caused by heavy rains of Typhoon No. 26 in October 2013, even though

about eight months have passed. The vegetation has not recovered there yet.
By incorporating false coloring through the use of polarized wave
information, we can generally see that green indicates vegetation, bright
purple or yellow-green indicates the town areas, while dark purple indicatesbare land.

©JAXA

14

Observation image of Izu-Oshima obtained by PALSAR-2 mounted on ALOS-2 (3m resolution) on 19 June 2014
*Polarization color composite image with HH, HV, HH/HV polarized waves assigned to each image as red, green, and blue, respectively.

©JAXA

Solution case study: Disasters

Providing Information About Disasters Around the World Through International Cooperation
When disaster occurs, it is important to obtain observation images ofaffected areas as quickly as possible. However, the observation satelliteof the affected country may not necessarily be orbiting above theaffected areas in a timely. Hence, an international cooperation
framework has been established in which countries work together
during a disaster to provide one another with observation data obtained
from their respective satellites. The largest such framework is “theInternational Charter on Space and Major Disasters”. Approximately
300 cases of large-scale disasters, such as earthquakes, floods, andtyphoons, which call for emergency response, occur around the world
every year. For example, the International Charter on Space and Major
Disasters worked for 40 cases in 2012. More than 20 countries andorganizations, including Europe, the United States, China, South Korea,
and Russia, are members of the Charter, and Japan also participated in
the initiative after the launch of ALOS.
Sentinel-Asia can be described as the Asian version to this Charter.
This initiative is led by Japan, with the participation of countries
including India, Thailand, and Taiwan. JAXA has also concluded
separate cooperative agreements with Italy and Canada to exchangesatellite data during disasters. Since ALOS operation was completed in2011, Japan has become unable to provide data. However, After thelaunch of ALOS-2, Japan has been providing much data.
Image of the areas affected by the tsunami in the Great East Japan Earthquake, provided by German
Aerospace Center (DLR) through the International Charter on Space and Major Disasters. The image is asuperimposition of SAR image (TerraSAR-X) with population density data.

Using Satellite Images in Local Governments’ Disaster Prevention Plans
If we predict potential hazards such as earthquakes and tsunamis,
volcanic eruptions, landslides, and floods, to formulate evacuationplans beforehand, the preparation can facilitate smooth response for
actual disasters and may save as many lives as possible.
Until now, JAXA has provided disaster prevention authorities andagencies as well as local governments with “DAICHI Disaster
Prevention Map”. This is a topographic map that has beensuperimposed with road information and detailed optical image data

captured using ALOS.
Disaster report data obtained through ALOS-2 is currently used inconjunction with other information sources, and is contributing to theformulation of disaster readiness plans by the national and local
governments more than ever before.
Satellite data hold great potential for disaster prevention andcountermeasures like this.

DAICHI Disaster Prevention Map

15

Solution case study: Civil Engineering

SO L U T I O N

Civil Engineering

Protecting Cities from Land Deformation
ALOS-2 is able to capture deformation of the Earth’s surface with an accuracy of a few centimeters.
By capturing invisible deformation, the information can be used as fundamental materials for countermeasures toprevent land subsidence and to maintain infrastructure.

Land Subsidence Monitoring Work With Greater Precision, and at Lower Costs
Since around the Taisho era, Japan has been drawing up groundwater
for use as industrial water. As a result, land subsidence has advanced
over the long years of such activity, particularly in metropolitan areas.
The collection of groundwater has been regulated, and there has been atrend toward the abatement of land subsidence in recent years. However,there are regions where land subsidence is still ongoing even today, andmonitoring and observation, as well as countermeasures to counter land
subsidence, continue to be an important part of the work of administrative
organizations.
The Ministry of the Environment published the Guidelines for
Monitoring Ground Subsidence in 2005,which sets out the technological
guidelines and methods for monitoring land subsidence. These guidelines
are based on technologies such as leveling and groundwater level
observation. However, new measuring technologies that harness aircraft
and satellite have emerged in recent years, and interference analysis(interferometry) through the use of SAR images from ALOS/ALOS-2
has become a useful technological means for measuring land subsidence.
The methods of utilizing this technology and examples of actual analysis

conducted have been summarized for practitioners from local publicorganizations, and published in May 2017 as the Guidebook for theUtilization of Satellites in Monitoring Ground Subsidence.
While it had only been possible to carry out observations of land
subsidence in places where benchmarks are located, the use of SAR
images enables planar observation across wide areas. By using SAR
images, it is possible to reduce the number of leveling surveys conducted,
and as a result of that, reduce the cost of such monitoring work by 30%- 40% depending on the conditions, according to estimates drawn up by
the Ministry of the Environment.
Going forward, by widely disseminating information about thismanual, we hope that land subsidence monitoring operations in therespective regions can be carried out with greater precision, and at lower
costs.

* Measuring the distance from the satellite to the ground surface, and comparing two sets of data obtained
for the same location on different dates and times.

AscendingObservation range

Descending
Observation range

Degree of subsidence
Uplift 2.5cm
Subsidence
2.5cm

Drawn up based on the Guidebook for the Utilization of Satellites in Monitoring Ground Subsidence

Original Data ©JAXA
Land subsidence distribution map of the Kujukuri Plain observed by ALOS-2

The image shows the result of a time-series analysis. It is possible to reduce measurement
errors, and to assess uplifts and subsidence based on the color tones.

16

Source: Guidebook for the Use of Satellites in Monitoring Ground SubsidenceSolution caseUser
study:
interview
Disasters

Reducing Cost and Labor in Leveling Work
Through the Use of SAR Images Observed by ALOS-2“ALOS-2 data is useful in the observation of land subsidence.”—The Ministry of the Environment has drawn up a
manual summarizing the methods and benefits of using ALOS-2
data. We spoke to the officer-in-charge about the objectives
and outlook for this technology.

Masatoshi Yamaguchi (left)
Office for Groundwater and Ground EnvironmentU S ER
INTERVIEW

Environmental Management Bureau
Ministry of the Environment

Kazuhiko Ito (right)
Deputy Director—— In May 2017, the Ministry of the Environment published the
Guidebook for the Utilization of Satellites in Monitoring Ground
Subsidence. Could you tell us about the background leading to the
publication of this manual?
Having drawn up groundwater for use as industrial water, various partsof Japan, particularly in metropolitan areas such as Tokyo, Osaka, andNagoya, have experienced significant land subsidence for many years.
While cases of subsidence are now gradually declining, there are stillregions experiencing advancing land subsidence, for example whengroundwater is drawn up at the same time as the mining of natural gas,or when groundwater is used to melt snow.
The Ministry of the Environment published the Guidelines for Monitoring
Ground Subsidence in 2005,which sets out the guidelines and methods
for monitoring land subsidence through technologies such as levelingand groundwater level observation. Thereafter, amidst reviews on thepossibility of using new measuring technologies, we learned that interferometry (refer to p.31) based on SAR images is useful in the measurement of land subsidence. This Guidebook for Monitoring Ground Subsidence summarizes information about how to use this technology as
well as examples of analysis. The objective is to help practitioners of
local governments who are engaged in the work of monitoring land
subsidence gain an understanding of the usefulness of SAR images,
and to promote the use of this technology.
—— Could you tell us some of the specific ways in which SAR
images observed by ALOS-2 can be used?
By superimposing two SAR images of the same location on different
dates and times, capturing the differences and processing the data appropriately, it is possible to obtain the displacement, which indicates theextent to which the ground moved during that period of time. This method is known as interferometry. Furthermore, by correcting this data, it isthen possible to find out the length of movement in the vertical direction, or in other words, the magnitude of land subsidence. While measurement through the leveling method can only shed light on the displacement of locations where benchmarks are present, this method
offers the advantage of making it possible to obtain displacement information for a wide surface area.
—— With the availability of SAR images observed by ALOS-2, does
this mean that leveling will no longer be necessary?

