Patent Publication Number: US-9415976-B2

Title: Crane collision avoidance

Description:
BACKGROUND 
     When using a lifting device, such as for example, a crane, it is often very difficult or impossible for an operator to see the area around and below the load that is being lifted, moved, or positioned by the lifting device. As but one example, some lifts are blind to an operator of the lifting device, such as when a load is dropped into a hole. As such, it is difficult and sometimes dangerous to perform lift activities. This is because the lifting device operator cannot see the position of the load, and the hazards that might hit or be hit by the load. Even routine lifts, where a lifting device operator can view the load, can be complicated by diminished situational awareness regarding the position of the load and/or potential hazards in the vicinity of the load. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of this application, illustrate and serve to explain the principles of embodiments in conjunction with the description. Unless noted, the drawings referred to this description should be understood as not being drawn to scale. 
         FIG. 1A  is an illustration of an RFID tower crane load locator system utilizing a single RFID reader for determining the location of a load according to one embodiment of the present technology. 
         FIG. 1B  is an illustration of an RFID tower crane load locator system utilizing two RFID readers for determining the location of a load according to one embodiment of the present technology. 
         FIG. 1C  is an illustration of an RFID tower crane load locator system utilizing three RFID readers for determining the location of a load according to one embodiment of the present technology. 
         FIG. 2  is a block diagram of an RFID tower crane load locator system, according to one embodiment of the present technology. 
         FIG. 3  is a flowchart of a method for utilizing RFID for locating the load of a tower crane, according to one embodiment of the present technology. 
         FIG. 4  is a map of a job site according to one embodiment of the present technology. 
         FIG. 5  is a map of a job site populated with recognized objects according to one embodiment of the present technology 
         FIG. 6  is a block diagram of a collision avoidance system according to one embodiment of the present technology 
         FIG. 7  is a flowchart of a method for avoiding a crane load collision, according to one embodiment of the present technology. 
         FIG. 8  is a block diagram of an example computer system upon which embodiments of the present technology may be implemented. 
         FIG. 9  is a block diagram of an example global navigation satellite system (GNSS) receiver which may be used in accordance with one embodiment of the present technology. 
     
    
    
     DESCRIPTION OF EMBODIMENT(S) 
     Reference will now be made in detail to various embodiments of the present technology, examples of which are illustrated in the accompanying drawings. While the present technology will be described in conjunction with these embodiments, it will be understood that they are not intended to limit the present technology to these embodiments. On the contrary, the present technology is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the present technology as defined by the appended claims. Furthermore, in the following description of the present technology, numerous specific details are set forth in order to provide a thorough understanding of the present technology. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present technology. 
     Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present description of embodiments, discussions utilizing terms such as “receiving”, “storing”, “generating”, “transmitting”, “inferring,” or the like, refer to the actions and processes of a computer system, or similar electronic computing device. The computer system or similar electronic computing device manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission, or display devices. Embodiments of the present technology are also well suited to the use of other computer systems such as, for example, mobile communication devices. 
     Overview 
     Embodiments of the present invention enable the determination of the GNSS position of the crane or portions of the crane which can then be integrated with a map or other representation of a job site to provide the operator of the crane with a visual depiction of the crane&#39;s location with respect to objects on the job site. In one embodiment, tags can be affixed to objects on the job site and optionally loaded with information such as a position/description of the objected to which affixed. A tag scanner on the crane interacts with the tags to actively locate them in the case of real time location system (RTLS) tags or to receive embedded location information in the case of radio frequency Identification (RFID) tags. In one embodiment, a database that is used by the collision avoidance system is updated with information associated with a particular tag number. For example, tag serial #YYY is emplaced on a high tension line power pole; or tags XXX 1 -XXX 4  designate upper corners of a building; etc. 
     In one embodiment, the locations of the tags, and corresponding tagged objects, are then integrated into the depiction of the job site. In other words, the tags mark objects on the job site which should be avoided during crane operations. In addition to improved situational awareness, the system can sound alarms when a 2D geofence or 3D geosphere/geovolume associated with a tagged object is encroached or about to be encroached by a portion of the crane. 
     By providing load location information at a user interface, embodiments of the present technology enable safer and more efficient operation of a tower crane, which results in lower operating cost and improved safety. Moreover, the information can also be disseminated to other users including project managers, foremen and the like. In so doing, additional layers of operational insight and tower crane safety are achieved. 
     Crane Load Locator 
     With reference now to  FIG. 1A , an illustration of a tower crane  100  including a tower crane load locator system for determining the location of a load is shown. 
     Tower crane  100  includes a base  104 , a mast  102  and a jib (e.g., working arm)  110 . The mast  102  may be fixed to the base  104  or may be rotatable about base  104 . The base  104  may be bolted to a concrete pad that supports the crane or may be mounted to a moveable platform. In one embodiment, the operator  130  is located in a cab  106  which includes a user interface  137 . 
     Tower crane  100  also includes a trolley  114  which is moveable back and forth on jib  110  between the cab  106  and the end of the jib  110 . A cable  116  couples a hook  122  and hook block  120  to trolley  114 . A counterweight  108  is on the opposite side of the jib  110  as the trolley  114  to balance the weight of the crane components and the object being lifted, referred to hereinafter as load  118 . 
     In one embodiment shown in  FIG. 1A , tower crane  100  also includes an RFID reader  126  and a number of RFID tags  124 . In one embodiment RFID reader  126  is battery powered and may include rechargeable characteristics including solar charging capabilities. In another embodiment, RFID reader  126  is electrically wired with tower crane  100 . 
     In  FIG. 1A , the RFID reader  126  is shown on trolley  114  and RFID tags  124  are located at hook block  120 , cab  106  and load  118 . However, in other embodiments RFID reader  126  may be located at a different location and the RFID tags  124  would be adjusted accordingly. For example, if RFID reader  126  was located on hook block  120  then RFID tags  124  could be located at trolley  114  and cab  106 . In another example, if RFID reader  126  was located at cab  106  then RFID tags  124  could be located at trolley  114  and hook block  120 . In yet another embodiment, there may be numerous RFID tags  124  located at different locations both on and off of tower crane  100 , such as for example on load  118 . 
