Abstract:
Methods and apparatus are disclosed to determine the location of endpoints of interest. An example method involves in response to detecting a transmission from the endpoint, determining whether the endpoint is an endpoint of interest. If the endpoint is the endpoint of interest, the example method involves sending a first command to the endpoint to increase a transmission rate of the endpoint, determining an estimated location of the endpoint using signal strengths of subsequent transmissions from the endpoint, and enabling the transmission rate of the endpoint to decrease.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    This disclosure relates generally to utility meter reading, and, more particularly, to locating endpoints of interest. 
       BACKGROUND 
       [0002]    Utility providers install, maintain, and/or collect utility usage data from endpoints within an automatic meter reading (AMR) collection network. These endpoints are data collection and transmitting devices that are either installed on existing utility meters or are integrated into the utility meters. Often, the endpoints communicate with data collection units (DCU) through radio frequency (RF) communication. Some endpoints transmit meter data at preset periodic intervals without any external prompting. 
         [0003]    To conserve battery life, such meters remain in a low-power mode (e.g. sleep mode) for a relatively long time (e.g., 30 seconds, 60 seconds, etc.) and wake up (e.g., bubble up) into a higher power mode for a relatively short time (e.g., 500 milliseconds, 1 seconds, etc.) to transmit meter data. Because an endpoint sleeps for a relatively long time and bubbles up periodically, transmitting meter data while a DCU is in range may only happen once or twice every meter data collection period (e.g., monthly, quarterly, etc.). Typically, this is not an issue because, in most cases, the DCU can record the meter data for a reporting period from one meter data transmission from a particular endpoint. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  illustrates an example system constructed in accordance with the teachings of this disclosure to locate endpoints of interest. 
           [0005]      FIG. 2  illustrates an implementation of an example endpoint locator that may be included in the example system of  FIG. 1  to estimate the location of endpoints of interest. 
           [0006]      FIG. 3  is an example diagram illustrating an interaction between the endpoint of interest and the data collection unit of  FIG. 1 . 
           [0007]      FIG. 4  illustrates an example graphical user interface displayed by the operator interface that may be used to interact with the operator of the data collection unit of  FIG. 1 . 
           [0008]      FIG. 5  is a flow diagram representative of example machine readable instructions that may be executed to implement the example endpoint locator of  FIGS. 1 and 2  to estimate the location of the endpoint of interest. 
           [0009]      FIG. 6  is a flow diagram representative of example machine readable instructions that may be executed to implement the example endpoint locator of  FIGS. 1 and 2  to estimate the location of the endpoint of interest. 
           [0010]      FIG. 7  is a block diagram of an example processor system that may execute the example machine readable instructions represented by  FIGS. 5  and/or  6  to implement the example apparatus of  FIGS. 1 ,  2  and/or  4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Examples disclosed herein may be used to estimate the location of utility meter endpoints of interest. A utility meter measurement entity (UMME) collects meter data (e.g., utility usage data, meter identifier, endpoint identifier, etc.) from endpoints installed on utility meters (e.g., electric meters, gas meters, water meters, etc.) to, for example, monitor and/or charge for utility usage. 
         [0012]    DCUs receive the meter data transmitted by endpoints and send (e.g., via a cellular data connection, via a wireless network, via a wired connection, etc.) the collected meter data to the UMME. In some examples, the DCU is part of a fixed network. In some examples, the DCU is mobile (e.g., hand held, attached to a vehicle, attached to a drone, etc.). 
         [0013]    To collect meter data, mobile DCUs travel routes (e.g., DCU routes) through geographical areas where endpoints are installed. In some examples, the mobile DCU travels a preplanned route (e.g., with predetermined turn-by-turn directions, etc.). In other examples, the mobile DCU travels an ad hoc route through an assigned geographical area. In both examples, the mobile DCU may maintain a list of the expected endpoints from which meter data should be received along the DCU route. The DCU may use the list of expected endpoints to identify endpoints of interest (e.g., the DCU received a transmission of an endpoint not on the list, etc.) and/or to designate suspected endpoints of interest (e.g., the DCU did not receive a transmission from an endpoint on the list, etc.). 
         [0014]    From time to time, the UMME may be unable to account for the location of a utility meter and/or the corresponding endpoint. For example, when an endpoint is installed, the geographic location (e.g., latitude and longitude coordinates, postal address, etc.) of the installation location may be recorded incorrectly in a database of installed endpoints. As another example, the utility meter and/or the corresponding endpoint may have been tampered with and moved to a different location. Because endpoints are powered by batteries, endpoints may continue to transmit even after removed from a meter or the meter is moved. 
