Patent Publication Number: US-11386567-B2

Title: Systems and methods for weakly supervised training of a model for monocular depth estimation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Application No. 62/871,108, filed on, Jul. 6, 2019, which is herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The subject matter described herein relates, in general, to systems and methods for training machine learning algorithms to determine depths of a scene from a monocular image, and, more particularly, to training a depth model using a multi-stage semi-supervised process that is weakly supervised through the use of sparse depth data. 
     BACKGROUND 
     Various devices that operate autonomously or that provide information about a surrounding environment use sensors that facilitate perceiving obstacles and additional aspects of the surrounding environment. For example, a robotic device may use information from the sensors to develop an awareness of the surrounding environment in order to navigate through the environment. In particular, the robotic device uses the perceived information to determine a 3-D structure of the environment in order to identify navigable regions and avoid potential hazards. The ability to perceive distances through estimation of depth using sensor data provides the robotic device with the ability to plan movements through the environment and generally improve situational awareness about the environment. However, depending on the available onboard sensors, the robotic device may acquire a limited perspective of the environment, and, thus, may encounter difficulties in distinguishing between aspects of the environment. 
     That is, various sensors perceive different aspects of the environment differently and also have different implementation characteristics. For example, a light detection and ranging (LiDAR) sensor is effective at perceiving depth in the surrounding environment but suffers from difficulties such as high costs and can encounter errors in certain weather conditions. Moreover, other sensors, such as stereo cameras, function to effectively capture depth information but also suffer from difficulties with cost, limited field-of-view, and so on. While monocular cameras can be a cost-effective approach, the sensor data from such cameras does not explicitly include depth information. Instead, the robot implements processing routines that derive depth information from the monocular images. 
     However, leveraging monocular images to perceive depth can also suffer from difficulties such as limited resolution, image artifacts, difficulties with training the processing routines (e.g., expensive or limited availability of training data), and so on. As such, many difficulties associated with determining depth data persist that may result in reduced situational awareness for a device, and, thus, difficulties in navigating or performing other associated functions. 
     SUMMARY 
     In one embodiment, example systems, and methods relate to an improved approach to training a depth model to derive depth estimates from monocular images. For example, a depth system is disclosed that employs a training architecture to support semi-supervised training. In general, the present approach to semi-supervised training of the depth model includes two separate stages, a first stage that is self-supervised and a second stage that is weakly supervised. In one example, the present approach weakly supervises the second stage using training data in the form of sparse LiDAR data or other sparsely annotated ground truth data. By including the second stage with weak supervision, the depth system improves the performance of the depth model and causes the depth model to be scale aware and learn metrically accurate depths without the use of extensive labeled training data. Consequently, the training architecture still uses a self-supervised stage with images from monocular video but improves the self-supervised process with an additional refinement stage that uses less complex and, thus, more easily acquired depth data to then improve the training process. In this way, the semi-supervised training with weak supervision improves the ability of the depth model to accurately infer depths without using extensively annotated training data from more complex sensors. 
     In one embodiment, a depth system for semi-supervised training of a depth model for monocular depth estimation is disclosed. The depth system includes one or more processors and a memory communicably coupled to the one or more processors. The memory stores a training module including instructions that when executed by the one or more processors cause the one or more processors to train the depth model according to a first stage that is self-supervised and that includes using first training data that comprises pairs of training images. Respective ones of the pairs include separate frames depicting a scene from a monocular video. The training module includes instructions to produce first stage loss values that update the depth model and a pose model. The pose model facilitates the first stage according to a structure from motion (SfM) process. The training module includes instructions to train the depth model according to a second stage that is weakly supervised and that includes using second training data to produce depth maps according to the depth model. The second training data comprising individual images with corresponding sparse depth data. The training module includes instructions to produce second stage loss values that are based, at least in part, on the depth maps and the depth data. The memory stores a network module including instructions that when executed by the one or more processors cause the one or more processors to provide the depth model to infer distances from monocular images in a device. 
     In one embodiment, a non-transitory computer-readable medium for semi-supervised training of a depth model for monocular depth estimation and including instructions that when executed by one or more processors cause the one or more processors to perform various functions is disclosed. The instructions include instructions to train the depth model according to a first stage that is self-supervised and that includes using first training data that comprises pairs of training images. Respective ones of the pairs include separate frames depicting a scene from a monocular video. The instructions include instructions to produce first stage loss values to update the depth model and a pose model. The pose model facilitates the first stage according to a structure from motion (SfM) process. The instructions include instructions to train the depth model according to a second stage that is weakly supervised and that includes using second training data to produce depth maps according to the depth model. The second training data comprising individual images with corresponding sparse depth data. The instructions including instructions to produce second stage loss values that are based, at least in part, on the depth maps and the depth data. The instructions include instructions to provide the depth model to infer distances from monocular images in a device. 
     In one embodiment, a method for semi-supervised training of a depth model for monocular depth estimation is disclosed. In one embodiment, the method includes training the depth model according to a first stage that is self-supervised and that includes using first training data that comprises pairs of training images. The pairs include separate frames depicting a scene of a monocular video and provide for producing first stage loss values to update the depth model and a pose model. The pose model facilitates the first stage according to a structure from motion (SfM) process. The method includes training the depth model according to a second stage that is weakly supervised and that includes using second training data to produce depth maps according to the depth model. The second training data comprises individual images with corresponding sparse depth data and provides for updating the depth model according to second stage loss values that are based, at least in part, on the depth maps and the depth data. The method includes providing the depth model to infer distances from monocular images in a device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various systems, methods, and other embodiments of the disclosure. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one embodiment of the boundaries. In some embodiments, one element may be designed as multiple elements or multiple elements may be designed as one element. In some embodiments, an element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale. 
         FIG. 1  illustrates one embodiment of a vehicle within which systems and methods disclosed herein may be implemented. 
         FIG. 2  illustrates one embodiment of a depth system that is associated with training a depth model. 
         FIGS. 3A-C  illustrate different examples of depth data for a scene. 
         FIG. 4  illustrates a diagram for one configuration of a depth model. 
         FIG. 5  illustrates a diagram for one configuration of a pose model. 
         FIG. 6  illustrates one embodiment of a training architecture that includes a depth model and a pose model for semi-supervised monocular depth estimation. 
         FIG. 7  is a flowchart illustrating one embodiment of a method for training a depth model. 
     
    
    
