Patent Publication Number: US-11663729-B2

Title: Network architecture for the joint learning of monocular depth prediction and completion

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Application No. 63/112,234, filed on, Nov. 11, 2020, which are herein incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The subject matter described herein relates, in general, to systems and methods for determining depths of a scene from a monocular image, and, more particularly, to a unique network architecture that performs depth prediction and depth completion. 
     BACKGROUND 
     Various devices that operate autonomously or that provide information about a surrounding environment often use sensors that facilitate perceiving obstacles and additional aspects of the surrounding environment. As one example, a robotic device uses information from the sensors to develop awareness of the surrounding environment in order to navigate through the environment and avoid hazards. In particular, the robotic device uses the perceived information to determine a 3-D structure of the environment so that the device may distinguish between navigable regions and potential hazards. The ability to perceive distances using sensor data provides the robotic device with the ability to plan movements through the environment and generally improve situational awareness about the environment. 
     In one approach, the robotic device may employ monocular cameras to capture images of the surrounding environment. While this approach can avoid the use of expensive light detection and ranging (LiDAR) sensors, the captured images do not explicitly include depth information. Instead, the robotic device can implement processing routines that derive depth information from the monocular images. Using monocular images alone to derive depth information can encounter difficulties, such as depth inaccuracies and various types of aberrations. Similarly, using LiDAR data alone to provide depth information also presents difficulties, such as high computational loads from the amount of data or issues with depth completion when the data is sparse. Consequently, difficulties persist with deriving depth data in a reliable manner. 
     SUMMARY 
     In one embodiment, example systems and methods relate to a novel network architecture for performing depth prediction and depth completion. As previously noted, different approaches to providing information about depth are generally associated with different types of sensor data. Moreover, the separate approaches generally suffer from different difficulties. For example, in the context of using monocular images, inaccuracies in metric scale can be a difficulty, whereas in the context of using explicit range data (e.g., LiDAR data), computational requirements can represent a specific difficulty. 
     Therefore, in one arrangement, a novel network architecture is disclosed that leverages both monocular images and range data (i.e., sparse depth data) to provide an improved output about the depth of aspects depicted in the monocular images/range data. For example, the novel network architecture includes a depth model that can use monocular images alone to provide depth estimates or that can also use sparse depth data provided via an integrated sparse auxiliary network (SAN) to derive improved depth estimates. Thus, the depth model can be said to be performing depth prediction and/or depth completion depending on the data that is available via the inputs. 
     As such, the depth model is more robust than a model utilizing a single input stream since the depth model can selectively integrate the sparse depth data into the depth estimates as the sparse depth data is available. That is, for example, the sensors of the device (e.g., a vehicle) may encounter difficulties, such as hardware failures during operation. As such, when the sparse depth data is unavailable, the depth model is still capable of producing depth estimates according to the monocular image. Moreover, because the depth model can operate without the sparse depth data, the depth model can be leveraged in various configurations that provide monocular images without explicit depth data, thereby improving the usability of the depth model overall. 
     In any case, the depth model implements an additional encoder, which is referred to herein as the sparse auxillary network (SAN), to process the sparse depth data and inject depth features derived from the sparse depth data into an encoder/decoder structure of the depth model. In at least one arrangement, the SAN injects the depth features via skip connections of encoder/decoder structure. The skip connections provide, for example, residual information about the encoding of image features at different resolutions between the encoder and the decoder. Thus, the SAN injects the depth features via the skip connections according to corresponding spatial dimensions of the image features, respectively. The depth model concatenates the image features and the depth features and provides the concatenated features into the decoder of the encoder/decoder structure, which then produces the depth estimates. In this way, the disclosed novel network architecture functions to improve the depth estimates through the use of monocular images in combination with sparse depth data while providing a robust framework. 
     In one embodiment, a depth system 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 network module including instructions that, when executed by the one or more processors, cause the one or more processors to generate depth features from sensor data according to whether the sensor data includes sparse depth data. The network module includes instructions to selectively inject the depth features into a depth model. The network module includes instructions to generate a depth map from at least a monocular image using the depth model that is guided by the depth features when injected. The network module includes instructions to provide the depth map as depth estimates of objects represented in the monocular image. 
     In one embodiment, a non-transitory computer-readable medium 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 generate depth features from sensor data according to whether the sensor data includes sparse depth data. The instructions include instructions to selectively inject the depth features into a depth model. The instructions include instructions to generate a depth map from at least a monocular image using the depth model that is guided by the depth features when injected. The instructions include instructions to provide the depth map as depth estimates of objects represented in the monocular image. 
     In one embodiment, a method is disclosed. The method includes generating depth features from sensor data according to whether the sensor data includes sparse depth data. The method includes selectively injecting the depth features into a depth model. The method includes generating a depth map from at least a monocular image using the depth model that is guided by the depth features when injected. The method includes providing the depth map as depth estimates of objects represented in the monocular image. 
    