Under current circumstances, that is not the case. The displacement
information obtained through SAR images is ultimately relative values;
hence, to find the actual height of the ground, it is still necessary to
carry out leveling. However, if displacement data obtained through SAR
images is available, it would be possible to obtain more precise information about the overall trend with a smaller number of leveling surveys than before. For this reason, it can help to reduce the labor required in measuring work, and, in turn, reduce the cost involved.
—— To what extent can the actual cost be reduced?
The use of SAR images incurs costs related to purchasing data andhiring a contractor to carry out the analytical work. However, as it can
reduce the amount of leveling work in the process, depending on theconditions, it can reduce overall costs by 30% - 40% as compared tocurrent processes where only leveling is used.
—— Are there any points to note in adopting this technology?
It may be necessary to purchase a large number of images at the start,
so initial costs may be somewhat high. However, from the long-term
perspective, this method should help in cost-cutting. Moreover, as it ispossible to capture land subsidence conditions more accurately acrosswide areas, we hope that it will become more widely used in the future.
—— Going forward, there are also plans to launch successor satellites for the ALOS-2. What can we look forward to in the future?
The observation of an even wider area at any one time is expected to
become possible. As a result, the number of images that users need topurchase will be reduced, so we anticipate a possible further reduction
in cost. In addition, as the observation frequency of the same location
will also increase, we believe it will be easier for users to procure theimages they need. We hope that the publication of this manual willprompt more widespread knowledge about the benefits offered by SAR
images in the observation of land subsidence, and we look forward to
the utilization of successor satellites in a wide variety of sectors.
Ministry of the Environment
http://www.env.go.jp/en/

Guidebook for the Utilization of Satellites in Monitoring
Ground Subsidence
http://www.env.go.jp/press/104084.html (Japanese Only)17

Solution case study: Civil Engineering

Reducing the cost of river maintenance and management through SAR images and analysis
In Japan, which experiences many floods due to typhoons and otherfactors, structures around rivers nationwide, such as embankments andsluice pipes (a covered conduit built for the purposes of drawing water/
draining water from rivers, such as water for agricultural uses), areinspected each year before and after periods when the rivers tend to rise.
The current method used is to have inspectors walk along all the rivers tovisually observe and study the conditions; however, this method requires
a great deal of labor and cost to implement. With economizing on
manpower as the top priority, Nippon Koei Co., Ltd. is working incooperation with JAXA to build an inspection system that can efficiently
carry out inspections by using SAR images observed by ALOS-2.
The basic method involves checking for any variations in theembankment by carrying out an interferometric analysis (refer to p.31)
of SAR images of rivers. Once variations are detected, it would then be
possible to make inferences on the probability that some form of
deformation could have occurred on the embankment nearby. Inspectors
would then be dispatched to these areas only to verify the situation inperson. The aim is to establish this process as the method of inspection.
However, embankments have different ground conditions, such asplaces with people and vehicular traffic and places with slopes extending
downward, and any vegetation growing on the slopes become “noise” inthe images; for these reasons, it takes skills to conduct an accurate
analysis. For example, in interferometric analysis, effort is constantly
made to find the most suitable analysis method, such as the use of timeseries analysis that superimposes as many as 15 SAR images in order tominimize this “noise.”
Furthermore, the potential for applying SAR images to the purposeof learning about the conditions of trees growing in the inner regions ofrivers, is also being explored. For all of these applications, reviews areunderway to investigate if SAR images can be used to carry out theoverall maintenance and management of rivers.
Currently, the maintenance and management of rivers imposes aheavy cost burden on local governments. There are hopes that ALOS-2
can demonstrate its capabilities and offer a solution to this problem.

Results of analysis of embankment deformation volume based on ALOS-2 data
[Estimation of the amount of topographical change using
SAR Interferometry (InSAR) time series analysis]

Specifications of measuring instruments from the satellite
Observation frequency•Using observation data from ALOS-2, an intensity analysis andDifferential SAR Interferometry (DInSAR) analysis were

L band (1.2GHz band)

Spatial resolution (m)3 (ALOS-2)

Observation width (km)50 (ALOS-2)

Specifications of measuring instruments from the satellite

carried out and compared with LP data.

Orbit•Based on the results of the observation, as shown in the tables
below, the trend for uplifts and subsidence had a validity of

Direction of observation

West-north-west fromeast-south-east

East-north-east from westsouth-west

Date of observation

February 13, 2015

September 15, 2014

August 14, 2015

February 16, 2015

September 25, 2015

June 22, 2015

December 4, 2015

October 12, 2015

March 11, 2016

December 7, 2015

June 17, 2016

March 14, 2016

July 29, 2016

May 9, 2016

August 26, 2016

June 20, 2016

November 18, 2016

November 21, 2016

above 80%, with the exclusion of areas below 11.5km on theleft bank. The margin of error was below 1.5cm, which means

Comparison of embankment deformation volume on the left bank of Maruyama
River (LP and ALOS-2)

Comparison of embankment deformation volume on the right bank of Maruyama
River (LP and ALOS-2)
Average yearly variation (m)Example of the result of InSAR time series analysis: Result of estimation ofamount of subsidence 0(Left: Ascending, Right: Descending)

Average yearly variation (m)it was kept within a targeted level of about 5cm.

Average margin of error δa=1.48cm
Consistency rate between subsidence/uplift = 65.6% (83%: 11.5k upstream)● Average yearly variation during the observation period○ ALOS-2 variation

Average margin of error δa=1.05cm
Consistency rate between subsidence/uplift = 88.7%● Average yearly variation during the observation period○ ALOS-2 variation

After carrying out differential interferometric analysis using ALOS-2 observation data, and comparing the data with airborne laser scanning data (LP data), the results had a correct answer rate of above 80%, and margin of error
below 1.5cm.

Embankment deformation detected through the analysis. The areas colored in red show the subsidence, while the areas colored in blue show the uplifts.

18

Source: Toyooka Office of River and National Highway, Kinki Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism

Solution caseUser
study:
interview
Disasters

Toward building an embankment maintenance and management system
To prevent flooding in the event of typhoons or torrential rains,
it is vital to monitor rivers.
There are plans to apply ALOS-2 to the maintenance andmanagement of embankments, which is a central part of rivermonitoring. We speak to the person-in-charge at the company
that is responsible for building this system.

Kentaro KageyamaU S ER
INTERVIEW

Deputy General Manager
River Basin & Urban Infrastructure Divisionengineers only to these areas to conduct a detailed check. If this could beRiver & Hydraulic Engineering Deptachieved, we should be able to save a considerable amount of labor as com-NIPPON KOEI CO.,LTD.

pared to the current method of conducting visual inspections on all embankments. We are now engaged in development work with the aim of building—— Could you give us an overview of the business of Nippon Koei

such a system.

Co., Ltd., and of your work, Mr. Kageyama?

—— The scheduled completion of the system is around 2018.

Nippon Koei Co., Ltd. was founded in 1946, and is mainly engaged in the

What are some of the challenges faced by the team?

business of consultancy work related to infrastructure in Japan and abroad. In

Embankments are shaped like trapezoids, and the conditions differ depending

Japan, its work includes conducting basic surveys in the design and planningon the section with the highest horizontal plane (levee crown) and the slope

stages of infrastructural construction carried out by the Ministry of Land, Infra-that extends downward from that plane (slope of the embankment). In addi-

structure, Transport and Tourism and local governments, and assessing thetion, the slope of the embankment is usually covered in vegetation, which cancondition of existing structures. Since I am in charge of river structures, myalso cause “noise” in the observation images; hence, it is not an easy task towork involves the design as well as maintenance and management of em-

carry out an accurate analysis using SAR images. Interferometric analysis isbankments among the various types of infrastructure. Recently, Japan has

usually carried out using two SAR images. However, in the case of embank-suffered much damage from the rising and flooding of rivers due to factors

ment observation, it is not possible to obtain an adequate degree of precisionsuch as typhoons and torrential rains. In that sense, it is very important towith just two images. For this reason, we use 15 images and apply the “timemonitor the conditions of embankments and ensure that appropriate mainte-series analysis” method. By coming up with various schemes like that, we aimnance and management is carried out.

to establish an algorithm which observations based on the actual situation and—— What is the background behind the plans to apply ALOS-2 tothe satellite match with an adequate degree of accuracy. However, we still

the maintenance and management of embankments?

have to conduct a number of investigations and reviews moving forward.

The rivers of Japan span a distance of close to 8,700 km (embankments span-—— Even though the system is still under development, the sys-ning 13,000 km) when considering only those managed by the Government oftem can apparently realize significant cost savings once it isJapan. Currently, the maintenance and management of embankments is car-launched.

ried out by having engineers walk along the sites periodically to conduct visu-

Even after it has been completed, the current method will continue to be used

al inspections. This incurs enormous costs. This method also poses otherfor some time, so costs may not fall dramatically at once. However, as suchproblems such as a decline in the number of engineers, and dependence on

systems are definitely necessary from the long-term perspective, we feel thatthe competence of individual engineers. Hence, reviews were undertaken to

the development of this system holds great significance.

see if maintenance and management can be carried out efficiently and accu-

Separately from embankments, it is also necessary to capture and manage therately through the use of satellite data. Among the various methods consid-

situation of trees growing in rivers, as they can cause the cross-sectional area

ered, interferometric analysis using SAR images turned out to be the most ef-

of a river to contract. We are also currently reviewing the methods for assess-fective method for capturing the deformation of embankments, and theing this using SAR images. In this way, we aim to eventually reach a point

decision was made to build a maintenance and management system for em-

where it is possible to use this system to carry out overall maintenance andbankments using SAR images observed by ALOS-2.

management for rivers, and not just embankments.