     DETAILED DESCRIPTION 
     Systems, methods, and other embodiments associated with an improved approach to training a model to derive depth estimates from monocular images are disclosed herein. As previously noted, perceiving aspects of the surrounding environment can represent different challenges depending on which sensors a device employs to support the endeavor. In particular, difficulties with using monocular cameras to perceive depths in the surrounding environment can complicate the use of such sensors. That is, because a system trains and implements additional routines to derive the depth data from monocular images, difficulties can arise in relation to incomplete depth data and/or aberrations in the derived depth data from characteristics of the processing approach (e.g., scale ambiguity). The difficulties can cause the depth estimates to be unreliable for resolving aspects of the environment, thereby resulting in an incomplete situational awareness of the environment. 
     Therefore, in one embodiment, a depth system is disclosed that employs a training architecture to support semi-supervised training from a combination of monocular video and sparse depth data to overcome the noted difficulties. In general, the present approach to semi-supervised training of the depth model includes two separate stages that involve both self-supervised learning and weakly supervised learning, which is an adapted approach to supervised learning. Whereas various approaches to supervised training of a depth model may use comprehensive depth maps (e.g., nearly per-pixel annotations) that correlate with images or may use stereo images to provide self-supervision of a training process, the depth system implements the training architecture to use images from monocular video in the first stage, thereby avoiding a need for specialized sensors, and sparse depth data in the second stage as additional ground truth information thereby using depth labels from less expensive LiDAR or other depth sensors. Thus, the depth system improves the training process by using standard monocular cameras to capture monocular video, and supplementing the self-supervised training with the second stage that refines the depth model using sparse depth data to weakly supervise the second stage. 
     That is, because annotated training data can be expensive to produce due to the use of expensive sensors (e.g., 64 beam LiDAR devices), and/or manual labeling processes, and because monocular video alone under a self-supervised process may result in scale ambiguities in the understanding of the trained depth model, the present systems and methods overcome the noted difficulties by using sparse depth data to supervise a refining stage (i.e., the second stage) without reliance on more comprehensive/dense depth data from depth sensors having a high fidelity. The sparse depth data is, in one approach, LiDAR data (e.g., a point cloud) from a LiDAR device that produces a less dense perception of the surrounding environment. 
     In one example, as opposed to providing a LiDAR device with a multiplicity of scanning beams (e.g., 64 beams) that provide depth data at nearly a per-pixel level with a corresponding image, the depth system uses a less complex LiDAR (e.g., 4 scanning beams) to produce the sparse depth data that includes less than 0.5% (e.g., 77 points) of the fidelity of a fully annotated depth map for the image. Consequently, the training architecture still relies on the self-supervised training using monocular video, but improves the self-supervised process with the additional refinement second stage that uses less complex and, thus, more easily acquired depth data to improve the training process. In this way, the semi-supervised training with weak supervision improves the ability of the depth model to infer metrically accurate depths without using extensively annotated training data. 
     Moreover, as an additional aspect of the training architecture in order to facilitate training on monocular video and the intrinsic depth data included therein (also referred to as structure from motion (SfM)), the training architecture implements a pose model in addition to the depth model to support training the depth model under the self-supervised approach. The pose model, in at least one example, provides for estimating ego-motion between different frames of the monocular video that is parameterized as, for example, a 6-DoF transformation. The transformation, in combination with depth data from the depth model, permits the depth system to synthesize a target monocular image (i.e., the original monocular image input to the depth model as training data) from which the depth system derives training values in the form of losses. The depth system can then use the losses to adapt hyper-parameters of the depth and pose models to perform the training. 
     Thus, the training architecture of the present approach implements a two-stage training process with the first stage including self-supervised learning on monocular video images and the second stage including the self-supervised learning combined with weakly supervised learning that uses the sparse depth data to refine training of the depth model. In this way, the disclosed approach to semi-supervised training improves the understanding of the depth model while avoiding a need for denser annotated depth data to provide scale-aware depth estimates. 
     Referring to  FIG. 1 , an example of a vehicle  100  is illustrated. As used herein, a “vehicle” is any form of powered transport. In one or more implementations, the vehicle  100  is an automobile. While arrangements will be described herein with respect to automobiles, it will be understood that embodiments are not limited to automobiles. In some implementations, the vehicle  100  may be any electronic/robotic device or another form of powered transport that, for example, perceives an environment according to monocular images, and thus benefits from the functionality discussed herein. In yet further embodiments, the vehicle  100  may instead be a statically mounted device, an embedded device, or another device that uses monocular images to derive depth information about a scene or that separately trains the depth model for deployment in such a device. 
     In any case, the vehicle  100  (or another electronic device) also includes various elements. It will be understood that, in various embodiments, it may not be necessary for the vehicle  100  to have all of the elements shown in  FIG. 1 . The vehicle  100  can have any combination of the various elements shown in  FIG. 1 . Further, the vehicle  100  can have additional elements to those shown in  FIG. 1 . In some arrangements, the vehicle  100  may be implemented without one or more of the elements shown in  FIG. 1 . While the various elements are illustrated as being located within the vehicle  100 , it will be understood that one or more of these elements can be located external to the vehicle  100 . Further, the elements shown may be physically separated by large distances and provided as remote services (e.g., cloud-computing services, software-as-a-service (SaaS), distributed computing service, etc.). 
     Some of the possible elements of the vehicle  100  are shown in  FIG. 1  and will be described along with subsequent figures. However, a description of many of the elements in FIG.  1  will be provided after the discussion of  FIGS. 2-7  for purposes of the brevity of this description. Additionally, it will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, the discussion outlines numerous specific details to provide a thorough understanding of the embodiments described herein. Those of skill in the art, however, will understand that the embodiments described herein may be practiced using various combinations of these elements. 
     In either case, the vehicle  100  includes a depth system  170  that functions to train and implement a model to process monocular images and provide depth estimates for an environment (e.g., objects, surfaces, etc.) depicted therein. Moreover, while depicted as a standalone component, in one or more embodiments, the depth system  170  is integrated with the autonomous driving module  160 , the camera  126 , or another component of the vehicle  100 . The noted functions and methods will become more apparent with a further discussion of the figures. 
     With reference to  FIG. 2 , one embodiment of the depth system  170  is further illustrated. The depth system  170  is shown as including a processor  110 . Accordingly, the processor  110  may be a part of the depth system  170  or the depth system  170  may access the processor  110  through a data bus or another communication path. In one or more embodiments, the processor  110  is an application-specific integrated circuit (ASIC) that is configured to implement functions associated with a network module  220  and a training module  230 . In general, the processor  110  is an electronic processor such as a microprocessor that is capable of performing various functions as described herein. In one embodiment, the depth system  170  includes a memory  210  that stores the network module  220  and the training module  230 . The memory  210  is a random-access memory (RAM), read-only memory (ROM), a hard disk drive, a flash memory, or other suitable memory for storing the modules  220  and  230 . The modules  220  and  230  are, for example, computer-readable instructions that when executed by the processor  110  cause the processor  110  to perform the various functions disclosed herein. 
     Furthermore, in one embodiment, the depth system  170  includes a data store  240 . The data store  240  is, in one embodiment, an electronic data structure such as a database that is stored in the memory  210  or another memory and that is configured with routines that can be executed by the processor  110  for analyzing stored data, providing stored data, organizing stored data, and so on. Thus, in one embodiment, the data store  240  stores data used by the modules  220  and  230  in executing various functions. In one embodiment, the data store  240  includes training data  250 , a depth model  260 , a depth map(s)  270 , a pose model  280 , and a transformation(s)  290  along with, for example, other information that is used by the modules  220  and  230 . 
