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3.2.1. Need Analysis
Need Analysis was done by interviewing and questioning the stakeholders to acquire all possible variables referring multicriteria and possible alternative
routes which are relevant to determining the CNG pipeline network. The method used to choose the stakeholders was purposive sampling by considering that the
stakeholders are the experts who understand the problem that is occurred and has ability to perform the policy or give suggestion relevant to decision making.
3.2.2. Defining Goal and Objective
Defining the goal and objective were based on interview with the stakeholders by considering the entire criteria and possible alternatives. In order to
reach the goal, there are some sets of objective that also should be considered as stated below:
• What kind of site the pipeline will be installed • Engineering specification and piping standard that proper to the site
• Where the pipeline should be installed • All factors that may be considered for the proximity to the source, CNG
pipeline, and CNG station SPBG
3.2.3. Conceptual Design
Conceptual design is the step in GIS design where the contents of the data and methods are identified and described. Figure below shows the steps to build a
model in GIS.
19 Figure 5. Conceptual Model
• Stating the Problem
To solve the spatial problem, it needs to be started off by clearly stating the problem to solve and the goal to achieve.
• Breaking Down the Problem
Once the goal is understood, it must break the problem down into a series of objectives, identify the elements and their interactions that are needed
to meet the objectives, and create the necessary input datasets to develop the representation models.
By breaking the problem down into a series of objectives, it will discover the necessary steps to reach the goal, which will help to solve the
problem. If the goal was to find the best route for CNG pipeline, and the objectives might be to find out where the pipeline should be laid down, what
land used types should the most proper, and so on.
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• Exploring Input Dataset
It is useful to understand the spatial and attribute relationships of the individual objects in the landscape and the relationships between them. To
understand these relationships, it needs to explore the data.
• Performing Analysis
At this stage, it needs to identify the tools used to build the overall model. In ArcGIS Spatial Analysis provides a wide variety of tools to serve
this purpose. In CNG pipeline case, it may need to identify the tools necessary to select and weight certain land used types, buffer housing, building, utilities
and roads, and weight them appropriately.
• Verifying the Model Result
Check the result from the model in the field. Do certain parameters need to change to give a better result?
• Implementing the Result
Once the spatial problem already solved, verifying that the result from a particular model meets the initial expectations outlined in state the problem,
and then implement the result.
3.2.3.1. Data Preparation
Busway corridor is a vector line that connects the beginning and ending of a bus traveling with a potential point for SPBG. The base maps are collected data
such as utilities, public services, roads, houses, etc. While gas sources is an existing gas main pipe with a potential point to be branched to SPBG. Figure 6
displays the data preparation process.
21 Figure 6. Data Preparation
Pipeline data is relatively simple such as centerlines and value, but the surrounding data that determines its location can be more complex such as
proximity analysis criteria. Thereby, the entire data required are as listed below: 1. Jakarta base maps were collected from BIOTROP Training and
Information Centre BTIC and MIT program that include utilities, public services, roads network, buildings, and houses. Then, it was processed to
calculate information that quite difficult or even impossible to collect, such as proximity, and density.
2. Existing gas main pipe that were collected from PT. PGN Perusahaan Gas Negara Tbk.
3. Corridor VII of the Transjakarta Busway Route that was collected from BP Transjakarta.
4. While the decision criteria and alternatives were based on expert
interpretation and judgment that were acquired from interview. 3.2.3.2. Procedure
The procedure that was performed in this research consists of spatial analysis, rating method and analytical hierarchy process.
22
a Spatial Analysis
Spatial Analysis is able to perform cell-based raster analysis. Of the two main types of GIS data raster and vector, the raster data structure provides the
most comprehensive modeling environment for spatial analysis. In general terms, a model is a representation of reality. Due to the inherent
complexity of the world and the interactions in it, models are created as a simplified, manageable view of reality. Models help you understand, describe, or
predict how things work in the real world. There are two main types of model: • Representation models
Representation models try to describe the objects in a landscape, for example, buildings, roads, or utilities. The way representation models are created
in a geographic information system GIS is through a set of data layers. For Spatial Analysis, these data layers will be either raster or feature data. Raster
layers are represented by a rectangular mesh or grid, and each location in each layer is represented by a grid cell, which has a value. Cells from various layers
stack on top of each other, describing many attributes of each location. The representation model attempts to capture the spatial relationships
within an object for example, the shape of a building and between the other objects in the landscape for example, the distribution of buildings. Along with
establishing the spatial relationships, the GIS representation model is also able to model the attributes of the objects for example, who owns each building.
