Abstract:
Indicating a precise geographic extent and a precise geographic location of a dig area at a work site at which excavation is planned, to facilitate detection and/or marking of a presence or an absence of an underground facility in the dig area. A graphical user interface includes an aerial image of a geographic area proximate to and including the work site and the dig area, and a drawing tool to facilitate placement of one or more dig area indicators on the aerial image. A user uses the drawing tool to delimit the precise geographic extent and the precise geographic location of the dig area(s) on the displayed aerial image so as to form the dig area indicator(s), representing unbuffered dig areas, and thereby generate a marked-up aerial image. Geographic coordinates are determined corresponding to the unbuffered dig area(s) represented by the dig area indicator(s). A locate request ticket is generated that includes the marked-up aerial image itself, the geographic coordinates corresponding to the unbuffered dig area(s), and/or a link to a webpage at which the marked-up aerial image may be viewed and/or the geographic coordinates may be accessed.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application claims a priority benefit, under 35 U.S.C. 120, as a continuation (CON) of U.S. non-provisional application Ser. No. 12/050,555, filed Mar. 18, 2008 entitled “VIRTUAL WHITE LINES FOR DELIMITING PLANNED EXCAVATION SITES,” which application is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    Excavators are required to notify underground facility owners in advance of their excavation activities and to describe and communicate the geographic area of those activities to the underground facility owners. The geographic area so described is commonly referred to as “the dig area.” In turn, facility owners (which, as used herein, may include facility owners, operators, and/or their designated representatives) are required to determine if they own or operate any underground facilities at an identified dig area. The location of those underground facilities, if any, which exist within a dig area, is marked using paint or some other physical marking system, such as flags. The application of paint, flags, or some other marking object to indicate the presence of an underground facility is called a “locate.” The marks resulting from a locate are commonly called underground facility “locate marks.” Underground facility owners may perform locates with in-house employees or choose to hire independent contract locating firms to perform locates on their behalf as their designated representatives. 
         [0003]    Currently, excavators may communicate with facility owners through “one call centers.” These one call centers are generally owned, controlled, or funded by underground facility owners, such as telephone companies, cable television multiple system operators, electric utilities, gas utilities, or others. One call center operations may be managed by a non-profit entity or outsourced to a for-profit firm. Excavators are required to notify one call centers in advance of their excavation activities and identify through a “locate request” the dig area where individual excavating activities will be performed. Locate requests consist of information supplied by the excavator to the one call center regarding the specific geographic location of the dig area, date, time, purpose of excavation, etc. The locate request, in turn, requires activity from an underground facility owner to perform a locate operation in the specified dig area. 
         [0004]    One call centers may receive locate requests from excavators via electronic delivery or verbally through a telephone conversation between the excavator and a human operator working for a one call center. Whether communicated electronically or verbally, excavators must describe the planned geographic locations of dig areas. This description is ultimately reduced to text, which, along with other data about a locate request, is communicated to the appropriate underground facility owner or owners responsible for locating any underground facilities within the dig area so described. Textual descriptions of dig areas can be very imprecise as to exact physical locations. In addition, addresses which are provided may be unclear, not yet assigned, or only indicating cross streets and vague descriptions of the extent of the dig area. 
         [0005]    On occasion, information provided in the locate request is supplemented by the excavator, who travels to the actual dig area and physically marks the dig area in order to physically delimit the actual area to be excavated. These marks are commonly made using chalk or paint, and are generally known as “white lines.” In some states, white lining the path of excavation may be required by the responsible regulatory body. 
       SUMMARY 
       [0006]    In one aspect, a method may include sending an aerial image to a user via a network; receiving a marked-up version of the aerial image from the user via the network that includes one or more virtual white lines added to the aerial image that delimit a dig area in which excavation is planned; and providing the marked-up version of the aerial image, via one of an electronic or tangible delivery system, to another entity. 
         [0007]    In another aspect, a computer-readable medium may contain instructions for controlling at least one processor to perform a method. The method may include obtaining an aerial image; receiving user input specifying a location on the aerial image where excavation is planned; visually rendering virtual white lines on the aerial image based on the user input, where the virtual white lines delimit the location where the excavation is planned, in order to produce a marked-up digital image; receiving data that describes details of the planned excavation; and sending the marked-up digital image and the data that describes details of the planned excavation to a server across a network. 
         [0008]    In further aspect, a server may include a communication interface coupled to a network; and a processing unit. The processing unit may be configured to cause the communication interface to send an aerial image to a user via the network; receive a marked-up version of the aerial image from the user via the communication interface that includes one or more virtual white lines added to the aerial image which delimit a dig area; and cause the marked-up version of the aerial image to be provided, via one of an electronic or tangible delivery system, to another entity. 
         [0009]    In still another aspect, a method may include providing a dig area marking tool application to a computing device at a client via a network; receiving an aerial image from the client that has been marked up, using the dig area marking tool application, to delimit a dig area on the aerial image; and providing the marked-up aerial image, via an electronic or tangible delivery system to another entity. 
         [0010]    In another aspect, a system may include means for sending a digital aerial image to a user upon request of the user; means for receiving a marked-up version of the digital aerial image from the user that includes a virtual white line in the aerial image, where the virtual white line delimits at least a portion of a dig area; means for converting the virtual white line to latitude/longitude coordinates or geo-positioning coordinates; means for providing the marked-up version of the aerial image and the latitude/longitude coordinates or geo-positioning coordinates to another entity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments described herein and, together with the description, explain these embodiments. In the drawings: 
           [0012]      FIG. 1  is a diagram of a concept described herein; 
           [0013]      FIG. 2  is a diagram of an exemplary network in which systems and methods described herein may be implemented; 
           [0014]      FIG. 3  is a diagram of exemplary components of the user device of  FIG. 2 ; 
           [0015]      FIG. 4  is a diagram of exemplary components of the central server of  FIG. 2 ; 
           [0016]      FIG. 5  is a diagram of exemplary routines associated with the user device and/or central server of  FIG. 2 ; 
           [0017]      FIG. 6  is a flow diagram of exemplary activities of a central server for managing a locate request; 
           [0018]      FIG. 7  is a flow diagram of exemplary activities of a user device for submitting a locate request and for adding virtual white lines to an aerial image; 
           [0019]      FIG. 8  is a diagram of an exemplary data set that may be stored in the memory of a central server of  FIG. 4 ; and 
           [0020]      FIG. 9  is a diagram of an exemplary user interface that includes virtual white line marking tools that may be presented via the user device of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. Also, the following detailed description does not limit the invention. 