     The training data  250  generally includes one or more monocular videos that are comprised of a plurality of frames in the form of monocular images. As described herein, a monocular image is, for example, an image from the camera  126  that is part of a video, and that encompasses a field-of-view (FOV) about the vehicle  100  of at least a portion of the surrounding environment. That is, the monocular image is, in one approach, generally limited to a subregion of the surrounding environment. As such, the image may be of a forward-facing (i.e., the direction of travel) 60, 90, 120-degree FOV, a rear/side facing FOV, or some other subregion as defined by the characteristics of the camera  126 . In further aspects, the camera  126  is an array of two or more cameras that capture multiple images of the surrounding environment and stitch the images together to form a comprehensive 360-degree view of the surrounding environment. 
     In any case, the monocular image itself includes visual data of the FOV that is encoded according to a video standard (e.g., codec) associated with the camera  126 . In general, characteristics of the camera  126  and the video standard define a format of the monocular image. Thus, while the particular characteristics can vary according to different implementations, in general, the image has a defined resolution (i.e., height and width in pixels) and format. Thus, for example, the monocular image is generally an RGB visible light image. In further aspects, the monocular image can be an infrared image associated with a corresponding infrared camera, a black/white image, or another suitable format as may be desired. Whichever format that the depth system  170  implements, the image is a monocular image in that there is no explicit additional modality indicating depth nor any explicit corresponding image from another camera from which the depth can be derived (i.e., no stereo camera pair). In contrast to a stereo image that may integrate left and right images from separate cameras mounted side-by-side to provide an additional depth channel, the monocular image does not include explicit depth information such as disparity maps derived from comparing the stereo images pixel-by-pixel. Instead, the monocular image implicitly provides depth information in the relationships of perspective and size of elements depicted therein from which the depth model  260  derives the depth map  270 . 
     Moreover, the monocular video may include observations of many different scenes. That is, as the camera  126  or another original source camera of the video progresses through an environment, perspectives of objects and features in the environment change, and the depicted objects/features themselves also change thereby depicting separate scenes (i.e., particular combinations of objects/features). Thus, the depth system  170  may extract particular training pairs of monocular images from the monocular video for training. In particular, the depth system  170  generates the pairs from the video so that the pairs of images are of the same scene. As should be appreciated, the video includes a series of monocular images that are taken in succession according to a configuration of the camera. Thus, the camera may generate the images (also referred to herein as frames) of the video at regular intervals, such as every 0.033 s. That is, a shutter of the camera operates at a particular rate (i.e., frames-per-second (fps) configuration), which may be, for example, 24 fps, 30 fps, 60 fps, etc. 
     For purposes of the present discussion, the fps is presumed to be 30 fps. However, it should be appreciated that the fps may vary according to a particular configuration. Moreover, the depth system  170  need not generate the pairs from successive ones (i.e., adjacent) of the images, but instead can generally pair separate images of the same scene that are not successive as training images. Thus, in one approach, the depth system  170  pairs every other image depending on the fps. In a further approach, the depth system pairs every fifth image as a training pair. The greater the timing difference in the video between the pairs, the more pronounced a difference in camera position; however, this may also result in fewer shared features/objects between the images. As such, as previously noted, the pairs of training images are of a same scene and are generally constrained, in one or more embodiments, to be within a defined number of frames (e.g., 5 or fewer) to ensure correspondence of an observed scene between the monocular training images. In any case, the pairs of training images generally have the attributes of being monocular images from a monocular video that are separated by some interval of time (e.g., 0.06 s) such that a perspective of the camera changes between the pair of training images as a result of motion of the camera through the environment while generating the video. 
     Additionally, the training data  250 , in one or more embodiments, further includes depth data. The depth data indicates distances from a camera that generated the monocular images to features in the surrounding environment. The depth data is sparse or generally incomplete for a corresponding scene such that only sparsely distributed points within a scene are annotated by the depth data as opposed to a depth map that generally provides comprehensive depths for each separate depicted pixel. Consider  FIGS. 3A, 3B, and 3C , which depict separate examples of depth data for a common scene.  FIG. 3A  depicts a depth map  300  that includes a plurality of annotated points generally corresponding to an associated monocular image on a per pixel basis. Thus, the depth map  300  includes about 18,288 separate annotated points. 
     By comparison,  FIG. 3B  is an exemplary 3D point cloud  310  that may be generated by a LiDAR device having 64 scanning beams. Thus, the point cloud  310  includes about 1,427 separate points. Even though the point cloud  310  includes substantially fewer points than the depth map  300 , the depth data of  FIG. 3B  represents a significant cost to acquire over a monocular video on an image-by-image basis. These costs and other difficulties generally relate to an expense of a LiDAR sensor that includes produces a denser representation (e.g., 64 separate beams), difficulties in calibrating this type of LiDAR device with the monocular camera, storing large quantities of data associated with the point cloud  310  for each separate image, and so on. As an example of sparse depth data,  FIG. 3C  depicts a point cloud  320 . In the example of point cloud  320 , a LiDAR having 4 beams generates about 77 points that form the point cloud  320 . Thus, in comparison to the point cloud  310 , the point cloud  320  includes about 5% of the depth data as the point cloud  310 , which is a substantial reduction in data. However, the sparse information provides for sufficient supervision to facilitate overcoming scale ambiguities within the depth model when used as an additional refinement process for training in combination with the noted self-supervision process. 
     As an additional comparison of the  FIGS. 3A-3C , note that within  FIGS. 3A and 3B , the depth data is sufficiently dense to convey details of existing features/objects such as vehicles, etc. However, within the point cloud  320  of  FIG. 3C , the depth data is sparse or, stated otherwise, the depth data vaguely characterizes the corresponding scene according to distributed points across the scene that do not generally provide detail of specific features/objects depicted therein. Thus, this sparse depth data that is sporadically dispersed in a thin/scant manner across the scene may not provide enough data for some purposes such as object classification but does provide sufficient information to supervise a refinement stage of training the depth model  260 . 
     While the depth data is generally described as originating from a LiDAR, in further embodiments, the depth data may originate from a set of stereo cameras, radar, or another depth-related sensor that is calibrated with the monocular camera  126  generating the monocular video. Furthermore, the depth data itself generally includes depth/distance information relative to a point of origin such as the camera  126 , and may also include coordinates (e.g., x, y within an image) corresponding with separate depth measurements. 
     With further reference to  FIG. 2 , the depth system  170  further includes the depth model  260 , which produces the depth map  270 , and the pose model  280 , which produces the transformation  290 . Both of the models  260  and  280  are, in one embodiment, machine learning algorithms. However, the particular form of either model is generally distinct. That is, for example, the depth model  260  is a machine learning algorithm that accepts an electronic input in the form of a single monocular image and produces the depth map  270  as a result of processing the monocular image. The exact form of the depth model  260  may vary according to the implementation but is generally a convolutional type of neural network. 
     As an additional explanation of one embodiment of the depth model  260  and the pose model  280 , consider  FIG. 4  and  FIG. 5 .  FIG. 4  illustrates a detailed view of the depth model  260  and the pose model  280 . In one embodiment, the depth model  260  has an encoder/decoder architecture. The encoder/decoder architecture generally includes a set of neural network layers including convolutional components  400  (e.g., 2D and/or 3D convolutional layers forming an encoder) that flow into deconvolutional components  410  (e.g., 2D and/or 3D deconvolutional layers forming a decoder). In one approach, the encoder accepts the image  250 , which is a monocular image from the training data  250 , as an electronic input and processes the image to extract features therefrom. The features are, in general, aspects of the image that are indicative of spatial information that the image intrinsically encodes. As such, encoding layers that form the encoder function to, for example, fold (i.e., adapt dimensions of the feature map to retain the features) encoded features into separate channels, iteratively reducing spatial dimensions of the image while packing additional channels with information about embedded states of the features. Thus, the addition of the extra channels avoids the lossy nature of the encoding process and facilitates the preservation of more information (e.g., feature details) about the original monocular image. 
     Accordingly, in one embodiment, the encoder  400  is comprised of multiple encoding layers formed from a combination of two-dimensional (2D) convolutional layers, packing blocks, and residual blocks. Moreover, the separate encoding layers generate outputs in the form of encoded feature maps (also referred to as tensors), which the encoding layers provide to subsequent layers in the depth model  260 . As such, the encoder includes a variety of separate layers that operate on the monocular image, and subsequently on derived/intermediate feature maps that convert the visual information of the monocular image into embedded state information in the form of encoded features of different channels. 
