Patent Publication Number: US-11656076-B2

Title: Method of calibrating a total station using a GNSS device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application Ser. No. 62/671,934 filed May 15, 2018, U.S. Provisional Application Ser. No. 62/686,592, filed Jun. 18, 2018, and U.S. Provisional Application Ser. No. 62/798,657, filed Jan. 30, 2019, which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a portable Global Navigation Satellite System (GNSS), including Global Positioning System (GPS), GLONASS, Galileo, and other satellite navigation and positioning systems. 
     BACKGROUND OF THE INVENTION 
     Today, the number of applications utilizing GNSS information is rapidly increasing. For example, GNSS information is a valuable tool for geodesists. Geodesists commonly use GNSS devices to determine the location of a point of interest anywhere on, or in the vicinity of, the Earth. Often, these points of interest are located at remote destinations which are difficult to access. Thus, compact, easy-to-carry positioning devices are desired. 
     GNSS receivers work by receiving data from GNSS satellites. To achieve millimeter and centimeter level accuracy, at least two GNSS receivers are needed. One receiver is positioned at a site where the position is known. A second receiver is positioned at a site whose position needs to be determined. The measurement from the first receiver is used to correct GNSS system errors at the second receiver. In post-processed mode, the data from both receivers can be stored and then transferred to a computer for processing. Alternatively, the corrections from the first receiver, the known receiver, may be transmitted in real time (via radio modems, Global System for Mobile Communications (GSM), etc.) to the unknown receiver, and the accurate position of the unknown receiver determined in real time. 
     A GNSS receiver typically includes a GNSS antenna, a signal processing section, a display and control section, a data communications section (for real-time processing), a battery, and a charger. Some degree of integration of these sections is usually desired for a handheld portable unit. 
     Another challenge of portable GNSS units is precisely positioning a GNSS antenna on the point of interest for location measurement. Previously, bulky equipment such as a separate tripod or other external hardware was used to “level” the antenna. In other systems, light low-precision antennas were used. Such devices are bulky and difficult to carry. Thus, even as portable GNSS positioning devices become more compact, they suffer from the drawback of requiring additional bulky positioning equipment. 
     Thus, for high-precision applications, the use of multiple units to house the various components required for prior GNSS systems, and the requirement for cables and connectors to couple the units, creates problems regarding portability, reliability, and durability. In addition, the systems are expensive to manufacture and assemble. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     Embodiments of the present disclosure are directed to a handheld GNSS device for determining position data for a point of interest. The device includes a housing, handgrips integral to the housing for enabling a user to hold the device, and a display screen integral with the housing for displaying image data and orientation data to assist a user in positioning the device. The device further includes a GNSS antenna and at least one communication antenna, both integral with the housing. The GNSS antenna receives position data from a plurality of satellites. One or more communication antennas receive positioning assistance data related to the position data from a base station. The GNSS antenna has a first antenna pattern, and the at least one communication antenna has a second antenna pattern. The GNSS antenna and the communication antenna(s) are configured such that the first and second antenna patterns are substantially separated. 
     Coupled to the GNSS antenna, within the housing, is at least one receiver. Further, the device includes, within the housing, orientation circuitry for generating orientation data of the housing based upon a position of the housing related to the horizon, imaging circuitry for obtaining image data concerning the point of interest for display on the display screen, and positioning circuitry, coupled to the at least one receiver, the imaging circuitry, and the orientation circuitry, for determining a position for the point of interest based on at least the position data, the positioning assistance data, the orientation data, and the image data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
         FIG.  1    illustrates a perspective view of a handheld GNSS device according to embodiments of the invention; 
         FIG.  2    illustrates another perspective view of a handheld GNSS device according to embodiments of the invention; 
         FIG.  3    illustrates a back view of a handheld GNSS device including a display screen for a user according to embodiments of the invention; 
         FIG.  4    illustrates a bottom view of a handheld GNSS device according to embodiments of the invention; 
         FIG.  5    illustrates a top view of a handheld GNSS device according to embodiments of the invention; 
         FIG.  6    illustrates a side view of a handheld GNSS device including handgrips for a user according to embodiments of the invention; 
         FIG.  7    illustrates a front view of a handheld GNSS device including a viewfinder for a camera according to embodiments of the invention; 
         FIG.  8    illustrates an exploded view of a handheld GNSS device including a viewfinder for a camera according to embodiments of the invention; 
         FIG.  9 A  illustrates an exemplary view of the display screen of a handheld GNSS device including elements used for positioning the device; 
         FIG.  9 B  illustrates another exemplary view of the display screen of a GNSS handheld device oriented horizontally and above a point of interest; 
         FIG.  10    illustrates a flowchart of a method for measuring position using a handheld GNSS device according to embodiments of the invention; 
         FIG.  11    illustrates a logic diagram showing the relationships between the various components of a handheld GNSS device according to embodiments of the invention; and 
         FIG.  12    illustrates a typical computing system that may be employed to implement some or all of the processing functionality in certain embodiments. 