       Overview 
       [0022]      FIG. 1  is a diagram of an exemplary concept described herein. When a locate request is submitted by an excavator to a one-call center, it may be beneficial for the excavator to delimit the particular geographic location of the proposed excavation, such as a dig area  100 , in a permanent and reproducible manner. The delimited dig area  100  indicates to a locate technician the extent of the boundaries where a locate is to be performed at the request of the excavator. Physical white lines  110  may be used to physically delimit the dig area  100 . Physical white lines  110  generally may consist of chalk or paint on the surface of the ground to identify the dig area  100  boundary. However, these physical white lines  110  provide only a temporary indication of dig area  100 , as the physical white lines  110  may deteriorate or be eliminated over time by such events as precipitation, excessive pedestrian or vehicle traffic, erosion, the excavation process, or numerous other events. 
         [0023]    In the example of  FIG. 1 , a locate technician may be requested by an excavator to locate and mark underground facilities in dig area  100 . The precise geographic extent of dig area  100  as communicated by the excavator may be uncertain. This uncertainty as to the precise extent of dig area  100  may result in a locate operation which does not address the entirety of the planned excavation site or conversely may result in a locate operation which covers an area in excess of the precise extent of the planned excavation area. When performing the locate operation the locate technician may use paint, flags, or some other object with a particular color or other characteristic to mark the location of an underground facility. Referring to the example shown in  FIG. 1 , the locate technician may be required to mark a portion of underground power line  120  that lie within the dig area  100 . However, the locate technician may not be required to mark the portion of underground power line  120  that lies outside the dig area  100  or telecommunications line  130  that lies outside the dig area  100 . Additionally, telecommunication line  140  traverses only a small portion of dig area  100 . Without a precise and certain description of dig area  100 , the small portion of telecommunication line  140  within dig area  100  may not be located by the locate technician as the technician may believe that the presence of telecommunication line  140  is not of interest to the excavator. Thus, it is important that the locate technician is provided a clear and accurate boundary of dig area  100  to avoid, for example, an excavator later digging over an unmarked underground facility. Physical white lines  110  placed by the excavator and/or descriptive text provided by the one-call center may be used to delimit the dig area  100 . However, as noted above, these methods may lack permanency, accuracy, or certainty. 
         [0024]    An aerial image  150  is shown in  FIG. 1  displayed on a laptop computer  170 . The aerial image provides a view of the geographic area surrounding dig area  100 . Implementations described herein enable excavators to delimit, on aerial images of the earth, the specific dig areas where planned excavations will be performed. As used herein, an “aerial image” is intended to be broadly interpreted as any image taken from above the earth&#39;s surface, such as, for example, images generated using a satellite, airplane, helicopter, or other moving or fixed device. These aerial images may be indexed to Global Positioning System (GPS) coordinates or other coordinate that provides geo-spatial positioning. The aerial images may include geo-coding or other geographical identification metadata and may be provided in any computer-readable format. The aerial image may also include images of map symbols, such as roads and street names, that may be superimposed upon or displayed separately from an underlying geographic area. 
         [0025]    Virtual white lines  160  may be added to the aerial image  150  to graphically delimit the dig area  100 . Virtual white lines  160  may be added to the aerial image  150  through the use of a drawing application, or dig area marking tool application, which may superimpose over or otherwise display the virtual white lines  160  on the aerial image  150 . As used herein “virtual white lines” may include lines, drawing shapes, shades, symbols, coordinates, data sets, or other indicators to delimit on an aerial image the dig area in which excavation is to occur. 
         [0026]    The exemplary embodiments described herein may additionally communicate to the underground facility owner the images which indicate the boundary of the dig area both graphically and as a series of geographical coordinates. These images and coordinates enable locate technicians who are dispatched to locate the existing underground facilities to know with precision the dig area in which excavating activities are planned to occur regardless of whether physical white lines exist or whether a description of the area has been accurately provided. Implementations described herein may give excavators the ability to provide one call centers with virtual white lines as part of a locate request. Other implementations may provide virtual white lines to facility owners subsequent to the initial locate request to the one call center. 
         [0027]    Use of virtual white lines, as described herein, eliminates the uncertainty associated with imprecise excavator locate requests. This ensures that underground facility owners determine the presence of their underground facilities within a correctly communicated and certain dig area and mark the location of their facilities where excavators in fact plan to excavate. The precision and permanency of virtual white lines may reduce the occurrence of underground facilities not being marked within a dig area. Also, use of virtual white lines may result in less field communication between excavators and locate technicians about imprecise dig area descriptions and may reduce confusion about the exact location of a dig area. Confusion about precise dig area locations can result in costly damages to underground facilities which may imperil the general public. When excavators inadvertently excavate at locations where underground facility owners have not located existing underground facilities, damages to underground facilities are highly likely. Additionally, in jurisdictions where excavators are required to physically “white line” the dig area, implementations described herein may enable excavators (if they so choose and are permitted to do so) to identify the dig area boundaries with precision without being required to physically visit the site. The digital description of the dig area, on an aerial image generated by exemplary embodiments described herein, also creates a permanent record of the dig area that is associated with each locate request by an excavator. 
       Exemplary Network 
       [0028]      FIG. 2  is a diagram of an exemplary network  200  in which systems and methods described herein may be implemented. As shown in  FIG. 2 , the network  200  may include a user device  210  connected to a central server  220  and an image server  230  via a network  240 . A single user device  210 , central server  220 , and image server  230  have been illustrated as connected to network  240  for simplicity. In practice, there may be more or fewer user devices and/or servers. For example, in one alternative implementation, the user device  210  may operate as a comprehensive device and, thus, the network  200  may include no central server, with user device  210  communicating directly through network  240  to image server  230 . Also, in some instances, the user device  210  may perform one or more of the functions of the central server  220  and/or central server  220  may perform one or more of the functions of the user device  210 . In still another implementation, multiple user devices  210  may be connected to the central server  220  through the network  240 . 