     In one embodiment, the decoder  410  unfolds (i.e., adapt dimensions of the tensor to extract the features) the previously encoded spatial information in order to derive the depth map  270  according to learned correlations associated with the encoded features. That is, the decoding layers generally function to up-sample, through sub-pixel convolutions and other mechanisms, the previously encoded features into the depth map  270 , which may be provided at different resolutions  420 . In one embodiment, the decoding layers comprise unpacking blocks, two-dimensional convolutional layers, and inverse depth layers that function as output layers for different scales of the feature/depth map  270 . The depth map  270  is, in one embodiment, a data structure corresponding to the input image that indicates distances/depths to objects/features represented therein. Additionally, in one embodiment, the depth map  270  is a tensor with separate data values indicating depths for corresponding locations in the image on a per-pixel basis. 
     Moreover, the depth model  260  can further include skip connections  430  for providing residual information between the encoder and the decoder to facilitate memory of higher-level features between the separate components. While a particular encoder/decoder architecture is discussed, as previously noted, the depth model  260 , in various approaches, may take different forms and generally functions to process the monocular images and provide depth maps that are per-pixel estimates about distances of objects/features depicted in the images. 
     Continuing to  FIG. 5 , the pose model  280  accepts two monocular images (i.e., a training pair) from the training data  250  of the same scene as an electronic input and processes the monocular images (I t , I s ) to produce estimates of camera ego-motion in the form of a set of 6 degree-of-freedom (DOF) transformations between the two images. The pose model  280  itself is, for example, a convolutional neural network (CNN) or another learning model that is differentiable and performs dimensional reduction of the input images to produce the transformation  290 . In one approach, the pose model  280  includes 7 stride-2 convolutions, a 1×1 convolution with 6*(N−1) output channels corresponding to 3 Euler angles and a 3-D translation for one of the images (source image I s ), and global average pooling to aggregate predictions at all spatial locations. The transformation  290  is, in one embodiment, a 6 DOF rigid-body transformation belonging to the special Euclidean group SE(3) that represents the change in pose between the pair of images provided as inputs to the model  280 . In any case, the pose model  280  performs a dimensional reduction of the monocular images to derive the transformation  290  therefrom. 
     As an additional note, while the depth model  260  and the pose model  280  are shown as discrete units separate from the network module  220 , the depth model  260  and the pose model  280  are, in one or more embodiments, generally integrated with the network module  220 . That is, the network module  220  functions to execute various processes of the models  260 / 280  and use various data structures of the models  260 / 280  in support of such execution. Accordingly, in one embodiment, the network module  220  includes instructions that function to control the processor  110  to generate the depth map  270  using the depth model  260  and generate the transformation  290  using the pose model  280  as disclosed. 
     As a further explanation of the training architecture formed in relation to the depth model  260  and the pose model  280 , consider  FIG. 6  in relation to components previously described in relation to  FIG. 2 .  FIG. 6  illustrates one embodiment of a training architecture  600  that denotes various relationships between the depth model  260 , the pose model  280 , and inputs/outputs thereof. As shown in  FIG. 6 , the training data  250  includes a first image (I t )  610  and a second image (I s )  620  of a training pair, and also includes depth data  630  illustrated in the form of sparse LiDAR data. As an initial note about training using the illustrated architecture  600 , the training module  230  generally includes instructions that function to control the processor  110  to execute various actions associated with training the depth model  260  and the pose model  280 . For example, the training module  230 , in one embodiment, controls the training according to a two-stage process, as shown. In general, the first stage includes a self-supervised training process that involves synthesizing an additional image using the transformation  290  and the depth map  270  produced from the models  260 / 280  operating on the images  610 / 620  in order to generate a self-supervised loss in the form of photometric loss  650 . The second stage includes the same self-supervised training as the first stage supplemented with the depth data  630  to produce a supervised loss  660  in addition to the photometric loss  650 . Thus, in the first stage and the second stage, the training module  230  causes the network module  220  to execute the depth model  260  and the pose model  280  on the training data  250 , but also supplements the second stage with the additional supervised loss term  660 . 
     In any case, the network module  220  generally includes instructions that function to control the processor  110  to execute various actions associated with the depth model  260  and the pose model  280 . For example, in one embodiment, the network module  220  functions to process the first image  610  of a pair of training images from the training data  250  according to the depth model  260  to produce the depth map  270  for training. The network module  220 , in further embodiments, also uses the depth model  260  to generate the depth map  270  for additional purposes, once trained, such as resolving aspects of an environment for hazard avoidance, path planning, and so on. 
     In any case, the network module  220  also functions to execute the pose  280  to produce the transformation  290  (not illustrated), which functions as a basis for synthesizing the image  640  from which the training module  230  generates the photometric loss  650  as will be explained further subsequently. Moreover, the network module  220 , in one approach, executes the models  260 / 280  in concert (e.g., in parallel) for purposes of training, and at the direction of the training module  230 . Thus, in addition to executing the model  260 , the network module  220 , in one embodiment, processes the first image  610  and the second image  620  from the pair of training images to generate the transformation  290  using the pose model  280 . Thus, the network module  220  generally operates to execute the models  260  and  280  over the training data  250 , while the training module  230  functions to perform the explicit training processes such as generating the loss values and updating the models  260 / 280 . 
     In any case, once the network module  220  executes the models  260 / 280  over the images  610 / 620  to produce the depth map  270  and the transformation  290 , the training module  230  generates the synthesized image  640 . In one embodiment, the synthesized image  640  is, for example, a synthesized version of the second image  620  according to the depth map  270  and the transformation  290 . That is, the process of semi-supervised training of the depth model  260  in the structure from motion (SfM) context in the first and second stages involves synthesizing a different image from the first image  610  that is of the same scene from a different camera pose. The training module  230  generates the synthesized image  640  using a machine learning algorithm such as a generative neural network (e.g., encoder/decoder architecture, a generative adversarial network (GAN), an autoencoder, etc.), a convolutional neural network (CNN), or another suitable architecture that accepts the depth map  270  and the transformation  290  as input and produces the synthesized image  640  as output. 
     From this synthesized image  640 , the training module  230  can generate the loss  650  and a pose loss (not illustrated). Thus, the training module  230  formulates the generation of the depth map  270  as a photometric error minimization across the images  310 / 320  (e.g., I t−1  and I t+1 ). The training module  230  can then compare the synthesized image  340  and the original image  310  to determine the monocular loss  340 , which is embodied as, for example, the photometric loss. This loss characterizes an accuracy of the depth model  260  in producing the depth map  270 . Thus, the training module  230  can then use the calculated loss to adjust the depth model  260 . Additionally, the training module  230  uses the monocular loss  340  in combination with a velocity supervision loss that is derived from the instantaneous velocity to generate the pose loss  350 . 
     As further explanation consider that the self-supervised loss context for structure from motion (SfM), the training module  230  is generally configured with a goal of (i) a monocular depth model f D : I→D (e.g., depth model  260 ), that predicts the scale-ambiguous depth {circumflex over (D)}=f D (I(p)) for every pixel p in the target image I t ; and (ii) a monocular ego-motion estimator f x :(I t , I s ) (e.g., pose model  280 ), that predicts the set of 6-DoF rigid-body transformations for all s ∈ S given by 
                       x     t   →   s       =       (         R       t           0       1         )     ∈   SE       ,           (   3   )               
between the target image I t  and the set of source images I s  ∈ I S  considered as part of the temporal context. As a point of implementation, in one or more embodiments, the training module  230  uses frames I t−1  and I t+1  as source images, although a larger context, as previously noted, is possible. Additionally, the training module  230  uses the depth data from the training data  250  to (i) collapse the scale ambiguity inherent to a single camera configuration into a metrically accurate version of the depth model  260 , and (ii) improves the depth model  260  and the pose model  280  by leveraging cues from the depth data that are not appearance-based.
 
