19 The purpose of quantitative accuracy assessment is identification and
measurement of map errors. Quantitative accuracy assessment involves the comparison of a site on a map against reference information for the same site
Congalton and Green 1999. There are two types of map accuracy assessment: positional and thematic.
Positional accuracy deals with the accuracy of the location of map features, and measures how far a spatial feature on a map is from its true or reference location
on the ground Bolstad 2005 in Congalton and Green 2009. Thematic accuracy deals with the labels or attributes of the features of a map, and measures whether
the mapped feature labels are different from the true feature label Congalton and Green 2009.
Accuracy assessments include three fundamental steps Congalton and Green 2009: 1 designing the sample, 2 collecting data for each sample, and
3 analyzing the results. Each step must be rigorously planned and implemented. First, the accuracy assessment sampling procedures are designed, and the sample
areas on the map are selected. We use sampling because time and funding limitations preclude the assessment of every spatial unit on the map. Next,
information is collected from both the map and the reference data for each sample site. Thus, two types of information are collected from each sample:
• Reference accuracy assessment sample data: The position or class label of the accuracy assessment site, which is derived from data collected that are
assumed to be correct. • Map accuracy assessment sample data: The position or class label of the
accuracy assessment site, which is derived from the map or image being assessed.
Third, the map and reference information are compared, and results of the comparison are analyzed for statistical significance and for reasonableness. In
summary, effective accuracy assessment requires 1 design and implementation of unbiased sampling procedures, 2 consistent and accurate collection of sample
data, and 3 rigorous comparative analysis of the sample map and reference data.
20
III. METHODS
3.1 Time and Research Location
The research was started from problem identification, searching related references, and developing research methodology in order to develop the research
proposal. The research was continued with collecting, processing, and analyzing data which completed with result and discussion, and conclusion. The research
was conducted during 17 months that started from March 2009 to July 2010. Writing the research proposal and data collection was done during March –
August 2009 in Bogor Agricultural University and Siak District Indonesia, while processing and analyzing data, writing the result and discussion, and constructing
the conclusion of the research have been done in the University of Tsukuba Japan, during September 2009 – July 2010 in term of exchange research student
program has been conducted. The detail of the schedule is shown in Appendix 6.
Figure 3. The research location: Siak District, Riau Province The research location is Siak District which is located in Riau Province.
Siak District is an enlargement from some parts of Bengkalis District that was done in 1999. In this research, the land use change study in Siak District would be
started in 2002 which means 3 years after the district enlargement done administratively. The consideration in taking 2002 as starting time of the research
is during 1999 – 2002 was the transition period which some activities in Siak District related to the spatial planning and land management still used some
21 policies and the land management plans of Bengkalis District as mother district.
Since 2002, Siak District has started to manage their district independently. Geographically, Siak is situated in 0°21’19.50” - 1°14’43.87” north
latitude and 100°54’46.31” - 102°58’27.34” east longitude and located between 0 - 110 m above sea level. Siak neighbors with Bengkalis District in North, Kampar
District and Pekanbaru Municipality in South, Rokan Hulu District in West, and Bengkalis and Pelalawan District in East. Siak is loacated in Siak Watershed with
Siak River as the main river. The landscape of Siak mostly is wetlands, and only little part in west side is hilly. The majority of Forest land in Siak District is
Peatland Forest. Based on the spatial analysis, Siak District has area about 868,117.82 Ha,
and about 59 of the total area is allocated for crop and timber plantation and 9 for production forest. Furthermore, Siak Government has also allocated land for
other uses such as agriculture area. There are two types of agriculture area in Siak: wetland agriculture and dry land agriculture. The preeminent commodities of crop
plantation, which are managed, are rubber, oil palm, coconut and coffee which are run by private company and community. Siak also has large oil and gas resources,
incorporated by international company which contributes in increasing the economic growth there Siak District Government 2008.
3.2 Data Source
Data required in this research were divided into two categories: spatial data and non-spatial data. Spatial data can be distinguished into two types: raster
and vector data. Raster data, which were used in this research, is LANDSAT 7 ETM+ LANDSAT images year 2002, 2005, and 2008. LANDSAT images
would be interpreted to produce land use categories data year 2002, 2005, and 2008 which would be used either as object of the study land use change or
relevant factors of land use changes. Other raster data used were SRTM-DEM 90m of Siak District that would be processed to produce altitude and slope data.
Vector data consisted administration boundary, land useland cover data from previous years, infrastructure development such as road and market place, river