    
     
       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 providing depth estimates according to monocular images and sparse depth data. 
         FIGS.  3 A-C  illustrate different examples of depth data. 
         FIG.  4    illustrates a diagram of one embodiment of an architecture of a depth model. 
         FIG.  5    illustrates a detailed diagram of one embodiment of a depth model. 
         FIG.  6    illustrates a flowchart of one embodiment of a method associated with generating depth maps using a depth model that can use monocular images and sparse depth data. 
     
    
    
     DETAILED DESCRIPTION 
     Systems, methods, and other embodiments associated with a novel network architecture for performing depth prediction and depth completion are disclosed. As previously noted, different approaches to providing information about depth are generally associated with different types of sensor data. Moreover, the separate approaches generally suffer from different difficulties. For example, in the context of using monocular images, inaccuracies in metric scale can be a difficulty that arises from using monocular images without a source of ground truth depth. Additionally, in the context of using explicit range data (e.g., LiDAR data), computational requirements from the quantity of data and/or extrapolating sparse data into a complete representation can represent a specific difficulty with acquiring comprehensive depth information. 
     Therefore, in one arrangement, a novel network architecture is disclosed that leverages both monocular images and range data (i.e., sparse depth data) to provide an improved depth map as an output. For example, the novel network architecture includes a depth model that can use information in addition to monocular images to provide depth estimates. The depth model uses monocular images and can also selectively integrate sparse depth data into the process of generating the depth map when available. To achieve this, in one arrangement, the depth model includes an additional structure in the form of an integrated sparse auxiliary network (SAN) that functions alongside an encoder/decoder structure of the depth model. 
     As such, the depth model is more robust than a model utilizing a single input stream since the depth model can selectively integrate the sparse depth data into the depth estimates as the sparse depth data is available. For example, the sensors of the device (e.g., a vehicle) may encounter difficulties, such as hardware failures, software failures, or other circumstances during operation that make the explicit depth data unavailable. As such, when the sparse depth data is unavailable, the depth model is still capable of producing depth estimates according to the monocular image. 
     In any case, the depth model implements an additional encoder, which is referred to herein as the sparse auxillary network (SAN), to process the sparse depth data. The SAN is a machine learning algorithm, such as a convolutional neural network (CNN). The SAN accepts range information in the form of the sparse depth data from a range sensor and outputs depth features. The sparse depth data is range/distance information provided by a range sensor, such as a LiDAR or other range sensor. The depth data is referred to as being sparse since the depth data is not provided on a per-pixel basis as in the case of a depth map corresponding to a monocular image but instead may sparsely depict distances across an observed scene. 
     The depth model, in at least one arrangement, injects depth features derived from the sparse depth data into an encoder/decoder structure of the depth model. In at least one configuration, the SAN injects the depth features via skip connections of encoder/decoder structure. The skip connections provide, for example, residual information about the encoding of image features at different resolutions between the encoder and the decoder. Thus, the SAN injects the depth features via the skip connections according to corresponding spatial dimensions of the image features. The depth model concatenates the image features and the depth features and provides the concatenated features into the decoder of the encoder/decoder structure to provide the depth features as a passive input into the decoder. In this way, the disclosed novel network architecture functions to improve the depth estimates through the use of monocular images in combination with sparse depth data while providing a robust framework that continues to function in the absence of the sparse depth data. 
