Abstract:
A method for unmanned delivery of an item to a desired delivery location includes receiving, at an unmanned vehicle, first data representative of an approximate geographic location of the desired delivery location, receiving, at the unmanned vehicle, second data representative of a fiducial expected to be detectable at the desired delivery location, using the first data to operate the unmanned vehicle to travel to the approximate geographic location of the desired delivery location, upon arriving at the approximate geographic location of the desired delivery location, using the second data to operate the unmanned vehicle to detect the fiducial; and upon detecting the fiducial, using the fiducial to operate the unmanned vehicle to travel to the delivery location and deliver the item.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/920,913, filed Dec. 26, 2013, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    This invention relates to unmanned delivery of items to specified locations. 
         [0003]    Traditionally, delivery companies such as UPS and FedEx deliver items to customers using delivery vehicles (e.g., trucks) which are operated by delivery people. The delivery vehicles travel a predetermined route and deliver packages to customer locations along the route. At the customer location, the delivery person verifies that the delivery location (e.g., customer address) is correct and then leaves the package in a safe place at the delivery location. 
         [0004]    In recent years the use of unmanned aerial vehicles (UAVs) has become widespread, particularly in military and recreational applications. Until recently, commercial use of UAVs was limited due to the technological constraints of UAVs (e.g., limited range, poor reliability, etc.) as well as the relatively high cost of UAVs. 
         [0005]    Due to advances in technology and an increased prevalence of UAVs, UAVs are becoming cost effective and sufficiently reliable for use in commercial applications. 
         [0006]    At the same time, there is a need for a cost effective, efficient means of delivering items to customers over the last miles between a delivery hub/fulfillment center and the customer&#39;s location. 
         [0007]    Many groups have proposed using drones for delivery: Matternet and TacoCopter. Recently, Amazon.com presented the idea of delivering packages to customer locations over the last mile using autonomous multi-rotor vehicles. It is unclear how the vehicles employed by these groups accurately deliver items, verify that the delivery location is correct, or decide where to safely leave packages. 
       SUMMARY 
       [0008]    In an aspect, in general, a method for unmanned delivery of an item to a desired delivery location includes receiving, at an unmanned vehicle, first data representative of an approximate geographic location of the desired delivery location, receiving, at the unmanned vehicle, second data representative of a fiducial expected to be detectable at the desired delivery location, using the first data to operate the unmanned vehicle to travel to the approximate geographic location of the desired delivery location, upon arriving at the approximate geographic location of the desired delivery location, using the second data to operate the unmanned vehicle to detect the fiducial, and upon detecting the fiducial, operating the unmanned vehicle to travel to the delivery location and deliver the item. 
         [0009]    Aspects may include one or more of the following features. 
         [0010]    The fiducial may be selected from a group including a two-dimensional code, a QR code, or a bar code. Using the second data to operate the unmanned vehicle to detect the fiducial may include capturing images using a camera mounted on the unmanned vehicle and processing the captured images to determine if the fiducial is represented in the images. Operating the unmanned vehicle to deliver the item may include operating a winch mounted on the unmanned vehicle to lower the item to the ground. Prior to operating the winch to lower the item to the ground, the unmanned vehicle may determine whether any obstructions are present in the delivery location. 
         [0011]    Delivery of the item to the delivery location may be aborted if the unmanned vehicle determines that obstructions are present in the delivery location. Operating the unmanned vehicle to deliver the item may include causing the vehicle to drop the item into a receptacle. The receptacle may be configured to soften the landing of the item. Operating the unmanned vehicle to deliver the item may include landing at the delivery location and then dropping the item at the delivery location. The method may also include notifying a customer that the item has been delivered to the delivery location after delivering the item to the delivery location. Notifying the customer may includes one or more of sending an email to the customer or sending a text message to the customer. 
         [0012]    The first data representative of an approximate geographic location of the desired delivery location may be determined from a mapping of street addresses to global positioning system coordinates. Using the first data to operate the unmanned vehicle to travel to the approximate geographic location of the desired delivery location may include notifying a customer of an estimated time of arrival of the item at the delivery location. Notifying the customer may include one or more of sending an email to the customer or sending a text message to the customer. The fiducial may include a radio-frequency beacon. The radio-frequency beacon may include a near-field communication radio frequency signal. 
         [0013]    Receiving the first data representative of an approximate geographic location of the desired delivery location may include receiving the first data from a mobile device and using the second data to operate the unmanned vehicle to detect the fiducial may include detecting the fiducial as generated from the mobile device. The method may also include updating the first data representative of an approximate geographic location of the desired delivery location as the mobile device moves. The fiducial may be a permanently installed fiducial associated with the delivery location. The fiducial may be a user-printed fiducial. 
