10th Asian Regional Conference of IAEG (2015)

The Road from National LiDAR mapping program to Zonation of the Geohazards in
Taiwan
Li-Yuan FEI(1), Yu-Chung HSIEH(1)(1)Environmental and Engineering Division, Central Geological Survey, Taiwan
E-mail:feily@moeacgs.gov.tw
Abstract
On August 8, 2009, when typhoon Morakot swept through Taiwan, the island nation
suffered a devastating disaster, the scope of which it had never seen before. Typhoon Morakot
in two days brought 211cm of heavy rain, and in some southern Taiwan areas as much as
300cm of rain was measured. The resulting landslides amounted to 40,594 separate incidents.
Responding to the Morakot disaster, our government enacted an emergency measure, entitled“Special Statute for Reconstruction of Post-typhoon Morokot Disaster”, which prodded Central
Geological Survey to initiate a dedicated project aimed at the preservation of land in zones
sensitive to geohazards, due to geomorphological and geological conditions.
As part of this project, airborne LiDAR was deployed to establish a new nationwide
DEM (Digital elevation model) with grid size of 1 m, and to obtain digital aerial photograph,with grid size of 50 cm, simultaneously. The first National LiDAR mapping program wasconducted by four survey teams and one quality assurance team. Survey teams operated avariety of laser sensor systems. Weather, terrain relief, and dense vegetation conditions were
the three most challenging issues, limiting the performance of this project. After overcoming
all the difficulties, we completed the project and achieved our goal, which is, establishing thefirst National LiDAR map of Taiwan.
In addition, the application of high resolution DEM database to investigate and analyze
geologically sensitive areas, geological and topographical characteristics, river system analysis
were all part of this project. The key work was to identify and analyze large-scale landslides.
We concluded that there were about 600 high-susceptible, large-scale landslide areas in central,southern and eastern Taiwan.
At present we are planning a second phase of National LiDAR program in the near
future to further study different issues of large-scale landslides to prevent the Shiaolin Village
disaster from ever occurring again.
Keywords: national LiDAR mapping program, large-scale landslides, geologically Sensitive Area
1. Introduction
Nearly three-quarters of the territory of Taiwan and
95% of its population are exposed to multiple, frequent
natural hazards. Typhoon Morakot hit Southern Taiwan
on August 8 and 9, 2009. It inflicted an area of ten
thousand square kilometers with massive landslides,
debris flows and flooding. Among the victims, Shiaolin
Village suffered the most with 681 casualties, 18 people
still unaccounted for, and the destruction of over 100
houses. Our government realized that the country waslacking in detailed, accurate and current terrain data, as
well as aerial imagery. In response, a national LiDAR
mapping and zonation of the geohazards program,
employing state-of-the-art technology of integrated
airborne LiDAR and digital photography, was launchedby Central Geological Survey (CGS) in 2010 andcontinued to this date. To confer and grant under1

conditions laid down in the “Special Statute for
Reconstruction of Post-typhoon Morakot Disaster”, aproject of “Investigation and Analysis for GeologicallySensitive Areas under the Program of National Land
Preservation” was initiated. It was the first national
mapping program with the aim of simultaneously
capturing the territory (36,000km2) terrain data by
airborne LiDAR and digital imagery in Taiwan. The
terrain data would include very detailed DEM andDSM (Digital surface model) of 1-meter grid anddigital aerial photograph of 50-centimeter grid.
LiDAR provides high resolution topographic datawith notable advantages over traditional surveying
techniques (Slatton et al., 2007). With LiDAR
techniques, it is possible to generate a bare-earth
elevation model, and this fast and preliminary data
could meet the requirements for geological harzard
identification and suitable for analyzing many major

10th Asian Regional Conference of IAEG (2015)

hydro-geomorphic processes. For CGS, using thisdatasets to establish a new landslide inventory andestimate landslide activity in areas partially orcompletely covered by dense vegetation, was thought tobe a new powerful innovative method, especially forlarge-scale landslide research.
Applications with those high resolution datasets ofterrain are many folds: (a) geological structures andstratum identification, (b) landform change of riverbeds, river terraces, and river channels, (c) highlandslide susceptible zones evaluation, (d) large-scalelandslides detection, and (e) detailed geologicalmapping and safety assessment for selected areas near
mountainous settlements are the other objectives of thisproject.
Both the establishment of high resolution terrain
datasets and the identification of the locations withgeohazards were some of the many challenges we faced.
In this paper, the status of the national LiDAR mapping
program will be summarized. In addition, someexamples of studying active geomorphology andgeohazards on a regional scale are offered todemonstrate the unique capability of these terrain
datasets, especially for the potential large-scalelandslides associated with settlements in themountainous areas.
2.

