The
following guidelines and recommendations will help you choose an optimal camera
and lens for surveying work:
·
Use a high-resolution camera. It is recommended to use
a camera with at least an 18-megapixel resolution. Typically, an 18-megapixel
camera provides a 1 to 2-centimeter (3 to 6 hundredth of a foot) measurement
accuracy at a distance of about 100 to 150 meters (110 to 160 yards, 330 to 480
feet).
·
Use a camera with a mechanical shutter. It is
recommended to use a camera with a mechanical shutter, as it will allow you to
take images while the drone is moving.
This results in a better utilization of battery resources allows
covering larger areas in less time.
·
Use a lens with a fixed focal length. DatuBIM requires
that the camera’s focal length will not change. Thus, it is strongly
recommended to use a fixed focal length lens, i.e., a lens without an optical
zoom.
·
Make sure your images cover at least four ground
control points (GCPs). Even though the minimum mathematical requirement to build
a model is three GCPs, it is strongly recommended to use at least four. Thus,
when control points are used, make sure that your images cover at least four
with each one appearing in at least three images.
·
Set your camera to maximum resolution. Note that some
camera models are preset to photograph in a resolution lower than their maximum
resolution. Make sure your camera is set to the maximum resolution provided.
·
Make sure camera is set to save the GPS location of the
images. This is essential for proper image processing.
·
Take your images in good and consistent lighting
conditions. Take all images in similar lighting conditions, preferably at the
same time of the day. Avoid photographing the survey area during different
times of the day. This will minimize changes in shadings and lighting
conditions that may degrade the performance of the automatic image processing
algorithms employed by DatuBIM.
·
Maintain proper overlap. It is recommended to maintain
at least a 75% front overlap and a 65% side overlap.
This
section describes the best practices for marking and measuring Ground Control
Points based on the area to be measured.
The
following guidelines and best practices will help you measure your control
points in the survey area in an optimal way:
Choosing Clearly Defined Control Points