         [0015]    After traveling a DCU route, if the DCU does not receive meter data from an expected endpoint, that endpoint may be flagged as an endpoint of interest. In some examples, an operator of the DCU may be directed to inspect last-known location of the unaccounted-for endpoint to determine if the endpoint is missing and thus is an endpoint of interest. In other examples, other employees of the UMME (e.g., a maintenance employee, a revenue protection employee, etc.) may be directed to determine if the endpoint is missing and thus is an endpoint of interest. For example, if an endpoint is in the last-know geographical location, but the endpoint&#39;s battery is discharged and/or the endpoint is damaged, the endpoint may be designated as requiring maintenance, but would not be designated as an endpoint of interest. 
         [0016]    The UMME may maintain a record (e.g., a database, a list, a spreadsheet, etc.) of endpoints of interest. In some examples, the record may be updated and communicated when a DCU returns to the UMME (e.g., via a wired connection, via a wireless connection, etc.). In some examples, the UMME maintains a real time connection (e.g., a cellular connection, etc.) with the mobile DCU to receive and send updates to the record. An endpoint may be designated an endpoint of interest and tracked by the UMME if, for example, the meter data is not received from the endpoint near the recorded installation location. As another example, an endpoint may be designated an endpoint of interest if, after analyzing tamper flags included in the meter data, the UMME determines that the endpoint was likely moved in an unauthorized manner. 
         [0017]    As disclosed herein, when a DCU receives meter data from an endpoint, the DCU determines whether the endpoint is an endpoint of interest. In some examples, to determine if the endpoint is an endpoint of interest, the DCU compares an endpoint identifier included in the meter data provided by the endpoint to the record of endpoints of interest. In some examples, the DCU compares the endpoint identifier included in the meter data to the list of expected endpoints and designates the endpoint as an endpoint of interest if the endpoint is not an expected endpoint. 
         [0018]    As discussed in further detail below, when an endpoint has been identified and/or designated as an endpoint of interest, the DCU sends a command to that endpoint of interest to increase the periodic interval at which the endpoint of interest transmits meter data. For example, the command may instruct the endpoint of interest to transmit meter data once every four seconds instead of once every thirty seconds. Using the meter data transmissions from the endpoint of interest, the DCU estimates the location of the endpoint of interest. More frequent transmissions allow the DCU to estimate the location of the endpoint of interest quickly because time the DCU is required to linger in the transmission range of endpoint of interest is reduced. Examples of estimating the location of the endpoint of interest are disclosed in U.S. Pat. No. 8,552,910, entitled, “System and Method of Locating Missing Nodes in Networks,” issued Oct. 8, 2013, to the instant assignee, which is incorporated herein by reference in its entirety. As discussed in further detail below, the DCU determines when a final estimated location has been generated. In some examples, the DCU informs the operator and/or directs the operator to the final estimated location. In some examples, the DCU stores the final estimated location in association with the corresponding record of the endpoint of interest. After the final estimated location is determined, the DCU allows or commands the endpoint of interest to resume its original periodic interval of transmitting meter data. Because transmitting meter data takes relatively more power compared to the low-power sleep mode, this allows the endpoint of interest to conserve battery life. 
         [0019]      FIG. 1  illustrates an example system  100  to identify and locate endpoints of interest  102 . In the illustrated example, a data collection unit (DCU)  104  receives meter data  106  from endpoints  108  (e.g. expected endpoints) and the endpoint(s) of interest  102 , each of which is installed on a corresponding utility meter (e.g., gas meters, electricity meters, water meters, etc.). The DCU  104  may be in a fixed location as part of a fixed network, or may be mobile (e.g., installed on a truck, built into a drone, be a handheld or backpack mounted unit, etc.). 
         [0020]    The example meter data  106  includes utility usage data, a meter identifier (ID), an endpoint ID, and/or tampers indicators, etc. The endpoints  102 ,  108  send meter data  106  at a periodic interval. When the DCU  104  receives meter data from an endpoint  102 ,  108 , the DCU  104  determines whether it is an endpoint of interest  102 . If the endpoint  102 ,  108  is an endpoint of interest  102 , the DCU  104  sends a command  112  to the endpoint of interest to change the periodic interval at which the endpoint of interest  102  transmits meter data  106 . More frequent transmissions allow the DCU  104  to calculate an estimated location of the endpoint of interest  102  quicker compared to if the periodic interval remained the same. In addition, the time the DCU  104  is required to linger in range of the endpoint of interest  102  is reduced. 