——Could you tell us the concrete ways in which SAR images are

I understand that the successor satellite, ALOS-4, offers improvements in theused?

frequency of recording images. If that is the case, we hope that it will be able

Basically, variations in the embankment are identified by carrying out interfer-

to capture river conditions more quickly during disasters and other times.

ometric analysis (refer to p. 31) using a range of data observed at different
periods of time. Once any variations are detected, we consider it probable thatsome form of deformation has occurred such as the development of cracks inthe embankment nearby. In this way, it is possible to identify the areas that are

NIPPON KOEI CO.,LTD.
https://www.n-koei.co.jp/english/

possibly problematic from among all the embankments in Japan, and dispatch

19

Solution case study: Civil Engineering

Capturing Information on Long-Term Crustal Movements to Contribute to Earthquake Prediction Research
Crustal movements is the movement of the Earth’ crust from a few

sure crustal movements over the long-term by using methods such as lev-

millimeters to a few centimeters per year in the long term. This movement
brings the phenomenon on the Earth’s surface such as earthquakes, volcanoes. Japan lies over four tectonic plates. The movement of plates deep
below the surface of the Earth and fault is thought to be closely tied tovolcanoes and earthquakes. Hence, monitoring crustal movements overthe long-term can contribute to elucidating the mechanism of earthquakes
and volcanic activity.
The Geospatial Information Authority of Japan has attempted to mea-eling, triangulation, and GPS. Now, they are willing to incorporate the new
method of using the perspective from space.
This image of the Chiba and Tokyo area was captured using the ALOSPALSAR, and processed using interferometry. The areas in red show thelocations where the Earth’s surface has become depressed and is therefore
further away from the satellite. In particular, it has succeeded in capturing
land subsidence in a large part of the Kujukuri Plains.

©Analysis by GSI
from ALOS raw data of JAXA, METI

20

Solution case study: Civil Engineering

Utilizing for Maintenance, Inspection, andManagement of Roads and Rails
In Japan, it is not uncommon to see roads and rails surrounded by
impenetrable mountains.
The right figure is the SAR image of Tenkawa Village, Yoshino-gun,Nara Prefecture, taken by the Pi-SAR-L2. The river flowing among mountains is indicated dark on the image. With a resolution of about 3m by
ALOS-2, it is possible to identify rivers.
For locations where it is difficult to monitor from the ground, it ispossible to gain an understanding of the situation of river flooding and cliff
collapse by comparing SAR images that are taken at regular intervals. It isalso possible to assess priorities for checkout and repair work for roads andrails in mountains and near rivers.

©JAXA
Roads in Tenkawa Village, Yoshino-gun, Nara Prefecture(Observation by SAR mounted on an airplane on 18 June 2012)

Utilizing for the Management of Bridges
SAR is also able to capture the appearance of bridge over a wide river.
The figure shows a TerraSAR-X image of Rokko-ohashi Bridge,
which connects Namegata City and Hokota City in Ibaraki Prefecture. As
a part of the Rokko-ohashi Bridge collapsed in the Great East Japan Earthquake, the line is cut off on the image. The new, large-scale Rokko-ohashi
Bridge on the north side is also shown imperfectly-shaped, but this is because this new bridge is still under construction. This image was provided
to the Cabinet Office, disaster prevention authorities and agencies, andlocal governments after the earthquake.
The periodic observation by ALOS-2 leads to grasp the situation ofroads and bridges.

New Rokko-ohashi Bridge(under construction)

Hokota City
Namegata City
Rokko-ohashi
Bridge (collapsed)©TerraSAR-X @German Aerospace Center（DLR）2011
Commercial exploitation rights：Infoterra
Rokko-ohashi Bridge collapsed by the Great East Japan Earthquake
Provided through the International Charter on Space and Major Disasters(Observation by TerraSAR-X on 13 March 2011)

Managing Huge Structures
Huge structures may cause land subsidence by their own weight. It isnecessary to conduct periodic inspections to avoid the danger including
structure collapse.
The two images below shows Tokyo Dome (the big baseball stadium inJapan) and its surroundings. The right is an optical image, and the left is SAR

image (photographed from SAR mounted on an airplane).
As PALSAR-2 on ALOS-2 is also able to obtain images under the same
resolution condition as SAR on the airplane, conducting periodic
observations of massive structures such as Tokyo Dome using SAR can help
us to capture land movements that cannot be shown by the optical images.

©JAXA
SAR image (observation by SAR mounted on an airplane on 18 April 2012)
The red areas show HH polarization, while the green areas show HV polarization.

©JAXA
Optical image (observation by ALOS/AVNIR-2)

21

Solution case study: Forests

SO L U T I O NForests

Forests are Our Responsibility to Future Generations
It is very difficult to grasp changes over vast areas of land from the ground, caused by illegal logging, drought anddesertification. SAR satellites are able to observe cloud-shrouded mountains and equatorial regions without being
affected by weather, regardless of day and night.

Observing Forests for Optimum Thinning
L-Band SAR has the feature to look though cloud and vegetation. It
therefore enables to observe tropical rainforests often covered withcloud. Japan has continuously observed forests using L-band SAR.
Japan has obtained observation data for over 11 years, even if including
a blank period by JERS-1 (FUYO-1) launched in 1992 and ALOS which
completed its operations in 2011.
The types of radio waves that can be used for observation on ALOS2, launched in 2014, have increased, making it possible to obtain evenmore information than before (refer to P.30).For example, ALOS-2 haspotential to identify kinds of trees and its height, and it is expected that
we can get information on tree classification and its distribution forafforestation and thinning projects. As it is likely that this will enable
very precise calculation of the amount of carbon on the planet and theabsorption of CO2 by forests, it is also expected that such information
leads to global monitoring of logging and the decision-making process incountries and international organizations toward prevention of climatechange.

©JAXA, METI analyzed by JAXA
Left: Whole Earth Forest Map (observed by ALOS/PALSAR in 2009)
Right: Logging in Rondonia State, Brazil (Top: observation by JERS-1/SAR in 2009, below: observation by ALOS/PALSAR in 1996)©JAXA, METI

22

©JAXA

Solution case study: Forests

The Potential of JJ-FAST
A New Forest Monitoring System that Uses ALOS-2
Until now, Japan has continued to carry out forest monitoring using
L-band SAR. Starting with the JERS-1 (FUYO-1) launched in 1992,
then developing and transitioning to ALOS and ALOS-2, the history offorest monitoring spans as many as 25 years. The data obtained over thislong period of time has also been used in policymaking by various
countries and international organizations. For example, in Brazil’s
project to monitor illegal logging activities in forests, this data contributed
to the detection of deforestation in 1,000 locations as well as illegal
logging activities in 150 locations during the period from 2010 to 2011.
Based on these accumulated results, the new forest monitoring
system that uses ALOS-2 was established in 2016 by the Japan
International Cooperation Agency (JICA) and JAXA. This new system isknown as JJ-FAST, an acronym for JICA-JAXA Forest Early Warning
System in the Tropics. It carries out observation of forests in 77 countries
and regions of the world, which covers virtually all the tropical forests of
the world, every 1.5 months (ScanSAR mode, resolution 50m), and is asystem that can be freely accessed from any location in the world.
Through the JJ-FAST website, users can verify the situation of forest
decline for the world’s tropical forests from April 2016 to the present day
on the map of the world. Clicking on the areas of forest decline enlarges
the map and draws up information such as the name of that region, its
surface area, and its location. It is also possible to input detailed feedback
from the local site. In addition, GIS data that indicates the areas where
logging activities have been detected is also available for download.
In the SAR images, areas with many trees appear bright, while areas
with few trees appear dark. The basic principle is that this property
makes it possible to infer that deforestation activities have been carriedout when an area that used to be bright becomes darker. Going forward,
we aim to further improve detection precision, make it possible to also
identify small tracts of logging areas (currently, such areas can be
identified up to 5ha), and achieve full automation of the system. To that
end, efforts are ongoing to improve the system and there are highexpectations for this system to play an important role in countries andregions where forest monitoring is a pressing issue.

JJ-FAST was unveiled to the world during the 22nd session of the Conference of the Parties (COP22) to the United Nations
Framework Convention on Climate Change held in November 2016.

