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
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
following guidelines and best practices will help you photograph the survey
area in an optimal way. Here you will find some general recommendations, as
well as recommendations for taking oblique images and for taking vertical
images. Please refer to Best Practices for Drone Photography
article as well.
Use a drone to take images using Datumate’s automatic flight
planner DatuFly Professional if possible. This will increase the probability
that images will be stitched into one cluster.
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.
section describes the best practices for marking and measuring Ground Control
Points based on the area to be measured.
following guidelines and best practices will help you measure your control
points in the survey area in an optimal way:
- Measure at least four control points in the survey area
of a small project. It is very strongly recommended to measure and mark four or
more control points. Measuring and marking more control points in additional
images will improve the resiliency of the geo-referencing process, assuming
that the measurement of the control points is accurate itself. You may measure
point coordinates in either a local or a national grid. The software will allow
you to work with three control points marked in two images each.
- Measure as many control points as possible of
large-scale areas. It is very important that you cover all safely reachable
areas, especially on the perimeter of the area of interest.
- Choose clearly defined control points. Choose control
points that have a high contrast to the area around it and which will be
unambiguously and accurately identifiable in the images. Use available
landmarks or deploy your own prominent objects or marks in the survey area if
no appropriate landmarks are available. Alternatively, paint your own marks in the area. Good examples of both landmarks and painted marks are shown below.
Choosing Clearly Defined Control Points
Painting your own marks
- Avoid measuring points on slanted surfaces. This is
specifically important when using a Total Station with in reflector-less model.
- Accurately measure the position and elevation of the
control points. Carefully measure the position and elevation of control points
with an accuracy of better than 2 cm (0.79 inch). Remember, the accuracy of
measuring the position and elevation of control points sets the accuracy
baseline for all the measurements and drawings related to the images.
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