     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 robotic device or form of powered transport that, for example, observes surroundings to provide determinations therefrom, and thus benefits from the functionality discussed herein. In yet further embodiments, the vehicle  100  may be a statically mounted device, an embedded device, or another device that uses monocular images to derive depth information about a scene instead of being a motive device. 
     In any case, the vehicle  100  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), 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 - 6    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 any case, the vehicle  100  includes a depth system  170  that functions to generate depth estimates (i.e., depth maps) using a novel network architecture that can employ multiple sources of information. 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 . Additionally, as noted previously, one or more components of the depth system  170  may be cloud-based elements that are remote from 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 . 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/or other modules that may function in support of generating depth information. 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 module  220 . The network module  220  is, for example, computer-readable instructions that, when executed by the processor  110 , cause the processor  110  to perform the various functions disclosed herein. In further arrangements, the network module  220  is a combination of logic gates, an integrated circuit, or a purpose-built processor. 
     Furthermore, in one embodiment, the depth system  170  includes a data store  230 . The data store  230  is, in one embodiment, an electronic data structure stored in the memory  210  or another data store, 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  230  stores data used by the module  220  in executing various functions. For example, as depicted in  FIG.  2   , the data store  230  includes sensor data  240 , a depth model  250 , and a depth map  260  along with, for example, other information that is used and/or produced by the module  220 . 
     The sensor data  240  includes, for example, monocular images from the camera  126  or another imaging device. The monocular images are generally derived from one or more monocular videos that are comprised of a plurality of frames. As described herein, the monocular images are, for example, images from the camera  126  or another imaging device 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 imaging characteristics (e.g., lens distortion, FOV, etc.) of the camera  126 . In various aspects, the camera  126  is a pinhole camera, a fisheye camera, a catadioptric camera, or another form of camera that acquires images without a specific depth modality. 
     An individual monocular image itself includes visual data of the FOV that is encoded according to an imaging standard (e.g., codec) associated with the camera  126  or another imaging device that is the source. In general, characteristics of a source camera (e.g., 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  250  derives the depth map/estimates. 
     Additionally, the sensor data  240 , in one or more arrangements, further includes depth data about a scene depicted by the associated monocular images. The depth data indicates distances from a range sensor that acquired the depth data to features in the surrounding environment. The depth data, in one or more approaches, is sparse or generally incomplete for a corresponding scene such that the depth data includes sparsely distributed points within a scene that are annotated by the depth data as opposed to a depth map (e.g., depth map  260 ) that generally provides comprehensive depths for each separate depicted pixel. Consider  FIGS.  3 A,  3 B, and  3 C , which depict separate examples of depth data for a common scene.  FIG.  3 A  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.  3 B  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.  3 B  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 robust LiDAR sensor that includes 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.  3 C  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 depicted by point cloud  320  is generally insufficient to develop a comprehensive assessment of the surrounding environment. 
     As an additional comparison of the  FIGS.  3 A- 3 C , note that within  FIGS.  3 A and  3 B , 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.  3 C , 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 dispersed in a minimal manner across the scene may not provide enough data for some purposes. 