         [0014]    In another aspect, in genera, a method for unmanned delivery of an item to a desired delivery location includes receiving, at an unmanned vehicle, first data representative of an approximate geographic location of the desired delivery location, receiving, at an unmanned vehicle, second data including a mapping of wireless network identifiers to representations of geographic locations, using the first data to operate the unmanned vehicle to travel to the approximate geographic location of the desired delivery location, and upon arriving at the approximate geographic location of the desired delivery location, using the second data to operate the unmanned vehicle to travel to the delivery location and deliver the item. 
         [0015]    Aspects may include one or more of the following features. 
         [0016]    Using the second data to operate the unmanned vehicle to travel to the delivery location may include determining the delivery location using triangulation of a plurality of wireless networking signals in an area of the delivery location. 
         [0017]    In another aspect, in general, an unmanned aerial vehicle for delivery of a package includes a fuselage including a package bay and a lifting surface, a plurality of rotors affixed to the fuselage, wherein the unmanned aerial vehicle is operable in a first mode with the rotors operating in a substantially horizontal configuration, and the unmanned aerial vehicle is operable in a second mode with at least some of the rotors operating in a substantially vertical configuration. 
         [0018]    Aspects may have one or more of the following advantages. 
         [0019]    Among other advantages, certain aspects employ a first navigation technology to travel to an approximate area of a delivery location and then use a second navigation technology to very accurately travel to the exact delivery location. 
         [0020]    Other features and advantages of the invention are apparent from the following description, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0021]      FIG. 1  is an unmanned vehicle delivery system. 
           [0022]      FIG. 2  is an unmanned vehicle detecting a fiducial. 
           [0023]      FIG. 3  is an unmanned vehicle delivering a package onto a fiducial. 
           [0024]      FIG. 4  is an unmanned vehicle detecting a fiducial on a customer&#39;s mobile device. 
           [0025]      FIG. 5  is an unmanned vehicle delivering a package to a customer. 
           [0026]      FIG. 6  is an unmanned vehicle performing visual location matching. 
           [0027]      FIG. 7  is an unmanned vehicle navigating using WiFi signals. 
           [0028]      FIG. 8  is an unmanned vehicle delivering a package to a delivery site using WiFi signals. 
           [0029]      FIG. 9  is an unmanned vehicle courier system. 
           [0030]      FIG. 10  is an unmanned vehicle courier system delivering an item. 
           [0031]      FIG. 11  is an unmanned aerial vehicle in a multi-copter mode. 
           [0032]      FIG. 12  is an unmanned aerial vehicle in a first forward flight mode. 
           [0033]      FIG. 13  is an unmanned aerial vehicle in a second forward flight mode. 
           [0034]      FIG. 14  is a side view of the unmanned aerial vehicle of  FIG. 13 . 
           [0035]      FIG. 15  is a side view of an unmanned aerial vehicle with a rotatable spar and rotor. 
           [0036]      FIG. 16  is a package receptacle including a decelerating slide. 
           [0037]      FIG. 17  is a package receptacle including a net. 
       
    
    
     DESCRIPTION 
     1 Overview 
       [0038]    Referring to  FIG. 1 , an unmanned vehicle delivery system  100  receives an order for an item  102  from a user  104  via, for example, a computer  105 . Using information included in the order, the system  100  delivers the item  102  to a delivery location  106  specified by the user  104  using an unmanned delivery vehicle  108  (e.g., an unmanned aerial vehicle). 
         [0039]    When the user  104  places the order, the order is transmitted over a network  110  (e.g., the internet) to a retailer (e.g., an online retailer)  112  where the order is initially processed. After initially processing the order, the retailer  112  sends order information to a regional distribution center  114  which is located in the same geographical region as the delivery location  106 . At the regional distribution center  114 , the item  102  is attached to the unmanned delivery vehicle  108 . The unmanned delivery vehicle  108  is also programmed with instructions (e.g., GPS coordinates associated with the delivery location  106 ) for delivering the item to the delivery location  106 . 
         [0040]    Once the unmanned delivery vehicle  108  has the item  102  attached thereto and is programmed with instructions for delivering the item  102  to the delivery location  106 , the unmanned delivery vehicle  108  launches and delivers the item  102  to the delivery location  106 . 
         [0041]    After delivering the item  102 , the unmanned delivery vehicle  108  returns to the regional distribution center  114  where it retrieves another item, is reprogrammed, and repeats the delivery process. 
         [0042]    While the general unmanned delivery process described above seems simple, a number of challenges to the process exist. The examples described in detail below address the challenges to the unmanned delivery process and improve the overall performance of the process. 