     Tower crane  100  also includes a jib direction determiner  128 . In general, jib direction determiner  128  determines the direction that jib  110  is facing. In various embodiments, jib direction determiner  128  may be a compass, a heading indicator, a satellite navigation position receiver offset from a known position, a satellite navigation position receiver utilizing two antenna located at different points along the jib, at least two satellite navigation position devices located at different points along the jib or a combination thereof. In one embodiment, such as shown in  FIG. 1C , no jib direction determiner is utilized. 
       FIG. 1A  additionally includes a sway determiner  133  coupled with hook block  120 . In one embodiment, sway determiner  133  may be an accelerometer, a gyro, GNSS, a camera and the like. In general, sway determiner  133  is used to determine sway of the load  118 . Although sway determiner  133  is shown as coupled with hook block  120 , in another embodiment, the sway determiner  133  may be coupled with the load  118  or the hook  122 . 
     Referring now to  FIG. 1B , an illustration of a tower crane  145  including an RFID tower crane load locator system utilizing two RFID readers for determining the location of a load is shown. 
     For purposes of clarity in the discussion, the description of some of the components of  FIG. 1B  that are similar to and previously described in  FIG. 1A  are not repeated herein. 
     In one embodiment, in addition to the components described in  FIG. 1A ,  FIG. 1B  includes a second RFID reader  126  located at a different location than the first RFID reader  126 . In addition, since a number of RFID reader&#39;s  126  are utilized, one or more components may have both an RFID reader  126  and an RFID tag  124  coupled therewith. In another embodiment, RFID reader  126  may include an RFID tag  124 . 
     For example, in  FIG. 1B , a first RFID reader  126  with an RFID tag  124  is located at trolley  114 . The second RFID reader  126  with an RFID tag  124  is located at cab  106 . Although the two locations are shown, the technology is well suited for locating RFID readers  126  at various other locations, such as, but not limited to, hook block  120 , load  118 , mast  102 , jib  110  and the like. 
     Range measurement paths  187 ,  188  and  189  are also shown in  FIG. 1B . In general, range measurement paths illustrate a pulse sent from an RFID reader  126  and returned from the RFID tag  124 . As described in more detail herein, these range measurements are used to determine distances. 
       FIG. 1B  also includes GNSS devices  140 . In general, GNSS device  140  may be a complete GNSS receiver or just a GNSS antenna. In one embodiment, there are two GNSS devices  140 . One is located at the front of the jib  110  and the other is located at counterweight  108 . Although two GNSS devices  140  are shown, in another embodiment,  FIG. 1B  may only utilizes one GNSS device  140 . For example, one GNSS device  140  may provide a location while jib direction determiner  128  determines the direction that jib  110  is facing. In yet another embodiment jib direction determiner  128  may be a GNSS receiver utilizing two GNSS antenna located at different points along the jib such as those designated by GNSS devices  140 . In addition, the locations of GNSS devices  140  may be in different areas, the illustration of the two GNSS devices  140  locations in  FIG. 2B  is provided merely for purposes of clarity. 
     Referring now to  FIG. 1C , an illustration of a tower crane  166  including an RFID tower crane load locator system utilizing at least four RFID components  125  to provide RFID range measurements between the at least four RFID components  125 . 
     For purposes of clarity in the discussion, the description of some of the components of  FIG. 1C  that are similar to and previously described in  FIGS. 1A and 1B  are not repeated herein. 
     In one embodiment,  FIG. 1C  includes at least four RFID components  125 . In one embodiment, the at least four RFID components include at least three RFID readers  126  and at least one RFID tag  124 . In one embodiment, at least one of the RFID components  124  is not in the same plane as the mast  102  and the jib  110  of the tower crane. For example, in one embodiment, at least one of the four RFID components  125  is located separately from the tower crane  166 . In the example shown in  FIG. 1C , the off-tower RFID component  125  is a handheld device. In one embodiment the off-tower RFID component  125  is carried by a user  131 . As will be described in more detail herein, the user may be a foreman, safety inspector, or the like. In another embodiment, user  131  may be the tower crane operator and as such operator  130  would not need to be in the cab  106 . 
     In general, since at least four RFID components  125  are utilized, it is possible to utilize the RFID range measurements independent of any other aspects of the crane to determine a location of load  118 . For example, by utilizing four RFID components  125  without the jib determiner  128  or sway determiner  133 , the RFID load locator would provide information regarding the location of the load  118 . In addition, since the four RFID components do not require additional input from the crane or crane operator to provide load location information, in one embodiment, the components can be provided as a stand-alone load locating device that can be added to an existing tower crane without requiring any modification or manipulation of existing crane components. 
     With reference now to  FIG. 2 , a tower crane RFID load locator  200  is shown in accordance with an embodiment of the present technology. In one embodiment, RFID load locator  200  includes an RFID range measurer  210 , a load position determiner  230  and a load information generator  240 . In one embodiment, RFID load locator  200  may also include a jib direction determiner  128 . However, in another embodiment, RFID load locator  200  may optionally receive jib direction determiner  128  information from an outside source. Similarly, RFID load locator  200  may optionally receive sway determiner  133  information from an outside source. 
     In one embodiment, RFID range measurer  210  provides RFID range measurements between at least four RFID components  125 . Load position determiner  230  utilizes the range measurements with or without any other optional inputs described herein to determine a location of the load  118 . Load information generator  240  provides the location of the load information suitable for subsequent access by a user. In one embodiment, the location of the load information is output in a user accessible format  250 . For example, the load information may be output to a graphic user interface (GUI), such as GUI  137 . In another embodiment, the load information provided in user accessible format  250  may be sent to or accessed by a plurality of devices such as a handheld device, GUI  137 , or other devices. In another embodiment, the RFID range measurer may be at a tower crane in a first location and the range measurements may be provided to a load position determiner  230  at a remote location. In yet another embodiment, the load information generator  240  may also be remotely located or may be remotely accessible by authorized personnel. For example, the load location information may be processed in a local office at the work site, remote from the work site or the like and the load information generator  240  may be stored in “the cloud”. 