     While the depth data is generally described as originating from a LiDAR, in further embodiments, the depth data may originate from a stereo camera, radar, or another range sensor. Furthermore, the depth data itself generally includes depth/distance information relative to a point of origin, such as the range sensor that may be further calibrated in relation to the camera  126 , and may also include coordinates (e.g., x, y within an image) corresponding with separate depth measurements. 
     Further detail about the depth system  170  of  FIG.  2   , including the depth model  250 , will be provided in relation to  FIG.  4    and subsequent figures. Thus, with reference to  FIG.  4   , one embodiment of the depth model  250  is shown. As illustrated in  FIG.  4   , the depth model  250  includes a sparse area network (SAN)  400 , an image encoder  410 , a depth decoder  420 , and skip connections  430 . It should be appreciated that while  FIG.  4    illustrates the various aspects of the depth model  250  as being a separate component, in various aspects, the network module  220  includes instructions to apply the depth model  250 , and the depth model  250  may be integrated with the network module  220 . 
     In general, the network module  220  controls the depth model  250  to process the sensor data  250 , which includes sparse depth data  440  and a monocular image  450 , as shown in  FIG.  4   . However, it should be appreciated that the sparse depth data  440  may become unavailable due to various circumstances, such as a sensor failure. Accordingly, the depth model  250 , in at least one arrangement, still functions but without the depth features from the SAN  400 . That is, the image encoder  410  processes the monocular image  450 , but depth features are not concatenated via the skip connections  430  into the depth decoder  420  to generate the depth map  260 . In this way, the depth model  250  is flexible to continue operation when the sparse depth data  440  is unavailable. 
     In one configuration, the SAN  400  is a convolutional neural network (CNN). In further arrangements, the SAN  400  is configured with sparse convolutions, such as Minkowski convolutions. The SAN  400  may further include sparsification and densification layers, as will be discussed in greater detail subsequently. In any case, the SAN  400  produces depth features from the sparse depth data  440 . The depth features are encoded features from the sparse depth data  440  that are provided at multiple different spatial resolutions. The different spatial resolutions correspond with spatial resolutions of image features from the image encoder  410  derived from the monocular image  450 . Thus, as the SAN  400  processes the sparse depth data  440 , the image encoder  410  processes the monocular image  450  of the same scene. 
     The skip connections  430  function to carry over the image features at varying spatial dimensions into depth decoder  420  as residual information. As part of this, the skip connections concatenate the depth features with the image features of respective corresponding spatial resolutions. Accordingly, while the depth decoder  420  receives a feature map of image features from the image encoder  410  and iteratively decodes the feature map through subsequent spatial dimensions, the skip connections provide the residual image features concatenated with the depth features into the respective iterations. In this way, the depth model  250  injects the sparse depth data  440  into the encoder/decoder structure and improves an accuracy of the depth map  260  as the final output. 
     As further detail about the depth model  250 , consider  FIG.  5   , which illustrates a detailed view of the depth model  250 . As shown in  FIG.  5   , the separate encoder/decoder structures  400 ,  410 , and  420  are comprised of multiple different layers as set forth in the included legend. Moreover, the SAN  400  further includes learned weights  500  and  510 . The learned weights  500  adjust the influence of the depth features while the learned weights  510  adjust the influence of the image features that are ultimately concatenated with information in the image decoder  420 . By learning the weights  500  and  510  as part of training, the depth model  250  can better integrate the sparse depth data  440 . Moreover, as previously noted, the SAN  400  can include Minkowski convolutions, a densification layer, and a sparsification layer. 
     As further explanation, a sparse tensor S is written as a coordinate matrix C and a feature matrix F, as shown in equation (1). 
     