         [0029]    The user device  210  may encompass a computer device, such as laptop computer  170 , a personal computer, a tablet device, a personal digital assistant (PDA), a cellular radiotelephone, a mobile computing device, a touch-screen device, a touchpad device, or generally any device including, or connected to, a processor and a display. The user device  210  may be portable so as to be separately carried by the user at a prospective dig area. Alternatively, the user device  210  may be integrated with or affixed to another moveable object, such as a vehicle. In other implementations, the user device may be a desktop or laptop computer located at, for example, an office of an excavating company. In another implementation, the user device may be a computer located at the one call center, to be used by, for example, a one call center representative or another person present at the one call center. 
         [0030]    The central server  220  may include a computer device that may store information received from or provided to the user device  210  and/or the image server  230 . The central server may be maintained by, for example, a one call center. In some implementations, central server  220  may be a web-based server to facilitate a remote interface through, for example, an Internet browsing application on user device  210 . The central server  220  may include storage capacity and/or optionally include networked access to one or more separate hardware components, such as image cache  235 , to store cached images and the like. Central server may also store applications, such as image drawing applications, that can be accessed by user device  210  to manipulate the cached images. 
         [0031]    The image server  230  may include a computer device that may store and provide aerial images of geographic locations. The image server  230  may be associated with the same, or a different, party that maintains the central server  220 . For example, the image server  230  may be associated with a party that provides aerial images for a fee. Generally, the aerial images provided by the image server may be of sufficient resolution at an optimal elevation to be useful to effectively delimit a dig area on the image. The aerial images from the image server  230  may include geocoding or other geographical identification metadata and may be provided in any computer-readable format, such as JPEG file interchange format (JPEG), tagged image file format (TIFF), portable document format (PDF), graphics interchange format (GIF), bitmap (BMP), portable network graphics (PNG), Windows® metafile (WMF), and/or the like. Also, aerial images from the image server  230  may include a combination of images or overlays, such as overlays of street names, regions, landmark descriptions, and/or other information about areas displayed in an image. The aerial images from the image server  230  may be supplied by a third-party provider if the coverage area of the third-party image provider overlaps with the desired area of the user. 
         [0032]    The network  240  may include a local area network (LAN), a wide area network (WAN), a telephone network, such as the Public Switched Telephone Network (PSTN) or a cellular network, an intranet, the Internet, one or more communications links, or a combination of networks. The user device  210 , central server  220 , and image server  230  may connect to the network  240  via wired and/or wireless connections. The user device  210 , central server  220  and image server  230  may communicate using any communication protocol. 
       Exemplary User Device Architecture 
       [0033]      FIG. 3  is a diagram of exemplary components of user device  210 . User device  210  may include a bus  310 , a processing unit  320 , a memory  330 , an input device  340 , an output device  350 , a location identification unit  360 , and a communication interface  370 . In another implementation, user device  210  may include more, fewer, or different components. For example, location identification unit  360  may not be included, or location identification unit  360  may be included as a device located external to user device  210 , such as a device worn or carried by a user of user device  210 . 
         [0034]    Bus  310  may include a path that permits communication among the components of user device  210 . Processing unit  320  may include a processor, a microprocessor, or processing logic that may interpret and execute instructions. Memory  330  may include a random access memory (RAM), a read only memory (ROM), a memory card, a magnetic and/or optical recording medium and its corresponding drive, or another type of memory device. Generally, memory  330  may be sufficient to store and manipulate aerial images, such as those stored in a local image cache  335 . In one implementation, local image cache  335  may include one or more aerial images of a dig area to be marked by a user. In another implementation, local image cache  335  may include a series of aerial images that correspond to the geographical region to which a particular user is assigned. For example, local image cache  335  may include a collection of high-resolution images of a particular zip code or town. In a further implementation, local image cache  335  may include aerial images of previously-delimited dig areas, such as dig areas where a user of user device  210  has previously requested locate operations. In still another implementation, local image cache  335  may include an entire set of aerial images intended to be made available to multiple users. 
         [0035]    Input device  340  may include one or more mechanisms that permit a user to input information to user device  210 , such as a keyboard, a keypad, a touchpad, a mouse, a stylus, a touch screen, a camera, or the like. Alternatively, or additionally, input device  340  may include a microphone that can capture a user&#39;s intent by capturing the user&#39;s audible commands. Alternatively, or additionally, input device  340  may interact with a device that monitors a condition of the user, such as eye movement, brain activity, or heart rate. Output device  350  may include one or more mechanisms that output information to the user, such as a display, a speaker, or the like. 
         [0036]    Location identification unit  360  may include a device that can determine its geographic location to a certain degree of accuracy, such as a global positioning system (GPS) or a global navigation satellite system (GNSS) receiver. In another implementation, location identification unit  360  may include a device that determines location using another technique, such as tower (e.g., cellular tower) triangularization. Location identification unit  360  may receive location tracking signals (e.g., GPS signals) and determine its location based on these signals. In one implementation, location identification unit  360  may be capable of determining its location within approximately thirty centimeters or less. In another implementation, location identification unit may receive and store location coordinates from an external device. 
         [0037]    Communication interface  370  may include any transceiver-like mechanism that enables user device  210  to communicate with other devices and/or systems. For example, communication interface  370  may include mechanisms for communicating with another device or system via network  240 . For example, communication interface  370  may enable communications between user device  210  and central server  220  and/or image server  230  over network  240 . 
         [0038]    As will be described in detail below, user device  210  may perform certain operations relating to the documentation of locate requests and/or the creation of virtual white lines. User device  210  may perform these operations in response to processing unit  320  executing software instructions contained in a computer-readable medium, such as memory  330 . A computer-readable medium may be defined as a physical or logical memory device. 
         [0039]    The software instructions may be read into memory  330  from another computer-readable medium, or from another device via the communication interface  370 . The software instructions contained in memory  330  may cause processing unit  320  to perform processes that will be described later. Alternatively, hardwired circuitry may be used in place of, or in combination with, software instructions to implement processes described herein. Thus, implementations described herein are not limited to any specific combination of hardware circuitry and software. 
       Exemplary Central Server Architecture 
       [0040]      FIG. 4  is a diagram of exemplary components of central server  220 . Central server  220  may include a bus  410 , a processing unit  420 , a memory  430 , an input device  440 , an output device  450 , and a communication interface  460 . In another implementation, central server  220  may include more, fewer, or different components. 
         [0041]    Bus  410  may include a path that permits communication among the components of central server  220 . Processing unit  420  may include a processor, a microprocessor, or processing logic that may interpret and execute instructions. 