         [0021]    In the illustrated example of  FIG. 1 , the DCU  104  communicates with a utility meter measurement entity (UMME)  114  through a network  116 . In some examples, the DCU  104  communicates with the UMME  114  through the network  116  while the DCU  104  is in the field (e.g., via a cellular network, etc.). In some such examples, the DCU  104  receives an updated list of endpoints to interest  102  from the UMME  114  and/or the DCU  104  sends data (e.g., meter data  106 , information related to endpoints of interest  102 , etc.) to the UMME  114  while in the field (e.g., while traveling along the DCU route). In some examples, the DCU  104  communicates with the UMME  114  while the DCU  104  is proximate the UMME  104  (e.g. via a Wi-Fi network, via a wired connection, etc.). 
         [0022]    In the illustrated example of  FIG. 1 , the DCU  104  includes an example endpoint communication unit  118 , an example endpoint data gatherer  120 , an example endpoint locator  122 , an example endpoint database  124 , an example operator interface  126 , and an example DCU communication unit  128 . The example endpoint communication unit  118  receives meter data  106  from the endpoints  102 ,  108  and send commands  112  to the endpoint(s) of interest  102  via RF transmissions. The example endpoint communication module  118  includes hardware (e.g., radio(s), omnidirectional and/or unidirectional antenna(s), etc.) and software (e.g., encoders/decoders, communication buffers, etc.) to communicate with the endpoints  102 ,  108  in range of the DCU  104 . 
         [0023]    The example endpoint data gatherer  120  gathers, processes and/or stores meter data  106  received by the example endpoint communication module  118 . For example, when the DCU  104  receives meter data  106  from an endpoint  102  that corresponds to an endpoint on the list of expected endpoints, the endpoint data gatherer  120  stores the received meter data  106 . In some examples, endpoint data gatherer  120  indicates on the list of expected endpoints that meter data  106  has been received for the corresponding endpoint  102 . In some examples, the endpoint data gatherer  120  validates received meter data  106  for transmission errors and/or send requests (via the endpoint communication unit  118 ) for retransmission to the corresponding endpoint  102 . 
         [0024]    In the example illustrated in  FIG. 1 , the endpoint locator  122  determines whether the meter data  106  received by the endpoint communication unit  118  is from an endpoint of interest  102 , estimates the location of the endpoints of interest  102 , and generates commands  112  to send to the endpoints of interest  102 . In some examples, the endpoint locator  122  maintains a list of the endpoints  108  from which meter data  106  should be received along the DCU route (e.g., expected endpoints). In the illustrated example, the endpoint database  124  stores information (e.g., endpoint ID, last known location, etc.) related to endpoints of interest  102  received from the UMME  114 . 
         [0025]    The example operator interface  126  displays information (e.g., a status of meter data collection, a map, notifications, directions, etc.) to an operator of the example DCU  104 . In some examples, the operator interface  126  receives input from the operator. 
         [0026]    The example DCU communication unit  128  communicates with the UMME  114 . In some examples, the DCU communication unit  128  includes a satellite position system receiver  130  (e.g., a global positioning system (GPS) receiver, a global navigation satellite system (GLONASS) receiver, etc.) to provide the endpoint locator  112  with the satellite position system (SPS) coordinates (e.g., latitude and longitude coordinates) of the DCU  104 . 
         [0027]    In the illustrated example of  FIG. 1 , the UMME  114  includes an example UMME communication unit  132  and an example endpoint database  134 . The example UMME communication unit  132  receives meter data  106  gathered by the DCU  104 , receives information related to endpoints of interest  102  (e.g., new endpoints of interest, final estimated location of endpoints of interest, found endpoints of interest, etc.), and/or sends at least a portion of the endpoint database  134  to the DCU  104 . The example endpoint database  134  stores information related to the endpoints of interest  102 . In some examples, the endpoint database  134  stores information related to the endpoints of interest  102  collected by multiple DCUs  104 . 
         [0028]      FIG. 2  illustrates an example endpoint locator that may be included in the example system of  FIG. 1  to estimate the location of endpoints of interest  102  ( FIG. 1 ). In the illustrated example, the endpoint locator  122  includes an example endpoint determiner  200 , an example command generator  202 , an example distance calculator  204 , an example location estimator  206 , and an expected endpoint database  207 . 