         FIG.  13 A  depict various views of an exemplary total station coupled with and without an exemplary GNSS device. 
         FIG.  13 B  depict various views of an exemplary total station coupled with and without an exemplary GNSS device. 
         FIG.  13 C  depict various views of an exemplary total station coupled with and without an exemplary GNSS device. 
         FIG.  13 D  depict various views of an exemplary total station coupled with and without an exemplary GNSS device. 
         FIG.  13 E  depict various views of an exemplary total station coupled with and without an exemplary GNSS device. 
         FIG.  14 A  illustrates an occupation point and a backsight point during backsight calibration. 
         FIG.  14 B  depict various stages of backsight calibration. 
         FIG.  14 C  depict various stages of backsight calibration. 
         FIG.  14 D  depict various stages of backsight calibration. 
         FIG.  14 E  depict various stages of backsight calibration. 
         FIG.  14 F  illustrates an exemplary process for using a GNSS device and total station automatically together for backsight calibration. 
         FIG.  15 A  illustrates an occupation point and two known points during resect calibration. 
         FIG.  15 B  depicts various stages of resect calibration. 
         FIG.  15 C  illustrates various information about an occupation point and two known points during resect calibration. 
         FIG.  15 D  illustrates an exemplary process for using a GNSS device and total station automatically together for resect calibration. 
         FIG.  16 A  depicts various stages of astro-seek calibration. 
         FIG.  16 B  depicts various stages of astro-seek calibration. 
         FIG.  16 C  depicts various stages of astro-seek calibration. 
         FIG.  16 D  depicts various stages of astro-seek calibration. 
         FIG.  17 A  illustrate various information being displayed during a collection phase using a GNSS device and total station. 
         FIG.  17 B  illustrate various information being displayed during a collection phase using a GNSS device and total station. 
         FIG.  18 A  depicts various stages of a stakeout of a region using a GNSS device and total station. 
         FIG.  18 B  depicts various stages of a stakeout of a region using a GNSS device and total station. 
         FIG.  18 C  depicts various stages of a stakeout of a region using a GNSS device and total station. 
         FIG.  18 D  depicts various stages of a stakeout of a region using a GNSS device and total station. 
         FIG.  19    illustrates an exemplary process for calibrating the alignment between a camera module and a laser module of a total station. 
     
    
    
     In the following description, reference is made to the accompanying drawings which form a part thereof, and which illustrate several embodiments of the present invention. It is understood that other embodiments may be utilized and structural and operational changes may be made without departing from the scope of the present invention. The use of the same reference symbols in different drawings indicates similar or identical items. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is presented to enable a person of ordinary skill in the art to make and use the various embodiments. Descriptions of specific devices, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the invention as claimed. Thus, the various embodiments are not intended to be limited to the examples described herein and shown, but are to be accorded the scope consistent with the claims. 
     Embodiments of the invention relate to mounting a GNSS antenna and communication antennas in a single housing. The communication antennas are for receiving differential correction data from a fixed or mobile base transceiver, as described in U.S. patent application Ser. No. 12/360,808, assigned to the assignee of the present invention, and incorporated herein by reference in its entirety for all purposes. Differential correction data may include, for example, the difference between measured satellite pseudo-ranges and actual pseudo-ranges. This correction data received from a base station may help to eliminate errors in the GNSS data received from the satellites. Alternatively, or in addition, the communication antenna may receive raw range data from a moving base transceiver. Raw positioning data received by the communication antenna may be, for example, coordinates of the base and other raw data, such as the carrier phase of a satellite signal received at the base transceiver and the pseudo-range of the satellite to the base transceiver. 
     Additionally, a second navigation antenna may be connected to the handheld GNSS device to function as the primary navigation antenna if the conditions and/or orientation do not allow the first GNSS antenna to receive a strong GNSS signal. 
     The communication antenna is configured such that its antenna pattern is substantially separated from the antenna pattern of the GNSS antenna such that there is minimal or nearly minimal mutual interference between the antennas. As used herein, “substantial” separation may be achieved by positioning the communication antenna below the main ground plane of the GNSS antenna, as shown in  FIG.  1   . According to embodiments of the invention, a substantial separation attenuates interference between the communication antenna and the GNSS antenna by as much as 40 dB. Furthermore, the communication antenna and the GNSS antenna are positioned such that the body of the user holding the GNSS device does not substantially interfere with the GNSS signal. 
     Moreover, as mentioned above, to properly measure the position of a given point using a GNSS-based device, the GNSS antenna must be precisely positioned so that the position of the point of interest may be accurately determined. To position a GNSS device in such a manner, external hardware, such as a tripod, is commonly used. Such hardware is bulky and difficult to carry. Thus, according to embodiments of the invention, compact positioning tools, included in the single unit housing, are useful for a portable handheld GNSS device. 
     As such, various embodiments are described below relating to a handheld GNSS device. The handheld GNSS device may include various sensors, such as a camera, distance sensor, and horizon sensors. A display element may also be included for assisting a user to position the device without the aid of external positioning equipment (e.g., a tripod or pole). 