     Optional Jib direction determiner  128  determines the direction the jib is facing. Optional sway determiner  133  is used to determine sway of the load  118 . Although sway determiner  133  is shown as coupled with hook block  120 , in another embodiment, the sway determiner  133  may be coupled with the load  118  or the hook  122 . 
     In one embodiment, in addition to utilizing the range measurements to determine a location of the load, load position determiner  230  may also utilize the optional jib direction information or the sway determiner  133  information or both the jib direction information and the sway determiner  133  information to determine the location of the load  118 . 
       FIG. 3  is a flowchart of a method for utilizing RFID for locating the load of a tower crane, according to one embodiment of the present technology. 
     With reference now to  302  of  FIG. 3  and  FIG. 1A , one embodiment generates range measurements from an RFID reader coupled with the tower crane to at least a first and a second RFID tag coupled with the tower crane. 
     In other words, RFID reader  126  can be used in conjunction with RFID tags  124  to determine distances. For example, RFID reader  126  would measure the range to the RFID tag  124  located on hook block  120 . In so doing, the distance  188  between hook block  120  and trolley  114  can be determined. 
     Similarly, RFID reader  126  can measure the range to the RFID tag  124  located on cab  106 . In so doing, the distance of leg  189  between cab  106  and trolley  114  can be determined. 
     In another embodiment, such as shown in  FIG. 1B  where RFID reader  126  is located at hook block  120  or cab  106 , similar measurements can be made between the RFID tags and once two sides of the triangular plane are known, the third side can be calculated. For example, assuming the RFID reader  126  was located at cab  106 ; leg  189 : the distance between cab  106  and trolley  114  could be measured. Similarly leg  187 : the distance between cab  106  and hook block  120  could also be measured. Then, distance  188  could be solved for using a formula such as the Pythagorean Theorem. 
     With reference still to  302  of  FIG. 4  and  FIGS. 1B and 1C , another embodiment generates range measurements from a plurality of RFID readers to a plurality of RFID tags coupled with the tower crane. For example, in  FIG. 1B , a first RFID reader  126  with an RFID tag  124  is located at trolley  114 . The second RFID reader  126  with an RFID tag  124  is located at cab  106 . Although the two locations are shown, the technology is well suited for locating RFID readers  126  at various other locations, such as, but not limited to, hook block  120 , load  118 , mast  102 , jib  110  and the like. 
     In addition, since a number of RFID reader&#39;s  126  are utilized, one or more components may have both an RFID reader  126  and an RFID tag  124  coupled therewith. In another embodiment, RFID reader  126  may include an RFID tag  124 . 
     As described herein, these range measurements are used to determine distances. 
     In one embodiment, a third RFID reader  126  may be located separately from the tower crane  166 . As shown in  FIG. 1C , the third RFID reader  126  may be a handheld device. Since three RFID reader&#39;s  126  are utilized, it is possible to utilize the range measurements to determine a load  118  location that is outside of a plane. For example, the third RFID reader  126  would provide information that could be utilized to determine a sway of load  118 . 
     Moreover, in one embodiment the third RFID reader  126  is carried by a user  131 . User  131  may be a foreman, safety inspector, manager, owner, developer, or the like. In another embodiment, user  131  may be the tower crane operator and as such operator  130  would not need to be in the cab  106 . 
     Although RFID is described herein as one embodiment to find the location of the load, a number of other load location providers may be utilized. For example, the load may be located by installing a GNSS system directly on the load or on the hook. 
     In another embodiment, lasers or long range radar may be utilized. Therefore, although RFID is the method described herein, it is provided for purposes of clarity as one example of the finding the location of the load, not as the only method for defining the location of the load. 
     For example, with respect to laser measuring, in one embodiment a reflective strip is located at trolley  114  and an additional reflective strip is located at hook block  120 . Although two locations are shown, the technology is well suited for locating reflective strips at various other locations, such as, but not limited to, cab  106 , load  118 , mast  102 , jib  110  and the like. In another embodiment no reflective strip is needed for the operation of laser measuring. For example, the reflective strips may be utilized to provide a level of accuracy with respect to the location upon which the beam from the laser measuring unit is being reflected. However, it should be appreciated that other means for determining the location at which the beam is being reflected may also be utilized. 
     With respect to long range radar, a radar may be mounted on cab  106 . In addition a downward pointing dish a bent pipe and a cab facing dish would be utilized to direct the radar from the cab to the hook and back. 
     With reference now to  304  of  FIG. 4  and  FIGS. 1B and 1C , one embodiment determines a jib direction. In one embodiment, one or more GNSS devices  140  coupled with the tower crane are utilized to determine the jib direction. 
     In general, GNSS device  140  may be a complete GNSS receiver or just a GNSS antenna. In one embodiment, there are two GNSS devices  140 . One is located at the front of the jib  110  and the other is located at counterweight  108 . Although two GNSS devices  140  are shown, in another embodiment, only one GNSS device  140  may be utilized. For example, one GNSS device  140  may provide a location while jib direction determiner  128  determines the direction that jib  110  is facing. In yet another embodiment jib direction may be determined by a GNSS receiver utilizing two GNSS antenna located at different points along the jib such as those designated by GNSS devices  140  at  FIG. 1C . In another embodiment, the locations of GNSS devices  140  may be in different locations on the tower crane. 
     With reference now to  305  of  FIG. 3  and  FIG. 1B , one embodiment fixedly couples a sway determiner  133  with a hook block of the tower crane, the sway determiner  133  to provide sway information with respect to the hook block  120 . Although sway determiner  133  is stated as being coupled with hook block  120 , in another embodiment, the sway determiner  133  may be coupled with the load  118  or the hook  122 . 
     With reference now to  306  of  FIG. 3  and  FIG. 1B , one embodiment combines the range measurements, the jib direction and the sway determiner information to generate a location of the load. For example, by using two RFID readers  126  a plurality of distance measurements for legs  187 ,  188  and  189  can be determined. 
