and other features all over the Internet. The
United States Geological Survey (https://
water.usgs.gov/maps.html) and Census
provide useful files.
I downloaded the county outlines file
from the Census Bureau and added it by
clicking the “Add Vector Layer” button
(Figure 10). The layers can be reordered and
their coloring changed in the layer window at the bottom
left (Figure 11). As you can see, the mapped area really is
very small compared to the county (Figure 12). A shapefile
of the houses to be built could be set on the map though,
as well as street placement and other important features.
The textured results are a little bit more difficult.
MeshLab ( www.meshlab.net) is a great tool to start with.
In the odm_texturing directory, you will find the objects
odm_textured_model_geo.obj. These are the same except
for georeferencing in the _geo.obj file. Open the textured
meshes with MeshLab. There are three rings you can click
on and use to rotate the mesh (Figure 13). The scroll wheel
of the mouse zooms into and out of the image; command
and drag pans the image.
Textured meshes are generally
not perfect. If all of the photos are
very nearly straight down, it is not
really possible to get the structure
of the sides of objects. Roofs and
short objects seem to be rendered
very well, but the sides of some
taller objects were missing the side
Taking photos from multiple
angles would be a good solution,
but only if that information is
important for your application. I
could imagine a camera on a
pan/tilt head or multiple cameras
being really useful here.
Lastly, you can open the
with MeshLab as well. This is a dense point cloud file that
should have the points of the 3D reconstruction available.
These files can also be read into many common CAD tools
such as Solid Works and the AutoDesk products.
Now that we have ODM up and running, we’re ready
to collect some data of our own. Next time, we will talk
about different cameras that can be used, affix one to our
quad, and take some real world data. We’ll process it with
ODM and see if we can take some measurements.
Until next month, fly safely. SV
SERVO 04.2017 51
Figure 12: You can barely see the mapped area (circled in green) in the county
outline. Adding a shapefile of streets, property boundaries, or other important
landmarks could help further tie the survey into other datasets.
Figure 13: The textured mesh shows the 3D shape of many of the objects on the ground.
Grabbing the rings lets you pivot the image around. Zooming is accomplished with the mouse
wheel and panning with command/control and drag.
Figure 11: In the layer
window, you can turn various
layers on and off, reorder
layers, change their display
properties, etc. With some
fiddling of the settings, very
professional and complicated
maps can be made.