       
         
           
             
               
                 
                   
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     Where {u n , v n } are pixel coordinates, s n  is the sample index in the batch, and f n ∈  is the corresponding feature vector. Assuming a batch size of 1 and disregard the batch index, an input W×H×1 depth map {tilde over (D)} is sparsified by the sparsification layer by gathering valid pixels (i.e., pixels with positive values) as coordinates and depth values as features, such that:
 
 {tilde over (S)}={{u   n   ,v   n   },{d   n   }}∀u,v∈{tilde over (D)}|{tilde over (D)} ( u,v )&gt;0.0  (2)
 
     Similarly, a sparse tensor {tilde over (S)}={{tilde over (C)}, {tilde over (F)}} can be densified by scattering its pixel coordinates and feature values into a dense W×H×Q matrix {tilde over (P)}, such that: 
     
       
         
           
             
               
                 
                   
                     
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     Once the input depth data is sparsified, the SAN  400  can encode the information through a series of novel Sparse Residual Blocks (SRB), which are generally comprised of sparse convolutional blocks (e.g., Minkowski convolutions). In any case, the depth features from the SAN  400  are encoded information about depths represented in the sparse depth data while the image features are, in general, aspects of the image that are indicative of spatial information that is intrinsically encoded therein. One example of an architecture for the encoding layers that form the image encoder  410  may include a series of layers that function to 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  450  while packing additional channels with information about embedded states of the features. 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  450 . 
     Accordingly, in at least one approach, the image encoder  410  is comprised of multiple encoding layers formed from a combination of two-dimensional (2D) convolutional layers, packing blocks, and residual blocks. While the image encoder  410  is presented as including the noted components, it should be appreciated that further embodiments may vary the particular form of the encoding layers (e.g., convolutional and pooling layers without packing layers), and thus the noted configuration is one example of how the depth system  170  may implement the depth model  250 . 
     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  250 , including specific layers of an image decoder  420  via skip connections that may function to provide residual information between the image encoder  410  and the image decoder  420 . Thus, the image encoder  410  includes a variety of separate layers that operate on the monocular image  450 , and subsequently on derived/intermediate feature maps that convert the visual information of the monocular image  450  into embedded state information in the form of encoded features of different channels. In any case, the output of the image encoder  410  is, in one approach, a feature map having a particular dimension (e.g., 512×H/32×W/32) that is transformed in relation to the image  450  (e.g., 3×H×W). 
     With continued reference to  FIG.  5   , the depth model  250  further includes the image decoder  420 . One example of how the image decoder  420  functions includes unfolding (i.e., adapting dimensions of the tensor to extract the features) the previously encoded spatial information in order to derive the depth map  260  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  260 . In one or more arrangements, the decoding layers comprise unpacking blocks, two-dimensional convolutional layers, and inverse depth layers that function as output layers for different spatial scales. In further aspects, the image decoder  420  may also receive inputs via the skip connections  430  from another model, such as the SAN  400 . While the image decoder  420  is presented as including the noted components, it should be appreciated that further arrangements may vary the particular form of the decoding layers (e.g., deconvolutional layers without unpacking layers), and thus the noted configuration is one example of how the depth system  170  may implement the image decoder  420 . 
     In any case, returning to  FIG.  2   , the depth system  170 , in one embodiment, employs the depth model  250  to produce the depth map  260 , which, in one or more arrangements, may be provided as an inverse mapping having inverse values for the depth estimates. In general, however, the depth map  260  is a pixel-wise prediction of depths for the image  450 . That is, the depth model  250  provides estimates of depths for different aspects depicted in the image  450 . Of course, in the present approach, the depth model  250  further integrates information from the sparse depth data  440  to supplement the image  450  in producing the depth map  260 . 
     It should be appreciated that, in one embodiment, the network module  220  generally includes instructions that function to control the processor  110  to execute various actions to control the depth model  250  to produce the depth map  260 . The network module  220 , in one or more approaches, acquires the sensor data  240  including the sparse depth data  440  and the monocular image  450  by controlling the camera  126  and a LiDAR  124  to capture the sensor data  240  from a data bus, or electronic memory, or another available communication pathway. Accordingly, the depth system  170  may acquire the sparse depth data in parallel with the monocular image to provide corresponding sparse depth information for the image. 
     Additional aspects of the joint learning of depth prediction and depth completion will be discussed in relation to  FIG.  6   .  FIG.  6    illustrates a flowchart of a method  600  that is associated with generating depth maps using a depth model that can use both monocular images and sparse depth data as an input. Method  600  will be discussed from the perspective of the depth system  170  of  FIGS.  1 - 2   . While method  600  is discussed in combination with the depth system  170 , it should be appreciated that the method  600  is not limited to being implemented within the depth system  170  but is instead one example of a system that may implement the method  600 . 