     However, when the second RFID reader  126  is located at hook block  120  or cab  106 , while the measurements can be made between the RFID tags and once two sides of the triangular plane, the sway determiner information can be added to further refine the third side calculation. For example, assuming one of the RFID readers  126  was located at cab  106 , legs  187  and  189  could be measured. By including the sway determiner  133  information, solving for the length of leg  188  can now be performed by a more accurate method such as the Law of Cosines, where the sway determiner information is used to determine the cosine for the angle. 
     In another embodiment, such as shown in  FIG. 1C , three RFID readers can be used to make range measurements and utilize the measurements to provide a position fix utilizing methods such as “trilateration.” For example, to solve for the load  118  position information, the information from RFID readers  126  located at the trolley  114 , the cab  106  and the hand-held device held by user  131  is used to formulate the equations such as for three spherical surfaces and then solving the three equations for the three unknowns, x, y, and z. This solution can then be utilized in a Cartesian coordinate system to provide three-dimensional information. 
     Range measurements can be made, in one embodiment, by counting the time interval from time of transmission of a pulse to a reader to its return to the reader from the tag, and dividing by 2. So for a round-trip elapsed time interval of 60 nanoseconds, the true one-way time of flight is 30 nanoseconds, which corresponds to 30 feet. Such elapsed time measurements involve the use of a precision clock with start-stop trigger capabilities. In one embodiment, the RFID reader is equipped with this type of range measurer. Other methods for making range measurements include estimating distance include signal strength (RSSI), “instantaneous phase” which is similar to real-time-kinematic (RTK) GPS methods, and integrated phase which continuously tracks phase as if it were a tape measure. 
     In one embodiment, the additional jib direction information, the sway determiner information, or both can also be added to the trilateration information to generate additional useful information regarding load location, motion, rotation, and the like. 
     With reference now to  308  of  FIG. 3  and  FIGS. 1B and 1C , one embodiment provides the information on a user interface in a user accessible format. That is, the information may be presented on a user interface, such as a graphical user interface (GUI) or the like. For example, the information may be a presented as plan and/or elevation views of the tower crane with the location of the load illustrated spatially with relation to an illustration of the tower crane. In addition, the information may be presented as an overlay on a map such as a site map or the like. 
     For example, the site map may indicate the location (or range of locations) where contact between the tower crane and another object is possible. Thus, in addition to providing information to be presented on the user interface, one embodiment may also provide warning information. In another embodiment, an automated stop or override may also be utilized. 
     For example, the load location information can be used to alert operators when they are not moving safely in terms of location, speed, acceleration, shock, load, jerk, etc. The information can also be used in automatic collision avoidance. 
     Site Map 
     With reference now to  FIG. 4 , a map of a job site is shown in accordance with one embodiment of the present technology. In general, map  400  is user selectable and may be an aerial map, a topographic map, a terrain map, a physical map, a road map, a satellite image or the like. In addition, the map may be scaled based on the type of crane  100  being utilized, the size of the site, the desired granularity, or the like. Moreover, the scale may be adjusted either automatically or manually. In general, once the map  400  is selected for display on a graphical user interface (GUI), the collision avoidance system will project the location of crane  100  onto the map. In addition, in one embodiment, a radius of operation  402  will also be provided on the map  400 . In another embodiment, any roads  406  may be provided on the received map. 
     For example, if the crane  100  is working in a specific location, the imagery may be zoomed in such that the area within the operational radius  402  of the crane is clearly visible. However, if the crane is moving across the site, the imagery may be zoomed out to afford a more complete picture of the area being traversed. 
     In one embodiment, the map  400  is downloaded from the internet. For example, in one embodiment the map may be sourced from an application such as TrimbleOutdoors or from a website such as mytopo or Trimbleoutdoors.com. In another embodiment, map  400  may be automatically downloaded based on the crane&#39;s GNSS location or may be downloaded based input from a user such as: latitude and longitude, geodetic datums such as NAD 83 and WGS 84, or the like. In yet another embodiment, the map may be taken from a map database stored on a CD, DVD or other digital input coupled with the crane database without requiring an Internet connection. 
     Site Map Population 
     With reference now to  FIG. 5 , the site map  400  populated with recognized objects is shown in accordance with one embodiment of the present technology. In general, once the map  400  is selected for display on a graphical user interface (GUI), the collision avoidance system  600  will project the location of crane  100  onto the map and then begin to populate the map with any obstacles found thereon. For example, the collision avoidance system  600  may access survey data to establish building  502  locations, heights and the like. In addition, additional objects such as: power lines  515 , people  131 , no enter zones  504 , and the like are also displayed. 
     With reference now to  FIG. 6 , a collision avoidance system  600  is shown in accordance with one embodiment. In general, Collision avoidance system  600  includes input received from load locator  200  received at mapping module  601 . In addition, Collision avoidance system  600  includes a map receiver module  620  which can receive map information from sources such as Internet  605  and a map database  635 . Map receiver module  620  provides the map information to mapping module  601 . 
     Collision avoidance system  600  also includes tag scanner  610  which monitors the area around crane  100  for any tags and provides any information received to mapping module  601 . Mapping module  601  outputs the combined user accessible information  650  which may be provided via a GUI or the like. In one embodiment, collision avoidance system  600  also includes proximity monitor  640  which monitors mapping module  601  for any proximity information. For example if an object was in the path of crane  100 , proximity monitor  640  may provide a signal  675  to alert the crane operator. Similarly, if proximity monitor  640  determines that a collision is imminent or that a safe barrier distance has been breached, proximity monitor  640  may provide automatic crane control override  677  to automatically stop the collision from occurring. 
     With reference now to  FIG. 6  and  FIG. 5 , collision avoidance system  600  may scan for tags such as RFID tags, RTLS tags, or the like, that are placed on objects, vehicles or personnel. For example, tag scanner  610  may scan for power lines  515 , people  131 , buildings  502  and the like. In one embodiment, tags can be affixed to objects on the job site and optionally loaded with information such as, but not limited to: position, elevation, and description of the objected to which the tag is affixed. In one embodiment, tag scanner  610  interacts with the tags to actively locate them in the case of RTLS tags or to receive embedded location information in the case of RFID tags. In one embodiment, database  635  may be updated with information associated with a particular tag number. For example, tag serial #YYY is emplaced on a high tension line power pole; or tags XXXA-XXXD designate upper corners of a building; etc. 