         [0029]    The example endpoint determiner  200  of  FIG. 2  determines whether the meter data  106  ( FIG. 1 ) received by the endpoint communication unit  118  was sent by an endpoint of interest  102 . In some examples, the endpoint determiner  200  compares an endpoint ID  208  included with the meter data  106  to endpoint IDs  208  in the endpoint database  124 . In such examples, if the endpoint ID  208  included with the meter data  106  matches an endpoint ID  208  in the endpoint database  124 , the endpoint determiner  200  determines that such an endpoint is an endpoint of interest  102 . In some examples, the endpoint determiner  200  may maintain the database of expected endpoints  207  for the current DCU route. In such examples, if the endpoint ID  208  included with the meter data  106  is not included in the database of expected endpoints  207 , the endpoint determiner  200  determines that the respective endpoint is an endpoint of interest  102 . In some examples, the database of expected endpoints  207  includes expected location information (e.g., a geographical area where a particular endpoint should be detected, etc.) for the expected endpoints. In such examples, the endpoint determiner  200  may determine that the respective endpoint is an endpoint of interest  102  if the endpoint is detected outside the expected location. 
         [0030]    The example command generator  202  of  FIG. 2  marshals a command  112  to send to the endpoint of interests  102  identified by the example endpoint determiner  200 . When the endpoint of interest  102  is detected, the command generator  202  generates a command to increase the transmission rate (e.g., the transmission rate  110  of  FIG. 1 ) of the endpoint of interest  102 . In some examples, when the location estimator  206  determines a final estimated location of the endpoint of interest  102 , the command generator  202  generates a command  112  to decrease the transmission rate of the endpoint of interest  102 . In the illustrated example, the command generator  202  generates a command  112  based on the capabilities (e.g., based on the type and/or model of the endpoint) of the endpoint of interest  102 . In some examples, the command generator  202  generates a command  112  that instructs the endpoint of interest  102  to switch between predefined modes. For example, the endpoint of interest  102  may have a standard mode in which the endpoint bubbles up every thirty seconds and an express mode in which the endpoint bubbles up every four seconds. 
         [0031]    In some examples, the command generator  202  generates a command  112  that reprograms periodic transmission interval of the endpoint of interest  102 . Additionally, the command  112  may include a period of time after which the endpoint of interest  102  is to resume the periodic transmission interval. In such an example, after the period of time has elapsed, the endpoint of interest resumes the previous periodic transmission interval without receiving an additional command  112  from the DCU  104 . In this manner, the endpoint of interest  102  returns to a lower power consumption mode if the DCU  104 , for example, leaves the transmission range of the endpoint of interest  102  and/or otherwise cannot send a command  112  to the endpoint of interest  102 . In some examples, the command generator  202  may generate an additional command  112  if the final estimated location of the endpoint of interest  102  is not determine before the specified period of time has elapsed. For example, the command generator  112  may generate a command  112  that reprograms the endpoint of interest  102  to transmit every ten seconds for five minutes. 
         [0032]    The example distance calculator  204  of  FIG. 2  estimates the scalar distance between the endpoint of interest  102  and the DCU  104 . In the illustrated example, the distance calculator  204  measures a signal strength indicator (e.g., received signal strength indicator (RSSI) or other signal level parameter, etc.) for the RF transmission containing the meter data  106  from the endpoint of interest  102 . The example distance calculator  204  estimates the distance between the DCU  104  and the endpoint of interest  102  based on the measured signal strength indictor. In some examples, the calculated distance is weighted by weighing factors based on, for example, environmental factors (e.g., urban, rural, flat, mountainous, etc.), weather, the speed of the DCU  104 , etc. The example distance calculator  204  combines the estimated distance with geographical location (e.g., the SPS coordinates, etc.) of the DCU  104  to generate a triangulation data point. 
         [0033]    The example location estimator  206  of  FIG. 2  triangulates one or more provisional estimated locations of the endpoint of interest  102  based on the triangulation data points provided by the example distance calculator  204 . In some examples, the location estimator  206  does not make an initial provisional estimate of the location of the endpoint of interest  102  until after receiving a threshold number of the triangulation data points. For example, the location estimator  206  may make an initial provisional estimate of the location of the endpoint of interest  102  after receiving four triangulation data points. Upon receiving or retrieving one or more additional triangulation data points, the example location estimator  206  may update the provisional estimated location by triangulating the estimated location using the additional triangulation data points. In some examples, the location estimator  206  provides the provisional estimated location(s) to the operator interface  126 . In some examples, when calculating the estimated location, the location estimator  206  accounts for geographical locations that the endpoint of interest  102  is unlikely to be located (e.g., bodies of water, sports stadiums, etc.). For example, the location estimator  206  may discard provisional estimated locations that place the endpoint of interest  102  in a lake or a river. 
