Precision Mapping and 3D Surface Modeling With Close Range Photogrammetry
I-Map Data Systems provides the following surveying and mapping services using drone photography, RTK GPS surveying, and 3D surface modeling.
- Total Station & RTK GPS Surveying & Field Mapping
- Drone Aerial Photography
- Air Photo Georeferencing & Mosaicing
- Close Range Photogrammetry / Orthophoto Development
- Dense Surface Modeling and Digital Elevation Model Development
- 3D Modeling with Texture Mapping and Physical Based Rendering
- Digital Panoramic Photography
- CAD Drafting and GIS Development
Bill Isenberger is I-Map Data Systems' aerial photography expert. He custom builds drone helicopters and maintains a fleet of them for close range aerial photography. He also maintains a stock of interchangeable parts that allow changes in propeller size and power modifications as needed. Bill has years of experience in capturing aerial photography from kites and drones at archeological sites in the Middle East. He has designed and built his own drone helicopters for several years. His custom built drone quadcopter model DMG 560 (shown below) is registered with the Federal Aviation Administration with an FFA exemption request for commercial drone operation in the US.
Bill's field equipment includes:
- Topcon Odyssey-E (RTK-GPS) and Accessories
- Sokkai SET 5 30R3 Reflectorless Total Station and Accessories
- Pathfinder Pro XR Sub-meter Differential GPS (DGPS)
- DMG 560 Custom Quadcopter, 22" diameter, 6.3" height, 1.3 kg
- Canon Powershot S110 Camera
- Canon EOS M Camera
The following examples show geo-referenced 3D surface models developed with quadcopter aerial photography and RTK GPS control points.
3D Texture Mapped Surface Model
The images above show the development of a 3D surface model using drone photography aquired by the DMG 560 Quadcopter. The model is created by developing a 3D surface from multiple photos and wrapping a composite image of the photos onto the surface with texture mapping.
The lefttop image shows a sparse point cloud of image tie points. The image tie points include feature points recognized from multiple drone photos and GPS ground control points used for image registration and elevation calibration. The tie points are used to connect the images together and compute the camera positions shown above the point cloud.
A dense point cloud is formed by triangulating the 3D positions of image points from the computer determined camera positiions. Points within the dense point cloud are connected together as vertices in a 3D wireframe mesh that can be viewed as a solid 3D surface. The pixels from a composite image of the drone photos are mapped onto the 3d surface to create a 3D texture mapped model as shown on the rightbottom.
3D surfaces generated by this process can be used to create raster based digital elevation models and orthorectified images with georeferenced positional accuracies of several centimeters.
3D Interactive Display
The interface below allows 3D interactive viewing of the above surface model. Your browser and computer graphics card must be capable of rendering with WebGL for the interactive display to be fully enabled. A high end graphics card will provide a highly responsive full screen display. The 3D display will also work on cell phones with high graphics capabilities. After the model is fully loaded, you may click the full screen icon in the lower right corner of the view to go full screen.
Interactive Viewing Controls
Use the left mouse button to change the viewing angle.
Use the right mouse button to shift the image position
Use the mouse wheel to zoom in and out.
Digital Elevation Models and Aerial Orthophotos
The images below show a digital elevation model (DEM) with one foot contours and an orthophoto produced from drone photography. The DEM shown on the lefttop is a continuous raster grid with 13 centimeter grid cells containing floating point elevation values in feet. The DEM is derived from a 3D surface model produced from drone photography as described above. Elevation values for the DEM are correlated to RTK GPS target points set in conjunction with the drone aerial survey. The topographic contours are computer generated from the DEM at one foot intervals. Contours in the trees and brush were individually deleted by inspection.
The DEM was used to orthorectify the composite aerial image shown on the rightbottom. The photos used to generate the composite image were captured by the DMG 560 Quadcopter at an altitude of 400 feet. The orthophoto pixel resolution is 3.25 centimeters and the horizontal positional accuracy is +/- 6 centimeters.
The orthophoto shows part of an oil production site where ground elevations were previously determined at well locations. These elevations were used to check the vertical accuracy of the 3D surface model.
The image below shows well locations with ground elevations recorded to one tenth of a foot by previous conventional surveys. Contours generated from the DEM are labeled adjacent to the well locations for easy comparison. The contours show that the DEM values are typically within a few tenths of a foot of the measured ground elevations. The ground surface is plowed or brushy, so this is the best accuracy that can be expected.
View a 3D interactive model of this site on Sketchfab.
The example above shows that close range photogrammetry can provide superior 3D site information for environmental assessments, site planning, construction engineering, and hydrologic analysis. The high resolution DEM created by this process would be impractical to produce with conventional surveying.   The resulting orthorectified and geo-referenced high resolution imagery allows precise measurements of site features to be made without additional survey measurements.
The image below illustrates gas line measurements made from the oil field orthophoto.
3D Archeological Models
Applications for archeological site development and 3D modeling can be viewed on Bill Isenbeger's Sketchfab page at: bisenberger at Sketchfab.
Contact Mark Phillips at 417-866-6400 for more information.