     In one embodiment, the locations of the tags, and corresponding tagged objects, are then integrated into the depiction of the job site on the GUI. In other words, the tags mark objects on the job site which should be avoided during crane operations. 
     Collision Avoidance 
     In addition to improved situational awareness, the system can sound alarms when a 2D geofence or 3D geosphere/geovolume associated with a tagged object is encroached or about to be encroached by a portion of the crane  100 . For example, the load location information from load locator  200  is compared to the location of other objects at mapping module  601 . In addition, safety zones can be established around different objects. For example, if power lines  515  are 30 feet high, a safety zone window between the heights of 25-35 feet may be established. If the safety zone is breached, or a breach appears imminent based on the load movement, a signal  675  can be generated. In one embodiment, the signal may be an audible signal, visual cue, or the like to provide warning to the crane operator about the potential collision. 
     In another embodiment, the load location can be compared to pre-defined “do not enter” spaces such as  504 . In other words, pre-planning establishes areas or zones  504  that should not be entered by particular devices. When it is determined that a load is about to enter, a “do not enter” zone, a warning can be generated and provided to the operator. The warning can help prevent collisions between the tower crane and other objects. 
     In yet another embodiment, in addition to providing a warning, the operation of the tower crane may be automatically stopped or otherwise manipulated to stop a collision or boundary incursion from actually occurring. For example, the system may include a first warning distance from an object or area having a first radius and also a second automatic override distance from an object or area at a smaller radius. That is, if the safety threshold is breached, the proximity monitor  640  may activate an automatic crane control override  677  to stop the collision from occurring. 
     As such, if a load was approaching another object, as the warning distance is breached, the system would provide a user warning. However, if the load breached the automatic override distance, the operation of the tower crane may be automatically stopped, reversed, or the like. In so doing, significant safety risks and property damage may be automatically avoided. 
     It is appreciated that the autonomous position of the tower crane can be used to generate a real-time graphical representation of a work site. In one embodiment, the autonomous position of the tower crane is reported to a remote location where the activity can be monitored. 
     In Operation 
     With reference now to  FIG. 7 , a flowchart  700  of a method for avoiding a crane load collision is shown in accordance with one embodiment. 
     Referring now to  702  of  FIG. 7  and to  FIGS. 5 and 6 , one embodiment determines a location of a load of a crane  100  and provides the location information to a mapping module  601 . In one embodiment, a display and location system is provided to the crane operator and apprises the operator in real time about the location of crane  100  including direction of rotation of crane, direction of movement of crane, etc. 
     Referring now to  704  of  FIG. 7  and to  FIGS. 5 and 6 , one embodiment obtains a map of an area around the location of the crane and providing the map to the mapping module  601 . The location information about the position and movements of the crane is plotted on or integrated with a graphical representation of the job site on which the crane is operating so that the operator can be situational aware in real time of where portions of the crane are located with respect to mapped objects on the job site. In one embodiment, the information is provided in a 2D format. However, in another embodiment, the information may be presented in a 3D format. In one embodiment, all information can be displayed on the display and location system which is viewable at least in the cab of the crane and could also be viewed remotely from the crane itself. This is useful because operators have limited views from an operating cab especially behind, to the sides, and directly below the facing direction of the cab. 
     Referring now to  706  of  FIG. 7  and to  FIGS. 5 and 6 , one embodiment scans the area around the location of the crane for one or more tags defining an obstacle and providing the obstacle information to a mapping module  601 . That is, in addition to using a map of the job site, in one embodiment, one or more interactive wireless tags such as RFID tags and/or RTLS tags can be affixed to objects that are on the job site. The tagged objects can include the crane itself, other cranes or items of construction equipment, buildings, power poles, antennas, etc. Essentially, a wireless tag can be affixed to anything on a job site that a crane could collide with during its operation. Tags may be placed at locations such as base of power poles, highest point of an object, one or more corners of an object (e.g., a building). The tags may be dumb and not loaded with information other than a serial number or unique identifier or may have other information stored on them when affixed. 
     Alternatively, information associated with a tag ID may be stored in a database  635  which is accessible by the a tag scanner  610  or other portion of the collision avoidance system  600 . Some types of the other information can include 2D or 3D coordinates associated with an object to which they are affixed (especially useful for immobile objects such as power poles, antennas, buildings and the like), the type of the item (e.g., power pole, truck, etc.), a class of the item (mobile, immobile), etc. 
     In one embodiment, a tag scanner  610  or scanners located in on the crane constantly scans for the tags, and provides received tag information to the display and location mapping module  601 . In one embodiment, the tag scanner  610  can operate to locate RTLS tags, and to some extent RTLS tags can locate themselves and other nearby tags via built in mesh networking or can provide received information to the mapping module  601 . 
     Referring now to  708  of  FIG. 7  and to  FIGS. 5 and 6 , one embodiment combines the load location information, the map and the obstacle information into a user accessible information package at a mapping module. For example, mapping module  601  integrates the received tag information with location information from load locator  200  regarding the crane or portions thereof and visually depicts the real time location of the crane with respect to the tags/tagged objects and the locations of any other modeled or represented job site objects. 
     In one embodiment, collision avoidance system  600  may take further actions such as connecting lines between power poles to represent the location of power lines  515 . In addition, collision avoidance system  600  may associate a buffer zone in the form of a virtual geofence or geosphere/geovolume with an object, such as  404  that is tagged or otherwise represented as being on the job site in the operating area of the crane. 
     This buffer zone association may be manual or may be automatic for some objects such as power poles/lines  515 . 
     Referring now to  710  of  FIG. 7  and to  FIGS. 5 and 6 , one embodiment displays the user accessible information on a graphical user interface that includes the area around the location of the crane. By providing the information to a visual display, one embodiment allows the crane operator to visualize proximity to such tagged objects or buffer zones associated with tagged or otherwise represented objects in real time. In addition to improve situational awareness, collision avoidance system  600  can sound provide a signal  675  when a 2D geofence or 3D geosphere/geovolume associated with a tagged object is encroached or about to be encroached by a portion of the crane  100 . For example, collision avoidance system  600  can warn the operator when an operating condition of the crane violates a rule or buffer zone with respect to crane proximity to an object. For example an alarm might sound when a portion of the crane is within 20 feet of a power pole  515 , 5 feet of a building  502 , 30 feet of a portion of another crane, etc. Such rules could be from a standard list or customizable by a user/operator/manufacturer/asset owner/rental company etc. 