         [0034]    In the illustrated example of  FIG. 2 , the location estimator  206  determines a final estimated location. In some examples, the location estimator  206  determines that the latest provisional estimated location is the final estimated location after receiving a threshold number of triangulation data points (e.g., ten triangulation data points). In some examples, the location estimator  206  determines that the latest provisional estimated location is the final estimated location when the provisional estimated location does not change by a threshold amount (e.g., ten feet, twenty feet, etc.) after triangulating with an additional triangulation data point. In some examples, the location estimator  206  provides the final estimated location to the operator interface  126 . Additionally or alternatively, the location estimator  206  may include the final estimated location correlated with the endpoint ID  208  on an endpoint report  210 . The example endpoint report  210  may be sent to the UMME  114  via the DCU communication unit  128 . 
         [0035]    In some examples, the location estimator  206  may not determine the final estimated location. In some examples, the DCU  104  may leave the range of the endpoint of interest  102  (e.g., the DCU  104  does not receive additional meter data  106  from the endpoint of interest  102 ) before determining a final estimated location. In some such examples, the location estimator  206  may, via the operator interface  126 , may alert the operator and request that the DCU  104  be moved back into range of the endpoint of interest  102 . In some such examples, upon returning to the range of the endpoint of interest  102 , the command generator  202  may send a command  112  to decrease the periodic transmission interval of the endpoint of interest  102 . In some examples, the provisional estimated location may change greater than a threshold distance (e.g., fifteen feet, twenty feet, etc.) after a threshold number triangulation data points (e.g., ten triangulation data points, twenty triangulation data points, etc.). In some such examples, the location estimator  206  may provide one or more of the provisional estimated locations to the operator interface  126 . Additionally or alternatively, one or more of the provisional estimated locations may be included on the endpoint report  210 . 
         [0036]    While an example manner of implementing example endpoint locator  122  of  FIG. 1  is illustrated in  FIG. 2 , one or more of the elements, processes and/or devices illustrated in  FIG. 2  may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example endpoint determiner  200 , the example command generator  202 , the example distance calculator  204 , the example location estimator  206  and/or, more generally, the example endpoint locator  122  of  FIG. 1  may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example endpoint determiner  200 , the example command generator  202 , the example distance calculator  204 , the example location estimator  206  and/or, more generally, the example endpoint locator  122  of  FIG. 1  could be implemented by one or more analog or digital circuit(s), logic circuits, programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)). When reading any of the apparatus or system claims of this patent to cover a purely software and/or firmware implementation, at least one of the example endpoint determiner  200 , the example command generator  202 , the example distance calculator  204 , the example location estimator  206  and/or the example endpoint locator  122  of  FIG. 1  is/are hereby expressly defined to include a tangible computer readable storage device or storage disk such as a memory, a digital versatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc. storing the software and/or firmware. Further still, the example endpoint locator  122  of  FIG. 1  may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated in  FIG. 2 , and/or may include more than one of any or all of the illustrated elements, processes and devices. 
         [0037]      FIG. 3  is a diagram illustrating an example interaction between the endpoint of interest  102  and the data collection unit  104  of  FIG. 1 . Initially, at time T 0 , the endpoint of interest  102  bubbles up (e.g., wakes up and transmits meter data  106 ) at a standard rate (e.g., once every thirty seconds, etc.) during a period  300  that the DCU  104  is out of RF range. At time T 1 , the DCU  104  comes within RF range of the endpoint of interest  102 . At time T 2 , the endpoint of interest  102  bubbles up at the standard rate. The DCU  104  receives the RF transmission containing meter data  106  and determines whether the meter data  106  was sent from an endpoint of interest  102 . At time T 3 , after determining that the meter data  106  did come from the endpoint of interest  102 , the DCU  104  sends a command  112  to increase the periodic transmission interval to the endpoint of interest  102 . 