As shown in Fig. 1, the small rectangles on the map are
the tiles of a 1:5,000 map-sheet with an area of around
7 square kilometers. In total, 5,519 tiles with 37,603
square kilometers (including parts of sea area) are to becompleted in six years. The typhoon Morakot disasterarea was divided into 10 survey blocks and theremaining area sub-divided into 12 survey blocks;
surveys would be conducted by four local companies.
Each year a survey team had to complete from 2,500(inMorakot disaster area) to 1,000(remaining area) square
kilometers. In addition, another 1,600 square kilometers
would still need to be surveyed in the events of typhoon,
severe rainfall, or earthquake.

Airborne LiDAR survey

In the last ten years techniques of Airborne LiDAR
have been developed and experimentally applied inland surveying and mapping since they provide notableadvantages over traditional survey techniques in
Taiwan. Establishing a national spatial database of highresolution DEM and DSM is very important for allphases of disaster management cycle, frompreparedness to response, to recovery, and is afoundation for national land preservation policy.
From the beginning of the project, there have been
multitudes of difficulties to overcome, such as: (a) 4different survey teams with different airborne LiDAR
scanning sensors with unequal experience level, (b)chronic shortage of aircrafts, (c) flight plans requiring
immediate approval, (d) frequent heavy clouds
unsuitable for executing aerial survey, (e) densely
developed urban and heavy forest coverage, (f)establishing surveying protocols and a strict, nearly
automatic review process, (g) complicated terrain relief
conditions, (h) matching of margins of survey blocks of
DEM,DSM and digital aerial photograph, (i) schedulingconstraints for carrying out the project.
Here, I shall focus on the survey plan, specifications,and the major challenges we are still facing.
2.1 The survey plan
Map tiles of survey plan are the basis of the framesof a large-scaled national map of scale 1:5,000 series.

2

Fig. 1 LiDAR survey plan in 2010-2015 of Taiwan .
For this project, the LiDAR scanning sensors including
Leica ALS70-HP, Riegl LMS-Q680i, ALTM Pegasus,
and Leica ALS60, belonged to 4 different companies.
For digital aerial photograph, they used DMC, AIC pro
P65+, IGI DigiCAM, Dimac Ultralight 60MP+,
Trimble Aerial Camera P65+cameras for this national
survey project.
Quality assurance was assigned to a team organized10th Asian Regional Conference of IAEG (2015)

by a survey professor. Team members were put incharge of maintaining the quality of LiDAR and digital
aerial photograph results, monitoring the whole process
and verifying the results of each survey team. Also,
quality assurance team assisted the survey teams inresolving unexpected events, completing quality
checkup manuals, providing instructions and updates of
the inspection procedures. Lastly, it designed at least 20
check-list tables for different processed results; some ofthem were checked automatically by computer
programs. The supervision and examination of the casefor the LiDAR measurement system, included in thehigh resolution LiDAR DEM Generation QA/QC in
Taiwan for the first time, has been very successful. We
believe that this is the key procedure for the completionof the survey plan.
2.2 Specifications
Although airborne LiDAR have been developed atleast ten years in Taiwan, many issues still remain forfurther discussions when applied to the entire island.
Deliverables, flight parameters, and the major
challenges, included in the specifications of this LiDAR
survey will be discussed here.
2.2.1 Deliverables
In addition to interim and final reports, three majordeliverables are required for this LiDAR survey: (a)LiDAR point clouds, (b) Synchronous colour aerial
photographs, (c) Digital Terrain Models.
For LiDAR point clouds, classified point clouds
were the main issue to be considered. An area of small
block representing a map unit of 1:5,000 map-sheet wasused for point cloud editing. One of the four classes
should be assigned to each point, namely outlier, water,
ground, and others. Outliers including low points, highpoints, and other possible noises should be identified
and filtered before going further for other point editing.
Water points should be assigned to all points that fell
on water-bodies as interpreted by ancillary informationsuch as colour aerial photographs. Intensive manual
editing was required to further distinguish groundpoints and others. Classified point clouds should bedelivered by data files of map-sheet with nomenclatureof 1:5,000 national map series.
Synchronous medium format colour aerial
photographs were required with the laser scanning.
Exterior orientation parameters of each frame of aerial
photographs had to be estimated by direct georeferencing and control points as applied to raw LiDAR
strips. Orthophotos with a GSD of 0.5m should be
generated and delivered along with the medium format
aerial photographs. Because colour aerial photographs
and airborne LiDAR needed different sky conditions tofly, the results were solved by increasing new flight
strips for survey team. Different colour or tone of theaerial photographs could be confusing, until the quality
control team could define a standard sampling.