Representation models are sometimes referred to as data models and are considered descriptive models.
• Process models Process models attempt to describe the interaction of the objects that are
modeled in the representation model. The relationships are modeled using spatial analysis tools.
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b Rating Method
The procedure was assigning arbitrary weight to the most important alternatives. Proportionately smaller weights were then given to alternative lower
in the order. The procedure was continued until a score was assigned to the least important alternative. Then the score assigned to the least important attribute was
taken as an anchor point for calculating the ratios. Specifically, the value for the least important alternative was divided by the value for each alternative.
c Analytical Hierarchy Process
Weighting of the criteria was achieved using a portion of the Analytical Hierarchy Process AHP as a systematic method for comparing decision criteria
with a simple equation “Gas Pipeline Route = fSPBG, Route”. The procedure involves mathematically summarizing paired comparisons of the relative
importance of the criteria. The result was applied to perform matrix multiplication with alternative scoring to produce decision score.
3.2.3.3. Required Tools Hardware Requirements
• PC Pentium 4 2.8GHz that appropriate for digital image processing and GIS data modeling with 512 Mb of DDR memory NVidia G-Force FX 5200 video
graphic adapter.
Software Requirements
• ER Mapper 6.4 • ArcGIS 9.1 Full Package Edition
• AutoCAD Map 2000i • Criterium DecisionPlus 3.0
• Google Earth non commercial use
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3.2.4. Spatial Data Processing 3.2.4.1. Map Projection
Map projection is designed for specific purposes. One map projection might be used for large-scale data in a limited area, while another is used for a
small-scale map of the world. In this case we use Universal Transverse Mercator UTM.
3.2.4.2. Formatting and Editing
In this step the projected data was being manipulated in addition to mapmaking and map analysis by creating and editing geographic data as well as
tabular data creating and modifying new features and editing attribute.
3.2.4.3. Euclidean Distance Analysis
The Euclidean distance functions described each cells relationship to a source or a set of sources. There are three Euclidean functions:
• Euclidean Distance gives the distance from each cell in the raster to the closest source. Example of usage: What is the distance to the SPBG?
• Euclidean Allocation identifies the cells that are to be allocated to a source based on closest proximity. Example of usage: What is the SPBG?
• Euclidean Direction gives the direction from each cell to the closest source. Example of usage: What is the direction to the SPBG?
3.2.4.4. Proximity Analysis
Proximity analysis is almost the same with Euclidean distance by buffering the features for certain purposes.
3.2.5. Decision Making
This step generated the probability of alternatives for CNG Pipeline network that meet the entire criteria. In terms of Analytical Hierarchy Process,
each criteria was being compared in full pairwise comparison while the alternatives by performing rating method.
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3.2.5.1. Criteria Weighting
A scale from 1= equally important through 9= extremely important was used to record the relative level of importance for the pairwise combinations of
the decision elements. It had confirmed that a scale of nine units was reasonable and reflected the degree which could discriminate the intensity of relationships
between elements. Each member of the group first orders the decision elements to be compared so the statement “element A is preferred over element B”was
correct, and then recorded the appropriate rating value 1 to 9 for the strength of the opinion.
Tabel 1. Importance Level
RATING IMPORTANCE LEVEL
1 Equally important
2 Equally to moderately more important
3 Moderately more
important 4
Moderately to strongly more important 5 Strongly
more important
6 Strongly to very strongly more important
7 Very strongly more important
8 Very strongly to extremely more important
9 Extremely more important
The number of judgments needed for a particular matrix of order n, the number of element being compared, was nn-12 because it is reciprocal and the
diagonal elements are equal to unity. An element of pairwise comparison matrix a
ij
represented a relative importance of element I compared with element j. A consistent pairwise comparison held the following conditions:
ij ij
a a
1 =
≠∝ ≥
ij ij
a a
;
ij ik
jk
a a
a =
For n
k j
i ,...
