Preserving Precious Green

October 28, 2002
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Updating Thailand's forestland boundaries through GIS and GPS.



Staff workers look on as a colleague marks the appropriate data for a forestland boundary line, seen in red.
Thailand, located in the heart of southeast Asia, has a rich topography, including the mountainous north, fertile Central Plains and a semi-arid plateau in the northeast. As a result of the southern monsoons that sweep through the country’s coastline, Thailand boasts rich, moist, evergreen forests mainly in the southern and central areas of the country. One of Thailand’s main industries is agriculture (50 percent of the country’s 30 million workers are farmers); hence, land is highly valuable to the government and villagers. Local villagers looking for cash crop lands have rapidly depleted forestlands and removed boundary posts erected on forest grounds.

The Royal Forest Department (RFD) of Thailand, founded in 1896, establishes long-term guidelines for development and use of forestlands that is most beneficial to the national economy, security and the environment. To meet these guidelines, the Department needs updated, efficient maps. And because the current maps contain outdated data, the RFD was charged in 1999 with resurveying and mapping the national forestlands. The most recent update was in 1992; the current project should be completed in 2003. In the past, RFD spent more than 30 years attempting to complete fieldwork and mapping of the national forestlands using compasses, theodolites and measuring tapes. If the same procedures were used now, it would take the RFD another 30 years to complete this project.

For this update the RFD was given two provisions on the project: the fieldwork had to be completed within 24 months, and the data gathered had to have an accuracy level better than 3 meters. To gather data on the field, and to prepare and manage this monumental project, the RFD used 100 Leica Geosystems’ (Norcross, Ga.) GS5+ GPS receivers, Leica’s latest offering to the GPS receiver market, and ESRI’s (Redlands, Calif.) ArcPad GIS units. Fieldwork began this past June.

Deep in the forest, RFD personnel come upon a red-outlined forestland boundary line.

Mission Objectives

The RFD project is part of the Agricultural Sector Program Loan (ASPL). The office of ASPL (located in the Ministry of Agriculture and Cooperatives) supervises and controls project expenses and work plans. The Forest Engineering Division (FED) of the RFD is responsible for executing the project, including collecting and editing data, and building the database. Because this project effects a large number of Thais and requires large government expenditures, the parliament created a special ad-hoc committee to monitor the project.

The project, dubbed Revision of National Forest Land Boundary Maps, is funded by loans granted to the Thai government by the Asian Development Bank (ADB) with the following objectives:

  • To revise national forest maps by transferring the current publication of the national forest land map to the national topographic map scale, (1:50,000).
  • To build a GIS database depicting national forest land boundaries to serve government and non-government agencies that use forestland information in their projects.
  • To run the test pilot project of the demarcation that occurred in five areas of forestland by hiring a private surveying company to study how different forestland owners can best work and cooperate with each other. The pilot project is to be executed in 2003.
  • To enable the RFD to take more aggressive steps in forest protection efficiency and reduce the number of conflicts that arise between RFD and local villagers. As national forest maps are based on small-scale maps, the margin of error in marking boundaries on these maps is greater, resulting in more boundary conflicts between villagers and the RFD. This project will reduce the margin of error in boundary maps.

The RFD often works in conjunction with the Department of Lands (DOL), which oversees and conserves Thailand’s forestlands and farmlands to determine and issue land deeds and permits. In the past, boundary errors made deed and certificate issuance a lengthy, painstaking process. Both government agencies and villagers now have a faster process, as well as a more accurate land issuance process.

"This project will decrease past land boundary inconsistencies between the RFD and the DOL," says Sukanya Vareesri, director of the aerial photogrammetry mapping subdivision of the Mapping Technology Bureau, Department of Lands. "Now, if the RFD knows where forestland boundaries are located, the DOL can efficiently issue (land) title deeds and land use certificates with complete confidence."

An RFD staff worker tests the GS5+ GPS receiver before embarking on the Forestland National Forest Land Boundary Maps project to determine the boundary lines of the Thailand’s forests.

Preparing Forestland Area

Almost all national forestlands are close to private land property. The RFD must make certain the fieldwork is carried out carefully and accurately. Personnel are using Differential GPS (DGPS), i.e. using different code corrections to achieve an enhanced positioning accuracy of 0.5 to 5 meters to attain accurate boundaries close to private lands. Initially, forestland data (including data sheets, maps and aerial photos) was taken from numerous forestry offices throughout the country. Next, they recorded the boundary lines and posts on the topographic maps in ArcPad GIS. The points and lines were digitized in ArcView. The forestland boundaries were superimposed (vector) on the raster background of the maps. The boundary lines were edited and marked with natural features, political features and infrastructure features. The unique identification codes will be applied to all forestlands through the duration of the project.

Colleagues take data readings and write down notes as they mark one of Thailand’s numerous forestland boundary posts.

Gathering GPS Data

GPS data was gathered in the field with the GS5+, a 12-channel L1 GPS receiver with a 3-meter autonomous accuracy that can track data through dense foliage with its patented MaxTrak technology. The staff force (gathered from 21 regional forest offices) formed a total of 84 field survey parties. The number of parties in each regional forest was determined by the length and distance of the areas in which GPS data was to be collected.

Once in the field, they used the Navigation function of the GS5+, operated from a Pocket PC screen, to lead them to boundary posts. The 1 GB memory card stores all the Shapefiles and scans in the topographic maps in each regional forest area as they go. Staff workers are able to maintain about a 2-meter accuracy when gathering GPS data. Representatives from the local villages are also participating so they can oversee the data gathering process and confirm and accept the boundary results. The RFD brought local villagers into the demarcation process to make certain that boundary results could be agreed upon by both sides and finalized, instead of rehashed in the future, as has often been the case.

Villagers and RFD personnel review the boundary lines and boundary posts recorded and decide whether to accept or reject them. They consider the topographic features in the forests, such as creeks, channels and methods of land use, and take a consensus on whether the marked boundary lines and posts are acceptable. If rejected, they can move the lines and posts to another position, delete them or insert new ones until a consensus is reached. Once the boundary lines are determined, the Universal Transverse Mercator (UTM) coordinates of the line (used to make Thailand’s previous topographic maps) and post Shapefiles are recorded in the Pocket PC memory card. After the fieldwork is completed each day, the files are downloaded to the desktop PC and sent to the RFD Bangkok office where the data is updated in the GIS database. The RFD estimates that the GS5+ receivers will be able to cover about 3 kilometers of forestland per day.

GPS/GIS Benefits

The use of GPS and GIS technology for forestland mapping was a milestone and set a new precedent for the RFD, as it reduced field survey time from 30 years to just two years. By applying GIS technology, the RFD was also able to filter out lines that did not need to be resurveyed, reducing the amount of land to be covered by over 60,000 kilometers.

GPS fieldwork is faster and more efficient than previously used instruments with the same accuracy level, such as total stations. GPS also reduces the manual calculation time and amount of data to sift through in the field. By providing accurate forest boundary maps, the information in the RFD’s GIS database will help Thai government officials, environmental organizations and the general public to protect and monitor the forestlands from trespassers, and help solve longtime land tenure problems.

With previous trial-and-error boundary demarcation, villagers and government organizations may have unfairly been granted less land or less desirable land than they were due. Additionally, unreliable forest boundaries inadvertently forced the government to deviate from national rural planning and conservation plans. “Because we will have more accurate forestland boundary maps, human resources and rural settlement planning can now fall in line with existing national resources and management conservation plans,” Vareesri says.

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