       2 Fiducial Landing Pad or Drop Zone 
       [0043]    Referring to  FIGS. 1 and 2  when a customer orders an item as described in  FIG. 1 , the customer provides a shipping address (i.e., the address where they want their item delivered). The retailer then provides the customer with a printable fiducial  216 . In some examples, the printable fiducial is in the form of a QR code or a bar code which is specific to the customer (and possibly unique to the order). The online retailer then instructs the customer to print the fiducial and to place it outdoors in a location where they want their item to be delivered (i.e., the delivery location  106 ). In some examples, the online retailer also instructs the customer to place the fiducial in a location that is easily accessible by a UAV (e.g., a location unobstructed by trees, fences, power lines, and so on). The customer prints the fiducial, places the printed fiducial in a location outside of their house  218 , and waits. 
         [0044]    At the same time at the regional distribution center  114  near the customer&#39;s house  218 , a package including the customer&#39;s item  102  is loaded onto an unmanned aerial vehicle (UAV)  108  (e.g., a multi-rotor UAV) and the UAV  108  is programmed to fly to a Global Positioning System (GPS) coordinate associated with the customer&#39;s address. In some examples, the GPS coordinate is obtained from a mapping service such as Google Maps which approximately maps GPS coordinates to street addresses. 
         [0045]    Once programmed, the UAV  108  leaves the regional distribution center  114  and flies toward the GPS coordinate associated with the customer&#39;s address. When the UAV  108  reaches the GPS coordinate, the UAV  108  begins to fly around the GPS coordinate in an efficient manner. At the same time, a camera  220  on board the UAV  108  is activated and begins taking still photographs or video of the surrounding area. An image processor processes the photographs or video to determine whether the fiducial  216  is present in the photographs or video. 
         [0046]    Referring to  FIG. 3 , once the fiducial  216  is detected, the UAV  108  flies toward the fiducial  216  until the UAV  108  is directly above the fiducial  216 . The UAV  108  then flies to a sufficiently low altitude such that it can safely deliver (e.g., drop) the package including the customer&#39;s item  102  onto the fiducial  216 . 
         [0047]    Once the package has been delivered, the UAV  108  flies back to the regional distribution center  114  where it retrieves the next customer&#39;s package and the delivery process repeats. 
         [0048]    In some examples, rather than having a customer print out a fiducial for each order, the customer may have a permanent fiducial installed at their location. For example, a customer could install a tile mosaic which appears to be decorative but is actually a re-usable and weatherproof fiducial for UAV delivery. 
         [0049]    In some examples, the package is connected to a winch on the UAV. When the UAV arrives above the fiducial, the package is lowered onto the fiducial using the winch. The package is then disconnected from the winch and the winch is retracted before the UAV returns to the regional distribution center. In some examples, if there is a person, animal, or some other object which could potentially be harmed by the lowering of the package, the UAV will not lower the package. In some examples, the package is not lowered onto the fiducial but is instead lowered onto a visual map point. 
         [0050]    In some examples, rather than dropping the package onto the fiducial or winching the package down to the fiducial, the UAV simply lands on the fiducial and places the package on the fiducial. 
         [0051]    In general, it is not a strict requirement that the package end up directly on the fiducial. For examples, there may be an acceptable margin of error (e.g., a 5 ft. radius around the fiducial) for placement of the package on or around the fiducial. 
         [0052]    In some examples, once the package is delivered, the UAV causes a text message, an email, or some other suitable notification to be sent to the customer, indicating that their package has been delivered. 
         [0053]    In some examples, as the UAV travels to the customer&#39;s location, the UAV communicates with the regional distribution center such that an estimated time of delivery is continually updated. This estimated time of delivery can be provided to the user via any number of communications means (e.g., text message, email, the online retailer&#39;s website, and so on). 
         [0054]    In some examples, the presence of a fiducial can be used to easily verify that the delivery location is correct and determine where to safely leave packages. 
       3 Non-Landing Deliveries 
       [0055]    Presently, if a person wants to purchase an item, they generally need to either order the item and wait a number of days for the item to be delivered or go out to a store and buy the item there. If a person is out of their home, wants the instant gratification of immediately obtaining an item, and is unable or unwilling to go to a store, they currently have no way of obtaining their item. For example, a person walking around a city may want to purchase a drink for immediate consumption but may not have the time or the desire to walk to a convenience store to purchase the drink. This person would have no way of obtaining their drink. 
         [0056]    Referring to  FIGS. 4 and 5 , in some examples, items can be ordered by a customer  422  using, for example, a mobile device  424  and delivered by an unmanned aerial delivery vehicle  108  (UAV) directly to the customer  422  at the location of their mobile device  424  without ever requiring the UAV  108  to land. 