         [0038]    At times T 4  and T 5 , the endpoint of interest  102  sends meter data  106  at the increased periodic transmission interval. In the illustrated example, the period of time between time T 4  and time T 5  is less than the period of time between time T 0  and time T 2 . In some examples, after receiving the meter data  106 , the DCU  104  determines a provisional estimated location. At time T 6 , after receiving the meter data  106  from the endpoint of interest  102 , the DCU  104  determines a provisional estimated location. In the illustrated example, the DCU  104  determines whether the provisional estimated location is the final estimated location (e.g., the location of the provisional estimated location did not change after recalculating with the additional RF transmission of the meter data  106 , the DCU  104  received a threshold number of RF transmissions of the meter data  106 , etc.). In the illustrated example, at time T 6 , the DCU  104  determines the final estimated location has not been calculated. At time T 7 , after receiving an additional RF transmission of meter data  106 , the DCU determines that a final estimated location has been calculated. At time T 8 , DCU  104  sends a command  112  to the endpoint of interest  102  to decrease the periodic transmission interval of the endpoint of interest  102 . At time T 9 , the endpoint of interest  102  bubbles up at the standard rate. 
         [0039]      FIG. 4  illustrates an example graphical user interface (GUI)  400  displayed by the operator interface  126  ( FIG. 1 ) that may be used to interact with the operator of the DCU  104  of  FIG. 1 . In the illustrated example, the GUI  400  has an example notification window  402 , an example map display  404 , and example user inputs  406   a - 406   b . The GUI  402  communicates the status of the DCU  104  generally, and/or the endpoint locator  122  ( FIGS. 1 and 2 ) specifically. The example notification window  402  displays information related to locating endpoints of interest  102  ( FIG. 1 ). For example, the notification window  402  may alert the operator that an endpoint of interest  102  has been detected (e.g., an RF transmission containing meter data  106  including the endpoint ID  208  has been received, etc.) and/or may alert the operator that a provisional and/or final estimated location has been calculated. In some examples, the notification window  402  alerts the operator that the DCU  104  has moved out of range of the endpoint of interest  102  (e.g., an RF transmissions from the endpoint of interest  102  are no longer being received, etc.). In some examples, the notification window  402  provides turn-by-turn directions for the DCU route of the DCU  104 . In some such examples, the notification window  402  provides turn-by-turn directions to locate the endpoint of interest  102  (e.g., after a final estimated location has been calculated, etc.). 
         [0040]    In the illustrated example of  FIG. 4 , the map display  404  displays a map of the geographic region around the DCU  104 . In the illustrated example, the map display  404  displays a DCU marker  408  to represent the location of the DCU  104  and an estimated location marker  410  to represent the estimated location of the endpoint of interest  102 . In some examples, the map display  404  displays end point marker(s)  412  to represent locations of endpoint(s)  108  along the DCU route. In some examples, the map display  404  displays a DCU route marker  414  to represent the DCU route the DCU  104  is scheduled to traverse to collect meter data  106  from endpoints  108  along the route. In some examples, the endpoint locator  122  may instruct the operator interface  126  to change the DCU route marker  414  to direct the DCU  104  to locations that may narrow down the location of the endpoint of interest  102 . 
         [0041]    In the illustrated example of  FIG. 4 , user inputs  406   a - 406   b  allow the operator to input information to the DCU  104 . The user inputs  406   a - 406   b  may take the form of input elements, such as buttons, text boxes, drop down menus, etc. For example, the GUI  400  may display a button (e.g., the user input  406   a ) that allows the operator to indicate that he/she has physically located the endpoint of interest  102 . In some examples, a button (e.g., the user input  406   b ) may be displayed that allows the operator to indicate that the DCU  104  is leaving the area. In some such examples, after the operator indicates that the DCU  104  is leaving the area, the endpoint locator  122  may send a command  112  ( FIG. 1 ) to the endpoint(s) of interest  102  to decrease their periodic transmission interval (e.g., the periodic transmission interval  110  of  FIG. 1 ). 
         [0042]    Flowcharts representative of example machine readable instructions for implementing the example endpoint locator  122  of  FIGS. 1 and 2  are shown in  FIGS. 5 and 6 . In this example, the machine readable instructions comprise a program for execution by a processor such as the processor  712  shown in the example processor platform  700  discussed below in connection with  FIG. 7 . The program may be embodied in software stored on a tangible computer readable storage medium such as a CD-ROM, a floppy disk, a hard drive, a digital versatile disk (DVD), a Blu-ray disk, or a memory associated with the processor  712 , but the entire program and/or parts thereof could alternatively be executed by a device other than the processor  712  and/or embodied in firmware or dedicated hardware. Further, although the example program is described with reference to the flowcharts illustrated in  FIGS. 5 and 6 , many other methods of implementing the example endpoint locator  122  of  FIGS. 1 and 2  may alternatively be used. For example, the order of execution of the blocks may be changed, and/or some of the blocks described may be changed, eliminated, or combined. 