     In another embodiment, for example, in the case of “Safety” only RTLS tags are used on the end of the “booms” for the different type of cranes to detect “close proximity” and “collision avoidance”. This embodiment does not require GNSS but instead relies upon RTLS tags and one or more readers at strategic areas of a job site, or at the crane for simple operations where there is only one crane on site. 
     In yet another embodiment, the RTLS tags may also be used to define obstacles of interest. For example, RTLS tags may be placed at the corners of a building. The RTLS tags would then be “grouped” with specific attributes to define an “avoidance zone”. In other words, if RTLS tags A, B, C and D were placed at the corners of building  502 , collision avoidance system  600  would “group” tags A, B, C and D. That “group” of tags would then be given an “attribute” that “closes the loop” and makes an “object” in 2D. In another embodiment, map receiver module  620  then accesses database  635  to find group information such as the “height” component of that structure, thus providing the final “avoidance” area to be monitored. 
     Similarly, a group of tags may be used to define power poles. For example, a “group” of tags is selected to define the power poles and an “attribute” is assigned to those tags that “ties” the power poles into a “Line” and defines the “height” requirement associated with Power poles at a particular site, to be avoided. Collision avoidance system  600  would then use the transmitted position of the RTLS tags to compute the defined minimum thresholds/buffer zones. 
     In one embodiment, by using RTLS tags only, an entry point for ‘collision avoidance’ and situational awareness can be established. For example, by monitoring the “boom tips” from one tip to one another or other defined areas of interest, without requiring the infrastructure for RTK corrections or the like. 
     Computer System 
     With reference now to  FIG. 8 , portions of the technology for providing a communication composed of computer-readable and computer-executable instructions that reside, for example, in non-transitory computer-usable storage media of a computer system. That is,  FIG. 8  illustrates one example of a type of computer that can be used to implement embodiments of the present technology.  FIG. 8  represents a system or components that may be used in conjunction with aspects of the present technology. In one embodiment, some or all of the components of  FIG. 1  or  FIG. 3  may be combined with some or all of the components of  FIG. 8  to practice the present technology. 
       FIG. 8  illustrates an example computer system  800  used in accordance with embodiments of the present technology. It is appreciated that system  800  of  FIG. 8  is an example only and that the present technology can operate on or within a number of different computer systems including general purpose networked computer systems, embedded computer systems, routers, switches, server devices, user devices, various intermediate devices/artifacts, stand-alone computer systems, mobile phones, personal data assistants, televisions and the like. As shown in  FIG. 8 , computer system  800  of  FIG. 8  is well adapted to having peripheral computer readable media  802  such as, for example, a floppy disk, a compact disc, and the like coupled thereto. 
     System  800  of  FIG. 8  includes an address/data bus  804  for communicating information, and a processor  806 A coupled to bus  804  for processing information and instructions. As depicted in  FIG. 8 , system  800  is also well suited to a multi-processor environment in which a plurality of processors  806 A,  806 B, and  806 C are present. Conversely, system  800  is also well suited to having a single processor such as, for example, processor  806 A. Processors  806 A,  806 B, and  806 C may be any of various types of microprocessors. System  800  also includes data storage features such as a computer usable volatile memory  808 , e.g. random access memory (RAM), coupled to bus  804  for storing information and instructions for processors  806 A,  806 B, and  806 C. 
     System  800  also includes computer usable non-volatile memory  810 , e.g. read only memory (ROM), coupled to bus  804  for storing static information and instructions for processors  806 A,  806 B, and  806 C. Also present in system  800  is a data storage unit  812  (e.g., a magnetic or optical disk and disk drive) coupled to bus  804  for storing information and instructions. System  800  also includes an optional alpha-numeric input device  814  including alphanumeric and function keys coupled to bus  804  for communicating information and command selections to processor  806 A or processors  806 A,  806 B, and  806 C. System  800  also includes an optional cursor control device  816  coupled to bus  804  for communicating user input information and command selections to processor  806 A or processors  806 A,  806 B, and  806 C. System  800  of the present embodiment also includes an optional display device  818  coupled to bus  804  for displaying information. 
     Referring still to  FIG. 8 , optional display device  818  of  FIG. 8  may be a liquid crystal device, cathode ray tube, plasma display device or other display device suitable for creating graphic images and alpha-numeric characters recognizable to a user. Optional cursor control device  816  allows the computer user to dynamically signal the movement of a visible symbol (cursor) on a display screen of display device  818 . Many implementations of cursor control device  816  are known in the art including a trackball, mouse, touch pad, joystick or special keys on alpha-numeric input device  814  capable of signaling movement of a given direction or manner of displacement. Alternatively, it will be appreciated that a cursor can be directed and/or activated via input from alpha-numeric input device  814  using special keys and key sequence commands. 
     System  800  is also well suited to having a cursor directed by other means such as, for example, voice commands. System  800  also includes an I/O device  820  for coupling system  800  with external entities. For example, in one embodiment, I/O device  820  is a modem for enabling wired or wireless communications between system  800  and an external network such as, but not limited to, the Internet. A more detailed discussion of the present technology is found below. 
     Referring still to  FIG. 8 , various other components are depicted for system  800 . Specifically, when present, an operating system  822 , applications  824 , modules  826 , and data  828  are shown as typically residing in one or some combination of computer usable volatile memory  808 , e.g. random access memory (RAM), and data storage unit  812 . However, it is appreciated that in some embodiments, operating system  822  may be stored in other locations such as on a network or on a flash drive; and that further, operating system  822  may be accessed from a remote location via, for example, a coupling to the internet. In one embodiment, the present technology, for example, is stored as an application  824  or module  826  in memory locations within RAM  808  and memory areas within data storage unit  812 . The present technology may be applied to one or more elements of described system  800 . 