3

One meter grid of DEM and DSM were the twomost important products to be delivered in this project
because they would be used by geologists forgeohazard interpretations. Both DEM and DSM were
measured at 1m grid resolution. DEMs at 1m grid wasinterpolated from ground points whereas DSM from all
points was filtered out of all outliers and water points.
2.2.2 Flight parameters
Flight plans would be checked by the quality
control team and approved by the authorities (to avoid
flying over military base). The technical parameters forflight plan included: (a) Point density should be at least
2 points per m2 in an above-mean-sea-level elevation
below 800m and at least 1.5 points per m2 above 800m.
(b) Point density should be more than 2 points per m2 inan mountainous areas with settlements for geoharzds
analysis, using more denser flight strips or full-wave
form technique to increase ground points if needed, (c)Normal flight lines should be parallel with at least 40%
overlap, (d) Cross flights perpendicular to normal
flights were required every 20km, (e) The FOV
scanning angle should not exceed 40 degrees, (f) Two
ground control GPS stations should be installed in a
distance less than 20km to the airplane for a flight
mission. The GPS receivers should be dual-frequency.
2.3 The major challenges
Weather and terrain relief conditions were the two
fateful issues limiting the execution of the project.
Other problems were of lesser consequences, comparedwith these two natural issues.
2.3.1 Weather conditions
Air sortie for data collection was dependent entirely
on weather conditions. Survey areas were located atlatitude from 21 to 25 degrees in tropical andsubtropical zones. The sky was cloudy most of the time
all year long, which made data acquisition difficult andimposed additional requirements for re-flight to fill thecloud gaps. Fig. 2 shows the statistics of de-facto flight
hours of a survey plane for aerial photography in thesecond half from years 2007 to 2009. Normally there
were at least 240 hours of day-light time in a month.
But, we were only able to log 68 hours of flight time inAugust of 2008. In overall average, there are only 30
hours of flight for a month, and only 200 hours for ayear. Some specific southern mountainous areas of
Taiwan have clouds over the sky over the years,
according to the past ten-years aerial photographrecords. The 4 survey teams installed some CCTV
stations in the key locations of the surveying areas toobserve the increment weather patterns in real-time inthese unfavorable conditions.

10th Asian Regional Conference of IAEG (2015)

teams were raised for discussion. Experiences wereshared. Some experiences were translated into survey
parameters as for renewed regulation. Finally, all theparticipants cooperated to make it a success of such achallenging project.

Hours for aerial survey

80
70

Y2007

60

Y2008

50

Y2009

40

Average

30
20
10

3.

0
June

July

Applications in geological Aspects

August September October November December AverageMonth of the year

Fig. 2 Statistics of flight hours of a survey plane from2007 to 2009, showing that most of the time the sky is
not suitable for aerial photography.
2.3.2 Terrain relief conditions
Terrain relief herein with is defined as the altitudedifference within one kilometer grid, which isapproximated by a swath of LiDAR scans. Taiwan is a
mountainous island with its highest point of Central
range, Yushan, at 3,952 meters above sea level.
Mountains account for 30% of its total area, hills andplateaus for 40%, and plains for the remaining 30%,
and there are more than 100 mountains higher than
3,000 meters. The valleys are very narrow, steep anddeep, in mountainous areas, that increases thedifficulties of airborne LiDAR and aerial photography.
In this high relief area, MPiA(Multi-Pulse in Air) modecannot be applied to give a higher density and thespacing of flight lines has to be closely distributed.
Using the multi-angle laser scanners or increasing flight
strips from different incident angle may raise theairborne LiDAR penetration rate and add effective
ground points.
In addition, human factors such as limitations due tonational security, air traffic clearance, and militarytraining all increase the difficulties of execution.
Military facilities or establishments are always
forbidden to be mapped by high resolution aerial
sensors operated by civilians. In the beginning, it would
take two to three months to obtain a survey permit
before any aerial operation could be conducted. The
limitation due to national security requirement wasnecessary. As shown in Fig. 1, the widest distancestretching east to west of Taiwan is only 144km.
Therefore, the sky is too crowded to allow many
airplanes in the air at the same time. In addition,
military training has the top priority. In some areas,
only weekends are available for civilian aerial survey.
On Aug 30, 2012, an airplane crashed while executing
the project in the eastern, mountainous areas, causing
three crew members to lose their lives, the saddest
event for this project.
The key for success of the project may be attributed
to the monthly meetings. Four LiDAR survey teams
and one team for quality check were invited to attend
the meeting. CGS hosted monthly meetings to monitor
the progress of all parties. Flaws found by the third
party team and issues encountered by all four survey