         [0057]    When the customer  422  places their order, order information is sent from their mobile device  424  to a retailer  112  and then to a regional distribution center  114 . In some examples, the order information includes an identifier of the ordered item  102  and a location of the customer (e.g., a GPS coordinate). 
         [0058]    At the distribution center  114 , the ordered item  102  is loaded onto a delivery UAV  108  and the customer&#39;s GPS coordinate is programmed into the delivery UAV  108 . 
         [0059]    Once programmed, the UAV  108  leaves the distribution center  114  and flies toward the GPS coordinate associated with the customer  422 . When the UAV  108  reaches the GPS coordinate, the UAV  108  begins to fly around the GPS coordinate in an efficient manner. 
         [0060]    At the same time, a validation system (not shown) included in the UAV  108  searches for a validation beacon  426  associated with the customer  422 . In some examples, the validation beacon  426  is a fiducial such as a QR code or bar code displayed on the screen of the customer&#39;s mobile device  424 . In this case, a camera  220  on board the UAV  108  takes still photographs or video of the surrounding area as the UAV  108  flies around the GPS coordinate. An image processor processes the photographs or video to determine whether the fiducial  426  is present in the photographs or video. Once the fiducial  426  is detected, the UAV  108  flies toward the fiducial until the UAV  108  is directly above the fiducial  426  (and presumably the customer  422 ). The UAV  108  then flies to a sufficiently low altitude such that the item  102  can be safely delivered to the customer  422 . 
         [0061]    In other examples, the validation beacon is a near-field communications signal such as a Bluetooth signal, a WiFi signal, or an infrared signal. In this case, a sensor such as a Bluetooth, WiFi, or infrared sensor monitors the environment as the UAV flies around the GPS coordinate. When the UAV detects the validation beacon signal the UAV flies in such a way that the received signal strength is maximized. At this point the UAV is presumably closest to the customer. The UAV then flies to a sufficiently low altitude such that the item can be safely delivered to the customer. 
         [0062]    In some examples, the UAV delivers the package by flying to an altitude where the customer can grab their item from the UAV. In some examples, the package is touch sensitive such that the customer can touch the package and trigger a release mechanism on the UAV, releasing the package. For example, the package or the payload bay mechanism may be provided with a capacitive sensor which triggers a release mechanism on the UAV. 
         [0063]    In some examples, rather than directly handing the package to the customer, the UAV includes a winch which winches the package down to the customer. Such a winching scheme can increase the distance between the customer and the UAV, thereby increasing the safety of the transaction. In some examples, if there is a person, animal, or some other object which could potentially be harmed by the lowering of the package, the UAV will not lower the package. In some examples, the UAV lowers the package onto a point away from but in a vicinity of a person. 
         [0064]    In some examples, the customer may be on the move and the customer&#39;s mobile device can continually update the UAV with the customer&#39;s current GPS coordinate. In this way, the customer&#39;s location can be tracked by the UAV and the customer doesn&#39;t have to wait in one location for their delivery. 
         [0065]    In some examples, the UAV includes an on-board camera which captures still photographs or videos as the UAV flies. When the UAV approaches the customer to make its delivery, a people detection algorithm analyzes the still photographs or videos and recognizes people in the vicinity of the UAV. The UAV then plots a flight path which avoids the recognized people. In some examples, the people detection algorithm or a facial detection algorithm can be used to identify the customer. In this way, the UAV can fly to a position near the customer and make its delivery, even in a crowd of people. 
         [0066]    Once the package has been delivered, the UAV flies back to the distribution center where it retrieves the next customer&#39;s package and the delivery process repeats. 
         [0067]    In some examples, a customer may order an item and provide a GPS coordinate, other than their own, to which the item should be delivered. For example, a customer may purchase an item for their friend and provide their friend&#39;s GPS coordinate as the delivery destination. The friend is then sent an indication (e.g., an email or a text message) that the item is being delivered to them. When the item arrives, the friend can validate that the order is for them using any of the validation techniques described above (e.g., presenting a QR code on their mobile device). 
       4 Visual Location Matching 
       [0068]    Mappings of street addresses to GPS coordinates are currently in existence. One example of such a mapping is included in the Google Maps application. These mappings are generally approximate in nature and are not sufficiently accurate to be useful for automated delivery of items to a specific location at an address. 
         [0069]    Furthermore, once an automated delivery vehicle (e.g., a UAV) reaches a GPS coordinate associated with a customer&#39;s address, there is no way to validate that the GPS coordinate is actually associated with the customer&#39;s address. 
         [0070]    In this example, existing aerial photography (e.g., satellite images from, e.g., Google Maps) is used to identify a preferred delivery location. 