     The training module  230  implements the training objective for the depth model  260  according to two components. The two components include a self-supervised term (e.g., photometric loss  650 ) that operates on appearance matching    p  between the target image I t  and the synthesized image I s→t  (also annotated as Î t ) from the context set S={I S } s=1   S , with masking M s  and depth smoothness    smooth , and a supervised loss value that operates on a comparison between the predicted depth map  270  and the depth data (e.g., sparse LiDAR data) from the training data  250 .
 
 ( I   t   ,Î   t )= ⊙   p +λ 1     smooth +λ 2     supervised   (1)
 
     M p  is a binary mask that avoids computing the photometric loss on the pixels that do not have a valid mapping (e.g., pixels from the separate images that do not project onto the target image given the estimated depth), λ 1 , λ 2  represent weights for adjusting the loss terms in eq (1).    p  represents appearance matching loss and is implemented according to, in one embodiment, a pixel-level similarity between the target image I t  and the synthesized image Î t  using a structural similarity (SSIM) term combined with an L1 pixel-wise loss term inducing an overall photometric loss as shown in equation (2). 
     
       
         
           
             
               
                 
                   
                     
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     While multi-view projective geometry provides strong cues for self-supervision, errors due to parallax and out-of-bounds objects have an undesirable effect incurred on the photometric loss that can include added noise to the training. Accordingly, the training module  230  can mitigate these effects by calculating the minimum photometric loss per pixel for the source image according to (3). 
     
       
         
           
             
               
                 
                   
                     
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     The intuition involves the same pixel not occluding or be out-of-bounds in all context images, and that the association with minimal photometric loss should be the correct. Additionally, as shown below, the training module  230  masks out static pixels by removing pixels that have a warped photometric loss higher than a corresponding unwarped photometric loss, which the training module  230  calculates using the original source image (e.g., 620) without synthesizing the target. The mask (M p ) removes pixels that have appearance loss that does not change between frames, which includes static scenes and dynamic objects moving at a similar speed as the camera. 
     
       
         
           
             
               
                 
                   
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         s  represents depth smoothness loss and is implemented to regularize the depth in textureless low-image gradient regions, as shown in equation (5). The smoothness loss is an edge-aware term that is weighted for separate pyramid levels starting from 1 and decaying by a factor of two for the separate scales.
     s ( {circumflex over (D)}   t )=|δ x   {circumflex over (D)}   t   |e   −|δ     x     I     t     | +|δ y   {circumflex over (D)}   t   |e   −|     y     I     t     |   (5)
 
     Thus, the training module  230 , in one approach, calculates the appearance-based loss according to the above to include the photometric loss, the mask, and the depth smoothness terms for the self-supervised first stage of the semi-supervised training. Through this first training stage, the model  260  develops a learned prior of the monocular images as embodied by the internal parameters of the model  260  from the training on the image pairs in the training data  250 . In general, the model  260  develops the learned understanding about how depth relates to various aspects of an image according to, for example, size, perspective, and so on. However, after the first stage of training, the depth model  260  still lacks awareness of a metrically accurate scale. 
     Consequently, the training module  230  controls the network module  220  to execute the second stage that is a supervised training process in combination with the self-supervised process as previously described. Thus, the training module  230  further employs the second stage loss (e.g., supervised loss  660 ) in addition to the first stage loss to refine the depth model  260 . As shown in equations (6) and (7) below, the second stage loss may take different forms depending on a particular implementation. Thus, the second stage loss may be an L1 loss as shown in equation (6), a Berhu loss as shown in equation (7), or another suitable supervised loss term. 
     
       
         
           
             
               
                 
                   
                     