SO LU TI O N
PR O PO SAL

JJ-FAST user screen. Effort has been made to reduce data volume as far as possible, so that the data
can also be viewed in areas where high networks speeds are not fully guaranteed, such as in developing countries.

Use for forest monitoring in forest industry
ALOS-2 helps regular monitoring of tree growth and planning of planting, thinning and harvesting.

Use for forest monitoring to prevent desertification
ALOS-2 contributes to the formation of policy to stop desertification by monitoring vegetation in desert regions.

23

Solution case study: Oceans

SO L U T I O N

OceansObserving Boundless Oceans from
Boundless Space
It is essential for a marine nation, Japan to secure the safety of maritime transport.
It is expected that SAR data can be utilized in the term of maritime applications such as safety confirmation of shipping
routes and new energy developments.

Improving Observation Frequency with ALOS-2 Monitoring Sea Ice to Prevent Accidents at Sea
The Sea of Okhotsk is a treasure-trove of fishery resources, but isalso known as the only waters near Japan where sea ice is present.
Visually, sea ice may evoke a beautiful and poetic winter scene;
however, it poses an obstacle to the navigation of ships, and issometimes the cause of accidents. With the primary objective ofpreventing such accidents at sea, the Ice Information Center under the
1st Regional Coast Guard Headquarters of the Japan Coast Guard
disseminates navigational warnings and the sea ice condition chart,
containing information such as the status on the distribution of sea ice.
It draws up the data based on information obtained from multiple
organizations, and the sea ice condition chart is updated every day
during the sea ice season (from the end of December to early May).
After 2003, when the sea ice condition chart issued by the Center
became available on the Internet, the number of accidents at sea has
declined.
This sea ice condition chart utilizes data observed by ScanSAR
Mode of ALOS-2. During the winter season, the Sea of Okhotsk

experiences many days of stormy weather, and the skies above are often
obscured by clouds. As such, SAR images observed by ALOS-2, which
is not impacted by clouds, serve as a valuable source of information. In
recognition of these contributions, JAXA was presented an award in
September 2017 by the Commandant of the Japan Coast Guard.
ALOS-2, which replaced ALOS, increased the frequency ofobservation by significantly reducing the recurrent period andexpanding the observation width. Nevertheless, as it is impacted byfactors such as the observation conditions, its data utilization for the sea
ice condition chart is currently limited to about once every three to fourdays.
The successor satellite for ALOS-2, which is currently being
developed, is aimed at producing greater improvements in observation
frequency by further increasing the observation width. For that reason,
SAR images are expected to play an even greater role than presently inthe field of sea ice observation.

Sea ice condition chart drawn up based on an analysis of information from multiple sources (dated 7 March,2017). This was the day during the sea ice season when the greatest spread of sea ice was recorded in the Seaof Okhotsk.

Image of sea ice in the Sea of Okhotsk, observed by ALOS-2. Date and time of observation: 11:25 a.m., 13 February,2017 (JST). Images can be observed without being affected by the time of day (day/night) and weather conditions.

24

Solution case
Userstudy:
interview
Forests

With ALOS-2— Possible to Observe Sea Ice without Being Affected by Weather Conditions
To prevent shipping accidents caused by sea ice, the Ice
Information Center of the Japan Coast Guard monitors sea
ice and disseminates such information. In doing so, howdoes it utilize data observed by ALOS-2? We find out theanswer to this question from someone on the frontlines ofsea ice monitoring.

Akira Furuta
U S ER
INTERVIEW

Director
Hydrographic and Oceanographic Department
1st Regional Coast Guard Headquarters
Japan Coast Guard—— Could you tell us about the role of the Ice Information Center, andabout your work?
The Ice Information Center, established under the Japan Coast Guard, fulfills the primary role of capturing and disseminating information about sea
ice distribution and trends, with the aim of preventing accidents at sea
caused by sea ice. Specifically, we analyze and organize data obtained
through observations carried out by aircraft, patrol boats, and coast guard
offices along the coast, as well as sea ice observation information obtainedby other cooperative organizations and satellite observation data. Based on
this, we provide information about the status of the distribution of sea ice
every day through the sea ice condition chart, and provide navigational
warnings to ships as and when necessary, with information about sea icethat poses a high degree of risk to navigational safety.
—— How, and at what frequency, is the sea ice condition chart drawn
up?
Using GIS (geographical information system) software, the observation information collected is superimposed and displayed. The person-in-charge
checks this information visually, and at the same time, sketches the distribution of sea ice and its concentration (the value that indicates the percentage of sea surface covered by ice), as well as the distribution of cloud,onto the map to create a chart. This work is carried out every day fromabout 20 December when the sea ice emerges around Hokkaido, to aroundthe beginning of May the following year, and the sea ice condition chart isupdated daily at about 5:00 p.m. It can be viewed by anyone on the center’s website.
—— It must be difficult for someone to draw up the condition chart
manually every day. What are the points that you pay particular attention to in drawing up the charts?
In truth, it is very difficult (laughs). The production of the sea ice condition
charts is a job that spans a long period of time, including days off, and isdrawn up by the staff in the office working in rotating shifts. Hence, thequality differs depending on the individual, but we take care to try andmake it as uniform as possible. Data is collected from about 1:00 p.m., andit takes the person-in-charge until about 5:00 p.m. to analyze and review
all that data, and to draw up the map. After that, it is checked by all thestaff, corrections are added if necessary, and the condition chart is thus
completed. We of course pay careful attention to accuracy, but of particularimportance are situations where sea ice emerges in areas where there istypically no sea ice, and the edges of the sea ice areas. That is because
these are areas where accidents occur easily.
—— In drawing up the sea ice condition charts based on observation
information from multiple sources, what role do images obtained from

ALOS-2 play?
In drawing up the condition charts, we place the greatest importance on
visual information obtained from sources such as aircraft. However, as aircraft can only fly about once a week, data obtained from satellites is alsovaluable to us. If the weather is fine, we can see the sea ice more clearlyon images taken by optical satellites; when it is very cloudy, images observed by ALOS-2 are very useful due to its ability to observe sea ice
across a wide area without being affected by weather conditions. Whenobserving sea ice from aircraft during periods of consecutive cloudy days,
we try to carry out the observation while taking reference from ALOS-2
images so as to obtain information as efficiently as possible. In that sense,
ALOS-2 images are also used to determine the flight paths. Incidentally, weused 43 ALOS-2 images in the winter season from 2016 – 2017, and estimate that we will use 78 images for the winter season from 2017 – 2018.
—— In September 2017, JAXA received an award from the Commandant of the Japan Coast Guard for the provision of sea ice observation
data over many years. What aspects of this activity was it commended
for?
JAXA made adjustments to the data area and carried out its own dataprocessing to enable our Center to promptly utilize the images obtained
from satellites such as ALOS-2. The accumulation of such activities contributed greatly to preventing the occurrence of sea ice accidents, and wevalue it highly.
—— The launch of a successor satellite for ALOS-2 has been planned
for the future. From the perspective of sea ice monitoring, what are
your expectations for its launch?
I understand that the successor satellite will be able to obtain images more
frequently as a result of an expansion in observation width. Furthermore,through improvements in spatial resolution capabilities, it will also be able
to identify areas of thin ice and small-scale sea ice, which we look forward
to. On the other hand, image capacity will increase significantly, so thetransmission of images is expected to take more time than before. As time
is a decisive factor in the drawing up of sea ice condition charts, we hopethat measures can be taken to improve matters on that point.

Japan Coast Guard
http://www.kaiho.mlit.go.jp/ (Japanese Only)

Sea ice breaking news site
http://www1.kaiho.mlit.go.jp/KAN1/1center.html (Japanese Only)25

Solution case study: Oceans

Using Observations of Ocean Wind for Optimum Location for Wind Farms
Wind power is now a vital sustainable energy source. Increasingly, we

ter surface. With SAR imagery, smooth surfaces are dark, while rough,are looking to the sea for wind farm locations, where the wind blows stronger than on land. This means a more stable supply of energy, and it also
reduces the noise and landscape impacts of wind turbines.
In order to build wind farms offshore, it is first necessary to find locations with strong winds and to find out how powerful they are. This iswhere SAR data comes into its own.
Wind on the surface of the ocean causes friction and this generates
waves. They start as small waves (ripples) and develop into big waves as
the wind strengthens. In other words, when the wind blows and waves
form on the surface of the water, the water loses its smoothness. We canestimate the strength of the wind by observing the “roughness” of the wa-

wavy surfaces look bright. Since ALOS-2 has higher sensitivity than
ALOS, we will be able to see the dark areas more clearly and it will bepossible to estimate the strength of winds with increased accuracy.
The original name of ALOS-2 being “DAICHI-2” (daichi means“earth” in Japanese), the main target of observation remains land, but theobservation plan includes areas out to 200km from the coast. Therefore, itwill be able to forecast ocean wind strengths in coastal waters around theworld.
Currently, all countries are debating their future electricity and energyplans. The ability to forecast ocean wind strengths anywhere in the world
is likely to be an extremely valuable business.