         [0071]    Referring to  FIGS. 1 and 6 , when a customer orders an item from, for example, an online retailer&#39;s website, the customer provides a shipping address (i.e., the address where they want their item delivered). The customer is also prompted to select a desired delivery location  106  on a map by placing an icon (e.g., a bullseye or an arrow) on an image of his/her house  218  derived from aerial or satellite imagery, for example, the icon could be placed in the center of a path, a backyard, a driveway, etc. 
         [0072]    Subsequently, at a regional distribution center  114  near the customer&#39;s house  218 , a package including the customer&#39;s item is loaded onto a UAV (e.g., a multi-rotor UAV) and the UAV is programmed to fly to a GPS coordinate associated with the desired delivery location  106 . In some examples, the GPS coordinate is obtained from a mapping service such as Google Maps. 
         [0073]    Once programmed, the UAV  108  leaves the regional distribution center  114  attempts to fly to a position above the specified location or an offset from the specified location and it gets there within the GPS/map registration accuracy. Once the UAV  108  has reached the GPS coordinate associated with the delivery location  106 , the UAV  108  is ostensibly in range to capture imagery around the delivery location  106 . From this point the UAV  108 , augments its navigation with visual imagery by comparing its real time imagery (acquired using a camera  220 ) with the imagery associated with the user-specified delivery location  106  (e.g., Google Maps imagery). For example, the UAV  108  matches features in the terrain captured in its real time imagery with features from the map, allowing the vehicle to hover over a location that is much closer to the user-specified delivery location  106 . The UAV  108  then either lands and makes the drop or lowers the package, including the customer&#39;s item onto the user-specified delivery location. 
         [0074]    Once the package has been delivered, the UAV  108  flies back to the regional distribution center  114  where it retrieves the next customer&#39;s package and the delivery process repeats. 
         [0075]    In some examples, the SSID associated with the customer&#39;s WiFi network is also programmed into the UAV making it easier to get into range to see the drop-off location. In some examples, WiFi signals emitted by access points in and/or around a customer&#39;s house can also be used to accurately deliver an item to a location specified by the customer and to validate that the delivery location is correct. 
         [0076]    In some examples, the customer selects the desired drop-off location by pointing to it (mouse of touchscreen) on an aerial image. 
         [0077]    One advantage of this approach is that using terrain map in addition to a GPS system (and in some cases a WiFi signal) can result in highly accurate delivery of the customer&#39;s item to a customer designated location. 
         [0078]    Another advantage of this approach is that imagery can be used to validate that the package is placed where the customer wants it to a greater precision than if GPS alone were used. 
         [0079]    In some examples, when the customer places their order, a GPS coordinate associated with specific location on the customer&#39;s property (e.g., the customer&#39;s doorstep) is provided to the retailer&#39;s website. The UAV can then deliver the customer&#39;s item to this specific location using the above-described combination of GPS and vision based positioning systems. 
         [0080]    In some examples, trees, houses, and large objects can be identified a-priori on the map and then used to geo-reference locally at the delivery site. 
       5 Wi-Fi Location Validation 
       [0081]    As is described above, mappings of street addresses to GPS coordinates such as those included in the Google Maps application are generally approximate in nature and are not sufficiently accurate to be useful for automated delivery of items to a specific location at an address. For situations where GPS is not sufficiently accurate or is unreliable, companies such as Google, Skyhook, and Navizon have developed WiFi positioning systems which rely on a mapping of wireless access points to GPS coordinates. In some examples, WiFi positioning systems use these mappings to triangulate a location of a device (e.g., a smart phone or a UAV) based on a measured received signal strength from a number of access points which are both in the vicinity of the device and represented in the mapping. 
         [0082]    Furthermore, once an automated delivery vehicle (e.g., a UAV) reaches a GPS coordinate associated with a customer&#39;s address, there is no way to validate that the GPS coordinate is actually associated with the customer&#39;s address. 
         [0083]    To solve these problems, WiFi signals emitted by access points in and/or around a customer&#39;s house can be used to accurately deliver an item to a location specified by the customer and to validate that the delivery location is correct. 
         [0084]    Referring to  FIGS. 1 and 7  when a customer orders an item  102  from, for example, an online retailer&#39;s website, the customer provides a shipping address (i.e., the address where they want their item delivered). In some examples, identifying information related to the customer&#39;s WiFi network  226  (e.g., the Service Set Identifier (SSID) for their WiFi network) is also provided to the retailer&#39;s website. 
