Sains Malaysiana 46(1)(2017): 27–34
http://dx.doi.org/10.17576/jsm-2017-4601-04
Representing Landslides as Polygon
(Areal) or Points? How Different Data Types Influence the Accuracy of Landslide
Susceptibility Maps
(Mempersembahkan Tanah Runtuh dalam Bentuk
Poligon (Luas) atau Titik? Bagaimana Jenis Data Berbeza Mempengaruhi Ketepatan
Peta Kecenderungan Tanah Runtuh)
NORBERT SIMON1*, MAIREAD DE ROISTE1, MICHAEL CROZIER2 & ABDUL GHANI RAFEK3
1Geology Program, School of Environmental
& Natural Resources Sciences, Faculty of Science and Technology, Universiti
Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia
2School of Geography, Environment and Earth Sciences, Victoria
University of Wellington
New Zealand
3Department of Geosciences, Universiti Teknologi PETRONAS,
Bandar Seri Iskandar
31750 Tronoh, Perak Darul Ridzuan, Malaysia
Diserahkan: 19 November 2015/Diterima: 19
April 2016
ABSTRACT
In the literatures, discussions on
the accuracy of different models for landslide analysis have been discussed
widely. However, to date, arguments on the type of input data (landslides in
the form of point or polygon) and how they affect the accuracy of these models
can hardly be found. This study assesses how different types of data (point or
polygon) applied to the same model influence the accuracy of the model in
determining areas susceptible to landsliding. A total of 137 landslides was
digitised as polygon (areal) units and then transformed into points; forming
two separate datasets both representing the same landslides within the study
area. These datasets were later separated into training and validation
datasets. The polygon unit dataset uses the area density technique reported as
percentage, while the point data uses the landslide density technique, as means
of assigning weighting to landslide factor maps to generate the landslide
susceptibility map that is based on the analytical hierarchy process (AHP)
model. Both data groups show striking differences in terms of mapping accuracy
for both training and validation datasets. The final landslide susceptibility
map using area density (polygon) as input only has 48% (training) and 35%
(validation) accuracy. The accuracy for the susceptibility map using the
landslide density as input data achieved 89% and 82% for both training and
validation datasets, respectively. This result showed that the selection of the
type of data for landslide analysis can be critical in producing an acceptable
level of accuracy for the landslide susceptibility map. The authors hope that
the finding of this research will assist landslide investigators to determine
the appropriateness of the type of landslide data because it will influence the
accuracy of the final landslide potential map.
Keywords: AHP;
Geographic Information System (GIS); landslide; landslide
density; landslide susceptibility map
ABSTRAK
Kajian lepas
telah banyak membincangkan kejituan model tanah runtuh yang berlainan. Walau
bagaimanapun, sehingga sekarang, perbincangan mengenai jenis data (tanah runtuh
dalam bentuk titik atau poligon) dan bagaimana jenis data ini mempengaruhi
kejituan model-model tanah runtuh ini agak sukar untuk ditemui. Kajian ini menilai bagaimana pelbagai jenis data (titik atau
poligon) mempengaruhi ketepatan model dalam menentukan kawasan-kawasan yang
cenderung untuk mengalami tanah runtuh. Sebanyak 137 tanah runtuh telah
didigitkan sebagai unit poligon (keluasan) dan data yang sama ini kemudiannya diubah kepada data titik; membentuk dua set data yang
berasingan dengan kedua-duanya mewakili tanah runtuh yang sama dalam kawasan
kajian. Set data ini kemudiannya dibahagikan kepada set latihan dan set penentusahan.
Unit data poligon menggunakan teknik ketumpatan keluasan dan dilaporkan dalam
bentuk peratusan, manakala data titik menggunakan teknik ketumpatan tanah
runtuh (frekuensi) sebagai kaedah untuk menentukan pemberat dalam peta faktor
tanah runtuh yang kemudiannya digunakan untuk menjana peta kecenderungan tanah
runtuh berasaskan model Proses Analisis Hierarki (AHP).
Kedua-dua kumpulan data ini menunjukkan perbezaan yang ketara daripada segi
ketepatan pemetaan untuk set data latihan dan penentusahan. Peta kecenderungan
tanah runtuh yang menggunakan ketumpatan kawasan (poligon) sebagai input hanya
mempunyai ketepatan 48% dan 35% masing-masing untuk set data latihan dan
pengesahan. Manakala ketepatan peta kecenderungan yang menggunakan ketumpatan
tanah runtuh (titik) sebagai data input mencapai 89% dan 82% untuk kedua-dua
set data latihan dan penentusahan. Keputusan ini menunjukkan
bahawa pemilihan jenis data untuk analisis tanah runtuh adalah kritikal dalam
menghasilkan peta kecenderungan tanah runtuh pada tahap ketepatan yang boleh
diterima. Penulis berharap hasil kajian ini dapat membantu para pengkaji
tanah runtuh untuk memastikan kesesuaian jenis data yang digunakan kerana
pemilihan jenis input data tersebut akan mempengaruhi
hasil akhir peta potensi tanah runtuh yang dihasilkan.
Kata kunci: AHP; ketumpatan tanah
runtuh; peta kecenderungan tanah runtuh; Sistem Maklumat Geografi (GIS); tanah runtuh
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*Pengarang untuk
surat-menyurat; email: norbsn@ukm.edu.my
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