FUNGSI ANALISIS GIS
GIS Analysis Functions
4 Katagori Umum ◦ ◦ ◦ ◦
Retrieval/Klasifikasi/Pengukuran Overlay (tumpang susun) Neighborhood (Kedekatan) Connectivity (Konektivitas)
RETRIEVAL /KLASIFIKASI /PENGUKURAN
Retrieval, Klasifikasi, & Fungsi Pengukuran
Retrieval ◦ Pencarian selektif (Selective Search)
Klasifikasi/Classification (Overlays, combine) ◦ Mengidentifikasi satu set obyek yang merupakan bagian dari grup obyek yang sama ◦ Mendefinisikan sebuah pola
Pengukuran/Measurement ◦ Jarak, panjang, luasan/area, dsb
Retrieval: Pencarian selektif (Selective Search)
Sebuah alamat terpilih karena berada dalam lingkaran
Reklasifikasi (Vector)
Dissolving untuk agregasi polygons
Reklasifikasi berdasarkan Luasan
Bekerja dengan luas > 80 ha
Reklasifikasi berdasarkan hubugan (Contiguity)
Bekerja dengan obyek individu, bukan dengan klas obyek secara keseluruhan
Reklasifikasi Nilai Bekerja dengan elevasi antara 20 and 40 m
Ubah feet ke meters
Operasi Jarak Vektor: Buffers & Setbacks
Gambar sederhana dari operasi buffers dan setback. NOTE: buffers go outward from lines or areas; setbacks run inside of areas (not lines). Image Source: Chrisman, Nicholas.(2002). 2nd Ed. Exploring Geographic Information Systems. p 154. fig. 6-1
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Buffer: Illustrasi
Image Source: Chrisman, Nicholas.(2002). 2nd Ed. Exploring Geographic Information Systems. p 60. fig. 6-3
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OVERLAY (TUMPANG SUSUN)
2. Fungsi Overlay (Tumpang Susun)
Aritmatika ◦ penambahan, pengurangan, pembagian, perkalian
Logika ◦ menemukan di mana kondisi tertentu terjadi (and, or, >, <, etc.)
Perbedaan metode Raster & Vector ◦ Vektor baik untuk data yang tidak terlalu komplek/jarang ◦ Raste mudah dalam kalkulasinya
Overlay (demo – addition)
Overlay untuk Vector
3 tipe utama vector overlay ◦ point-in-polygon ◦ line-in-polygon ◦ polygon-on-polygon
Vector based overlay
Contoh point-on-polygon
Vector based overlay
Contoh line-on-polygon
Vector based overlay
Contoh polygon-in-polygon
Overlay Dasar Raster: Penjumlahan sederhana (Simple Addition)
Image Source: Chrisman, Nicholas.(2002). 2nd Ed. Exploring Geographic Information Systems. p 144. fig. 5-12
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Raster Overlay: Kombinasi Boolean
Image Source: Chrisman, Nicholas.(2002). 2nd Ed. Exploring Geographic Information Systems. p 125. fig. 5-3
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Fungsi Neighborhood membentuk keluaran nilai dari setiap sel lokasi sesuai dengan kedekatan dengan yang lainnya.
NEIGHBORHOOD (LINGK-SEKITAR)
3. Fungsi Neighborhood
Fungsi Dasar ◦ Rata-rata, perbedaan, mayoritas, minimum/maksimum, dan total
Parameter yang dicari: ◦ Lokasi Target ◦ Spesifikasi dari lingkungan sekitar ◦ Fungsi untuk melaksanakan dalm neighborhood element
3. Neighborhood Function (cont)
Operasi pencarian ◦ most common neighborhood operation
Contoh ◦ Menghitung jumlah dari pelanggan yang berjarak 2 km dari sebuah toko.