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     The training module  230  imposes the supervised loss as shown in equation (6) or (7) to further refine the depth model  260 . The additional supervised loss allows the depth model  260  to learn metrically accurate estimates resulting in the depth model  260  improving predictions. Of course, as previously described, this second stage uses additional training data in the form of sparse depth data that may be LiDAR data or another suitable source. 
     It should be appreciated that the training module  230  trains the depth model  260  and the pose model  280  together in an iterative manner over the training data  250  that includes a plurality of monocular images from video and a plurality of monocular video images with corresponding depth data. Through the process of training the model  260 , the training module  230  adjusts various hyper-parameters in the model  260  to fine-tune the functional blocks included therein. Through this training process, the model  260  develops a learned prior of the monocular images as embodied by the internal parameters of the model  260 . In general, the model  260  develops the learned understanding about how depth relates to various aspects of an image according to, for example, size, perspective, and so on. Consequently, the network module  220  can provide the resulting trained depth model  260  in the depth system  170  to estimate depths from monocular images that do not include an explicit modality identifying the depths. In further aspects, the network module  220  may provide the depth model  260  to other systems that are remote from the depth system  170  once trained to perform similar tasks. In this way, the depth system  170  functions to improve the accuracy of the depth model  260  while using minimal annotated data in a supervising refinement stage of training as opposed to relying on comprehensive training data sets that include extensively annotated data. 
     Additional aspects of generating depth estimates from monocular images will be discussed in relation to  FIG. 7 .  FIG. 7  illustrates a flowchart of a method  700  that is associated with semi-supervised training of a depth model for monocular depth estimation. Method  700  will be discussed from the perspective of the depth system  170 . While method  700  is discussed in combination with the depth system  170 , it should be appreciated that the method  700  is not limited to being implemented within the depth system  170  but is instead one example of a system that may implement the method  700 . 
     As an additional note about the general structure of the method  700 , training the depth model  260  according to the first stage that is self-supervised is generally represented at blocks  710 ,  720 ,  730 , and  760 . By contrast, the second stage that is supervised is generally represented at blocks  710 ,  720 ,  730 ,  740 ,  750 , and  760 . Thus, the second stage encompasses the first stage in addition to further aspects corresponding with added blocks  740 , and  750 . Thus, training according to the separate stages will generally be described according to method  700  overall. However, it should be appreciated that training according to the separate stages generally occurs independently and over multiple iterations with the first stage executing over a plurality of iterations prior to training according to the second stage over a plurality of separate iterations occurring after the first stage. In any case, once the depth model  260  is trained overall according to both stages, the depth model  260  provides a metrically accurate mechanism for inferring depths from monocular images, which the network module  220  may then provide to another device or use within the existing device to perceive information about an environment. 
     At  710 , the training module  230  receives the training data  250  including a pair of monocular training images, and depth data when training in the second stage. In one embodiment, the training module  230  acquires the training images locally from co-located systems with the depth system  170  (e.g., the camera  126 ) in an active manner along with the depth data, while in further embodiments, the training module  230  may acquire the training images and depth data through a communication link with a remote system or from a repository of such information as included in the data store  240 . Thus, while the depth system  170  can be implemented within a particular device that is, for example, actively navigating an environment, the depth system  170  may also function as a cloud-based computing service to train the depth model  260  and/or to analyze monocular images for depth information, and thus may receive the training data  250  from separate sources. 
     Furthermore, receiving the training data  250  also includes, in one embodiment, receiving depth data associated with the monocular video in order to facilitate the supervised training stage. That is, whether the depth data is embedded with the monocular training images or is provided separately, the training data  250  includes the depth data for, in one approach, at least a subset of the image from the video. As previously mentioned, the depth data is sparse depth data (e.g., derived from a LiDAR having four scanning beams) that correlates with the video from the camera  126 . Thus, the camera  126  and a LiDAR  124  are generally calibrated together in order to correlate the depth data with the images. As previously described, the monocular video from which the training images are derived may have different characteristics according to different implementations but is generally a single monocular video (i.e., from a camera having a single imaging device) that does not include explicit depth information, but may be selectively supplemented with the sparse depth data to facilitate the supervised training stage. Moreover, when functioning in a capacity separate from training, the depth system  170  generally accepts individual monocular images that may or may not be from a video source and that do not include explicit depth data. 
     At  720 , the training module  230  causes the network module  220  to execute the depth model  260  and the pose model  280  on a pair of training images from the training data  250 . In one embodiment, the network module  220  executes the depth model  260  to process a first image of a training pair to generate the depth map  270 . In general, execution of the depth model  260  to produce the depth map  270  at  720  is a routine execution of the depth model  260 . That is, in general, there is no variation in the way in which the model  260  is executed during training since the overall goal is to have the model  260  produce the depth map  270  according to learned weights and as would occur in normal operating conditions so that the training module  230  can subsequently assess the performance of the model  260  according to the loss functions. 
     Additionally, at  720 , the network module  220  executes the pose model  280  to process the first image and a second image of the training pair to generate the transformation  290 . The execution of the pose model  280  is generally routine occurs under normal operating conditions. Although the pose model  280  may be used in various circumstances for generating transformations, the depth system  170  generally uses the pose model  280  for the limited application of training the depth model  260 . Thus, when implemented as part of the depth system  170 , the pose model  280  may reside in an idle state when the system  170  is not training the depth model  260 . In any case, the training module  230  induces the network module  220  to execute the models  260 / 280  in parallel during training to generate the depth map  270  and the transformation  290  to facilitate the overall self-supervised training process. That is, the pose model  280  functions to facilitate the self-supervised structure from motion (SfM) training regime by providing the transformation  290  from which the training module  230  may assess the performance of the depth model  260 . Of course, as an additional aspect of using the pose model  280  to generate the transformation  290 , the training module  230  also trains the pose model  280  and does so, in one embodiment, in combination with the depth model  260 . Moreover, it should be appreciated that executing the depth model  260  and the pose model  280  for the first and the second stage generally occurs in the same manner for both stages. However, in the second stage of training at least the first image further includes the corresponding depth data for subsequent use in generating the second stage loss values as discussed in greater detail subsequently. 
     At  730 , the training module  230  computes the self-supervised loss(es) (e.g., photometric loss, depth smoothness loss, etc.) as either independent losses for the first stage or as one component of a second stage loss. In one embodiment, the training module  230  also computes a pose loss at  730 . In any case, in one embodiment, the training module  230  initially calculates the self-supervised loss according to a comparison between a synthetic image and the target image (i.e., the first image of the pair) according to the photometric loss function, which may include an appearance loss, a regularization/depth smoothness loss, and/or other components that are appearance-based. 
     Thus, the training module  230  uses this appearance-based loss as both the first stage loss to account for pixel-level similarities and irregularities along edge regions between a synthesized image derived from depth predictions of the depth model and a target image that is the original input into the depth model  260 . In one approach, the training module  230  synthesizes a target image Î t  from the depth map  270  and the transformation  290 . This synthesized target image Î t  generally corresponds to the first training image I t  as opposed to the second training image I s  of the pair I t , I s  that is provided into the depth model  260  and to which the depth map  270  {circumflex over (D)} t  corresponds. Thus, the training module  230  generates the synthetic target image Î t  as a regenerated view of the same scene depicted by the depth map  270  and the first training image I t . In one embodiment, the training module  230  generates the synthetic image according to a warping operation that functions to adapt a viewpoint of the camera in order to recover the original first image as the synthesized image. In various approaches, the training module  230  may implement different algorithms to perform the warping, which may include a convolutional neural network (CNN) or other machine learning architecture. 
     At  740 , the training module  230  determines whether the current training stage is the first or second and jumps to adjusting the depth model  260  if at the first stage or generating the additional second-stage supervised loss if at the second stage. In one embodiment, as previously noted, the first stage of training is a self-supervised structure from motion (SfM) training process that accounts for motion of a camera between the training images of a pair to cause the depth model to learn how to infer depths without using annotated training data (i.e., without the depth data). However, because the resulting depth model  260  from solely training on the self-supervised process does not accurately understand scale (i.e., is scale ambiguous), the training module  230  further imposes the second stage to refine the depth model  260 . That is, The training module  230  trains the depth model according to the second stage to refine the depth model  260  using second training data that includes the annotations about depth in the individual images. As previously noted, the sparse depth data includes selective dispersed ground truths providing limited supervision over depth estimates of the individual images. 
     At  750 , the training module  230  generates the second stage loss values using a second stage loss function. In one embodiment, the training module  230  generates the second-stage loss using the second stage loss function (e.g., equation (6) or (7)), which is a supervised loss function that compares values between the depth map  270  and corresponding depth data that correlates with the input image I t . This comparison provides a non-appearance based assessment of how well the depth model  260  is producing the depth map  270  in relation to ground truth data. Thus, refining the depth model  260  using the ground truth data as a point of comparison causes the depth model  260  to learn metrically accurate scale for depths thereby improving the depth model  260  over the second stage of training from the originally trained model after the first stage. As previously noted, the depth data itself may take different forms such as LiDAR, radar, etc. but serves as a mechanism for directly supervising the depth model  260  using sparse data points as opposed to a comprehensive annotated data to further refine the model  260 . 