4

The understanding of a country's geomorphologicaland geological conditions is essential for combating andresponding to natural disaster. In the years 2005 to
2011, CGS mapped active faults, volcanic and othergeological features of northern Taiwan by using DEM
extracted from airborne LiDAR point-clouds. Although
this mapping project was very successful, only 5,400
square kilometers DEM mapping was completed inseven years. To establish the datasets of DEM, DSM
and digital orthoimages of the whole island were very
important, and applications with these high resolution
data of terrain to mitigate future natural disaster were
urgent for the authorities in the aftermath of theMorakot disaster in 2009. As Professor Paolo
Tarolli(2014) pointed out: the limits of using highresolution DEM, did not directly represent geology, andapplications to geologically complex areas might bedifficult. We believe only agency such as CGS, has thecapability and responsibility for both air surveying andgeological interpretation missions.
3.1 Large-scale landslide
Shiaolin Village became the focal point, nationallyand internationally, immediately after Typhoon
Morakot stuck. The press media wanted to know why
we couldn’t have predicted or prevented this kind ofdisaster. The public wanted to know who should beheld responsible for this tragedy. The experts andscholars wanted to research the mechanisms of thisgigantic and devastating landslide. In the mean time,
we learned that the Japanese government had publisheda map of “deep-seated landslides in Japan” in recent
years. To our regret, we could not even identify thiskind of landslide at the time. In the past, we at CGS
focused our attention mostly on the shallow landslide,slow moving landslide, and rock fall etc. The main
reason was attributed to the lacking of high resolution
datasets of terrain. So the first priority of theapplication with the datasets was to identify the largescale landslide by the results of new nationwide DEM
from year to year.
Definition and a universal scientific name were thefirst issue to be decided. Although there had not been
any consensus until now, we recommended 10,000
cubic meters in volume and 10 meters in depth as adefinition for reference. Considering human life, thesafety of inhabitants in the disaster-prone areas would
be the only exception to the above-mentioned definition.
For the official disaster reduction agency,
NCDR(National Science and Technology Center for10th Asian Regional Conference of IAEG (2015)

Disaster Reduction) has a different definition, it would
only consider the critical human infrastructure, disasterprone areas, and the landslide disaster magnitude etc.
affected by large-scale landslide and other triggered
disasters.
Because recognition of areas where large-scalelandslides may occur has become a critical issue forlandslide hazard mitigation for the government and forthe people living in mountainous areas of Taiwan,
zonation of large-scale landslide potential areas assoon as possible became our agency’s duty. Geologists
have adequate knowledge of geomorphology andgeology to identify large-scale landslide both in the lab
and in the field. So, compiling a detailed and constantly
updated inventory map of large-scale landslide was thefirst step of this strategy.
For large-scale landslides, detection andcharacterization are the most important task before any
mitigation measure can be taken or any inference oflandslide kinematics and mechanics can be made. After
Shiaolin Village disaster and similar landslides
occurred in other countries recently, many researchers
have paid more attention to this issue from different
aspects such as identification, investigation,
characterization, monitoring, simulation, hazard
assessment, risk evaluation, warning etc. Only theissues of identification, investigation, monitoring will
be presented and discussed in this paper.
Although automatic and objective method has beendeveloped, based on the use of thresholds obtained by
the statistical analysis of variability of landformcurvature (Lin et al., 2013). For example, introducing
simple topographic indexes of surface roughness
enables the automatic mapping of landslide
morphology and estimation of landslide activity,
providing a preliminary landslide inventory map (Paolo
Tarolli, 2014). But traditional expert-based method ismainly used for the detection of large-scale landslides
in this national program. Surface topography indicativeof past large bedrock landslides is very common incertain landscapes. In some areas large-scale landslides
have transformed steep, high relief topography into
lower-relief and lower-gradient topography, thereby
reducing the occurrence of shallow failures in theaffected areas. Unlike incipient shallow landslides in
bedrock hollows, large-scale landslides often show
signs of instability such as crown cracks, scarps,
tension cracks, transverse ridges and tipped trees.
Because most of the large-scale landslides are either
latent or located under forest cover, only a few of themwhich are in creeping or newly-happened in a
catastrophe can be identified in the past, but from
DEM-derived shading map and aerial photography aremuch easier to recognize. The merit of this newtechnology is obvious. Glenn et al. (2006) demonstrates
that high-resolution topographic data have the potential
to differentiate morphological components within alandslide, and they can support the analysis of the