3. Neighborhood Functions (cont)
Point atau Line dalam Operasi Poligon ◦ Fungsi pencarian spesifik
Buffers (demo - point, line, polygon) Thiessen Polygons Operation
◦ defines the individual area of influence around a point ◦ used to predict values at surrounding points from a single point observation
Example: Neighborhood Function
Thiessen Polygons
Fungsi Neighborhood: Contoh
Tema Zona: Watersheds (DAS) Nilai tema: Elevasi Statistic type: Mean
Output: Rata-rata elevasi dari tiap watershed
Fungsi Neighborhood: 10x10 filter rata-rata dalam DEM
CONNECTIVITY
4. Fungsi Connectivity Digunakan untuk akumulasi nilai di atas sebuah area yang di analisis Parameter yang dicari:
◦ Spesifikasi bagaimana cara element2 spasial terkoneksi ◦ Aturan yang secara spesifik membolehkan pergerakan antar koneksi ◦ Unit ukuran
4. Fungsi Connectivity (cont).
Operasi Proximity ◦ Pengukuran jarak antara dua obyek ◦ Tidak terbatas pada jarak saja; bisa noise, time, pollution, etc.
Parameter yang dicari: ◦ Lokasi target ◦ Unit dari pengukuran ◦ Fungsi untuk menghitung proximity (distance/time/noise) ◦ Area yang akan di analisis
Example: Connectivity (Vector)
Proximity Operation: Road Buffer
Example: Connectivity (Vector)
Proximity Operation: Buffer Generation
Example: Connectivity (Vector)
Points
Lines
Polygons
Proximity Operation: Buffer Types
Example: Connectivity (Vector) Proximity Operation - Buffers & Setbacks
Diagram of simple buffers and a setback. NOTE: buffers go outward from lines or areas; setbacks run inside of areas (not lines).
Image Source: Chrisman, Nicholas.(2002). 2nd Ed. Exploring Geographic Information Systems. p 154. fig. 6-1.
4. Fungsi Connectivity (cont).
Operasi Contiguity ◦ spatial units are connected - defines “unbroken area”
Contiguity measures: ◦ size of neighboring area(s) ◦ shortest/longest straight line distance across adjacent area(s) ◦ specific shape of neighboring area(s)
Contiguity Functions
Combines adjacent units together when they share a common attribute
4. Fungsi Connectivity (cont).
Operasi Jaringan (Network Operations) ◦ set of interconnected lines that represent a set of features through which resources flow
Fungsi jaringan umum (Common network functions) ◦ Permasalahan shortest path ◦ location-allocation modeling (resource allocation) ◦ traveling salesperson problem (route optimization) ◦ route tracing (prediction of network loading)
4. Connectivity Functions (cont).
Operasi Analisis Visibiliti ◦ identification of areas of terrain that can be seen from a particular point on the surface
Viewshed Operation ◦ uses digital elevation model data (DEMs) or..... ◦ digital terrain model data (DTMs) or...... ◦ triangulated irregular network data (TINs)?
Connectivity Function Example: Viewshed Analysis
Image Source: Chrisman, Nicholas.(2002). 2nd Ed. Exploring Geographic Information Systems. p 198. fig. 8-14
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Viewshed aka Intervisibility
Environmental Impact Analysis
3D landscape model impact on natural beauty
Another term: Surface Analysis
Surface functions ◦ density, contour, interpolation functions ◦ aspect, slope, hillshade, etc. ◦ watershed analysis and modeling (flow direction, flow accumulation, flow length, watershed delineation, stream ordering) ◦ visibility modeling/mapping determine the area that can be "seen" from the target location
The 3rd Dimension: Height Analysis
Contours Hill shading Spot height symbols Cliff & slope symbols Viewpoint symbols
Analysis: Summation GIS does not always provide exact answers to problems, but by identifying trends based on geography, GIS can reveal patterns that can help us make informed decisions. A GIS can improve decision-making; it cannot make decisions for us.
Flood Risk
3D height data changing water levels-danger areas
Derived Mapping: Data from images
Numerical Values
Color Representation
Derived Mapping: Data from images
Aerial Imagery
Digitized Buildings
Derived Mapping: Data from images
Satellite Imagery
Derived Area Map
This is a goal: Not there yet!
Retail: Site Selection
Existing stores, 15 min. drive time, demograhics
Airport Noise Pollution
noise complaints mapped by address location