         [0042]    Memory  430  may include a magnetic and/or optical recording medium and its corresponding drive, a RAM, a ROM, a memory card, or another type of memory device suitable for high capacity data storage. Generally, memory  430  may be sufficient to store aerial images of particular geographic locations, such as those stored in a central image cache  435 . In one implementation, central image cache  435  may include a set of aerial images that correspond to the geographical regions to which a group of users are assigned. In still another implementation, central image cache  435  may include the entire set of aerial images intended to be made available to any of a group of users. For example, central image cache  435  may include a collection of high-resolution aerial images of a particular county, state or other geographic region. In another implementation, as shown in  FIG. 2 , central image cache  435  may be replaced or supplemented with one or more networked storage components, such as image cache  235 . 
         [0043]    Input device  440 , similar to input device  340  of user device  210 , may include one or more mechanisms that permit an operator to input information to central server  220 . Output device  450  may include one or more mechanisms that output information to an operator of the central server, such as a display, a speaker, or the like. 
         [0044]    Communication interface  460  may include any transceiver-like mechanism that enables central server  220  to communicate with other devices and/or systems. For example, communication interface  460  may include mechanisms for communicating with another device or system via network  240 . For example, communication interface  460  may enable communications between central server  220  and user device  210  and/or image server  230  over network  240 . 
         [0045]    As will be described in detail below, central server  220  may perform certain operations to facilitate the documentation of locate requests and/or virtual white lines and to disseminate locate requests (and corresponding virtual white line information) to appropriate locate technicians and/or other parties. Central server  220  may perform these operations in response to processing unit  420  executing software instructions contained in a computer-readable medium, such as memory  430 . 
         [0046]    The software instructions may be read into memory  430  from another computer-readable medium, or from another device via communication interface  440 . The software instructions contained in memory  430  may cause processing unit  420  to perform processes that will be described later. Alternatively, hardwired circuitry may be used in place of or in combination with software instructions to implement processes described herein. Thus, implementations described herein are not limited to any specific combination of hardware circuitry and software. 
       Exemplary Routines 
       [0047]      FIG. 5  is a diagram of exemplary software routines for central server  220  and user device  210 . Central server  220  may include an image retrieval routine  510 , a central image cache routine  520 , a data extraction routine  530 , and a ticket manager routine  540 . User device  210  may include a image request routine  550 , an image display routine  560 , and a user input routine  570 . As discussed in more detail herein, the examples of routines associated with central server  220  and user device  210  may be interchangeable between central server  220  and user device  210 . Furthermore, some or all of routines  510 ,  520 ,  530 ,  540 ,  550 ,  550 ,  560 , and  570  need not be performed exclusively by any one of central server  220  or user device  210 .  FIG. 5  indicates communication between user device  210  and facility owner  580  and/or image server  230  passes through central server  220 . However, it should be noted that in other implementations facility owner  580  and/or image server  230  may communicate directly with user device  210 , 
         [0048]    Generally, in one implementation, user device  210  may permit a user, such as an excavator or a person at a one call center, to receive an aerial image and submit virtual white line information in association with a locate request placed to a one call center. Central server  220  may permit the one call center to associate the virtual white line information with the locate request and to provide instructions to a facility owner  580  who is required to conduct a locate. Instructions from the one call center (via, for example, central server  220 ) to the facility owner  580  may be provided as a compilation of information, called a “locate request ticket.” The virtual white line information may be associated with the locate request ticket in the form of, for example, a marked-up aerial image and/or geographic coordinates of the virtual white lines. Facility owner  580  may be a facility owner, facility operator, or any contracted representative acting on their behalf. 
         [0049]    Central image cache routine  510 , image retrieval routine  520 , data extraction routine  530 , and ticket manager routine  540  of central server  220  may include a variety of functionalities. In certain implementations, central image cache routine  510  may receive information about specific locate requests and parse each locate request in order to discern location information. For example, a locate request may identify the property associated with a dig area by an address of the property, a nearby street intersection, or by geographic coordinates. The locate request might also specify, for example, the description of the dig area to be delimited, and the day and/or time that excavations are scheduled to begin. 
         [0050]    Central image cache routine  510  may also convert location information for the property associated with the dig area to latitude/longitude coordinates or geo-positioning coordinates. When location information from a locate request is sufficiently precise to allow for identification of corresponding imagery associated with property surrounding a dig area, central image cache routine  510  may calculate the image extent (which may be generally defined as the bounding region of the property of interest), and generate a locate request ticket for the facility owner with the calculated extent. The image extent may, for example, include the coordinates of the corners of the bounding region (e.g., the lower left x and y coordinates and the upper right x and y coordinates). In one implementation, central image cache routine  510  may determine an image date, coordinates, and resolution of each image that may be stored in central image cache  435  or in another location. In another implementation, when location information from a ticket is imprecise (or “fuzzy”), central image cache routine  510  may mark the locate request ticket to indicate that no corresponding image was able to be retrieved based on the locate request. 
         [0051]    Image retrieval routine  520  may catalog and store images from image server  230  to central server  220 . For example, images may be stored in central image cache  435  in memory  430  of central server  220 . In one implementation, image retrieval routine  520  may query central image cache  435  or other cache for an image associated with a particular planned dig area relating to a locate request, and determine, based on (for example) the age and resolution of the cached image, whether the image in central image cache  435  needs to be updated from image server  230 . 
         [0052]    In another implementation, image retrieval routine  520  may interface with multiple image providers and/or image servers  230 . Image retrieval routine  520  may determine which image provider is the best source for the image corresponding to a particular dig area relating to a locate request based on algorithms that factor, for example, each image provider&#39;s geographical coverage, image resolution, cost, and availability. Regarding geographical coverage, it will be beneficial to confirm that the image provider&#39;s area of coverage includes the desired extent. 
         [0053]    Regarding image resolution, available resolution may be measured in meters (or centimeters, feet, or inches) per pixel. For example, one provider may offer thirty centimeters per pixel, while another offers fifteen centimeters or less per pixel, for the same coverage area. If an image is requested at a standard altitude, then image retrieval routine  520  may choose a pre-defined optimal scale (for example, thirty centimeters per pixel for a rural area, but fifteen centimeters per pixel for an urban area) and determine which provider provides images at the pre-defined optimal scale. Alternatively, if the image of interest is at a less granular scale (for example, a community or neighborhood image that allows the locator to pan around the image), then resolution may not be a significant factor. 