         [0085]    Subsequently, at a regional distribution center  114  near the customer&#39;s house  218 , a package including the customer&#39;s item  102  is loaded onto a UAV  108  (e.g., a multi-rotor UAV) and the UAV  108  is programmed to fly to a GPS coordinate associated with the customer&#39;s address. In some examples, the GPS coordinate is obtained from a mapping service such as Google Maps which approximately maps GPS coordinates to street addresses. In some examples, the SSID associated with the customer&#39;s WiFi network  226  is also programmed into the UAV  108 . 
         [0086]    Once programmed, the UAV  108  leaves the regional distribution center  114  and flies toward the GPS coordinate. Once the UAV  108  has reached the GPS coordinate associated with the customer&#39;s address, the UAV  108  is ostensibly in range of the WiFi network with identifying information (e.g., SSID) which matches the identifying information provided by the customer. At this point, the UAV  108  enables a WiFi signal sensor associated with a WiFi positioning system in addition to its GPS system. In general, the WiFi positioning system utilizes a mapping of access points associated with surrounding WiFi signals to GPS coordinates to pinpoint the UAV&#39;s  108  location. In some examples, such a mapping is provided by a third party such as Google Location Services, Navizon, or SkyHook. 
         [0087]    Referring to  FIG. 8 , The UAV  108  uses the WiFi positioning system to efficiently move in a direction toward the WiFi signal associated with the SSID provided by the customer (and presumably toward their actual address). At some point (e.g., when it is determined that the received signal strength of the customer&#39;s WiFi signal is above a threshold) the UAV  108  is considered to be at the delivery location  106  at the customer&#39;s address. At this point the UAV  108  flies to a sufficiently low altitude such that it can safely deliver (e.g., drop) the package including the customer&#39;s item  102  onto the customer&#39;s lawn. 
         [0088]    Once the package has been delivered, the UAV flies back to the regional distribution center where it retrieves the next customer&#39;s package and the delivery process repeats. 
         [0089]    One advantage of this approach is that using a WiFi positioning system in addition to a GPS system can result in highly accurate delivery of the customer&#39;s item to the customer&#39;s location. 
         [0090]    Another advantage of this approach is that an SSID of the customer&#39;s wireless network (provided by the customer) can be used to validate that the UAV is delivering the customer&#39;s item to the customer&#39;s address. 
         [0091]    In some examples, when the customer places their order, a GPS coordinate associated with specific location on the customer&#39;s property (e.g., the customer&#39;s doorstep) is provided to the retailer&#39;s website. The UAV can then deliver the customer&#39;s item to this specific location using the above-described combination of GPS and WiFi positioning systems. 
         [0092]    In some examples, rather than determining the customer&#39;s GPS coordinates from a service such as Google maps, the customer&#39;s GPS coordinates are determined by consulting a database which maps identifying information of WiFi networks (e.g., SSIDs) to GPS coordinates. In particular, such a database is searched for the SSID associated with the customer&#39;s WiFi network and, if found, the GPS coordinate associated with the SSID is used as the delivery coordinate. 
         [0093]    In some examples, as the UAV travels around the regional distribution center delivering packages, the UAV monitors WiFi networks in the area to create its own database relating WiFi networks and GPS coordinates. This database can be used in conjunction with the WiFi positioning system described above. 
       6 Commercial Courier Applications 
       [0094]    Even with the advent of electronic communications such as email text messaging, there is still a need for communication via paper. One common example is a document (e.g., a contract) which requires original signatures. The completion of such documents is often a time sensitive matter, requiring the signing of the document to be completed in a matter of hours. 
         [0095]    While delivery using email or text message is nearly instantaneous, an original signature cannot be transmitted using these technologies. Conversely, original signatures can be obtained using services such as the U.S. Postal Service, FedEx, or UPS. However, these services generally take one or more days to deliver documents (even if the documents only need to be delivered across a city). 
         [0096]    For this reason, courier services (e.g., bicycle couriers, automobile couriers, and so on) exist. These services involve a human retrieving a small package or document from a sender and quickly delivering the document to a recipient (usually within a small geographic area such as a city). Use of such courier services can be expensive and, since they involve humans, can result in mistakes due to human error. 
         [0097]    To overcome some of the drawbacks of using courier services, Unmanned Aerial Vehicles (UAVs) can be used as couriers, delivering documents and small packages between locations within a small geographic area. 
         [0098]    Referring to  FIG. 9 , a UAV  108  (e.g., a multi-rotor unmanned aerial vehicle) is parked on a first base station  928  on a roof of a first building  930 . A second building  932  has a second base station  934  on its roof. In some examples, each of the base stations  928 ,  934  includes a fiducial (e.g., a QR code or a bar code) which is visible from the airspace above the base station. 