         [0043]    As mentioned above, the example processes of  FIGS. 5 and 6  may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a tangible computer readable storage medium such as a hard disk drive, a flash memory, a read-only memory (ROM), a compact disk (CD), a digital versatile disk (DVD), a cache, a random-access memory (RAM) and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term tangible computer readable storage medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, “tangible computer readable storage medium” and “tangible machine readable storage medium” are used interchangeably. Additionally or alternatively, the example processes of  FIGS. 5 and 6  may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a non-transitory computer and/or machine readable medium such as a hard disk drive, a flash memory, a read-only memory, a compact disk, a digital versatile disk, a cache, a random-access memory and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term non-transitory computer readable medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, when the phrase “at least” is used as the transition term in a preamble of a claim, it is open-ended in the same manner as the term “comprising” is open ended. 
         [0044]      FIG. 5  is a flow diagram representative of example machine readable instructions  500  that may be executed to implement the example endpoint locator  122  of  FIGS. 1 and 2  to estimate the location of the endpoint of interest  102  ( FIG. 1 ). The endpoint determiner  200  determines whether a transmission containing meter data  106  was received (e.g., via the endpoint communication unit  118  of  FIG. 1 ) from an endpoint  102 ,  108  (block  502 ). If a transmission containing meter data  106  was received, the endpoint determiner determines whether the endpoint is an endpoint of interest  102  (block  504 ). Otherwise, if a transmission containing meter data  106  was not received, the endpoint determiner waits for the next transmission. 
         [0045]    The endpoint determiner  200  determines whether the detected transmission containing the meter data  106  (block  502 ) corresponds to an endpoint of interest  102 . In some examples, the endpoint determiner  200  determines that the detected endpoint is an endpoint of interest  102  based on the endpoint ID  208  included in the meter data  106 . For example, the endpoint determiner  200  may determine that the endpoint is an endpoint of interest  102  if an endpoint ID  208  matches an endpoint ID stored in an endpoint database  124 . Additionally or alternatively, if the endpoint ID  208  is not included a database of expected endpoints  207 , endpoint determiner  200  may determine that the endpoint is an endpoint of interest  102 . If the transmission containing meter data  106  corresponds to an endpoint of interest  102 , the command generator  202  generates a command  112  to increase the periodic transmission interval of the endpoint of interest  102  (block  504 ). Otherwise, if the transmission containing meter data  106  does not correspond to an endpoint of interest  102 , the endpoint determiner  200  waits for the next transmission. 
         [0046]    The command generator  202  sends a command  112  (e.g., via the endpoint communication unit  118  of  FIG. 1 ) to increase the periodic transmission period to the endpoint of interest  102  (block  506 ). The distance calculator  204  and/or the location estimator  206  determines an estimated location (e.g., the estimated location  410  of  FIG. 4 ) of the endpoint of interest  102  (block  508 ). The command generator  202  enables the transmission rate of the endpoint of interest  102  to decrease (block  510 ). In some examples, the command generator  202  send a command  112  to the endpoint of interest  102  to decrease the periodic transmission interval of the endpoint of interest  102 . The example program  500  then ends. 
         [0047]      FIG. 6  is a flow diagram representative of example machine readable instructions  508  that may be executed to implement the example endpoint locator  122  of  FIGS. 1 and 2  to estimate the location of the endpoint of interest  102  ( FIG. 1 ). The distance calculator  204  ( FIG. 2 ) calculates an estimated distance based on a measured signal strength indicator of the RF transmission from the endpoint of interest  102  (block  600 ). In some examples, the distance calculator  204  correlates the calculated distance with SPS coordinates of the current location of the DCU  104  to generate a triangulation data point. The location estimator  206  determines whether enough triangulation data points have been generated to determine an estimated location (block  602 ). In some examples, the determination is based on a threshold number of triangulation data points. If the location estimator  206  determines that enough triangulation data points have been generated to determine an estimated location, the location estimator  204  calculates an estimate location of the endpoint of interest  102  (block  602 ). Otherwise, if not enough triangulation data points have been generated to determine an estimated location, the distance calculator  204  waits for another transmission from the endpoint of interest  102  (block  604 ). 
         [0048]    The distance calculator  204  determines whether another transmission has been detected from the endpoint of interest  102  (block  604 ). If another transmission has been detected from the endpoint of interest  102 , the distance calculator  204  calculates a distance of the endpoint of interest (block  600 ). Otherwise, if another transmission has not been detected from the endpoint of interest  102 , the distance calculator  204  waits for another transmission from the endpoint of interest  102  (block  604 ). 