         [0054]    Regarding cost, image retrieval routine  520  may have access to pricing information for a variety of image providers. Image retrieval routine  520  may identify which provider has the lowest cost for the desired image. Cost analysis may be based on images desired for an individual ticket or the algorithm may account for a group of image requests, including volume incentives and/or penalties from each image provider. 
         [0055]    Regarding availability of image providers, image retrieval routine  520  may identify what providers are available and/or operational. Also, if an image provider has a regular latency profile (for example, if a provider has a particular server that is busiest 3-5 PM Pacific time), then image retrieval routine  520  may manage requests to be provided to another image provider or to a particular server of that image provider to efficiently load share the image retrieval. 
         [0056]    When an image provider is selected, image retrieval routine  520  may download the image from the selected image provider&#39;s server, which may be image server  230 . The downloaded image may be stored locally, for example, in the central image cache  435 . 
         [0057]    It should be understood that some of the routines and/or functionalities described above with respect to central image cache routine  510  and image retrieval routine  520  may be performed by one or both of the routines  510  and  520  above, and the arrangement of functionalities are not limited to the implementations disclosed herein. 
         [0058]    In certain implementations, data extraction routine  530  may obtain geographic coordinates (e.g., Global Positioning System (GPS) coordinates, other geo-positioning coordinates, or latitude and longitude coordinates) based on a marked-up aerial image provided by, for example, user input routine  570  in user device  210 . Marked-up aerial images may also include text or other indicators including, for example, text blocks describing the dig area; offsets to environmental landmarks; a locate request ticket number; the address or lot number of the dig area; and/or the date, time, and purpose of the excavation. This additional data may also be extracted from the aerial image and stored as a dataset associated with the marked-up aerial image. 
         [0059]    In one implementation, central server  220  may interface with a ticket management program for coordinating multiple locate request tickets and for providing locate request information to a facility owner  580 . Ticket manager routine  540  may facilitate such an interface. The ticket management program for coordinating multiple tickets may also reside on central server  220 , for example, or on a separate server that is accessible to central server  220 . Generally, locate request ticket information may be stored on central server  220  and disseminated to a facility owner  580 . When a user submits a locate request, the user may also subsequently submit a set of virtual white lines on an aerial image to associate with the locate request. In another implementation, the user may submit a set of virtual white lines on an aerial image simultaneously with the user&#39;s initial locate request. The ticket manager routine  540  may allow the user to update data regarding the locate request and to synchronize the images and user input. Ticket manager routine  540  may send virtual white lines from central server  220  to facility owner  580  for locate request tickets that need to be completed, and will copy the input from facility owner  580  to central server  220  for completed tickets. Ticket manager routine  540  may interface with the routines described above to correlate assigned locate request tickets with images and virtual white lines for those tickets and download the images to facility owner  580  from central server  220 . 
         [0060]    Referring now to routines in  FIG. 5  that may be associated with user device  210 , image request routine  550  may solicit information from a user as the basis of an image to associate with a dig area for a locate request. For example, the user input may include a postal address, lot number, plat number, street intersection, a set of GPS coordinates relating to the planned dig area, or the like. The user device may send the location information to central server  220  to allow the central server (via, for example, image retrieval routine  520 ) to identify a corresponding image. 
         [0061]    In one implementation, image request routine  550  may identify an image to retrieve based on GPS coordinates of a GPS-enabled device associated with a user. For example, a user may arrive at an excavation site in a GPS-enabled vehicle and the GPS information from the vehicle may be used to identify coordinates corresponding to an image to be retrieved. GPS coordinates may also be obtained from other GPS-enabled devices being used by or in the vicinity of the user. As used herein a GPS-enabled device may include any device or combination of devices capable of interfacing with a global navigation satellite system, geo-spatial positioning system, or other location-identification system to determine a location. Examples of GPS-enabled devices may include a marking device (e.g., a paint wand) with an integrated GPS receiver; a locating device (e.g., a locating wand) with a GPS receiver; a wearable GPS-enabled device; a vehicle-mounted GPS system; certain PDAs, computers, and cellular telephones; and stand-alone GPS-enabled systems. 
         [0062]    In another implementation, a user may provide a street address or other property identification information. If the street address or other property identification information is insufficient to identify a specific property, image request routine may (by, for example, communicating with central server  220 ) suggest a list of possible matches or suggest another form of information suitable for identifying the property associated with a planned dig area. 
         [0063]    In still another implementation, image request routine  550  may identify one or more images to request based on a designated geographical area assigned to a user. For example, a user may be assigned to work in several dig areas associated with a particular section of a neighborhood. The user may input coordinates associated with the entire selected section of the neighborhood, and central image cache routine  510  and/or image retrieval routine  520  may then retrieve images for those coordinates. 
         [0064]    Once an image is loaded from local cache  335  and/or central server  220 , image display routine  560  may provide a variety of view options for the user. For example, image display routine  560  may support zooming in and out of the image by changing the image scale. Also, image display routine  560  may support panning horizontally and vertically in the image. Furthermore, image display routine  560  may support “roaming” outside the boundaries of the initial extent. Roaming generally occurs when the user zooms or pans, such that images beyond the boundaries of the stored images may be required to be retrieved from either local image cache  335  or central server  220 . The additional images retrieved from either local image cache  335  or central server  220  may be displayed and stitched together to display a complete image. 
         [0065]    User input routine  570  allows the user to add information to the image to delimit a planned dig area. User input routine  570  may accept user input from, for example, input device  340 , and may support the addition of lines, freehand forms (or scribbling), shading, drawing shapes such as circles and rectangles, or other markings which delimit the approximate location of the dig area. As used herein, a drawing shape may generally be any kind of drawing shape or mark. In addition to the delimiting of the dig area on the aerial image, user input routine  570  may also include offsets from environmental landmarks that may be displayed on the image in, for example, English or metric units. Environmental landmarks may also be marked and/or highlighted on the aerial image. An environmental landmark may include any physical object that is likely to remain in a fixed location for an extended period of time. Examples of an environmental landmark may include a tree, a curb, a driveway, a utility pole, a fire hydrant, a storm drain, a pedestal, a water meter box, a manhole lid, a building structure (e.g., a residential or office building), or a light post. For example, an edge of a dig area located two and a half meters behind the curb of a residential street would be documented as being offset two and a half meters behind the curb. 
         [0066]    In one implementation, there may be occasions where central server  220  is unable to provide an aerial image to associate with location information for a planned dig area. Instead, user input routine  570  may still be utilized without the underlying aerial image (e.g., a blank grid). For example, the user may use drawing tools in user input routine  570  to sketch environmental landmarks and virtual white lines sufficient to delimit a dig area. 
