Drone Mapping
High resolution models can be made from drone photography. A drone takes overlapping pictures of an area to be mapped. The pictures are stitched the together into a single image. A corresponding digital elevation model (DEM) shape is computed. The shape and image are used to make the model. Drone mapping offers centimeter feature resolution and accuracy. This enables fine model features and large scale.
Making a 3D Physical Model From Drone Photos ... Castle Rock
Figure 1 shows a 3D model of Rock Park in Castle Rock, Colorado (see figure 2), made with pictures acquired by drone. A DJI Phantom 4 drone (figure 3) took 660, 12 mega pixel pictures to make the model. Map Pilot (Apple App store) was used to plan and control the flight. Figure 4 shows the Map Pilot flight plan.
The pictures were stored on the Phantom 16 Giga Byte SD card. After the flight the pictures were downloaded to a Maps Made Easy account. Maps Made Easy combined the photos into one seamless image and made a digital elevation model (DEM) of the topographic shape (Figure 5). The Geotif image of Rock Park (261 MB) and DEM shape (17.3 MB) were downloaded to a PC desktop and imported into Global Mapper.
Note: Acquisiton of data to make the model is complete at this point. Line work, text, art, analytics can be added to the image before laser marking. The shape can be modified to show site pads, excavation or grading.
Global Mapper converted the image and shape to a Universal Transverse Mercator map projection to determine resolution, figures 6a, 6b, 6c. The image had 3” pixel width resolution. DEM shape had 12” inch grid spacing resolution. For comparison, highest available USGS image resolution is 1 foot and DEM shape is 1 meter grid spacing.
The drone was flown 297’ above the top of Castle Rock. Flying lower increases resolution and number of photos. Flight height is set in the Map Pilot App when planning a mission.
The Maps Made Easy DEM shape is a digital surface model (DSM). It includes terrain surface but also "added" objects suchs as trees, brush, stationary parked cars, houses, bridges, rocks, etc. Some of these “added” objects were manually removed in Global Mapper by using a terrain flattening tool. The resulting model was closer to a digital terrain model (DTM) … terrain surface without vegetation and man made objects, see figure 7a, 7b. After removing trees and buildings the image and shape were clipped around the park boundary.
The image was exported for grey scale laser marking (see figure 8). The shape was carved, coated and laser marked. Figure 9 shows the model being laser marked.
Click image to enlarge
Figure 1. “Rock Park”, 22”x30”x5.03”, 1” = 100’.
Figure 2. Castle Rock from the Rock Park parking lot.
Drone was flown from the top of Castle Rock.
Figure 3. Phantom 4 hovering on take off.
Remote controller with screen on ground.
Figure 4. Map Pilot Castle Rock fight plan.
A picture every 2.5 seconds on flight track.
Figure 5. Maps Made Easy map report. Dots in the overlap report show where each photo was taken.
Figure 6a. Global Mapper color coded view of Maps Made Easy DEM shape.
Figure 6b. Global Mapper view of the Maps Made Easy Geotif image.
Figure 6c. Global Mapper image overlayed on shape. Distortion in trees due to vertical drop in shape.
Figure 7a. Flattened triangulated areas show where trees and buildings were removed in Global Mapper
Figure 7b. Model without trees and buildings in shape. Refer to figure 6c.
Figure 8. Grey scale image for laser marking. Clipping applied to both shape and image.
Figure 9. Marking the image on the model after carving and coating. Image is marked at 500 pixels per inch, 11000 x 15000 pixels for this model. The shape was carved at 100 points per inch resolution, 1"= 100', 22" x 30" x 5.03".
Additional Drone Mapping Examples
I70 at the Hog Back, Denver, CO
Scale: 1" = 333'.
Map Pilot App flight path.
McCaslin Blvd at I36, Superior, CO Scale: 1" = 30'
Map Pilot App fight plan.
10 minute flight.
Devils Tower, Wyoming Scale: 1" = 80', Size 24" x 24" x 11.7", fine detail showing thousands of rock features, shape and image from 5000 drone photos.
Courtesy USGS Unmaned Aircraft Systems Project Office, Denver Colorado. Artist Diane Martin, Archetype 3D.
