Commodity RGB-D sensors capture color images along with dense pixel-wise depth information in real-time. Typical RGB-D sensors are provided with a factory calibration and exhibit erratic depth readings due to coarse calibration values, ageing and thermal influence effects. This limits their applicability in computer vision and robotics. We propose a novel method to accurately calibrate depth considering spatial and thermal influences jointly. Our work is based on Gaussian Process Regression in a four dimensional Cartesian and thermal domain. We propose to leverage modern GPUs for dense depth map correction in real-time. For reproducibility we make our dataset and source code publicly available.
Several research groups documented a strong thermal influence on the depth generation process of RGB-D sensors. @cite_3 note a severe depth shift due to internal or external thermal changes. @cite_9 document a nonlinear distortion effects during thermal changes. They also propose practical rules of thumb on reducing accuracy errors caused by thermal conditions.
@cite_9 @cite_3
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Several approaches to calibration of the Kinect as a range sensor have been presented in the past. Those approaches do not take into account a possible influence of thermal and environmental conditions. This paper shows that variations of the temperature and air draft have a notable influence on Kinect's images and range measurements. Based on these findings, practical rules are stated to reduce calibration and measurement errors caused by thermal conditions. We present a novel application of the Kinect™, an input device designed for the Microsoft® Xbox 360® video game system. The device can be used by Earth scientists as a low-cost, high-resolution, short-range 3D 4D camera imaging system producing data similar to a terrestrial light detection and ranging (LiDAR) sensor. The Kinect contains a structured light emitter, an infrared camera (the combination of these two produce a distance image), a visual wavelength camera, a three-axis accelerometer, and four microphones. The cost is US $100, frame rate is 30 Hz, spatial and depth resolutions are mm to cm depending on range, and the optimal operating range is 0.5 to 5 m. The resolution of the distance measurements decreases with distance and is ≤1 mm at 0.5 m and 75 mm at 5 m. We illustrate data collection and basic data analysis routines in three experiments designed to demonstrate the breadth and utility of this new sensor in domains of glaciology, stream bathymetry, and geomorphology, although the device is applicable to a number of other Earth science fields. Copyright © 2012 John Wiley & Sons, Ltd.