5material type and landslide activity.
Together with the identification results, landslide
inventory and the geological map, checking in the fieldis the second step. Excepting for discontinuities, suchas bedding plane, foliation plane, faulting structure,folding structure, and joint sets, creeping and buckling
are the two kinds of important deformation phenomena
associated with potential large-scale landslide in theargillite, slate formation, and also sedimentary rocks
easily observed in the field. For example, Shiaolin
landslide has very typical buckling deformation
observed by Tsou et al.(2010). The most difficulty isdifferentiating the fissure, fracture, uplift, bulging,depression, opening all observed in the hillslopes, roads,
retaining walls etc. as a result of large-scale landslide orshallow landslide. We presume that high-potential
shallow landslide will trigger large-scale landslide as a
key block in the future and a large-scale landslideconsists of many shallow landslides in a delineated area.
For the time being, we mark all the signs in the map as
the preliminary results and will collect more
information from further investigation activities.
Traditionally, there are many commercial
monitoring devices installed in the field, such as raingauge, observation wells with piezometer, inclinometer,
extensometer both in the ground surface and borehole
are very common for landslide monitoring. Andinnovative new adequate devices such as “Multipleborehole extensometer” , “wireless extensometer” and“SAA(Shape Acceleration Array)” , utilized for theobservation of large-scale landslide activity arenecessary. Also we have constructed a network ofsingle-frequency GPS for measuring a single largescale landslide for surface displacement.
The above-mentioned innovated monitoring
techniques are still in prospective state, needing moretime and data to verify its valuation.
For this six-year project, we selected an area
covering 100 map-sheets of scale 1:5,000 with total
area of around 700 square kilometers for detailed field
investigation each year. These selected areas may take
into account already existing protective structures, suchas houses, public buildings, villages or traffic
constructions etc. which located in the low-relief
slopeland or high-relief mountainous areas, allconsidered highly geologically sensitive for natural
hazards. The safety assessment of the first three years,
in the severe damaged areas caused by typhoon
Morakot, included 403 villages in the area 2,100 square
kilometers. 469 large-scale landslides with total area of
3,155 hectre acres were identified (Fig. 3), and about 56of them close to 42 villages. Within 42 villages, 45% ofthem were evaluated as dangerous and threatened by
nearby large-scale landslides, 38% of villages wereranked as safe in specific conditions, and the remaining
17% considered safe. But when we delineated thepotential large-scale landslide areas without
consideration of the villages and the traffic

10th Asian Regional Conference of IAEG (2015)

constructions factors, we estimated about 1,607 largescale landslides with total area of 532.42 square
kilometers which covered an area about 4,980 square
kilometers. Roughly speaking, that was about 10% of
the assessed areas with large-scale landslide
susceptibility in the slopeland or mountainous areas in
Taiwan. The above mentioned results would be used toevaluate the geological susceptibility of the wholeisland and to mitigate reoccurrence secondary hazards
in the future.
3.2 Active fault
Taiwan is situated on an active orogenic belt andpossesses high seismicity and frequent active fault
hazards. More than 9 severe inland earthquakes havebeen recorded since last century. The morphotectonic
analysis provides not only the precise location and theactivity of the faults, but also the fundamental
information for geological hazard assessment in somecases. To better constrain the potential threat broughtby fault movements, the active faults morphotectonic
study has thus been analyzed by using the Airborne
LiDAR data. In 4 years (2011-2014), we analyzed themorphtectonic features of 33 active faults in total, readmore tectonic deformation information from
topography, defined the fault zone more precisely, andunderstood better the characteristics of each fault. At
the end, we reached the following objectives, results
and conclusions: (a) generation of 3D anaglyph images,(b) analysis of detail structural characteristics, (c)digitization of the fault traces of active faults and theirassociated structures, (d) evaluation and modification of
the strip geological map (2 kilometers wide of eachfault) within the study area, and (e) generation nearfault
3D geological anaglyph images. The results mightsuggest some possible sites for field
investigation and provide GIS dataset for other further
applications
3.3 Geohazard analysis after typhoon Morakot
disasterCGS has completed a series of environmental
geological map of scale 1:25,000, the maps included:(a) Lithological assemblage map, (b) Rockmass
strength map, (c) Environmental geological map, (d)Landslide susceptibility map, a nine-year project (20022010) before typhoon Morakot. The information
provided with fundamental dataset for experts toanalyze the environmental potential geological risks fora site and also provided recommendations to theauthorities to minimize and/or mitigate secondary
natural disaster impacts.
After typhoon Morakot, we established a newlandslide inventory map and will continue to renew thegeohazard datasets by the interpretation of new LiDAR
images and other ancillary information. The results ofgeohazard mapping should include: (a) geologicalstructures, (b) landform change of river beds, river