     At  760 , the training module  230  updates the depth model  260  according to the loss values (e.g., first stage or first/second stage) as determined by the training module  230 . In one embodiment, the training module  230  updates the depth model  260  using the loss values to adapt weights in the model  260 . Therefore, the disclosed two-stage semi-supervised training approach implemented by the depth system  170  improves the understanding of the depth model  260  while using primarily self-supervised training that is supplemented with the additional refinement stage that uses a minimal set of sparsely annotated depth data. In this way, the depth system  170  improves the depth model  260  to produce improved depth estimates that translate into improved situational awareness of the implementing device (e.g., the vehicle  100 ), and improved abilities to navigate and perform other functions therefrom. 
     It should be appreciated that the network module  220  can further leverage the depth model  260  once trained to analyze monocular images from the camera  126  and provide the depth map  270  to additional systems/modules in the vehicle  100  in order to control the operation of the modules and/or the vehicle  100  overall. In still further aspects, the network module  220  communicates the depth map  270  to a remote system (e.g., cloud-based system) as, for example, a mechanism for mapping the surrounding environment or for other purposes (e.g., traffic reporting, etc.). As one example, the network module  220 , in one approach, uses the depth map  270  to map locations of obstacles in the surrounding environment and plan a trajectory that safely navigates the obstacles. Thus, the network module  220  may, in one embodiment, control the vehicle  100  to navigate through the surrounding environment. 
     In further aspects, the network module  220  conveys the depth map  270  to further internal systems/components of the vehicle  100  such as the autonomous driving module  160 . By way of example, in one arrangement, the network module  220  generates the depth map  270  using the trained depth model  260  and conveys the depth map  270  to the autonomous driving module  160  in a particular scale that the module  160  accepts as an electronic input. In this way, the depth system  170  informs the autonomous driving module  160  of the depth estimates to improve situational awareness and planning of the module  160 . It should be appreciated that the autonomous driving module  160  is indicated as one example, and, in further arrangements, the network module  220  may provide the depth map  270  to the module  160  and/or other components in parallel or as a separate conveyance. 
       FIG. 1  will now be discussed in full detail as an example environment within which the system and methods disclosed herein may operate. In some instances, the vehicle  100  is configured to switch selectively between an autonomous mode, one or more semi-autonomous operational modes, and/or a manual mode. Such switching can be implemented in a suitable manner, now known or later developed. “Manual mode” means that all of or a majority of the navigation and/or maneuvering of the vehicle is performed according to inputs received from a user (e.g., human driver). In one or more arrangements, the vehicle  100  can be a conventional vehicle that is configured to operate in only a manual mode. 
     In one or more embodiments, the vehicle  100  is an autonomous vehicle. As used herein, “autonomous vehicle” refers to a vehicle that operates in an autonomous mode. “Autonomous mode” refers to navigating and/or maneuvering the vehicle  100  along a travel route using one or more computing systems to control the vehicle  100  with minimal or no input from a human driver. In one or more embodiments, the vehicle  100  is highly automated or completely automated. In one embodiment, the vehicle  100  is configured with one or more semi-autonomous operational modes in which one or more computing systems perform a portion of the navigation and/or maneuvering of the vehicle along a travel route, and a vehicle operator (i.e., driver) provides inputs to the vehicle to perform a portion of the navigation and/or maneuvering of the vehicle  100  along a travel route. 
     The vehicle  100  can include one or more processors  110 . In one or more arrangements, the processor(s)  110  can be a main processor of the vehicle  100 . For instance, the processor(s)  110  can be an electronic control unit (ECU). The vehicle  100  can include one or more data stores  115  for storing one or more types of data. The data store  115  can include volatile and/or non-volatile memory. Examples of suitable data stores  115  include RAM (Random Access Memory), flash memory, ROM (Read Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The data store  115  can be a component of the processor(s)  110 , or the data store  115  can be operatively connected to the processor(s)  110  for use thereby. The term “operatively connected,” as used throughout this description, can include direct or indirect connections, including connections without direct physical contact. 
     In one or more arrangements, the one or more data stores  115  can include map data  116 . The map data  116  can include maps of one or more geographic areas. In some instances, the map data  116  can include information or data on roads, traffic control devices, road markings, structures, features, and/or landmarks in the one or more geographic areas. The map data  116  can be in any suitable form. In some instances, the map data  116  can include aerial views of an area. In some instances, the map data  116  can include ground views of an area, including 360-degree ground views. The map data  116  can include measurements, dimensions, distances, and/or information for one or more items included in the map data  116  and/or relative to other items included in the map data  116 . The map data  116  can include a digital map with information about road geometry. The map data  116  can be high quality and/or highly detailed. 
     In one or more arrangements, the map data  116  can include one or more terrain maps  117 . The terrain map(s)  117  can include information about the ground, terrain, roads, surfaces, and/or other features of one or more geographic areas. The terrain map(s)  117  can include elevation data in the one or more geographic areas. The map data  116  can be high quality and/or highly detailed. The terrain map(s)  117  can define one or more ground surfaces, which can include paved roads, unpaved roads, land, and other things that define a ground surface. 
     In one or more arrangements, the map data  116  can include one or more static obstacle maps  118 . The static obstacle map(s)  118  can include information about one or more static obstacles located within one or more geographic areas. A “static obstacle” is a physical object whose position does not change or substantially change over a period of time and/or whose size does not change or substantially change over a period of time. Examples of static obstacles include trees, buildings, curbs, fences, railings, medians, utility poles, statues, monuments, signs, benches, furniture, mailboxes, large rocks, hills. The static obstacles can be objects that extend above ground level. The one or more static obstacles included in the static obstacle map(s)  118  can have location data, size data, dimension data, material data, and/or other data associated with it. The static obstacle map(s)  118  can include measurements, dimensions, distances, and/or information for one or more static obstacles. The static obstacle map(s)  118  can be high quality and/or highly detailed. The static obstacle map(s)  118  can be updated to reflect changes within a mapped area. 
     The one or more data stores  115  can include sensor data  119 . In this context, “sensor data” means any information about the sensors that the vehicle  100  is equipped with, including the capabilities and other information about such sensors. As will be explained below, the vehicle  100  can include the sensor system  120 . The sensor data  119  can relate to one or more sensors of the sensor system  120 . As an example, in one or more arrangements, the sensor data  119  can include information on one or more LIDAR sensors  124  of the sensor system  120 . 
     In some instances, at least a portion of the map data  116  and/or the sensor data  119  can be located in one or more data stores  115  located onboard the vehicle  100 . Alternatively, or in addition, at least a portion of the map data  116  and/or the sensor data  119  can be located in one or more data stores  115  that are located remotely from the vehicle  100 . 
     As noted above, the vehicle  100  can include the sensor system  120 . The sensor system  120  can include one or more sensors. “Sensor” means any device, component, and/or system that can detect, and/or sense something. The one or more sensors can be configured to detect, and/or sense in real-time. As used herein, the term “real-time” means a level of processing responsiveness that a user or system senses as sufficiently immediate for a particular process or determination to be made, or that enables the processor to keep up with some external process. 
     In arrangements in which the sensor system  120  includes a plurality of sensors, the sensors can work independently from each other. Alternatively, two or more of the sensors can work in combination with each other. In such a case, the two or more sensors can form a sensor network. The sensor system  120  and/or the one or more sensors can be operatively connected to the processor(s)  110 , the data store(s)  115 , and/or another element of the vehicle  100  (including any of the elements shown in  FIG. 1 ). The sensor system  120  can acquire data of at least a portion of the external environment of the vehicle  100 . 
     The sensor system  120  can include any suitable type of sensor. Various examples of different types of sensors will be described herein. However, it will be understood that the embodiments are not limited to the particular sensors described. The sensor system  120  can include one or more vehicle sensors  121 . The vehicle sensor(s)  121  can detect, determine, and/or sense information about the vehicle  100  itself. In one or more arrangements, the vehicle sensor(s)  121  can be configured to detect, and/or sense position and orientation changes of the vehicle  100 , such as, for example, based on inertial acceleration. In one or more arrangements, the vehicle sensor(s)  121  can include one or more accelerometers, one or more gyroscopes, an inertial measurement unit (IMU), a dead-reckoning system, a global navigation satellite system (GNSS), a global positioning system (GPS), a navigation system  147 , and/or other suitable sensors. The vehicle sensor(s)  121  can be configured to detect, and/or sense one or more characteristics of the vehicle  100 . In one or more arrangements, the vehicle sensor(s)  121  can include a speedometer to determine a current speed of the vehicle  100 . 
     Alternatively, or in addition, the sensor system  120  can include one or more environment sensors  122  configured to acquire, and/or sense driving environment data. “Driving environment data” includes data or information about the external environment in which an autonomous vehicle is located or one or more portions thereof. For example, the one or more environment sensors  122  can be configured to detect, quantify and/or sense obstacles in at least a portion of the external environment of the vehicle  100  and/or information/data about such obstacles. Such obstacles may be stationary objects and/or dynamic objects. The one or more environment sensors  122  can be configured to detect, measure, quantify and/or sense other things in the external environment of the vehicle  100 , such as, for example, lane markers, signs, traffic lights, traffic signs, lane lines, crosswalks, curbs proximate the vehicle  100 , off-road objects, etc. 
     Various examples of sensors of the sensor system  120  will be described herein. The example sensors may be part of the one or more environment sensors  122  and/or the one or more vehicle sensors  121 . However, it will be understood that the embodiments are not limited to the particular sensors described. 
     As an example, in one or more arrangements, the sensor system  120  can include one or more radar sensors  123 , one or more LIDAR sensors  124  (e.g., 4 beam LiDAR), one or more sonar sensors  125 , and/or one or more cameras  126 . In one or more arrangements, the one or more cameras  126  can be high dynamic range (HDR) cameras or infrared (IR) cameras. 
     The vehicle  100  can include an input system  130 . An “input system” includes any device, component, system, element or arrangement or groups thereof that enable information/data to be entered into a machine. The input system  130  can receive an input from a vehicle passenger (e.g., a driver or a passenger). The vehicle  100  can include an output system  135 . An “output system” includes a device, or component, that enables information/data to be presented to a vehicle passenger (e.g., a person, a vehicle passenger, etc.). 