©New Energy and Industrial Technology Development

Left: Offshore wind farm, Kitakyushu
Organization (NEDO)
Right: Analysis of ocean winds off eastern Japan(observed by ALOS/PALSAR, 14 February, 2009)
The right figure shows ocean wind speeds as calculated from an observation
spanning from Hokkaido to the coast of east Japan using the PALSAR wide area
observation mode (350km wide) on 14 February, 2009. Warm colors signify strong
wind zones. At the time of observation, a trough is centered over Hokkaido, withwesterlies blowing over the south end of the island and easterlies to the north.
Coastal winds are strongly influenced by the adjacent topography, and here wesee a zone of strong westerly winds between the Tsugaru Strait and the seas off
the Sanriku Coast. Also visible is a pattern of oscillation in the strong wind zone
probably caused by mountain waves. Coastal zones are also affected by atmospheric stratification, but SAR is able to render ocean wind distribution in highresolution.

©JAXA, METI analyzed by JAXA

26

Solution case study: Oceans

Providing Navigation Services, and Safety
and Security for the Fishery Industry
Shipping movements can be monitored for the purposes of safe shipping, or to discover illegal fishing or suspicious vessels.
The right figure, taken by the ALOS/PALSAR, is of the coast of the
Kansai region. This is plotted overlapping data obtained by AIS data of thecoastal authorities around same time. The ALOS/PALSAR enabled to capture ships of 2–3 times the size of PALSAR’s resolution. ALOS-2 is thefirst satellite in the world to be equipped with both an SAR and an AIS
receiver. SAR imagery will be able to determine the position of ships, buteven more detailed information about shipping will be generated in combination with the AIS data.
Combining SAR imagery and AIS data in this way would be useful for
combating illegal fishing or investigating ships leaking oil, and could evenbe used to monitor shipping around marine installations such as offshore
wind farms or oil rigs. Shipping companies could also confirm shipping
traffic on their planned route and whether small craft are present.
©JAXA, METI analyzed by JAXA
Shipping off the coast of the Kinki region, also known as the Kansai region. AIS data (from the AIS coastal
authority) is imposed on an SAR image.
(observed by ALOS/PALSAR in 2010)

Understanding Marine Pollution,
and Formulating Countermeasures
On 20 April, 2010, a offshore oil rig in the Gulf of Mexico exploded,
leading to an enormous oil spill. The spill continued for months, releasing
crude oil over hundreds of square kilometers of ocean. The right figure is
SAR imagery taken by ALOS/PALSAR after explosion. Released oil covers the surface and forms oil slicks. As the oil slick is smoother than thenormal sea surface and its part shows dark on SAR imagery, it is easy to
distinguish oil slicks.
Such observation is also used for exploring for undersea resources.
While an accident such as oil slick in the Gulf of Mexico is observed temporary, an oozing oil from underwater oil field is observed constantly.

©JAXA, METI analyzed by JAXAThe oil spill in the Gulf of Mexico (the affected areas are within the yellow circles)(observed by ALOS/PALSAR in 2010)

SO LU TI O N
PR O PO SAL

Ensuring shipping safety
ALOS-2 assists fishing and shipping firms to check on the safety of ships at sea.

Site selection for renewable energy generation
ALOS-2 provides information about the location of offshore wind farms in Japan and overseas.

27

Solution case study: Energy

SO L U T I O NEnergyExploring Energy Resources
SAR data can be used for not only visible targets on the surface. It can also be used to explore for fossil fuels, minerals andother energy resources under ground.

Tracking Down Clues of Undersea Resources
In underwater oil field areas, oozing oil float on the sea surface andmight form belt-like oil slicks by oceanic currents and winds.

SAR data can also be used for land-based exploration for mineral
resources. Essentially, mineral deposits are formed though the process

Oil slicks appear darker than water in SAR imagery. We can find thethat chemical components dissolved in hot water underground rise up

possibility of oozing oil from the ocean floor by targeting constant oil

along fractures and faults in soil, and they get cool and hard near the

slicks and comparing some SAR images observed at different times.

surface. Outcrops of minerals (deposits on the surface) are good indica-

The left figure is a color composition of observation data at threetions that a large amount of the mineral is present. It is likely that we candifferent times by ALOS/PALSAR for the Gulf of Mexico, off thefind them using the SAR. L-band SAR in particular would be suitable forcoast of Louisiana, USA. It is possible to estimate the point where oil

exploration of mineral deposits in forested areas, because it can observe

oozes using this composition image that appears flowing oil from the

Earth surfaces through vegetation cover.

target point.

©J-spacesystems

Left: Color composition of oil slicks observed at three different times by PALSAR
Yellow: 25 June, 2006
Red: 13 June, 2006
Blue: 20 May, 2006
Right: Marine oil slick soon after oil surfacing (photographed by optical camera)*There is a high chance that this is a seabed oil seepage©J-spacesystems

S O LU TI O N
PR O PO SAL

Subsea oil exploration
ALOS-2 observes oil slicks to find underwater oil field.

Mineral resource exploration
ALOS-2 observes surface mineral deposits to find minerals.

28

Solution case study: Agriculture

Agriculture

S O LU T I O N

Securing Food Sources in the Future
Addressing the issues associated with the global population explosion is our major preoccupation.
It is also necessary to accurately grasp the state of agriculture for the food problem, because an imbalance between
supply and demand is predicted.

Monitoring Rice-Paddy Acreage with High Accuracy
Planting season©National Institute for Agro-Environmental
Sciences/RESTEC/JAXA
To obtain the imagery of rice paddies in planting season(observed from aircraft-mounted SAR, 10 June, 2013)©National Institute for Agro-Environmental
Sciences/RESTEC/JAXA

A paddy before planting acts as a mirror, deflecting
incoming microwaves in a different direction. Therefore the microwaves do not return to the satellite
meaning paddy field looks very dark on SAR imagery.

To extract water surfaces from imagery
The blue rectangles are water surfaces, the red rectangles are
not water surfaces.

Similarly, just after planting, the backscatter from paddy field is weak and the paddy field looks dark on SAR
imagery.

Growing season©National Institute for Agro-Environmental
Sciences/RESTEC/JAXA
To obtain the imagery of rice paddies in growing season(observed from aircraft-mounted SAR, 8 August, 2013)©National Institute for Agro-Environmental
Sciences/RESTEC/JAXA
To extract water surfaces. To estimate rice cropping by growing
condition of rice paddy extracted in growing season (blue rectangles)

With the growth of rice plants, the backscatter of microwave from rice paddy field is strong. The paddy
field looks bright on SAR imagery.

In order to address the food problem, we first need to grasp accurately

While ALOS only allowed small areas to be covered, it is expected

the cropping state of agricultural crops. In particular, Asian countries needthat detailed data on a broad area taken from ALOS-2 will be able to beaccurate and detailed data about rice paddy production, since rice is theused as basic data for food security over wide regions including prefec-

staple in Asia. However, current surveys do not have a high level of reli-tures in whole of Japan. The data is set to be used in Viet Nam, Indonesia

ability. This is where L-band SAR is useful.

and other countries in addition to Thailand.

Before paddy rice is planted, a paddy field needs to be flooded with

L-band SAR has a potential to distinguish other relatively large crops

water, so at first they look dark on SAR imagery. As the rice sprouts andsuch as corn and sugarcane besides rice, and its adaptation is also being

grows to hide the water, paddies look lighter. In other words, by comparing

considered for those crops.

SAR images observed at different time intervals, we can estimate that thearea changing brighter has been planted with rice.
In Thailand, the validation of using PALSAR data from ALOS in thisway has already been concluded. Currently, research is underway toward

There is always a need to know about cropping because farmers frequently leave paddies or fields fallow or change the crops being planted.
Agriculture can be managed more efficiently if SAR can be used to know
at once what is being planted over a wide range.

practical application, through the utilization of ALOS-2 data.

Grasping condition of various types of food crops

SO LU TI O N
PR O PO SALALOS-2 provides information leading to local food shortages domestically or globally in order to decide
investment or policy.