         [0099]    At some point, a first person in the first building  930  needs a document or small package to be delivered to a second person in the second building  932 . The first person has their document or package attached to the UAV  108  and indicates to the UAV  108  that the package should be delivered to a person at the second building  932 . In some examples, the first person provides an address for delivery and a computer program calculates an approximate GPS coordinate corresponding to the address using a mapping application such as Google Maps. 
         [0100]    Referring to  FIG. 10 , once the package is attached to the UAV  108  and the approximate delivery GPS coordinate is programmed into the UAV  108 , the UAV  108  launches from the first base station  928  and flies toward the GPS coordinate associated with the delivery location (i.e., the second building  932 ). When the UAV  108  reaches the GPS coordinate, the UAV  108  begins to fly around the GPS coordinate in an efficient manner. At the same time, a camera on board the UAV  108  is activated and begins taking still photographs or video of the surrounding area. An image processor processes the photographs or video to determine whether the fiducial associated with the second building  932  is present in the photographs or video. Once the fiducial is detected, the UAV  108  flies toward the fiducial and lands on the second base station  934  which is associated with the fiducial. 
         [0101]    The UAV  108  then causes a delivery notice (e.g., an email or a text message) to be sent to the second person in the second building  932 , indicating that they should retrieve their document or package. The second person then retrieves their document or package, completing the delivery. 
         [0102]    In some examples, the base stations on each of the buildings include a charger for the UAV. In such examples, the UAV may stay on the base station of the second building, charging its batteries as it waits for its next courier assignment. In other examples, the UAV may charge its batteries to ensure that it can safely return to the first building where it waits for its next courier assignment. 
         [0103]    In some examples, the base stations on each of the buildings include a weather station to monitor the weather. The weather information collected by the base stations can be used to determine whether it is safe for the UAVs to fly from one building to the other. 
         [0104]    In some examples, other types of fiducials can be used to accurately land the UAV on the base station. For example, visible or infrared light fiducials can be used. 
       7 Unmanned Delivery Airframe 
       [0105]    Amazon, Matternet, CyPhy Works and others have suggested the use of flying drones for package delivery. These drone prototypes have been portrayed as having a conventional multi-rotor configuration. One of the main technological challenges of this idea is the limited range, endurance and payload that current battery technology imposes on conventional multi-rotor vehicles. In some examples, enhancing these parameters to the point where the use of multirotor vehicles is practical requires a redesign of the multi-rotor configuration. 
         [0106]    At present, three main flying drone configurations have been used to deliver payloads: airplanes, multi-rotors and helicopters. For the proposed application the use of airplanes, which have an excellent range, endurance and payload capabilities, is not practical since they lack the VTOL and hovering capabilities to perform an accurate delivery. Multi-rotors and helicopters as previously mentioned require more power and have a limited range of operation. 
         [0107]    There is a fourth configuration that has been used mostly used in full-scale vehicles, the tilt rotors like the V-22 Osprey and the Bell XV-15 have their propellers on pods at the end of their wings. In hover or at low speed forward flight, the propellers are almost horizontal producing mostly vertical thrust. In forward flight the propellers are tilted forward using most of the thrust for propulsion while the wings provide the lift. These two flying modes result in excellent forward flight characteristics with flying speeds that largely exceed what a helicopter/multi-copter can achieve, while keeping the vertical take off and landing capabilities intact. 
         [0108]    Referring to  FIGS. 11 and 12 , a multi-rotor UAV  1102  includes an airframe  1100  which facilitates operation of the UAV  1102  in two modes: a multi-copter mode ( FIG. 11 ) and a forward flight mode ( FIG. 12 ). To enable the two modes of operation, the airframe  1100  includes a streamlined fuselage  1102  which is aerodynamically optimized such that it reduces the drag in forward flight while simultaneously working as a lifting surface. The fuselage is surrounded by an array of an even number of rotors  1106  (e.g.,  4 ,  6 ,  8 , or  10 ) that tilt back and forth when switching between multi-copter mode and forward flight mode. For example, referring to  FIG. 11 , in multi-copter mode the rotors  1106  are all in a substantially horizontal configuration (i.e., substantially parallel to the ground) allowing for vertical take-off and landing, hovering, and low speed flight. Referring to  FIG. 12 , to convert to forward flight mode, at least some of the rotors  1106  tilt or rotate such that they are in a substantially vertical configuration (i.e., substantially perpendicular to the ground) allowing for higher speed forward flight. 
