What is reflectance map pix4d?
A DSM is used to generate the Reflectance Maps. One Reflectance Map is generated for each band of each group of images, but only one DSM is generated, regardless of the number of images’ groups. The Reflectance Maps contain the reflectance values of each pixel and are used to generate the Index Maps.
What is a reflectance map used for?
A reflectance map compiles the relevant information about surface material, light source distribution, and viewing geometry into a single function. It is central to physics-based vision including shape from shading and photometric stereo.
How is Pix4D used to estimate reflectance?
A ll this information is used to come up with a good estimate of what we call the Hemispherical Conical Reflectance Factor (HCRF), a model we use to describe reflectance. Once the HCRF has been estimated, Pix4D blends different observations, giving more weight to nadir images.
Can a weighted average be used for a reflectance map?
For the reflectance map, no color balancing will be applied. The weight of every pixel (from the original images) in the weighted average is also computed differently. The goal is to produce a map where the value of each pixel faithfully indicates the reflectance of the object.
How is Pix4D used to calculate the HCRF?
Once the HCRF has been estimated, Pix4D blends different observations, giving more weight to nadir images. Direct sunlight, as well as scattered light, is reflected by the object of interest. The camera observes the reflected light in a cone defined by the geometry.
Why do we need reflectance maps in orthomosaics?
The information reflectance maps provide is something orthomosaics can’t capture or exploit to full potential. W hen making decisions based on an index map or deciding how much of a certain chemical to apply to your field, you need to be able to trust your map’s values.