Stereoscopy, DEM and Orthophoto - Concept Map
Stereoscopic Photogrammetry for 3D Terrain Capture and Orthophoto Production
Related concepts
Stereoscopy
Sub concepts
- Stereo pair formation
- Forward overlap (60%)
- Parallax measurement
- 3D model visualization
- Convergent and normal case photography
Relationship to central
Foundation for extracting 3D information from overlapping photographs
Base-Height Ratio (B/H)
Sub concepts
- Air-base measurement
- Flying height determination
- Height measurement sensitivity
- Vertical exaggeration factor
- Optimal B/H values for different applications
Relationship to central
Controls geometric strength and vertical exaggeration in stereo models
Digital Elevation Model (DEM)
Sub concepts
- Grid-based elevation data
- Triangulated Irregular Network (TIN)
- Photogrammetric extraction
- LiDAR acquisition
- InSAR radar methods
- Bare-earth elevation values
Relationship to central
Primary output for terrain representation and orthorectification
Relief Displacement
Sub concepts
- Vertical displacement due to elevation
- Radial displacement from nadir
- Image scale variation
- Tilt distortion effects
- Measurement errors in raw photos
Relationship to central
Image distortion caused by terrain variation that orthophotos eliminate
Orthophoto
Sub concepts
- Orthophoto production process
- Resampling methodology
- Uniform scale at specified datum
- Planimetric accuracy
- Orthomosaics
- Seamless base maps
Relationship to central
Final rectified product combining photographic detail with cartographic accuracy
Orthorectification
Sub concepts
- DEM-based correction
- Interior orientation parameters
- Exterior orientation parameters
- Geometric transformation
- Pixel resampling techniques
- Ground control points integration
Relationship to central
Critical process that uses DEM to produce orthophotos
Applications in Philippine Surveying
Sub concepts
- Land use mapping compliance with RA 4374
- Contour generation for topographic surveys
- Volume calculation for earthwork (PD 1529)
- Cadastral mapping (CA 141)
- Viewshed analysis
- Drainage and watershed delineation
- PPCS/UTM coordinate integration
Relationship to central
Practical use cases aligned with PRC standards and national mapping
Concept connections
- StereoscopyParallax MeasurementStereoscopic viewing enables human perception and measurement of parallax shifts between stereo image pairs
- Parallax Measurement3D CoordinatesParallax values, combined with collinearity equations and camera parameters, directly determine object heights and 3D positions
- Base-Height Ratio (B/H)Parallax Measurement AccuracyB/H controls the magnitude of parallax values; optimal B/H (0.5–0.7) provides good height sensitivity without excessive vertical exaggeration
- Base-Height Ratio (B/H)Vertical ExaggerationLarger B/H causes greater vertical exaggeration, making terrain features appear taller and steeper in the stereo model
- 3D CoordinatesDigital Elevation Model (DEM)Parallax-derived 3D points from stereo image pairs form the raw data that is gridded or triangulated into a DEM
- DEMOrthorectificationDEM is the essential input for orthorectification; it provides elevation corrections to remove relief displacement from raw imagery
- Relief DisplacementRaw Photo DistortionRelief displacement causes raw photos to have non-uniform scale and planimetric errors that make direct measurement impossible
- OrthorectificationOrthophotoOrthorectification process, using the DEM and camera parameters, geometrically corrects the raw image to produce a uniform-scale, map-accurate orthophoto
- OrthophotoOrthomosaicMultiple overlapping orthophotos are edge-matched, blended, and seamlessly tiled into an orthomosaic covering a larger area
- OrthophotoCartographic MeasurementUnlike raw photos, orthophotos have uniform scale and are free of relief and tilt distortion, allowing direct measurement of distances and areas like a map
- Interior OrientationGeometric TransformationInterior orientation parameters (focal length, principal point) define the camera's internal geometry essential for geometric transformation during orthorectification
- Exterior OrientationGeometric TransformationExterior orientation (camera position and rotation angles) combined with interior orientation enables transformation of image coordinates to ground coordinates
- Ground Control Points (GCP)Exterior OrientationGCP coordinates measured via GPS or conventional survey provide known ground positions essential for solving exterior orientation equations
- DEMContour GenerationDEMs are interpolated or traced to produce contour lines at regular intervals for topographic map representation
- DEMVolume CalculationDEMs enable calculation of terrain volumes, cut/fill quantities, and earthwork estimates required for engineering projects under PD 1529
- DEMViewshed AnalysisDEM grid values determine line-of-sight analysis, visibility zones, and intervisibility between survey stations or infrastructure points