         [0067]    User input routine  570  may also accept positioning information from external sources, such as a GPS-enabled device. In one implementation, where a blank grid is being used, the positioning information may be uploaded to the blank grid to provide, for example, points for relative spacing, proper scale, and dimensioning of a user&#39;s sketch. 
         [0068]    In another implementation, user device  210  may also communicate with external components to identify geographical positioning coordinates of various points related to a dig area, such as dig area boundaries, environmental landmarks, and the like. Particular coordinates may be stored in a memory of the external device, sent to user device  210 , and provided as information on the aerial image using, for example, user input routine  570 . The coordinates may appear, for example, as dots on the aerial image that can be connected or labeled by the user using user interface  570 . 
         [0069]    User input routine  570  may further include features to annotate the image with text and to revise user inputs by, for example deleting, dragging or pasting drawing shapes. In one implementation, when the user zooms the image view in or out, user input (e.g., lines and/or shapes) that have been added to the original image may adhere to the changing image scale and remain in the original user-input locations. 
         [0070]    The virtual white lines, which may be a compilation of the aerial image and user inputs, may be saved as an image file. In another implementation, the user inputs may be saved in a marked-up format, including the geo-coordinates of each drawing shape added to the image by the user. 
         [0071]      FIG. 6  provides a flow diagram  600  of exemplary activities of central server  220  for managing a locate request according to an implementation. In another implementation, at least some of the blocks of flow diagram  600  may be performed using user device  210 . In another implementation, one or more of the blocks of  FIG. 6  may be manually performed or performed by other devices. 
         [0072]    Flow diagram  600  may begin an excavator contacts a one call center to place a locate request. The user (e.g., the excavator or a person at the one call center) may use a computer or other user device  210  to submit the locate request to central server  220 . Central server  220  may include, generally, a virtual white line application and image storage service to facilitate locate requests. In one implementation, the user may be required to establish an account with central server  220 , which may include providing a log-in identifier and password. Another implementation may allow for access to central server  220  without an account. As part of the locate request, the user (via user device  210 ) may provide to central server  220  a geographic location or address associated with a planned dig area. The geographic location or address may be extracted from the locate request, so that the server may receive the dig area location information (block  610 ). 
         [0073]    In block  620 , aerial image coordinates may be associated with the geographic location or address information. For example, central server  220  may associate coordinates of an aerial image with the general location of the planned dig area that was provided in the locate request. Such association may include associating the address with geographic location information that has a defined image extent, such as global positioning coordinates for the image extent corresponding to the property address. 
         [0074]    In block  630 , a stored aerial image associated with the address may be retrieved from a cache of images and provided to the user device  210 . As previously described discussed herein with respect to  FIG. 5 , the cache of images may reside within central server  220 , a separate image server, or another storage device. Central server  220  may determine if the central image cache  435  (or other image cache) already has an aerial image stored for the dig area that corresponds to the calculated image extent. If so, central image cache  435  may return the stored aerial image to central server  220 . If central image cache  435  does not have a corresponding aerial image, then a determination may be made whether to obtain an updated image from image server(s)  230 . 
         [0075]    Central server  200  may send the particular image associated with the address to the user device (block  640 ). Along with the image, the central server  220  may provide a dig area marking tool application to a browser at user device  210 . Aspects of drawing virtual white lines with the dig area marking tool application are described further with respect to  FIG. 7  below. It should be noted that blocks  610  through  640  may be an iterative process. Also, if a user does not have a particular address, it may be possible to pan around a high-level (e.g., lower resolution) aerial image to eventually identify a more specific location associated with a planned dig area. 
         [0076]    After a user had added virtual white lines and any additional information to the image, the edited image and other information to complete the locate request may be sent from the user device  210  and received by central server  220  (block  650 ). If not previously accomplished by the user device, central server  220  may convert the virtual white lines to geographic coordinates (block  660 ). More specifically, the central server  220  may determine geographic coordinates (e.g., Global Positioning System (GPS) coordinates or latitude and longitude coordinates) of the dig area based on virtual white lines on the marked-up digital map. 
         [0077]    In block  670 , the central server  220  may associate the locate request with the mark-up image and coordinates of the virtual white lines. Upon receipt of the marked-up aerial image from user device  210 , central server  220  may forward the marked-up version of the aerial image to memory  430  (or another memory location) for storing in association with the locate request ticket information. The marked-up aerial image may subsequently be provided to an underground facility owner that will ascertain the location of any underground facilities within or near the dig area. Central server  210  may provide the marked-up aerial image (including geographic coordinates and other locate request information) to the underground facility owner(s) that will perform the underground facility locate operation. The locate request and virtual white lines may be sent to the facility owner  580  (block  680 ). The information may be provided via an electronic or tangible delivery system, which may include, for example, email, a webpage, facsimile, automated telephone service, printer, automated mailing, or other form of communication. 
         [0078]    While the flow diagram of  FIG. 6  is described in the context of an excavator contacting a one call center, other implementations may occur in the context of an excavator contacting a facility owner directly to place a locate request. In another implementation, a one call center may contact a facility owner to transmit a locate request. In still another implementation, the one call center representative may draft virtual white lines based on input from an excavator. 
         [0079]      FIG. 7  is a flow diagram  700  of exemplary activities of user device  210  for submitting a locate request. User device  210  may first request from central server  220  an aerial image that corresponds to an address or other location information for a planned dig area (block  710 ). In block  720 , user device  210  may receive the aerial image and allow a user to confirm that the aerial image properly corresponds to the actual location of the dig area. Along with the image, the user device  210  may receive a dig area marking tool application to allow a user to add data to the image. As noted above with respect to  FIG. 6 , the requesting (block  710 ) and receiving (block  720 ) of the aerial image may be an iterative process and may allow for panning a high level-aerial image to identify a particular dig area location. 
         [0080]    Once an acceptable image is received at user device  210 , user device  210  may associate the locate request data with the aerial image. The locate request data may include, for example, a locate request ticket number, an address of the dig area, and/or the date, time, and purpose of the excavation. Some or all of the locate request data may be included as metadata with the aerial image or otherwise associated with the image. 