     The vehicle  100  can include one or more vehicle systems  140 . Various examples of the one or more vehicle systems  140  are shown in  FIG. 1 . However, the vehicle  100  can include more, fewer, or different vehicle systems. It should be appreciated that although particular vehicle systems are separately defined, each or any of the systems or portions thereof may be otherwise combined or segregated via hardware and/or software within the vehicle  100 . The vehicle  100  can include a propulsion system  141 , a braking system  142 , a steering system  143 , throttle system  144 , a transmission system  145 , a signaling system  146 , and/or a navigation system  147 . Each of these systems can include one or more devices, components, and/or a combination thereof, now known or later developed. 
     The navigation system  147  can include one or more devices, applications, and/or combinations thereof, now known or later developed, configured to determine the geographic location of the vehicle  100  and/or to determine a travel route for the vehicle  100 . The navigation system  147  can include one or more mapping applications to determine a travel route for the vehicle  100 . The navigation system  147  can include a global positioning system, a local positioning system, or a geolocation system. 
     The processor(s)  110 , the depth system  170 , and/or the autonomous driving module(s)  160  can be operatively connected to communicate with the various vehicle systems  140  and/or individual components thereof. For example, returning to  FIG. 1 , the processor(s)  110  and/or the autonomous driving module(s)  160  can be in communication to send and/or receive information from the various vehicle systems  140  to control the movement, speed, maneuvering, heading, direction, etc. of the vehicle  100 . The processor(s)  110 , the depth system  170 , and/or the autonomous driving module(s)  160  may control some or all of these vehicle systems  140  and, thus, may be partially or fully autonomous. 
     The processor(s)  110 , the depth system  170 , and/or the autonomous driving module(s)  160  can be operatively connected to communicate with the various vehicle systems  140  and/or individual components thereof. For example, returning to  FIG. 1 , the processor(s)  110 , the depth system  170 , and/or the autonomous driving module(s)  160  can be in communication to send and/or receive information from the various vehicle systems  140  to control the movement, speed, maneuvering, heading, direction, etc. of the vehicle  100 . The processor(s)  110 , the depth system  170 , and/or the autonomous driving module(s)  160  may control some or all of these vehicle systems  140 . 
     The processor(s)  110 , the depth system  170 , and/or the autonomous driving module(s)  160  may be operable to control the navigation and/or maneuvering of the vehicle  100  by controlling one or more of the vehicle systems  140  and/or components thereof. For instance, when operating in an autonomous mode, the processor(s)  110 , the depth system  170 , and/or the autonomous driving module(s)  160  can control the direction and/or speed of the vehicle  100 . The processor(s)  110 , the depth system  170 , and/or the autonomous driving module(s)  160  can cause the vehicle  100  to accelerate (e.g., by increasing the supply of fuel provided to the engine), decelerate (e.g., by decreasing the supply of fuel to the engine and/or by applying brakes) and/or change direction (e.g., by turning the front two wheels). As used herein, “cause” or “causing” means to make, force, compel, direct, command, instruct, and/or enable an event or action to occur or at least be in a state where such event or action may occur, either in a direct or indirect manner. 
     The vehicle  100  can include one or more actuators  150 . The actuators  150  can be any element or combination of elements operable to modify, adjust and/or alter one or more of the vehicle systems  140  or components thereof to responsive to receiving signals or other inputs from the processor(s)  110  and/or the autonomous driving module(s)  160 . Any suitable actuator can be used. For instance, the one or more actuators  150  can include motors, pneumatic actuators, hydraulic pistons, relays, solenoids, and/or piezoelectric actuators, just to name a few possibilities. 
     The vehicle  100  can include one or more modules, at least some of which are described herein. The modules can be implemented as computer-readable program code that, when executed by a processor  110 , implement one or more of the various processes described herein. One or more of the modules can be a component of the processor(s)  110 , or one or more of the modules can be executed on and/or distributed among other processing systems to which the processor(s)  110  is operatively connected. The modules can include instructions (e.g., program logic) executable by one or more processor(s)  110 . Alternatively, or in addition, one or more data store  115  may contain such instructions. 
     In one or more arrangements, one or more of the modules described herein can include artificial or computational intelligence elements, e.g., neural network, fuzzy logic, or other machine learning algorithms. Further, in one or more arrangements, one or more of the modules can be distributed among a plurality of the modules described herein. In one or more arrangements, two or more of the modules described herein can be combined into a single module. 
     The vehicle  100  can include one or more autonomous driving modules  160 . The autonomous driving module(s)  160  can be configured to receive data from the sensor system  120  and/or any other type of system capable of capturing information relating to the vehicle  100  and/or the external environment of the vehicle  100 . In one or more arrangements, the autonomous driving module(s)  160  can use such data to generate one or more driving scene models. The autonomous driving module(s)  160  can determine a position and velocity of the vehicle  100 . The autonomous driving module(s)  160  can determine the location of obstacles, obstacles, or other environmental features including traffic signs, trees, shrubs, neighboring vehicles, pedestrians, etc. 
     The autonomous driving module(s)  160  can be configured to receive, and/or determine location information for obstacles within the external environment of the vehicle  100  for use by the processor(s)  110 , and/or one or more of the modules described herein to estimate position and orientation of the vehicle  100 , vehicle position in global coordinates based on signals from a plurality of satellites, or any other data and/or signals that could be used to determine the current state of the vehicle  100  or determine the position of the vehicle  100  with respect to its environment for use in either creating a map or determining the position of the vehicle  100  in respect to map data. 
     The autonomous driving module(s)  160  either independently or in combination with the depth system  170  can be configured to determine travel path(s), current autonomous driving maneuvers for the vehicle  100 , future autonomous driving maneuvers and/or modifications to current autonomous driving maneuvers based on data acquired by the sensor system  120 , driving scene models, and/or data from any other suitable source. “Driving maneuver” means one or more actions that affect the movement of a vehicle. Examples of driving maneuvers include: accelerating, decelerating, braking, turning, moving in a lateral direction of the vehicle  100 , changing travel lanes, merging into a travel lane, and/or reversing, just to name a few possibilities. The autonomous driving module(s)  160  can be configured to implement determined driving maneuvers. The autonomous driving module(s)  160  can cause, directly or indirectly, such autonomous driving maneuvers to be implemented. As used herein, “cause” or “causing” means to make, command, instruct, and/or enable an event or action to occur or at least be in a state where such event or action may occur, either in a direct or indirect manner. The autonomous driving module(s)  160  can be configured to execute various vehicle functions and/or to transmit data to, receive data from, interact with, and/or control the vehicle  100  or one or more systems thereof (e.g., one or more of vehicle systems  140 ). 
     Detailed embodiments are disclosed herein. However, it is to be understood that the disclosed embodiments are intended only as examples. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the aspects herein in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of possible implementations. Various embodiments are shown in  FIGS. 1-7 , but the embodiments are not limited to the illustrated structure or application. 
     The flowcharts and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments. In this regard, each block in the flowcharts or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. 
     The systems, components and/or processes described above can be realized in hardware or a combination of hardware and software and can be realized in a centralized fashion in one processing system or in a distributed fashion where different elements are spread across several interconnected processing systems. Any kind of processing system or another apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software can be a processing system with computer-usable program code that, when being loaded and executed, controls the processing system such that it carries out the methods described herein. The systems, components and/or processes also can be embedded in a computer-readable storage, such as a computer program product or other data programs storage device, readable by a machine, tangibly embodying a program of instructions executable by the machine to perform methods and processes described herein. These elements also can be embedded in an application product which comprises all the features enabling the implementation of the methods described herein and, which when loaded in a processing system, is able to carry out these methods. 
     Furthermore, arrangements described herein may take the form of a computer program product embodied in one or more computer-readable media having computer-readable program code embodied, e.g., stored, thereon. Any combination of one or more computer-readable media may be utilized. The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. The phrase “computer-readable storage medium” means a non-transitory storage medium. A computer-readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include the following: a portable computer diskette, a hard disk drive (HDD), a solid-state drive (SSD), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     Generally, module, as used herein, includes routines, programs, objects, components, data structures, and so on that perform particular tasks or implement particular data types. In further aspects, a memory generally stores the noted modules. The memory associated with a module may be a buffer or cache embedded within a processor, a RAM, a ROM, a flash memory, or another suitable electronic storage medium. In still further aspects, a module as envisioned by the present disclosure is implemented as an application-specific integrated circuit (ASIC), a hardware component of a system on a chip (SoC), as a programmable logic array (PLA), or as another suitable hardware component that is embedded with a defined configuration set (e.g., instructions) for performing the disclosed functions. 
     Program code embodied on a computer-readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber, cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for aspects of the present arrangements may be written in any combination of one or more programming languages, including an object-oriented programming language such as Java™ Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer, or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
     The terms “a” and “an,” as used herein, are defined as one or more than one. The term “plurality,” as used herein, is defined as two or more than two. The term “another,” as used herein, is defined as at least a second or more. The terms “including” and/or “having,” as used herein, are defined as comprising (i.e., open language). The phrase “at least one of . . . and . . . ” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. As an example, the phrase “at least one of A, B, and C” includes A only, B only, C only, or any combination thereof (e.g., AB, AC, BC or ABC). 
     Aspects herein can be embodied in other forms without departing from the spirit or essential attributes thereof. Accordingly, reference should be made to the following claims, rather than to the foregoing specification, as indicating the scope hereof.