visual interpretation for forest change detection in fiji
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Visual Interpretation for Forest Change Detection in Fiji. Vilisi Tokalauvere SOPAC Pacific GIS&RS Conference November 2011 Lotus Building, Suva. Purpose of Forest Mapping. Direct comparison of digital forest layers 1991 and 2001 did not work - PowerPoint PPT PresentationTRANSCRIPT
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Visual Interpretation for Visual Interpretation for Forest Change Detection in Forest Change Detection in
FijiFiji
Vilisi TokalauvereVilisi Tokalauvere
SOPACSOPACPacific GIS&RS ConferencePacific GIS&RS Conference
November 2011November 2011
Lotus Building, SuvaLotus Building, Suva
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Purpose of Forest MappingPurpose of Forest Mapping
• Direct comparison of digital forest Direct comparison of digital forest layers 1991 and 2001 did not worklayers 1991 and 2001 did not work
• Layer 1991 and layer 2001 had to be Layer 1991 and layer 2001 had to be adjusted through visual image adjusted through visual image interpretationinterpretation
• Forest layers 1991 and 2001 had to Forest layers 1991 and 2001 had to be geometrically correctedbe geometrically corrected
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Why visual Why visual interpretation? interpretation?
•Pacific Island Country Pacific Island Country conditions are different!conditions are different!–Transparent workTransparent work–Local knowledge addedLocal knowledge added–Difficult atmospheric Difficult atmospheric conditionsconditions
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Forest Cover Mapping 1991Forest Cover Mapping 1991
•Supervised maximum Supervised maximum likelihood classification with likelihood classification with DTM involvementDTM involvement
•Conducted by a company in Conducted by a company in northern Germanynorthern Germany
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Forest FunctionForest FunctionMap 1992Map 1992
Raster data GIS applicationRaster data GIS application
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Forest Inventory 2006Forest Inventory 2006• Conducted with image data recorded Conducted with image data recorded
2001/20022001/2002• Condition maximum likelihood Condition maximum likelihood
classification classification • Solution: Unsupervised classification Solution: Unsupervised classification
with maximum visual interaction with maximum visual interaction • Mask buildingMask building• Reducing 3 forest densities (1991) to 2Reducing 3 forest densities (1991) to 2
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Water Mask AppliedWater Mask Applied
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Digitising in MapInfoDigitising in MapInfoDigitising in MapInfoDigitising in MapInfo
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ERDAS Mangrove MaskERDAS Mangrove Mask
Mangrove mask Vanua Levu
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HazeHazeHazeHaze
Different thresholds
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Visual InterpretationVisual Interpretation
Mangrove Forest
Pine Plantation
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DigitisingDigitising
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Decisions During DigitisingDecisions During Digitising
Clouds Y/N ?Clouds Y/N ? YesYes Digitising from Forest Digitising from Forest Layer 1991Layer 1991
NoNo
Digitising from Digitising from PlantationPlantationLayer 1991Layer 1991
YesYesPlantation area Y/N ?Plantation area Y/N ?
Digitising from both image backdropsDigitising from both image backdrops
NoNo
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Toggle between BackdropsToggle between Backdrops
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Digitising 1991 LayerDigitising 1991 Layer
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Digitising 2001 Forest LayerDigitising 2001 Forest Layer
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10x 10 km GRID10x 10 km GRID
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Description DatabaseDescription Database
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Vector to RasterVector to Raster
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MapInfo to ERDASMapInfo to ERDAS
• Forest, Mangrove polygons exported Forest, Mangrove polygons exported (DXF) to ERDAS.(DXF) to ERDAS.
• Add Projection.Add Projection.• Convert to raster.Convert to raster.• Add to forest cover layer. Add to forest cover layer.
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Reducing to Mappable Reducing to Mappable Area Size Area Size
ClumpClump
EliminateEliminate
Cluster No. 23841.2 ha
All clusters < 1 hectare are joined with the next biggest neighbour class
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1Hectare Accumulation1Hectare Accumulation1Hectare Accumulation1Hectare Accumulation
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Field VerificationField Verification
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Next..Next..
• Fiji Department of Agriculture – Fiji Department of Agriculture – agriculture, bare land, pasture landagriculture, bare land, pasture land
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Vinaka !Vinaka !