Mapping Outputs Explained
Why It Matters
Processing generates a range of files: GeoTIFFs, LAS files, DXFs, OBJs. To a drone pilot, these are deliverables. To a client, they’re confusing data that needs translation. Understanding what each output is, when to use it, and how to present it distinguishes data collectors from mapping professionals.
A construction manager doesn’t need a point cloud. They need to know if the grading is on plan. A developer doesn’t need a DEM. They need to visualize their property.
Orthomosaic Maps
What It Is
A single, seamless aerial photograph of the entire mapping area, geometrically corrected so that every pixel has an accurate real-world coordinate. Scale is consistent across the entire image. A standard photo distorts distances through perspective.
How It’s Used
- Construction progress tracking: overlay current and previous orthomosaics to show what’s changed
- Site planning: measure distances, areas, and positions directly on the map
- As-built documentation: record the exact state of construction at a specific date
- Property mapping: visualize boundaries, structures, and features
- Google Earth overlay: export as KML/KMZ for easy client viewing
Key Specs to Report
- GSD (resolution): e.g., “2.3 cm per pixel”
- Accuracy: e.g., “RMSE of 3.2 cm horizontal”
- Coverage area: total hectares or acres mapped
- Date captured: critical for time-series comparisons
Digital Elevation Models
DSM (Digital Surface Model)
The elevation of everything on the surface: ground, buildings, trees, vehicles, equipment. Used for:
- Line-of-sight analysis: can you see point B from point A?
- Viewshed analysis: what’s visible from a specific location?
- Shadow analysis: how do buildings cast shadows at different times?
- Volume baseline: the “before” surface for stockpile calculations
DTM (Digital Terrain Model)
Bare earth elevation only. All buildings, trees, and objects are removed. Used for:
- Contour generation: the basis for topographic contour lines
- Flood modeling: where will water flow?
- Grading plans: what earthwork is needed to achieve design grades?
- Drainage analysis: where does stormwater go?
DEM Visualization
Most GIS software can display DEMs as:
- Color-coded elevation maps: blue (low) to red (high)
- Hillshade: simulated sun illumination showing terrain texture
- Slope maps: color-coded by steepness
- Aspect maps: color-coded by slope direction (north, south, etc.)
Contour Lines
What They Are
Lines connecting points of equal elevation, typically generated from the DTM at regular intervals (0.5m, 1m, 2m, etc.). Closely spaced contours indicate steep terrain; widely spaced contours indicate flat areas.
How They’re Used
- Topographic maps: standard engineering and planning reference
- Grading design: show existing grades vs proposed grades
- Drainage planning: identify ridgelines, valleys, and water flow paths
- Permit applications: many jurisdictions require contour maps for development permits
Contour Quality from Drones
Drone-generated contours can achieve 10cm intervals or finer, significantly more detailed than what’s available from public GIS data (typically 1-5 meter intervals). This level of detail is valuable for:
- Precise grading plans
- Detailed drainage design
- Road alignment studies
3D Models
What They Are
A textured, realistic 3D representation of the mapping area. The mesh provides geometry; the original photos provide color and texture. The model can be rotated, zoomed, and measured in 3D viewing software.
How They’re Used
- Virtual site tours: clients and stakeholders explore the site from any angle
- Progress monitoring: compare 3D models from different dates to track construction progress
- Design context: import into CAD/BIM software as site context for architectural design
- Marketing: real estate developers showcase properties with interactive 3D views
- Inspection: measure hard-to-reach areas without physical access
Export Formats
- OBJ/FBX: standard 3D formats for CAD and visualization software
- KMZ: for Google Earth viewing (most accessible for non-technical clients)
- 3D Tiles: for web-based 3D viewing platforms
Quick Check
Q: What makes an orthomosaic different from a regular aerial photo? A: It’s geometrically corrected so scale is consistent everywhere. You can measure real distances and areas directly from the image.
Q: What is the difference between DSM and DTM? A: DSM includes all surface objects (buildings, trees). DTM is bare earth only, with objects removed.
Q: What file format is most practical for delivering results to non-technical clients? A: KMZ. It opens directly in Google Earth, which is free and familiar.
What’s Next?
One of the most valuable applications of drone mapping: volume calculations for measuring stockpiles, excavation progress, and cut/fill quantities.