- DEMWatershed DelineationDEM slope and flow-direction algorithms delineate drainage basins, ridge lines, and water-flow paths for hydrological analysis
- Photogrammetric DEM ProductionLiDAR DEM ProductionBoth methods produce elevation data; photogrammetry uses image correlation while LiDAR uses active ranging; often integrated for improved DEMs
- Image MatchingParallax ExtractionAutomated image correlation algorithms identify homologous points between stereo images to measure parallax shifts and extract 3D coordinates
- Pixel ResamplingOrthophoto QualityResampling methods (nearest-neighbor, bilinear, bicubic) affect orthophoto visual quality, sharpness, and radiometric accuracy
- PRS92/WGS84 DatumOrthophoto GeoreferencingOrthophotos must be georeferenced to the Philippine Reference System (PRS92) and WGS84 datum for compliance with national surveying standards
- PPCS/UTM ProjectionOrthophoto CoordinatesPhilippine Positioning and Cadastral Survey (PPCS) uses UTM zones 51–53N for projected coordinate representation of orthophotos
- Cadastral Mapping (CA 141)Orthophoto ApplicationOrthophotos serve as base maps for property boundary delineation and cadastral surveys under the Land Registration Act (CA 141)
- Land Use Classification (RA 4374)Orthophoto Thematic MappingOrthophotos with orthomosaics provide the base imagery for land use and land cover (LULC) classification per RA 4374 requirements
- Earthwork Calculations (PD 1529)DEM-Based Volume ComputationDEM provides elevation data essential for computing cut/fill volumes and material quantities in infrastructure and construction projects
- Quality AssuranceOrthophoto AccuracyQuality verification includes horizontal accuracy testing against GCPs and vertical RMS validation of DEM elevations before product delivery
- Stereo OverlapStereoscopy SuccessApproximately 60% forward overlap ensures sufficient image similarity for stereo fusion and effective 3D model formation
- Convergent PhotographyB/H Ratio OptimizationConvergent camera angles can increase effective B/H without increasing physical air-base, improving height measurement strength
- DSM vs DEMOrthophoto Application SelectionChoice between DSM (includes surface objects) and DEM (bare-earth) affects orthophoto suitability for different surveying and planning applications
Diagrams
Stereoscopy, DEM, and Orthophoto - Concept Hierarchy
Comprehensive mind map showing the hierarchical relationships between stereoscopy fundamentals, geometric strength parameters (B/H), DEM creation methods, distortion effects, orthophoto production workflow, and practical geodetic applications relevant to Philippine surveying standards and PRC examination requirements.
Orthophoto Production Workflow
Detailed workflow diagram illustrating the complete orthophoto production process from aerial data acquisition through geometric and radiometric corrections to final deliverable. Includes quality checkpoints and iterative refinement loops typical in professional Philippine surveying projects following PRS92 and PPCS standards.
Stereo Image Pair Analysis and DEM Extraction
Flowchart showing the step-by-step process of analyzing stereo image pairs, calculating geometric parameters (B/H ratio), performing parallax extraction through image correlation, and generating a quality-validated DEM. Includes decision points for optimal configuration and quality assurance checkpoints.
DEM vs DSM vs DTM - Data Type Comparison and Selection
Comparative flowchart distinguishing between Digital Elevation Model (DEM), Digital Surface Model (DSM), and Digital Terrain Model (DTM), showing their characteristics, data sources, and specific geodetic applications. Clarifies selection criteria for different surveying and cartographic projects under Philippine standards.
Philippine Surveying Applications - DEM and Orthophoto Integration
Application-focused flowchart demonstrating how DEM and orthophoto technology integrates with Philippine surveying regulations and professional standards. Shows specific use cases for cadastral mapping (CA 141), engineering design (PD 1529), land use classification (RA 4374), and compliance with PRS92/WGS84 coordinate systems used in PPCS/UTM projections.
Image-to-Orthophoto State Progression
State diagram illustrating the progression of imagery data from raw aerial photography through all transformation stages to final orthophoto and orthomosaic products. Shows key processing states, validation checkpoints, and iterative refinement loops for quality assurance.
Parallax Measurement and Height Determination from Stereo Pairs
Detailed flowchart explaining the parallax measurement principle for height determination from stereo pairs, including the B/H ratio's critical role in measurement accuracy. Shows the progression from parallax observation through height calculation and DEM generation with quality control loops.