     At  610 , the network module  220  acquires the sensor data  240 . In general, the sensor data  240  is comprised of at least a monocular image (e.g., image  450 ), but may also include, as previously outlined, sparse depth data. The sparse depth data can be LiDAR data or depth data from another source, such as a radar. In any case, the sparse depth data provides a mechanism by which the depth system  170  can integrate further information about the surrounding environment in order to guide the generation of the depth map  260  and improve the quality of the depth estimates included therein. 
     At  620 , the network module  220  determines whether the sensor data  240  includes sparse depth data in addition to the monocular image. For example, as noted previously, the sensor data  240  may not include the sparse depth data for various reasons, such as an error in an associated range sensor, a slower refresh rate than the camera  126 , processing errors, an absence of a range sensor, and so on. Thus, the network module  220  can determine when the sensor data  240  includes the sparse depth data by, for example, analyzing the sensor data  240  for the presence of the sparse depth data as the network module  220  receives the sensor data  240 , e.g., by identifying the sparse depth data, reading a designated header value in a packet including the sensor data  240 , etc. 
     In any case, the network module  220  can determine the presence of the sparse depth data and may, in one or more arrangements, activate the SAN  400  to generate the depth features from the sparse depth data when the sparse depth data is present. Activating the network module  220  may include providing the sparse depth data to the SAN  400  for processing. 
     At  630 , the network module  220  generates depth features from the sensor data  240  according to whether the sensor data  240  includes sparse depth data. That is, the network module  220  selectively performs the task of generating the depth features according to the presence of the sparse depth data. Thus, when the sparse depth data is present, the network module  220  uses the SAN  400  to generate the depth features from the sparse depth data. It should be appreciated that while the use of the SAN  400  is discussed sequentially prior to generating the depth map  260  by the depth model  250 , the SAN  400  can execute in parallel with further components of the depth model  250  (e.g., image encoder  410 ) in order to provide depth features to the image decoder  420  in parallel with the image features. 
     At  640 , the network module  220  injects the depth features into the depth model  250 . For example, the network module  220  injects the depth features by concatenating the depth features with the image features and providing concatenated features into the image decoder  420  of the depth model  250 . Moreover, the network module  220  can further apply learned weights to the depth features and the image features prior to concatenating the separate features via skip connections of the depth model  250 . In general, injecting the sparse depth data via the depth features using the skip connections is an optimal approach to integrating this information and provides for performing depth completion and prediction without degradation of either process. Thus, the learnable weights provide for further conditioning the depth and image features, thereby enabling switching between tasks. 
     At  650 , the network module  220  generates a depth map from at least the monocular image  450  using the depth model  250  that is selectively guided by the depth features when injected. That is, as shown in the flowchart of  FIG.  6   , the network module  220  can generate the depth map  260  without using the sparse depth data by using the monocular image alone. However, when available, the addition of the sparse depth data generally improves the accuracy of the depth map  260 . As noted in relation to  FIGS.  4 - 5   , the network module  220  applies the depth model  250  to the monocular image by using the image encoder  410  to encode image features and uses the depth decoder  420  to decode the image features, and the depth features into the depth map  260 . In this way, the network module  220  generates the depth map  260  as a dense representation of depths for a depicted scene of the surrounding environment. 
     At  660 , the network module  220  provides the depth map  260  as depth estimates of objects represented in the monocular image. In one arrangement, the network module  220  provides the depth map  260  to control a device (e.g., the vehicle  100 ) to navigate through a surrounding environment. As should be appreciated, in one arrangement, the network module  220  electronically provides the map  260  to other systems of the vehicle  100  in support of, for example, autonomous planning and navigation of the vehicle  100 . Of course, in further implementations, the network module  220  communicates the map  260  to a remote device that originally provides the sensor data  240  as a response to an original request for depth information. In general, the depth system  170  and the depth model  250  can be employed in various contexts in support of active autonomous navigation, scene analysis, metadata analysis (e.g., traffic analysis), and so on. In either case, the approach embodied within the depth system  170  provides a unique and improved approach to leveraging monocular images in combination with sparse depth data to resolve high-resolution dense depth data that is metrically accurate. 
       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  (e.g., nearby vehicles). 
     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 , 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 any device, component, or arrangement or groups thereof that enable 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 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 - 6   , 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 standalone 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.