SuperMap's raster surface analysis functions, based on surface models, derive information or generate surfaces. Main features include:
Extract Isolines
Contour lines (Isolines) are one of the common methods for representing surfaces on maps. They connect adjacent points with equal values through smooth curves. Common types include: elevation contours, isobaths, isotherms, isobars, and isohyets.
The distribution of contour lines reflects value variations on raster surfaces. Densely distributed contours indicate rapid surface value changes (e.g., steep slopes for elevation data), while sparse distribution suggests gradual changes. Contour extraction helps locate positions with equal elevation, temperature, or precipitation values.
Key Concepts
The base value serves as the initial calculation reference for contour generation. Contours are calculated in both directions using the contour interval. The base value doesn't necessarily equal the minimum contour value.
The contour interval determines spacing between adjacent contours. Together with the base value, these parameters define extracted contour values and quantities. Example: With base value 0 and interval 50 for DEM data (120-999), extracted contours range from 150 to 950 (17 contours total).
Raw contours generated through raster interpolation appear as angular polylines. Smoothing methods (B-spline or corner-rounding) with adjustable smoothness levels (0-5) simulate natural contours. Recommended smoothness: 3.
- Base Value and Contour Interval
- Smoothness and Smoothing Methods
SuperMap supports three contour extraction methods from raster datasets:
- Extract All Isolines generates all qualified contours using base value and interval parameters.
- Extract Specific Isolines creates user-specified contours through direct input or automated value generation.
- Isolines from Click interactively extracts contours equal to clicked point elevations.
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| Figure: Contour Extraction Schematic |
Extract Isosurfaces
Isosurfaces consist of enclosed areas between adjacent contours, visually representing value changes for elevation, temperature, or other parameters. Surface analysis provides two extraction methods:
- Extract All Isosurfaces generates qualified isosurfaces using base value and interval parameters. Example: Base 0 and interval 50 produces 16 isosurfaces (150-950) for DEM data (120-999).
- Specified Isosurfaces creates user-defined specific-value isosurfaces.
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| Figure: Isosurface Extraction Schematic |
Line-of-Sight Analysis
Essential for navigation, military, and communication planning, this analysis includes:
Determines visible areas from observer points considering elevation offsets and analysis radius. Applications include radar placement and fire watchtower positioning.
- Observer Height: Combines surface elevation with user-defined offset
- View Radius: Limits analysis range (default: infinite)
- View Angle: Defines analysis direction (0-360°, clockwise from north)
Multi-Point Viewshed identifies cumulative visible areas (union) or common visibility areas (intersection). Supports both interactive point selection and dataset import.
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| DEM Dataset and Observation Points | Multi-Point Viewshed Result |
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| DEM Dataset and Observation Points | Multi-Point Visibility Result |
3D visualization enhances analysis interpretation:
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| 3D Scene Visualization of Multi-Point Analysis |
- Two-Point Visibility checks mutual visibility between two points, considering elevation offsets.
- Multi-Point Visibility analyzes pairwise visibility among multiple points.
Slope and Aspect
Measures terrain steepness using three units: degrees, radians, or percentages. Critical for construction planning and agricultural management.
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Identifies slope direction (0-360°) for environmental and geological studies. Flat areas return -1.
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Surface Cut Fill
Calculates material volume changes between pre- and post-construction surfaces. Result raster shows positive values (excavation) and negative values (fill).
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Computes cut/fill volumes between raster surfaces and specified planes (vector datasets or drawn regions).
Determines post-construction elevation based on given fill/cut volume, useful for material quantity planning.