Basic data in business development
ALOS-2 provides Data about planting and crop growth domestically and globally for business development orinvestment.

29

Image processing products

Learn About Image Analysis (Advanced Level)
So far we have explained what is possible by utilizing the special characteristics of SAR sensors.
Here we present in simple terms the principles and some examples of how analysis is performed.

What is a Polarized Wave?
Even for radio waves of the same frequency emitted by a radar,

their properties.

there are two wave types: linear horizontal to the ground (H) andOne strength of SAR is that the distinct features of each polar-linear vertical to the ground (V). These are called “polarized waves.”

ized wave, synthesized by a range of methods, enable very diverse

The waves transmitted by SAR are also either of these H or V

analysis.

types, and the waves received also are of these types. In combina-

Yet, it is not always possible to obtain imagery using all fourtion, therefore, there are four types of polarized waves: HH, HV, VH

polarized waves. The number of polarized waves depends on theand VV.

observation mode used. The highest resolution mode is only using

Each type of polarized wave has differing features and informa-

single polarized wave type (HH, VV or HV), while the mode for ob-

tion. For example, HH waves are highly penetrative, able to reachserving a wider area while losing some resolution uses two or full

the ground even in areas covered by forest for example. Using thispolarized waves, and it is also possible to obtain several images.

property, HH waves can detect movements on the Earth as a result

The ALOS-2 boasts more modes able to observe with multipleof earthquakes or subsidence. On the other hand, VV and HVpolarized waves, broadening the scope of analysis. We now pres-waves are able to detect whether a location is bare or forested

ent examples of key analysis methods that will be possible.

during observation of forests. HV and VH are essentially similar in

Horizontal polarized wave (H)Vertical polarized wave (V)HV (VH)VV

HH
Transmit H

Transmit V

Transmit H (V)Receive H

Receive V

Receive V (H)To see the ground reflected
through a forest

30

Horizontal
axis
Vertical axis

Vertical axis

Horizontal
axis

To see a tree trunk reflected

To see sticks and leaves reflectedImage processing products

PolSAR (Polarimetric Decomposition)

D-InSAR (Differential Interferometric SAR)

This is a method of extracting information (more than can be

While SAR interferometry is the comparison of two overlaid im-learned from single polarized wave types) from data obtained fromages (InSAR), D-InSAR is a way to find information on geologicalsynthesis of full polarized wave types by re-disassembly. When thechanges. This method is used to observe changes in the Earth’s

full polarized waves are analyzed, we can disassemble them bycrust such as subsidence and upthrust.
Practical examples of use: Geomorphic changes, fore-

whether the waves hit the object and were reflected once only (single scatter), twice (double scatter) or if the reflection was morecasting of volcanic eruptions, visualization of subsidencecomplicated (volume scattering, surface scattering). The observed
object can be further explored by investigating the ratio of each

SBAS-InSAR(Small Baseline Subset Interferometric SAR)

type of returning wave in the backscatter.
When using multiple wave types, we can calculate the amountof entropy. Entropy is the physical measure of “messiness” (generally, entropy is greater with increased mess).
For example, when trying to distinguish sea ice, calculating theentropy gives us a more precise picture of the ice (with ALOS, entropy could not be calculated in wide area observation mode, themode commonly used for sea ice observations, because only one
wave type was transmitted. This will be possible with ALOS-2.).
This can also be used to distinguish land slips, as entropy is reduced when earth is laid bare after a landslide.
Practical examples of use: obtaining information about
the density of forests, ocean winds or sea ice

This is a method of SAR interferometry time series analysis andis an extended version of interferometry. Interferometry is the comparison of two datasets taken at the same location at different
times, and SBAS-InSAR is the comparison of datasets taken at thesame location multiple times and analyzed together.
In the case of gradual subsidence, two datasets are not enoughto gain an accurate picture of the movement. But comparing further time series datasets allows the observation of minute movements.
Practical examples of use: Observation of movement inmillimeters per year such as volcanic activity, landslips and ageing structures

PS-InSAR (Permanent Scatters Interferometric SAR)
In imagery, many points change gradually in brightness. Butamong them, there are points that always maintain the same brightness, called persistent scatters (PS). Large built structures are obvious PS. This technique involves running interferometry on PS only.

Volumescatter

Surfacescatter

Selecting only points of stable brightness are more reliable than dark
points. By looking only at PS, it is possible to pick up extremely de-

Doublescattertailed changes on the Earth’s surface over a wide area.
As L-band SAR shows more PS than C-band or X-band, this isa method that is suited to the technology.
Practical example of use: Observation of subsidence inurban areas
Radio wave scattering over a forested region

PolInSAR (Multi-Polarization Interferometric SAR)

Surfacescatter

Triplescatter

Doublescatter

DirectscatterThis is a combination of polarimetric decomposition and interferometry (the technique of observing changes in data by observing
the same location twice or more; also known as SAR interferometryor InSAR). Data from four wave types is taken in the same location
twice, and the two datasets are analyzed by interferometry.
Practical example of use: Obtaining more detailed infor-

Sea surface

mation about vegetation such as forest height or biomass volRadio wave scattering over sea

ume, obtaining more precise land cover information

31

Image processing products

New Analysis Methods and Products
A range of satellite imagery analysis techniques already exist, but researchers are also developing new methods.
One example is SAR “colorizing technology.” We will also present new products.

From Monochrome to Color: Bringing the Earth’s Expressions Back to LifeAs SAR imagery is black and white, it often gives bigginerusers the impression of being difficult to deal with. To solve thisproblem, the Remote Sensing Technology Center of Japan(RESTEC) has developed the technology to turn monochrome
SAR images into color images.
In simple terms, the observed surfaces (rough or smooth) on
SAR imagery are expressed by difference of brightness. This isbecause different surfaces and forms cause the radio waves toreflect in different ways. As a result, the SAR imagery shows water as dark, vegetation as light-dark, and urban areas as bright.
The features of observation data (roughness, smoothness,distinction from surroundings, color differences, etc.) are analyzed for each pixel in the process of this coloration technology.
And its respective features are given numerical values, and thenits values are transposed to RGB colors. As a result, the colorized imagery similar to optical imagery is formed.
While not being same as all aspects of the optical image
because this technology is not able to distinguish different objects with the same surface conditions, (for example, a green
car and a red car would appear the same color because theirsurrounds and surfaces are the same), the colorized image be-©JAXA

low is closer to a photograph at first glance.
This technology allows us to be easy to understand intuitively SAR image and to change its negative impression, and theaim of the technology is to be recognized by more people that
SAR is easy to use.
One of expected applications of this technology is land cover classification mapping. It opens the possibility that such map
is created using SAR imagery though it has been created only
by optical images.
We hope that the coloration technology will increase thenumber of user and expand its utilizations.

Tsukuba Space Center and surrounds
Upper: Aircraft SAR (Pi-SAR-L2) image
Lower: Colorized aircraft SAR (Pi-SAR-L2) image

32©RESTEC included ©JAXA/METI (RESTEC patent pending)Image processing productsComparing Past and Present Conditions Using Archival Images Accumulated by ALOS
Using ALOS/PALSAR images, JAXA holds PALSAR mosaic
datasets for the whole planet at 10m or 25m resolution. This datain global warming and promote the REDD+ (Reducing Emissions
from Deforestation and Forest Degradation plus) campaign.

has been orthorectified, gradient corrected and mosaicked, makThe PALSAR earthwide orthomosaic dataset with 10m resolution (color
synthesized)

ing it easy to impose on maps. Images have also been preparedusing mosaic data to capture forested and unforested areas.
These images allow monitoring of changes over the years inforestry and land, as PALSAR is not subject to the vagaries of theweather. They can also be used in Japan or abroad to manage
forests and land management projects.
It is expected that ALOS-2 will renew these datasets with thesame kinds of observation, as it will observe the Earth over the sametimespan (June to October) under the same conditions. The continuous observation by ALOS-2 will enable to grasp changes in forest©JAXA, METI, analyzed by JAXA

land use over time, and it will allow us to identify land-based factors

Processing Level Definitions for PALSAR-2 Standard Products
Level

Definition

FormatLevel 1.1

This is complex number data on the slant range following compression of the range andazimuth. As one-look data, it includes phase information and will be the basis for later
processing. In wide-area mode, image files are created for each scan.

CEOS SAR/GeoTIFF

Level 1.5

This is multi-look data on the slant range from map projection amplitude data, withrange and azimuth compressed.

CEOS SAR/GeoTIFF

Level 2.1

Geometrically corrected (orthorectified) data using the digital elevation data fromLevel 1.1.