         [0049]    The location estimator  206  triangulates an estimated location of the endpoint of interest  102  using the triangulation data points generated by the distance calculator  204  (block  606 ). The location estimator  206  then determines whether the calculated estimated location is the final estimated location (block  608 ). In some examples, the location estimator  206  determines that the estimated location is the final estimated location after receiving a threshold number of triangulation data points (e.g., ten triangulation data points) from the distance calculator  204 . In some examples, the location estimator  206  determines that the estimated location is the final estimated location when the estimated location does not change by a threshold amount (e.g., ten feet, twenty feet, etc.) after calculating the estimated location with an additional triangulation data point. In some examples, the location estimator  206  determines that the estimated location is the final estimated location when, after receiving a threshold number of triangulation data points (e.g., ten triangulation data points) from the distance calculator  204 , the estimated location changes by more than a threshold amount (e.g., ten feet, twenty feet, etc.). If the location estimator  206  determines that the estimated location is the final estimated location (block  610 ), the example program  508  ends and/or control returns to a calling function or process such as the example process of  FIG. 5 . Otherwise, if the location estimator  206  determines that the estimated location is not the final estimated location, the distance calculator  204  waits for another transmission from the endpoint of interest  102  (block  604 ). 
         [0050]      FIG. 7  is a block diagram of an example processor platform  700  capable of executing the instructions of  FIGS. 5 and 6  to implement the endpoint locator  122  of  FIGS. 1 and 2 . The processor platform  700  can be, for example, a personal computer, a laptop computer, a mobile device (e.g., a cell phone, a smart phone, a tablet such as an iPad™), a personal digital assistant (PDA), or any other type of computing device. 
         [0051]    The processor platform  700  of the illustrated example includes a processor  712 . The processor  712  of the illustrated example is hardware. For example, the processor  712  can be implemented by one or more integrated circuits, logic circuits, microprocessors or controllers from any desired family or manufacturer. 
         [0052]    The processor  712  of the illustrated example includes a local memory  713  (e.g., a cache). The processor  712  of the illustrated example is in communication with a main memory including a volatile memory  714  and a non-volatile memory  716  via a bus  718 . The volatile memory  714  may be implemented by Synchronous Dynamic Random Access Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM) and/or any other type of random access memory device. The non-volatile memory  716  may be implemented by flash memory and/or any other desired type of memory device. Access to the main memory  714 ,  716  is controlled by a memory controller. 
         [0053]    The processor platform  700  of the illustrated example also includes an interface circuit  720 . The interface circuit  720  may be implemented by any type of interface standard, such as an Ethernet interface, a universal serial bus (USB), and/or a PCI express interface. 
         [0054]    In the illustrated example, one or more input devices  722  are connected to the interface circuit  720 . The input device(s)  722  permit(s) a user to enter data and commands into the processor  712 . The input device(s) can be implemented by, for example, an audio sensor, a microphone, a keyboard, a button, a mouse, a touchscreen, a track-pad, a trackball, isopoint and/or a voice recognition system. 
         [0055]    One or more output devices  724  are also connected to the interface circuit  720  of the illustrated example. The output devices  724  can be implemented, for example, by display devices (e.g., a light emitting diode (LED), an organic light emitting diode (OLED), a liquid crystal display, a cathode ray tube display (CRT), a touchscreen, a tactile output device, a printer and/or speakers). The interface circuit  720  of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip or a graphics driver processor. 
         [0056]    The interface circuit  720  of the illustrated example also includes a communication device such as a transmitter, a receiver, a transceiver, a modem and/or network interface card to facilitate exchange of data with external machines (e.g., computing devices of any kind) via a network  726  (e.g., an Ethernet connection, a digital subscriber line (DSL), a telephone line, coaxial cable, a cellular telephone system, etc.). 
         [0057]    The processor platform  700  of the illustrated example also includes one or more mass storage devices  728  for storing software and/or data. Examples of such mass storage devices  728  include floppy disk drives, hard drive disks, compact disk drives, Blu-ray disk drives, RAID systems, and digital versatile disk (DVD) drives. 
         [0058]    The coded instructions  732  of  FIGS. 5 and 6  may be stored in the mass storage device  728 , in the local memory  713 , in the volatile memory  714 , in the non-volatile memory  716 , and/or on a removable tangible computer readable storage medium such as a CD or DVD. 
         [0059]    From the foregoing, it will appreciate that examples have been disclosed which reduce the time which the data collection unit is required to search for a missing endpoint. 
         [0060]    Although certain example methods, apparatus and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the claims of this patent.