         [0081]    In block  740 , virtual white lines may be added to the aerial image that was received previously in block  720 . The information about the approximate geographic location of the dig area may be input by the user using the dig area marking tool application and an input device, such as input device  340  ( FIG. 3 ) of user device  210 . Additional aspects regarding use of the dig area marking tool are discussed in more detail below with respect to  FIG. 9 . 
         [0082]    Still referring to block  740 , information about the approximate geographic location of the dig area may also be received directly from a GPS-enabled device, such as the GPS-enabled locating device or marking device used in block  630 , and added to the retrieved image. For example, the approximate geographic location of the physical dig area white lines may be determined by identifying the current geographic location of a GPS-enabled device as it is located at points on the physical white lines of the dig area. In one implementation, the GPS-enable device may be a marking tool that stores the GPS coordinates of the marking tool as a user applies the physical white lines. The information from the GPS-enabled device may be communicated to user device  210  or central server  220  to be associated with the aerial image. The user may use a combination of received GPS information and manual entries to create virtual white lines for the dig area. 
         [0083]    In block  750 , information about offsets of the dig area from environmental landmarks may, if necessary, be added to the stored aerial image that was retrieved previously in block  620 . As with the input of the virtual white lines in block  640 , the location of the environmental landmarks may be input by the user using an input device, such as input device  340  ( FIG. 3 ) of user device  210 , or automatically input from a GPS-enabled device. The environmental landmark may be marked and/or labeled as an existing object shown on the aerial image, or the environmental landmark may be a separate item (e.g., not shown on the aerial image) that is added by the user. The offset information may be automatically calculated or input by the user. Offset information may also be obtained by identifying selected environmental landmarks on the retrieved image and automatically calculating the distance from the selected environmental landmarks to the virtual white lines added to the image. 
         [0084]    In block  760 , information about the location of the virtual white lines may, if necessary, be converted to GPS coordinates. The location of the virtual white lines and/or landmarks shown on the aerial image may be associated with approximate GPS (or other geographic) coordinates based on the geo-coding of the aerial image. Thus, in some implementations the GPS coordinates of the virtual white lines may be available to approximately delimit the dig area independent of the stored aerial image. In block  770 , the retrieved aerial image and information about the location of the virtual white lines may be stored in memory as a single image. The single image may be stored as, for example, a digital image or an interactive electronic map. Additionally or alternatively, in block  780 , the geographic coordinates of the virtual white lines may be stored in memory, such as memory  330  ( FIG. 3 ), as a separate data set. The data set may be compiled as, for example, a database of GPS coordinates and other information relevant to the locate request. An exemplary data set of the information that may be provided is described in more detail with respect to  FIG. 8 . In block  790 , the single image and/or separate data set may be transmitted to a central location, such as central server  220  ( FIG. 2 ). 
         [0085]      FIG. 8  is a diagram of an exemplary data set  800  that may be stored in memory  330  and/or transmitted to central server  220 . Some of the information in data set  800  may be automatically populated by a software program on user device  210  or central server  220 , such as the dig area marking tool application or a related application. As shown in  FIG. 8 , a data set  800  may include a timestamp field  810 , an excavator identifier field  720 , a dig area coordinates field  830 , an environmental landmark identifier field  840 , an environmental landmark location field  850 , an other information field  860 , a property address field  870 , and a ticket number field  880 . In another implementation, the data set  800  may include additional, fewer, or different fields. 
         [0086]    Timestamp field  810  may include time data that identifies the day and/or time that the completed locate request was submitted. The time data in timestamp field  810  is shown in  FIG. 8  as 9:43 a.m. Eastern Standard Time on Nov. 20, 2007—although any type of date and/or time code may be used. The information in timestamp field  810  may be useful in establishing when a locate request was initiated. 
         [0087]    The excavator identifier field  820  may include an identifier that uniquely identifies the entity submitting the locate request. The identifier in excavator field  820  is shown in  FIG. 8  as “Joe&#39;s Pool Center”—although any type of identifier may be used. Virtual white line coordinates field  830  may include geographic location information corresponding to the delimited dig area. In one implementation, the geographic location information may include a set of geographic points along the delimited dig area. The geographic location information in virtual white line coordinates field  830  is shown in  FIG. 8  as N38°51.40748, W077°20.27798; . . . ; N38°51.40784, W077°20.27865—although any type of geographic location information may be used. The information in virtual white line coordinates field  830  may be useful in graphically presenting the dig area on a map, and/or to verify that the dig area was accurately delimited with physical white lines. 
         [0088]    Environmental landmark identifier field  840  may include an identifier that uniquely identifies the type of environmental landmark being marked. The identifier in environmental landmark identifier field  840  is shown in  FIG. 8  as “curb”—although any type of identifier may be used. Environmental landmark location field  850  may include geographic location information corresponding to the environmental landmark identified in environmental landmark identifier field  840 . The geographic location information in environmental landmark location field  850  is shown in  FIG. 8  as N38°51.40756, W077°20.27805; . . . ; N38°51.40773, W077°20.27858—although any type of geographic location information may be used. 
         [0089]    Other information field  860  may store other data that may be useful, including user notes, such as distance information that identifies a distance between one or more environmental landmarks and one or more boundaries of the dig area. Other information field  860  is shown in  FIG. 8  as including “1.2 meters between curb and edge of dig area”—although any other data may be used. Additionally and/or alternatively, other information field  860  may include audio/voice data, transcribed voice-recognition data, or the like to incorporate user notes. 
         [0090]    Property address field  870  may be the property address associated with the dig area in the data set  800 . The property address field  870  may include, for example, the street address and zip code of the property. Other information in field  870  may include city, state, and/or county identifiers. The ticket number field  880  may include the ticket number associated with the locate request, such as ticket number “1234567” shown in  FIG. 8 . In some implementations, the ticket number may not be known at the time the data set  800  is provided from user device  210  to central server  220 ; and, thus, the ticket number  880  may be added to the data set  800  at a later time by the central server  220 . 
         [0091]    In one implementation, central server  220  may store multiple data sets corresponding to a single dig area. User device  210  may provide the data sets to server  220  in a batch—such as a batch corresponding to a group of marks delimiting a single dig area—or individually. The batch may be grouped together with other information generally relating to the locate request, such as the name of the company responsible for performing the locate operation, the name or other identification information of the locate technician, and the like. Additionally, or alternatively, the other information generally relating to the locate operation may be included in each data set. 