CEOS SAR/GeoTIFF

Level 3.1

Image quality-corrected (noise removed, dynamic range compressed) data from Level
1.5.

CEOS SAR/GeoTIFF*Level……more information on P.38 Q6

List of Data Sizes for Each Product (Gigabyte)
High resolution
Observation mode

Wide-area observation

Full polarimetry

350Km

Spotlight
3m

6m

10m

6m

10m

Mode (1)490Km
Mode (2)

Mode
(1)

Mode
(2)

Frequency range

84MHz 84MHz 42MHz 28MHz 42MHz 28MHz 14MHz 28MHz 14MHz 28MHz 14MHz 14MHz

Pixel spacing

0.625m

2.5m

4.3

5.2

2.4

3.1

1.2

6.1

2.4

L1.1 (georeferencing)*1
L1.5/L2.1/L3.1(Georeferencing)L2.1 (Geo-coded)*2

3.125m 6.25m

3.125

6.25m

1.0

5.5

2.1

0.8

0.2

0.7

0.1

0.4

0.5

1.5

0.5

5.7

0.9

0.7

1.1

- Georeferencing: Map projection based on the direction of the satellite orbit- Geo-coded: Map projection based on direction of map*1. Except full polarimetry, each figure indicates the size of a single polarized wave. In
the case of two polarized waves, these figures double.
*2. Data size of representative off-nadir/scan number*3. Expected largest data size

25m
3.5

6.9

27.1

54.1

6.0

46.8

- Mode (1) (Burst mode)
Range compression and one-look azimuth compression are performed for eachburst. Signal data is created for each burst, but data with the same scan and radio
wave is stored in the same image file in chronological order.
- Mode (2) (Full aperture mode)
Range compressed and one-look azimuth compressed, with zero padding between
bursts (analysis by scan and by radio wave).

33

Data processing software

I Want to View and Use SAR Images!
There are various software offerings available, free and paying, but in this book we introduce free software for handling ALOS/PALSAR data standard products. As ALOS-2 data can also be provided in the form of GeoTIFF data, it canbe displayed more easily than ALOS data.

JAXA Let’s SAR
A software package for geographic data including PALSAR mosaic image, which can be used to classify forestry, identify deforestation,and more.
- JAXA Let’s SAR package can be downloaded free of charge from the JAXA/EORC website (Windows 64-bit version).
http://www.eorc.jaxa.jp/ALOS/en/index.htm- The two types of software featured below currently come with forest-related processing functions.
LUC Land cover classification software equipped with object directional classification engine. It enables to classify local survey data with location informationas teacher data.
γ0 Change It enables to detect deforestation and forest degradation by detecting change volume of γ0 in PALSAR mosaic data observed at two different times.

ALOS2 Viewer
This is a multifunctional program that can process and display images from the synthetic aperture radar(PALSAR-2) mounted in ALOS-2.
- Developed by the Remote Sensing Technology Center of Japan (RESTEC).
- Available for download, free of charge, from RESTEC’s website.
https://www.restec.or.jp/en/knowledge/alos2-viewer-software- Users need to input their information, such as name, affiliation, and e-mail address.
- System requirements: OS: Windows 7 or later (32bit, 64bit), CPU: 2.2GHz or higher, Memory: 2GB or more,
Display resolution: 1024×768 or higher- Tiling of large image files from ALOS-2/PALSAR-2 to optimize them for display.
- Automatic generation and display of tiles for color display of ALOS-2/PALSAR-2 polarization synthesis.
- Automatic generation and display of tiles for display and superimposition of ALOS-2/PALSAR-2 images fromtwo different periods of time.
-Execution and display of interferometry processing through complex ALOS-2/PALSAR-2 of two different periods of time.
-Orthorectification and output of all tiled images, and the generation of text files in KML format (can be displayed on Google Earth).
-Generation of differential interferogram, and generation and KML output of coherence images.
-Statistical processing of radar reflection coefficient in multiple polygons, produced manually in the images, as well as output of files in CSV format. The polygon is
output in KML format.

PolSAR-Pro
Software for performing polarmetric analysis on SAR
imagery (see P.31).
- Developed by ESA (European Space Agency).
- Can be downloaded from the ESA website:
http://earth.eo.esa.int/polsarpro/install.html- E-mail address and other information will be required before downloading.
- Has versions for Windows, Mac OS, Linux and Unix-Solaris.
- Level 1.1 data is available in ALOS standard products for purpose ofpolarimetric analysis.

34

Data processing software

MultiSpec
Software for classifying satellite data.

- Can be downloaded from the website “A Freeware Multispectral Image Data Analysis System”:
https://engineering.purdue.edu/~biehl/MultiSpec/- E-mail address and other information will be required before
downloading.
- Has versions for Windows and Macintosh.
- The latest version for Windows is the 3.3 version.
- Cannot read ALOS standard products directly, but is able toread them in GeoTIFF format.

NEST (Next ESA SAR Toolbox)
Software for analyzing SAR imagery.

- Developed by ESA (European Space Agency).
- Can be downloaded from the ESA website:
https://earth.esa.int/web/nest/home- Level 1.1 and 1.5 georeference data are available in
ALOS standard products.

ASF MapReady
Software for geometric correction of SAR
imagery (giving correct geographicalcoordinates using standard points alignedwith a map).
- Can be downloaded from the Alaska Satellite
Facility website.
- User registration is required in advance.
- Has versions for Windows and Linux.
- The latest version is the 3.2.1 (beta) version.
- Levels 1.1 and 1.5 georeference data are available
in ALOS standard products.

35

Ground systems and observation operations

Ground system and observation operation
The ground system for DAICHI-2 consists of the following four major systems: “Spacecraft Control and Mission
Operation system,” “Earth Intelligence Collection and Sharing System,” “Tracking Network System,” and “DataAnalysis System.” They are at Tsukuba Space Center.”

1 Receiving requests, compiling observation requests
2 Operation planning

Telemetry

Ground Network System

control and tracking network
3 Satellite
operation

4 Observations

Masuda Station

Okinawa Station

Katsuura Station
Command

5 Observation data reception
6 Observation data processing

Range data

Unified Flight Dynamics System
GPS data
Orbit information

Telemetry

Integrated Netwo

7 Observation data delivery

36

Space Control and Mission Operation System

Earth Intelligence Collection and Sharing System

A system for compiling an observation plan, generating a command,
monitoring and controlling satellite conditions, transmitting observation data of the mission instrument and processing them with theLevel 0 process, and processing emergency observation data with theLevel 1 process.

A system for users to apply observation data, user interface for observation
requests, product orders, search and provisions, obsevation data storageand management and various processes for compiling products.

Tracking Network System

Data Analysis System

A system for compiling the network operation plan for satellite
control operations, orbit determination, monitoring and contorolling
ground stations and monitoring and control of ground stations forobservation data receiving operations.

A system for calibration and velification of SAR observation data,
construction and evaluatiing sensor models, and developing andevaluating higher-order processing software.

Ground systems and observation operations

Command

ALOS-2
CommandCommandCommand

Telemetry / Mission data

Data RelaySatellite
Command

Telemetry / Mission data

Telemetry / Mission data

High-latitude station

Telemetry / Mission data

Extension Network Station

Katsuura S/X Station

CommandCommand

Telemetry

Telemetry

Hatoyama X Station

Tsukuba Station
Command

Telemetry

Mission data

ork Interface for Tracking Network System

Mission data Network Infrastructure for Tracking network

NW operational plan

Data reception request

Command

Orbit information

Earth intelligence Collectionand Sharing System

Products

Products

Data Analysis System

Hatoyama Station

Tracking Network System

Svalbard Station

Space Network Station

Observation & processing plan
Product (L0, L1, L3)

Observation request
Observation parameter

Telemetry

Mission data

Satellite control and mission operations system

Observation request

User agencies

Overseas space agencies*The distribution of ALOS-2 data is scheduled to commence at the end of November 2014. Sale of data will be carried out through the distributors. Pleaseinquire with the Satellite Applications and Promotion Center of Japan Aerospace Exploration Agency.

37

FAQ

FAQ
Q1. W hat kinds of sensors do Earth observing
satellites carry?

equivalent to the “scene” (the sensor’s instantaneous field of view), which
is defined for each satellite.
There are two major types of products, Digital Products offered by

The main types of Earth observing satellite sensors are as follows:(1) Optical sensor……Measures the reflections and radiation of sunlight.
Able to take color images of the surface like a digital camera.
(2) Active microwave sensor……Emits microwaves from the sensor andgauges the microwaves reflected back from the subject. Effectively it is ascene, and Value Added with mosaicing (multiple images overlaid) or color
composition.