2 ,
1 ,
, =
j i
ij
w w
a =
26 From pairwise comparison matrix, relative priorities of the elements
compared are derived in the form of priority vector W. There are a number of ways to derive the vector of priorities W from the matrix
ij
a A
= . However,
emphasis on consistency led to an eigen value formulation below: W
W A
× =
×
max
λ where
max
λ is the maximum eigen value of matrix. The solution was obtained by raising the matrix to a sufficiently large
power, then summing over the rows and normalizing to obtain the priority vector
n
w w
w W
, ,
,
2 1
K =
. The process was stopped when the difference between components of the priority vector obtained at k
th
power and at the k+1
th
power had been less than some predetermined small value.
max
λ is always greater than or equal to n for positive, reciprocal matrices, and is equal to n if and only if A is a consistent matrix. Thus,
max
λ provides useful measure of the degree of inconsistency. Hereby,
,
max i
j ij
w w
a Σ
= λ
for j=1,2,…,n Normalizing this measured by the size of the matrix, consistency index
CI was defined as 1
max
− −
= n
n CI
λ
For each size of matrix n, random matrices were generated and their mean value, called as the random index RI was computed. These values were
illustrated in table 3.10. Using these values, the consistency ratio CR was defined as the ratio of CI to the RI. CR is a measure of how a given matrix
compared to a purely random matrix in terms of their CI’s. Therefore:
RI CI
CR =
27 Table 2. Random Consistency Index
n 1 2 3 4 5 6
RI 0 0.58 0.90 1.12 1.24
n 7 8 9 10
11 12
RI 1.32 1.41 1.49 1.51 1.53 1.56
n= size of pairwise comparison matrix
A value of CI andor 1
. ≤
CR is typically considered acceptable. Larger value
required the decision maker to reduce the inconsistency by revising judgments.
When using ArcGIS Spatial Analysis for processing, it will be able to access existing raster datasets and create new ones. It is important to understand
how raster data is represented in ArcGIS Spatial Analysis, how the ArcGIS Spatial Analysis functions alter the input data, and how the characteristics of the
input data and the settings it apply would affect the output data.
3.2.5.2. Alternative Scoring
This method requires the decision maker to allocate 100 points across the criteria of interest. Specifically, it is based on allocating points ranging from 0 to
100, where 0 indicates that the criteria can be ignored and 100 represents the situation where only one criteria need be considered in a given decision situation.
3.2.6. Selecting Alternative
This is the final step to select the alternative based on the highest decision score. By adjusting the weight, sensitivity analysis can be illustrated with respect
to the criteria.
IV. RESULTS AND DISCUSSIONS
4.1. Need Analysis
Based on previous study conducted by PT. Perusahaan Gas Negara PGN on 2004, there were six
users stakeholders DKI government, BP TransJakarta,
gas supplier, pipeline constructor, and compressor provider who involved in the pipeline project. Furthermore, by conducting a series of interview, discussion, also
questioning the stakeholders PT. Perusahaan Gas Negara, BP TransJakarta, and DKI Government and some respondents from residence and public services, the
criteria of pipeline path determination havedetermination have
been identified the
as follows: 1. The length of the pipe
2. Installing the pipe under the shoulder of existing roadways 3. Installing the pipe beside the existing utilities
4. Considering 25 meter site plan proximity to residential housing and building.
5. Considering 25 meter site plan proximity to public services hospital, industrial, institutional, commercial, and business.
6. Minimizing area of land ownership status. 7. Minimizing area of disruption that caused by construction
In addition, there were some existing conditions should be taken into consideration such as:
1. Existing gas main pipe 6” under the shoulder of Jagorawi Toll road up to Bypass Jakarta City Toll road.
2. Existing PPD Bus Depot at Cililitan and Kramat Jati that either would be taken over by BP Transjakarta for Busway pool and there would be
installed CNG Station called SPBG Stasiun Pengisian Bahan Bakar Gas.
3. Bus station at Kampung Rambutan, Cililitan, and Kampung Melayu which part of their area would be used by the BP Transjakarta as their
becoming Busway Pool and also where the CNG station would be installed.
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