     System  800  also includes one or more signal generating and receiving device(s)  830  coupled with bus  804  for enabling system  800  to interface with other electronic devices and computer systems. Signal generating and receiving device(s)  830  of the present embodiment may include wired serial adaptors, modems, and network adaptors, wireless modems, and wireless network adaptors, and other such communication technology. The signal generating and receiving device(s)  830  may work in conjunction with one or more communication interface(s)  832  for coupling information to and/or from system  800 . Communication interface  832  may include a serial port, parallel port, Universal Serial Bus (USB), Ethernet port, antenna, or other input/output interface. Communication interface  832  may physically, electrically, optically, or wirelessly (e.g. via radio frequency) couple system  800  with another device, such as a cellular telephone, radio, or computer system. 
     The computing system  800  is only one example of a suitable computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the present technology. Neither should the computing environment  800  be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the example computing system  800 . 
     The present technology may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. The present technology may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer-storage media including memory-storage devices. 
     GNSS Receiver 
     With reference now to  FIG. 9 , a block diagram is shown of an embodiment of an example GNSS receiver which may be used in accordance with various embodiments described herein. In particular,  FIG. 9  illustrates a block diagram of a GNSS receiver in the form of a general purpose GPS receiver  980  capable of demodulation of the L1 and/or L2 signal(s) received from one or more GPS satellites. For the purposes of the following discussion, the demodulation of L1 and/or L2 signals is discussed. It is noted that demodulation of the L2 signal(s) is typically performed by “high precision” GNSS receivers such as those used in the military and some civilian applications. Typically, the “consumer” grade GNSS receivers do not access the L2 signal(s). Further, although L1 and L2 signals are described, they should not be construed as a limitation to the signal type; instead, the use of the L1 and L2 signal(s) is provided merely for clarity in the present discussion. 
     Although an embodiment of a GNSS receiver and operation with respect to GPS is described herein, the technology is well suited for use with numerous other GNSS signal(s) including, but not limited to, GPS signal(s), Glonass signal(s), Galileo signal(s), and Compass signal(s). 
     The technology is also well suited for use with regional navigation satellite system signal(s) including, but not limited to, Omnistar signal(s), StarFire signal(s), Centerpoint signal(s), Beidou signal(s), Doppler orbitography and radio-positioning integrated by satellite (DORIS) signal(s), Indian regional navigational satellite system (IRNSS) signal(s), quasi-zenith satellite system (QZSS) signal(s), and the like. 
     Moreover, the technology may utilize various satellite based augmentation system (SBAS) signal(s) such as, but not limited to, wide area augmentation system (WAAS) signal(s), European geostationary navigation overlay service (EGNOS) signal(s), multi-functional satellite augmentation system (MSAS) signal(s), GPS aided geo augmented navigation (GAGAN) signal(s), and the like. 
     In addition, the technology may further utilize ground based augmentation systems (GBAS) signal(s) such as, but not limited to, local area augmentation system (LAAS) signal(s), ground-based regional augmentation system (GRAS) signals, Differential GPS (DGPS) signal(s), continuously operating reference stations (CORS) signal(s), and the like. 
     Although the example herein utilizes GPS, the present technology may utilize any of the plurality of different navigation system signal(s). Moreover, the present technology may utilize two or more different types of navigation system signal(s) to generate location information. Thus, although a GPS operational example is provided herein it is merely for purposes of clarity. 
     In one embodiment, the present technology may be utilized by GNSS receivers which access the L1 signals alone, or in combination with the L2 signal(s). A more detailed discussion of the function of a receiver such as GPS receiver  980  can be found in U.S. Pat. No. 5,621,426. U.S. Pat. No. 5,621,426, by Gary R. Lennen, entitled “Optimized processing of signals for enhanced cross-correlation in a satellite positioning system receiver,” incorporated by reference which includes a GPS receiver very similar to GPS receiver  980  of  FIG. 9 . 
     In  FIG. 9 , received L1 and L2 signal is generated by at least one GPS satellite. Each GPS satellite generates different signal L1 and L2 signals and they are processed by different digital channel processors  952  which operate in the same way as one another.  FIG. 9  shows GPS signals (L1=1575.42 MHz, L2=1227.60 MHz) entering GPS receiver  980  through a dual frequency antenna  901 . Antenna  901  may be a magnetically mountable model commercially available from Trimble® Navigation of Sunnyvale, Calif., 94085. Master oscillator  948  provides the reference oscillator which drives all other clocks in the system. Frequency synthesizer  938  takes the output of master oscillator  948  and generates important clock and local oscillator frequencies used throughout the system. For example, in one embodiment frequency synthesizer  938  generates several timing signals such as a 1st LO1 (local oscillator) signal 1400 MHz, a 2nd LO2 signal 175 MHz, a (sampling clock) SCLK signal 25 MHz, and a MSEC (millisecond) signal used by the system as a measurement of local reference time. 
     A filter/LNA (Low Noise Amplifier)  934  performs filtering and low noise amplification of both L1 and L2 signals. The noise figure of GPS receiver  980  is dictated by the performance of the filter/LNA combination. The downconverter  936  mixes both L1 and L2 signals in frequency down to approximately 175 MHz and outputs the analogue L1 and L2 signals into an IF (intermediate frequency) processor  30 . IF processor  950  takes the analog L1 and L2 signals at approximately 175 MHz and converts them into digitally sampled L1 and L2 inphase (L1 I and L2 I) and quadrature signals (L1 Q and L2 Q) at carrier frequencies 420 KHz for L1 and at 2.6 MHz for L2 signals respectively. 
     At least one digital channel processor  952  inputs the digitally sampled L1 and L2 inphase and quadrature signals. All digital channel processors  952  are typically identical by design and typically operate on identical input samples. Each digital channel processor  952  is designed to digitally track the L1 and L2 signals produced by one satellite by tracking code and carrier signals and to form code and carrier phase measurements in conjunction with the microprocessor system  954 . One digital channel processor  952  is capable of tracking one satellite in both L1 and L2 channels. 
