d Topographic map RBI in scale of 1:25.000, produced by the National
Mapping and Coordination Survey Agency BAKOSURTANAL. The RBI map is map that released in 2002.
e Multispectral image ALOS AVNIR-2, on June 17, 2009.
f BMKG’s tidal gauge annual report data of Semarang city.
g Data of global sea level rise from 1880 to 2009. This data has obtained from
CSIRO http:www.cmar.csiro.ausea levelsl_data_cmar.html in December 2011.
h Regional sea level time series data in Indonesian area. This data has
obtained in
December 2011
from http:sealevel.colorado.edu
contentregional-sea-level-time-series. i
Result of observation at the potential inundation areas and interview to the local resident. The interview has been conducted in February 2012.
3.3 Material Used
In order to fulfill the data required for purposes analysis, firstly must be conducted a data acquiring work to collect the ready available spatial data and
other data needed from various sources. These data might be in descriptive, tabular and spatial data type. Interpretation must be done for descriptive data,
tabular data need to query to filter it, while spatial data should be aggregate because it’s might be in various format before stored it in personal GIS
Geodatabase. While all of the data has been collected, there are several software and
hardware that needed to analyze it to become information. Personal computer, printer, global positioning system GPS, and digital camera is the example of
hardware that used in this research while software that used to for data collecting, processing, and analyzing is divided into opensource and licensed software.
3.4 General Method
The research has been conducted using combination of spatial and numerical modeling, remote sensing, and geographic information system. There are several
steps of data processing and analysis that must be done.
3.4.1. Measuring Daily Sea Level Change
One of the important factor affecting sea level change is tidal. Tidal level can be estimate using tides harmonic analyst where on of tools that can deriving
realistic tide model is FVCOM Finite Volume Coastal Ocean Model. FVCOM has incorporated the Foreman tidal forecasting program Chens,
2006 to compute realistic tidal elevation data for the initial conditions and on the open boundary. It needs coastline and bathymetry as the data to build
boundary of study area. Unstructured triangular mesh has to generate as the basic data to obtain tidal harmonic data as the input for the model. Up to six tidal
harmonic constituents can be included in the model. The six included tidal constituents are: 1 S
2
tide period = 12 hours; 2 M
2
tide period = 12.42 hours; 3 N
2
tide period=12.66hours; 4 K
1
tide period = 23.94 hours; 5 P
1
tide period = 24.06 hours, and O
1
tide period = 25.82 hours. The tidal forcing at the open boundary can be specified by either
amplitudephase of each tidal constituent. The harmonic analysis is carried out by using a least square fitting. In the second case, true clock time must be
specified and the results can be analyzed directly using Foreman’s harmonic analysis program. All of data input must be in the same directory and format so
that model can be run. UNIX programing was used to obtain the result of the model while some license software was used to displaying the result.
The general step of realistic tidal modeling using FVCOM can be seen in figure 3.2