         [0109]    In some examples, when the at least some rotors  1106  tilt or rotate from a substantially vertical configuration into a substantially horizontal configuration, the lifting surfaces on the spars  1103  connecting the at least some rotors  1106  to the center of the fuselage  1100  rotate from a substantially horizontal configuration into a substantially vertical configuration. Similarly, when the at least some rotors  1106  tilt or rotate from a substantially horizontal configuration into a substantially vertical configuration, the lifting surfaces on the spars  1103  rotate from a substantially vertical configuration to a substantially horizontal configuration. 
         [0110]    In other examples, when the at least some rotors  1106  tilt or rotate between a substantially vertical configuration and a substantially horizontal configuration, the lifting surfaces on the spars  1103  of the at least some rotors  1106  remain in a substantially horizontal configuration. 
         [0111]    In operation, the UAV  1102  performs vertical takeoffs and landings (e.g., when hovering to perform package delivery) in multi-copter mode and then switches to forward flight mode (i.e., tilted rotor configuration) when flying over longer distances. The faster speeds and reduced power consumption associated with forward flight mode allow the UAV  1102  to achieve a greater range and endurance than would be possible using a conventional multi-copter. 
         [0112]    In some examples, the UAV includes a large internal volume than can hold a payload. For example, the streamlined fuselage  1102  may include a package bay  1104  that holds a payload either by enclosing it on the inside or making the surface of the package part of the fuselage  1102  itself. In some examples, the package bay is inside of the fuselage to ensure that the streamlined aerodynamics of the fuselage are preserved. 
         [0113]    Referring to  FIG. 13  in another configuration, the UAV  1102  includes a streamlined fuselage  1100  including five spars  1103  extending from a central package bay  1104 . A number (i.e., four in this case) of the spars  1103  each include a rotor  1106  mounted in a substantially horizontal position relative to the ground for providing vertical thrust for the UAV  1102 . One (or more) of the spars  1103  includes a rotor  1107  mounted in a substantially vertical position relative to the ground for providing horizontal thrust for the UAV  1102 . 
         [0114]    Referring to  FIG. 14 , in operation, when hovering or traveling over short distances, the rotors  1106  that are mounted in a substantially horizontal position are used primarily, with the rotor  1107  mounted in a substantially vertical position being used little, if at all. When traveling over longer distances, the rotor  1107  mounted in a substantially vertical position relative to the ground acts as a propeller, moving the UAV  1102  in a lateral direction, with the streamlined fuselage  1100  providing lift (i.e., the UAV  1102  ‘flies’ like an airplane). When flying like an airplane, the UAV  1102  may use the rotors  1106  mounted in a horizontal position to provide additional lift, if necessary. 
         [0115]    Referring to  FIG. 15 , in some examples, the spar  1103  that the horizontally mounted rotor  1107  is mounted upon is rotatable relative to the other spars  1103  of the UAV  1102 . The spar  1103  may be rotated to alter the flight characteristics of the UAV  1102  and/or when the UAV switches between a hovering and a flying mode. 
       8 Package Receptacles 
       [0116]    Referring to  FIG. 16 , in some examples, to ensure that the item  102  being delivered isn&#39;t damaged by being dropped from an excessive height, the UAV  108  drops the item  102  into a receptacle  1604  including a decelerating slide  1606  and a container  1601 . When the item  102  is dropped into an open end  1612  of the decelerating slide  1606 , the item  102  is slowly decelerated as it travels along a gradual bend in the decelerating slide  1606 . After passing through the decelerating slide  1606 , the item is deposited into the container  1610  where it can be retrieved by a customer. 
         [0117]    Referring to  FIG. 17 , in some examples, to ensure that the item  102  being delivered isn&#39;t damaged by being dropped from an excessive height, the UAV  108  drops the item  102  into a net-like structure  1714  which catches and safely decelerates the item  102  before it hits the ground. 
       9 Packaging 
       [0118]    In some examples, to ensure that the item  102  being delivered isn&#39;t damaged by being dropped from an excessive height, items may be packaged using packing materials and/or methods which prevent damage due to impact with the ground or other items. For example, products may be packaged such that they are surrounded on all sides by airbags, Styrofoam, honeycombed cardboard, or other cushioning materials. 
       10 Alternatives 
       [0119]    While the above description relates mostly to the use of multi-rotor UAVs, other types of UAVs, such as those well known in the art can be used. 
         [0120]    In some examples, the UAV is programmed such that it always moves to a location where there are not people present directly underneath the UAV before it lowers or drops the package. 
         [0121]    While many of the UAV airframes described above include an even number of rotors, in some examples, an odd number of rotors can be used (e.g., in cases where one of the rotors is used for lateral movement of the UAV while the other rotors are used to provide vertical thrust). 
         [0122]    It is to be understood that the foregoing description is intended to illustrate and not to limit the scope of the invention, which is defined by the scope of the appended claims. Other embodiments are within the scope of the following claims.