         [0092]      FIG. 9  an exemplary diagram of a user interface  340  that may be presented via the user device  210 . The user interface  900  that may be implemented, for example, by a browser at user device  210 . User interface  900  may present an aerial image  905 , along with a image scale  910  overlaying aerial image  905 , and may also include various palettes, toolbars, or other interfaces that enable the user to manipulate (e.g., zoom in, zoom out) and/or mark up the aerial image. For example, user interface  900  may include a marking palette  915 , a sketching palette  920  and a navigation palette  925 . Marking palette  915  may group user interface buttons that the user can select (using, for example, the input device  340 ) in order to draw certain shapes (e.g., a polygon, a rectangle or a circle) or to orient or annotate the aerial image. Marking palette  915  may include a button (e.g., text button) that permits the user to add text boxes that can be used to add textual content for annotating the aerial image. Sketching palette  920  may group user interface buttons that the user can select in order to draw virtual white line shapes on aerial image  905 . Sketching palette  920  may include, for example, a freehand button that permits the user to draw virtual white lines freehand, or a line button that permits the user to draw straight lines on aerial image  905 . Navigation palette  925  may group user interface buttons that the user can select in order to zoom or pan the aerial image (e.g., zoom in, zoom out, zoom to, pan, pan left, pan right, pan up, pan down, etc.). Navigation palette  925  may additionally include one or more buttons that enable user drawn shapes to be accentuated (e.g., grayscale, transparency, etc.). The exemplary user interface  900  of  FIG. 9  additionally depicts an example circular virtual white line  930  that has been drawn on aerial image  905 .  FIG. 9  also depicts an example rectangular virtual white line  935  being drawn on map  905  using a line cursor  940 . 
       CONCLUSION 
       [0093]    Aspects of the invention as described herein enable a user (e.g., an excavator) to delimit a dig area when placing a locate request with, for example, a one call center. A server at the one call center may retrieve from a database the appropriate aerial image of a specific geographic location corresponding to a planned dig area where locate operations are to be conducted for underground facilities. The retrieved aerial image is provided to the user so that the user may draft, on the retrieved image, the approximate geographic boundaries of the planned dig area. The combination of the retrieved image and additional information drafted by the user may be saved in a variety of formats as virtual white lines. Other information regarding the specific geographic location of the dig area boundaries and environmental landmarks may be incorporated into the virtual white lines using direct input from GPS-enabled positioning tools and the like. 
         [0094]    In other implementations, a user may interface directly with a facility owner to provide a virtual white line image—eliminating the involvement of the one-call center. In such an implementation, functionalities of the one call center for enabling the user of virtual white lines may be assumed by the facility owner and or the user. 
         [0095]    Virtual white lines delimiting a dig area may serve several purposes. For example, virtual white lines as described herein may enhance excavators&#39; safety and protect the general public from risks associated with damage to underground facilities by ensuring locate technicians receive clearly-communicated boundaries for their locate operations. Furthermore, virtual white lines may enhance the completeness of locate operations ensuring that excavators do not excavate where locates have not been performed. Also, the virtual white lines may provide significant improvements in accuracy. In contrast, translation of textual descriptions of a dig area may be time consuming and imprecise. For example, a telephone call to a one call center may require an operator to transcribe an audible description of a planned dig area. The transcription may be eventually provided to a locate technician performing a locate operation of underground facilities. However, transcribed verbal descriptions of a location may lack precision, possibly communicating to a locate technician incorrect bounds of the dig area intended by the excavator, creating a significant risk of damage to underground facilities. As another benefit, virtual white lines as described herein may enable excavators to identify dig area boundaries with precision without being required to physically visit a dig area. Thus, an excavator may be able to save time and resources by eliminating certain trips to a dig area. Additionally, or alternatively, use of virtual white lines may provide for easier dissemination. Aerial images with virtual white lines can be associated with individual tickets and recalled electronically, avoiding the uncertainties and errors associated with manual filing systems. 
         [0096]    The foregoing description is not intended to be exhaustive or to limit the description to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the invention. 
         [0097]    For example, certain information has been described as being presented visually on a screen of user device  210 . In other implementations, this information may be audibly provided to the user. Also, particular information has been described as being input via an input device  340 , such as a screen of user device  210 . In other implementations, this information may be provided in other ways, such as by receiving inputs via input keys and/or buttons, by recognizing speech of the user, or by monitoring a condition of the user. More particularly, input device  340  may be capable of capturing signals that reflect a user&#39;s intent. For example, input device  340  may include a microphone that can capture a user&#39;s intent by capturing the user&#39;s audible commands. Alternatively, input device  340  may interact with a device that monitors a condition of the user, such as eye movement, brain activity, or heart rate. 
         [0098]    As another example, certain components, such as user device  210  and central server  220  have been described as using an image cache. In other implementations, user device  210  and/or central server  220  may communicate with an image server (such as imager server  230 ) in real-time, so that no image cache may be required. In still other implementations, user device  210  may, for example, communicate in real time with central server  220 . 
         [0099]    Also, implementations in  FIG. 5  herein generally described processes associating a one call center with central server  220 . In another implementation, facility owner  580  may provide a separate server to accomplish some of the routines of  FIG. 5 . For example, a facility owner may be informed by a one call center of a locate request that includes only a textual description of a planned dig area. Facility owner  580  may separately contact the excavator (e.g., user) who placed the locate request and provide and conduct virtual white line procedures with the use from a separate server, later associating the virtual white lines with the other ticket information. In still other implementations, the user may conduct an initial locate request in two parts by providing a conventional locate request to a one call center and then conducting a virtual white line process with a separate server operated by a facility owner  580 . 
         [0100]    As another example, it should be noted that reference to a GPS-enabled device is not limited to GPS systems only, and that any global navigation satellite system or other system that provides geo-spatial positioning may be used in implementations of the invention. 
         [0101]    Also, while a series of blocks has been described with regard to  FIGS. 6 and 7 , the order of the blocks may be modified in other implementations. Further, non-dependent blocks may be performed in parallel. 
         [0102]    Aspects, as described above, may be implemented in many different forms of software, firmware, and hardware in the implementations illustrated in the figures. The actual software code or specialized control hardware used to implement these aspects is not limiting of the description provided herein. Thus, the operation and behavior of the aspects were described without reference to the specific software code—it being understood that software and control hardware can be designed to implement the aspects based on the description herein. 
         [0103]    Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the invention. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. 
         [0104]    No element, act, or instruction used in the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Where only one item is intended, the term “one” or similar language is used. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.