Q4. W ho should I enquire to regarding use of
ALOS-2 data?

radar. ALOS-2 has this type of sensor. It can observe the Earth’s surface
regardless of conditions, whether the weather is poor or night has fallen.

Data can be obtained from JAXA or data distribution companies, corre-(3) Passive microwave sensor……Gauges the microwaves emitted by thesponding to the purposes of use. Please contact the JAXA Satellite Applica-

subject.

tions and Promotion Center in the first instance.

Q2. Where can I search and order satellite images?

Q5. W hat will be the level of processing for
ALOS-2 images?

JAXA satellite images can be searched and ordered from the website
below. Please refer to the following for websites that supply ALOS-2 data.
-You can search for ALOS-2 data.
https://auig2.jaxa.jp/ips/home

Observation data is provided as Level 1.1 or Level 1.5 products, withrange and azimuth compressed. For details, please see p.33.
As data from satellite observation cannot be used without analysis or- G-Portal (Earth observation satellite data provision system): Providing

interpretation, standard processing is applied as appropriate for purpose.

images and data from JAXA satellites and sensors.

The information retained by the data depends on the level of processing.

https://www.gportal.jaxa.jp/gp/top.html

For example, Level 1.1 includes information required to conduct inter-- E-Saerch (an online Earth observation satellite data website search sys-

ferometry analysis for crustal movement and others, but this level is nottem): Available to search across all JAXA websites offering all kinds ofprocessed as an image and therefore a high level of technology is required.

data.

Level 1.5 is processed as an imagery (regeneration treatment) andhttp://www.sapc.jaxa.jp/e-search/ (Japanese only)

thus can be used to view images or perform analysis of the numerical- DAICHI Image Gallery: Uploading images observed from all ALOS sensors

values embedded in images. However, it is not appropriate for overlay on

and practical examples of analysis.

maps as the altitude data of images is uncorrected.

http://www.sapc.jaxa.jp/gallery/ (Japanese only)- JAXA Digital Archives: Available to search images and footage from a
range of JAXA projects.

Q6. W hat is the radiometric resolution of ALOS-2
images?

http://jda.jaxa.jp/en/* If you wish to use images from the JAXA website, please read “How to use” on thewebsite and send your application if needed. Application is available on the website. For details, please read “Conditions for material usage” on the website.

Q3. W hat kind of format are the satellite images
provided in?
The images are provided as electronic data, at an image size that is38

16-bit.

FAQ

Q7. How accurate will ALOS-2 images be?

ro=10xlog10<DN²>+CF.

Radiometric accuracy (common for all the off-nadir angles)

Q9. What is orthorectification?

１dB (1σ) : Corner reflector

As images taken from satellites and aircraft appear distorted, for ex-

Noise equivalent sigma-naught-29dB or below

ample for observations made at an angle or elevated land forms and struc-

Amplitude ratio of VV/HH (PLR)

Within 5%

Absolute accuracy

Phase difference of VV and HH (PLR)

Under 5 degrees

Cross talk (PLR)-30dB or below
Single look in
azimuthResolution
In range

3m/5m
1.8m (84MHz)
3.6m (42MHz)
5.4m (28MHz)
10.8m (14MHz)

In azimuth-14dB or below

In range-14dB or below

Sidelobetures, these cannot be directly imposed on a map. Rectifying these distortions using orthogonal projection in order to fit an image to a map is called“orthorectification.”Q10. W hat is the difference between“Georeference” and “Geocoded?”Georeference
Projection of data on an image using the map projection method established by the processing parameters.
The orbital direction of a satellite is the top and bottom of an image.

Data used: Corner reflectors (CR) (calibration sites) and PALSAR-2 images

Geocoded

from observation of the Amazon rainforest.

A georeferenced image that has been turned so that the top of the

Evaluation method: The root mean square error (RMSE) of GRS80 ellipsoid

image is facing north.

projection corner reflector (calibration sites) location (calculated by GPS)

- Map North: North using the map projection method established by theand location measured by SAR imagery, using the 572 CR points worldwide.

processing parameters.
- True North: actual north (direction of the North Pole)

Ambiguity
In range

22dB or more

In azimuth

35dB or more

Q11. W hat is the pixel spacing used for eachmode of PALSAR-2?
Spotlight mode: 0.625 m

Geometric accuracy (common for all the off-nadir angles)
20 m

Spotlight, Stripmap

70 m

ScanSAR

Stripmap mode (3m resolution): 2.5 m
Stripmap mode (6m resolution): 3.125 m
Stripmap mode (10m resolution): 6.25 m
ScanSAR mode (350km instantaneous field of view): 25 m
ScanSAR mode (490km instantaneous field of view): 25 m

Q8. How do I convert it to physical measurements?
The standard deliverable is expressed in the surface reflection function (the backscatter coefficient, to be precise). Using the digital number(DN) contained in the data, it can be converted by the equation Sigma-ze39

Solution case study: Design and art

SO L U T I O N

Design and art

Satellite Imagery in
These Wonderful Products!
Satellite images are also used in design, art and education.
Optical images have a wide range of applications, but so do images and data observed by SAR.

Design1

FashionLines inspired by ALOS include a down jacket utilizing the contrasting blues and greens of an image of the Galapagos Islands, T-shirts
and more.

2

Astronomical telescope

The popular astronomical telescope retailed by
Vixen Co., Ltd. wrapped in satellite images.

© 有限会社 ファント3

T-shirts,iPhoneCase

Freely customize satellite images of your favorite locations,and create and purchase merchandise such as fully-printed
T-shirts and smartphone cases.

4

iPad app“Coasting” is an app enabling you to follow the coast on
screen while enjoying music from each place.
©Qosmo40

5High-definition CG silk print

By a fusion of high-definition CG silk print technology through Yuzen process, high-definition
data from ALOS is faithfully and artistically rendered on kimonos.
©Japan Style System http://jss-kyoto.jp

Solution case study: Design and art

Art Created from SAR data
Microcosm is a work that uses SAR imagery in its artistic expression.
This background image is a part of Microcosm. An infinite number ofwhite dots are shown on a black background, that seems like a starry sky.
This shows extracted land form changes from geological data ofKanazawa obtained by ALOS/PALSAR from 2007 to 2010. The changes
look similar to a starry sky.
The aim of the work is to integrate a planetary view with social awareness from an extraterrestrial perspective by recreating a miniature “space”
out of unremarkable changes in everyday life and changes of season.

Microcosm / November 29th, 2010 at 10:18p.m. in Kanazawa
PALSAR Level 4.1: Processed by ERSDAC, Ovserved raw data: Belong to METI and JAXA,
Changed from the original color by Hiroshi Suzuki.
Artists: Hiroyuki Suzuki, Masato Ohki
Created in: 2013

Experiment on a farm near Kanazawa(14 October, 2010)

Postscript
In this book, we have explained a number of possible solutions that ALOS-2

structure” for use in disasters, but as tools for application in business, society,can offer. Some may feel that SAR is a little difficult. But with a basic understand-civil life and international contributions. We would be truly delighted if ALOS-2

ing of the characteristics of SAR, surely others will now have a sense of theis made full use, leading the world as a Japanese technology in the SAR field.

possibilities it offers in a wide range of fields and occasions.
We hope that the attributes of ALOS-2 are not simply seen as “space infra-(Editorial committee)

If you would like to use ALOS-2, please contact JAXA Satellite Applications and Operations Center (Tokyo office) by e-mail: SAPC-INFO@jaxa.jp.
The copyright of the ALOS imagery used in this publication is held by Japan Aerospace Exploration Agency (JAXA) and Ministry of Economy, Tradeand Industry. Aircraft-mounted SAR (Pi-SAR-L2) imagery is the property of JAXA. This is the case even where the source/copyright mark is not noted.
Editorial assistance from: Remote Sensing Technology Center of Japan/Cross Media Marketing
Published: March 2018, third edition

41

Published by:

Japan Aerospace Exploration Agency (JAXA)
Satellite Applications Mission Directorate I,
Satellite Applications and Operations Center (SAOC) http://www.sapc.jaxa.jp/
Earth Observation Research Center (EORC) http://www.eorc.jaxa.jp/
For inquiries about ALOS-2 applications, please contact:

Satellite Applications Mission Directorate I, JAXA
Satellite Applications and Operations Center (Tokyo Office)Ochanomizu Sola City, 4-6 Kandasurugadai, Chiyoda-ku, Tokyo 101-8008, Japan

E-mail: SAPC-INFO@jaxa.jp