     Microprocessor system  954  is a general purpose computing device which facilitates tracking and measurements processes, providing pseudorange and carrier phase measurements for a navigation processor  958 . In one embodiment, microprocessor system  954  provides signals to control the operation of one or more digital channel processors  952 . Navigation processor  958  performs the higher level function of combining measurements in such a way as to produce position, velocity and time information for the differential and surveying functions. Storage  960  is coupled with navigation processor  958  and microprocessor system  954 . It is appreciated that storage  960  may comprise a volatile or non-volatile storage such as a RAM or ROM, or some other computer readable memory device or media. 
     One example of a GPS chipset upon which embodiments of the present technology may be implemented is the Maxwell™ chipset which is commercially available from Trimble® Navigation of Sunnyvale, Calif., 94085. 
     Differential GPS 
     Embodiments of the present invention can use Differential GPS to determine position information with respect to a jib of the tower crane. Differential GPS (DGPS) utilizes a reference station which is located at a surveyed position to gather data and deduce corrections for the various error contributions which reduce the precision of determining a position fix. For example, as the GNSS signals pass through the ionosphere and troposphere, propagation delays may occur. Other factors which may reduce the precision of determining a position fix may include satellite clock errors, GNSS receiver clock errors, and satellite position errors (ephemeredes). 
     The reference station receives essentially the same GNSS signals as rovers which may also be operating in the area. However, instead of using the timing signals from the GNSS satellites to calculate its position, it uses its known position to calculate timing. In other words, the reference station determines what the timing signals from the GNSS satellites should be in order to calculate the position at which the reference station is known to be. The difference between the received GNSS signals and what they optimally should be is used as an error correction factor for other GNSS receivers in the area. Typically, the reference station broadcasts the error correction to, for example, a rover which uses this data to determine its position more precisely. Alternatively, the error corrections may be stored for later retrieval and correction via post-processing techniques. 
     Real Time Kinematic System 
     An improvement to DGPS methods is referred to as Real-time Kinematic (RTK). As in the DGPS method, the RTK method, utilizes a reference station located at determined or surveyed point. The reference station collects data from the same set of satellites in view by the rovers in the area. Measurements of GNSS signal errors taken at the reference station (e.g., dual-frequency code and carrier phase signal errors) and broadcast to one or more rovers working in the area. The rover(s) combine the reference station data with locally collected position measurements to estimate local carrier-phase ambiguities, thus allowing a more precise determination of the rover&#39;s position. The RTK method is different from DGPS methods in that the vector from a reference station to a rover is determined (e.g., using the double differences method). In DGPS methods, reference stations are used to calculate the changes needed in each pseudorange for a given satellite in view of the reference station, and the rover, to correct for the various error contributions. Thus, DGPS systems broadcast pseudorange correction numbers second-by-second for each satellite in view, or store the data for later retrieval as described above. 
     RTK allows surveyors to determine a true surveyed data point in real time, while taking the data. However, the range of useful corrections with a single reference station is typically limited to about 70 km because the variable in propagation delay (increase in apparent path length from satellite to rover receiver, or pseudo range) changes significantly for separation distances beyond 70 km. This is because the ionosphere is typically not homogeneous in its density of electrons, and because the electron density may change based on, for example, the sun&#39;s position and therefore time of day. Thus for surveying or other positioning systems which must work over larger regions, the surveyor must either place additional base stations in the regions of interest, or move his base stations from place to place. This range limitation has led to the development of more complex enhancements that have superseded the normal RTK operations described above, and in some cases eliminated the need for a base station GNSS receiver altogether. This enhancement is referred to as the “Network RTK” or “Virtual Reference Station” (VRS) system and method. 
     Network RTK 
     Network RTK typically uses three or more GNSS reference stations to collect GNSS data and extract information about the atmospheric and satellite ephemeris errors affecting signals within the network coverage region. Data from all the various reference stations is transmitted to a central processing facility, or control center for Network RTK. Suitable software at the control center processes the reference station data to infer how atmospheric and/or satellite ephemeris errors vary over the region covered by the network. The control center computer processor then applies a process which interpolates the atmospheric and/or satellite ephemeris errors at any given point within the network coverage area and generates a pseudo range correction comprising the actual pseudo ranges that can be used to create a virtual reference station. The control center then performs a series of calculations and creates a set of correction models that provide the rover with the means to estimate the ionospheric path delay from each satellite in view from the rover, and to take account other error contributions for those same satellites at the current instant in time for the rover&#39;s location. 
     The rover is configured to couple a data-capable cellular telephone to its internal signal processing system. The surveyor operating the rover determines that he needs to activate the VRS process and initiates a call to the control center to make a connection with the processing computer. The rover sends its approximate position, based on raw GNSS data from the satellites in view without any corrections, to the control center. Typically, this approximate position is accurate to approximately 4-7 meters. The surveyor then requests a set of “modeled observables” for the specific location of the rover. The control center performs a series of calculations and creates a set of correction models that provide the rover with the means to estimate the ionospheric path delay from each satellite in view from the rover, and to take into account other error contributions for those same satellites at the current instant in time for the rover&#39;s location. In other words, the corrections for a specific rover at a specific location are determined on command by the central processor at the control center and a corrected data stream is sent from the control center to the rover. Alternatively, the control center may instead send atmospheric and ephemeris corrections to the rover which then uses that information to determine its position more precisely. 
     These corrections are now sufficiently precise that the high performance position accuracy standard of 2-3 cm may be determined, in real time, for any arbitrary rover position. Thus the GNSS rover&#39;s raw GNSS data fix can be corrected to a degree that makes it behave as if it were a surveyed reference location; hence the terminology “virtual reference station.” An example of a network RTK system in accordance with embodiments of the present invention is described in U.S. Pat. No. 5,899,957, entitled “Carrier Phase Differential GPS Corrections Network,” by Peter Loomis, assigned to the assignee of the present patent application and incorporated as reference herein in its entirety. 
     The Virtual Reference Station method extends the allowable distance from any reference station to the rovers. Reference stations may now be located hundreds of miles apart, and corrections can be generated for any point within an area surrounded by reference stations. 
     Although the subject matter is described in a language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.