6

Fig. 3 The distribution of potential large-scalelandslides in middle and southern Taiwan.
terraces, and river channels, (c) landslide features, (d)high landslide vulnerable zones, and (e) detailed
mapping and assessment for selected areas near
mountainous settlements. One result of this part is mapsheet of scale 1:25,000 to include: (a) GeologicallySensitive Area Map, (b) Geohazards and Susceptibility
Map, and (c) Geohazard Map of Key Area Survey.
On Dec. 1, 2011, Taiwan enacted the Geology Act,it might be the first law to govern the geology
investigation in the world. The purpose of this Act is toimprove the geological survey system, to effectively
manage geological data of national land, and toestablish basic geological information related tochanges in the nation’s environment and to enact land
resources management. According to the Act, theauthority shall publicly announce areas with special
geological scenery, special geological environments, or
potential geological hazards to be geologically sensitive
areas. One kind of the geologically sensitive areas is
Landslide-Landslip Geologically Sensitive Area, whichmeans the areas with landslide history or highsusceptible sliding conditions. The identification ofpotential large-scale landslide, sliding-affected area,and dip-slope were evaluated from LiDAR-DEM data,
combined with other geological database to delineate
the Landslide-Landslip Geologically Sensitive Area. To

10th Asian Regional Conference of IAEG (2015)

date, delineation and publicly announcement ofLandslide-Landslip Geologically Sensitive Area is
13,693 square kilometers, close to 38% of Taiwan
territory. Almost 50% of population shall incorporate
data pertaining to geologically sensitive areas forreference in land utilization plans, land development
reviews,
hazardprevention
andmitigation,
environmental protection, and resource development in
the future.
4.

Summary

Thus far, we have applied the high-resolution
LiDAR topographic datasets only in small portions ofearth science applications, mainly in large-scalelandslide detection and active fault analysis. Although
it has its limits of applications, it has the potential tosolve the research problems especially in densely
forested areas and also in densely-populated urban
areas. As Paolo Tarolli (2014) pointed out: suchanalysis would help in scheduling appropriate
environmental planning for sustainable development, tomitigate the consequences of anthropogenic alteration
and, of course, to better understand the evolution of ourPlanet. So we are looking forward to opening more
avenues for researches relating to earth surface
processes based on geomorphic signatures. Also we areplanning a second phase of National LiDAR program in
the near future to establish the renewed dataset interrain information for sustainable land preservation
purpose.
References
Glenn, N.F., Streutker, D.R., Chadwick, D.J., Thackray,
G.D., Dorsch, S.J. (2006): Analysis of lidar-derived
topographic information for characterizing anddifferentiating landslide morphology and activity,
Geomorphology, Vol. 73, pp. 131–148.
Lin, C.W., Tseng, C. M., Tseng, Y. H., Fei, L. Y.,
Hsieh, Y. C., Tarolli, P. (2013): Recognition of large
scale deep-seated landslides in forest areas of Taiwan
using high resolution topography, J. Asian Earth Sci.
Vol. 62, pp. 389–400.
Slatton, K.C., Carter, W.E., Shrestha, R.L., Dietrich,
W.E. (2007): Airborne laser swath mapping:achieving
the resolution and accuracy required for geosurficial
research. Geophys. Res. Lett. 34, L23S10.
http://dx.doi.org/10.1029/2007GL031939.
Tarolli , P. (2014): High-resolution topography forunderstanding Earth surface processes: Opportunities
and challenges, Geomorphology, Vol. 216, pp. 295–
312.
Tsou ,C. Y., Feng, Z. Y., Chigira, M. (2011):
Catastrophic landslide induced by Typhoon Morakot,
Shiaolin, Taiwan, Geomorphology, Vol. 127, pp.166–
178.

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