Today the U.S. Patent & Trademark Office published a patent application from Apple that reveals their work on a sophisticated 3D mapping and positioning technology. Apple notes that in urban environments where tall buildings surround a mobile device, the signals that the mobile device detects from various satellites might not be direct line-of-sight signals. In such an environment, at least some of the signals that the mobile device detects might actually be signals that have reflected off of building surfaces. This reflection can distort the mobile device's estimation of each satellite's distance from the mobile device. As a result, the mobile device might estimate its geographical coordinates with less accuracy than if the detected signals had not been reflected in this manner. Apple's invention provides a solution to this problem.
According to techniques described in Apple's patent application, a mobile device adjusts the extents to which it depends on various satellites to estimate its global position based on the predicted probability for each such satellite that a ray extending from that satellite to the mobile device is obstructed by a building. The mobile device can predict the probabilities of building obstructions based on a digital three-dimensional (3D) model of the environment in which the mobile device is estimated to be. The mobile device weights the extent of uncertainty for each satellite's pseudorange measurements based on the predicted probability of obstruction for that satellite. Using these weighted uncertainties, the mobile device selects the extents to which it relies on each satellite's global positioning data when estimating the mobile device's current global position.
Apple's patent FIG. 1 noted below is a diagram that illustrates a mobile device in an urban environment where some direct line-of-sight signals from some satellites may be obstructed by buildings or other objects.
As shown in FIG. 1, a mobile device 102 is actually located at ground-level on a street in between two buildings 104 and 106. However, although mobile device 102 might possess information that places the mobile device somewhere in the vicinity of buildings 104 and 106, the mobile device might not be able to estimate its position with high accuracy without relying on signals that the mobile device receives from one or more satellites. Because the mobile device can already possess some rough notion of the environment in which it is generally located, the mobile device can request, from a remote server, over one or more wireless networks, a digital 3D model of that environment.
Such a model might include wire frame objects representing buildings, trees, and other relatively permanent structures, for example. Thus, such a model can represent the dimensions and geographical coordinates of the objects in the environment. The model might encompass a 3D region having a specified volume. For example, the model might be a section of a grid occupying a specified quantity of cubic meters on a master map. Using the model, the mobile device can determine heights of all of the buildings in the vicinity of the area in which the mobile device is roughly estimated to be.
As shown in FIG. 1, the two satellites 108 and 110 actually orbit somewhere overhead of the mobile device. A direct line-of-sight ray traced from satellite 108 to the mobile device is actually obstructed by building 104. Therefore, a signal that the mobile device might detect from satellite 108 is highly likely to be a reflected signal rather than a direct line-of-sight signal. For example, if the mobile device detects a signal from satellite 108, then it is highly likely that the mobile device is detecting that signal after that signal has reflected off of one of the surfaces of building 106 or some other object.
If the mobile device possesses information suggesting that a detected signal from satellite 108 is highly likely to be reflected, then the mobile device can responsively reduce its reliance upon that detected signal for purposes of estimating its actual position. In contrast, a direct line-of-sight ray traced from satellite 110 to the mobile device is not obstructed by building 104, building 106, or any other known object. Therefore, a signal that the mobile device detects from satellite 110 is highly likely to be a direct light-of-sight signal, unreflected off of any surface. If the mobile device possesses information suggesting that a detected signal from satellite 110 is highly likely to be a direct line-of-sight signal, then the mobile device can responsively increase its reliance upon that detected signal for purposes of estimating its actual position.
Apple's patent FIG. 6 is a diagram that illustrates how signals from various satellites to various sampling points within a region can be occluded by buildings that are represented within a digital 3D model, according to an embodiment of the invention. As shown in FIG. 6, a sampling point P0 is at the center of an elliptical region in which the mobile device is roughly estimated to be. Sampling points P1-P8 surround sampling point P0 along the boundary of the elliptical region. Four buildings B1-B4 are represented within a digital 3D model within and around the region. Four satellites S1-S4 have known position, velocity, and time (PVT) values.
As can be seen, some signals from some of satellites S1-S4 to some of sampling points P0-P8 are occluded by some of buildings B1-B4. Specifically, in FIG. 6, a signal from satellite S3 to sampling point P2 is occluded by building B1. Similarly, a signal from satellite S4 to sampling point P0 is occluded by building B4. Some of the sampling points can be eliminated from consideration as eligible potential positions at which mobile device 102 is actually located, because those sampling points are located inside of some of the buildings represented within the digital 3D model. Specifically, in FIG. 6, sampling points P6, P7, and P8 are located within buildings B1, B2, and B4, respectively.
Apple's patent FIG. 5A noted below is a simplified block diagram of an implementation of a device; FIG. 5B is a simplified block diagram of an implementation of a digital 3D model server.
Apple patent application was originally filed in Q3 2014. Considering that this is a patent application, the timing of such a product to market is unknown at this time.
Patently Apple covered Apple's first patent application regarding the problem of urban canyons using a different approach back in 2014 in a report titled "Apple Introduces Sensor-Assisted Location Technology that will combat the Problems associated with Urban Canyons."
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