       FIG.  1    illustrates an exemplary handheld GNSS device  100 . Handheld GNSS device  100  utilizes a single housing  102 . Several GNSS elements are integral to the housing  102  in that they are within the housing or securely mounted thereto. A securely mounted element may be removable. Housing  102  allows the user to hold the handheld GNSS device  100  similar to the way one would hold a typical camera. In one example, the housing  102  may include GNSS antenna cover  104  to cover a GNSS antenna  802  (shown in  FIG.  8   ) which may receive signals transmitted by a plurality of GNSS satellites and used by handheld GNSS device  100  to determine position. The GNSS antenna  802  is integral with the housing  102  in that it resides in the housing  102  under the GNSS antenna cover  104 . 
     In one example, GNSS antenna  802  may receive signals transmitted by at least four GNSS satellites. In the example shown by  FIG.  1   , GNSS antenna cover  104  is located on the top side of handheld GNSS device  100 . An exemplary top side view of the handheld GNSS device  100  is illustrated in  FIG.  5   . 
     Handheld GNSS device  100  further includes covers for communication antennas  106  integral with the housing  102 . In embodiments of the invention there may be three such communication antennas, including GSM, UHF, and WiFi/Bluetooth antennas enclosed beneath covers for the communication antennas  106 . 
     An exemplary exploded view of handheld GNSS device  100  is shown in  FIG.  8   . Communication antennas  806  are positioned beneath the covers  106 . The GSM and UHF antennas may be only one-way communication antennas. In other words, the GSM and UHF antenna may only be used to receive signals, but not transmit signals. The WiFi antenna may allow two-way communication. The communication antennas  806  receive positioning assistance data, such as differential correction data or raw positioning data from base transceivers. 
     In the example shown in  FIG.  1   , the GNSS antenna cover  104  is located on the top of the housing  102 . In the same example of  FIG.  1   , the communication antenna covers  106  are located on the front of the housing  102 . 
     Handheld GNSS device  100  may further include at least one handgrip  108 . In the example shown in  FIG.  1   , two handgrips  108  are integral to the housing  102 . The handgrips  108  may be covered with a rubber material for comfort and to reduce slippage of a user&#39;s hands. 
     The GNSS antenna cover  104 , the communication antenna covers  106  and the handgrips  108  are shown from another view in the exemplary front view illustrated in  FIG.  7   . A front camera lens  110  is located on the front side of the handheld GNSS device  100 . A second bottom camera lens  116  may be located on the bottom side of the handheld GNSS device  100  in the example shown in  FIG.  4   . The camera included may be a still or video camera. 
     The handgrips  108 , in certain embodiments, may also be positioned to be near to the communication antenna covers  106 . Handgrips  108  are shown in a position, as in  FIG.  6   , that, when a user is gripping the handgrips  108 , the user minimally interferes with the antenna patterns of GNSS antenna  802  and communication antennas  806 . For example, the user&#39;s hands do not cause more than −40 dB of interference while gripping the handgrips  108  in this configuration, e.g., with the handgrips  108  behind and off to the side of the communication antenna covers  106 . 
     As shown in  FIG.  2    and  FIG.  3   , handheld GNSS device  100  may further include display  112  for displaying information to assist the user in positioning the device. Display  112  may be any electronic display such as a liquid crystal (LCD) display, light emitting diode (LED) display, and the like. Such display devices are well-known by those of ordinary skill in the art and any such device may be used. In the example shown by  FIG.  2   , display  112  is integral with the back side of the housing  102  of handheld GNSS device  100 . 
     Handheld GNSS device  100  may further include a camera for recording still images or video. Such recording devices are well-known by those of ordinary skill in the art and any such device may be used. In the example illustrated in  FIG.  1   , front camera lens  110  is located on the front side of handheld GNSS device  100 . A more detailed description of the positioning of front camera lens  110  is provided in U.S. patent application Ser. No. 12/571,244, filed Sep. 30, 2009, which is incorporated herein by reference in its entirety for all purposes. In one example, display  112  may be used to display the output of front camera lens  110 . 
     With reference to  FIG.  4   , handheld GNSS device  100  may also include a second bottom camera lens  116  on the bottom of handheld GNSS device  100  for viewing and alignment of the handheld GNSS device  100  with a point of interest marker. The image of the point of interest marker may also be recorded along with the GNSS data to ensure that the GNSS receiver  808  was mounted correctly, or compensate for misalignment later based on the recorded camera information. 
     Handheld GNSS device  100  may further include horizon sensors (not shown) for determining the orientation of the device. The horizon sensors may be any type of horizon sensor, such as an inclinometer, accelerometer, and the like. Such horizon sensors are well-known by those of ordinary skill in the art and any such device may be used. In one example, a representation of the output of the horizon sensors may be displayed using display  112 . A more detailed description of display  112  is provided below. The horizon sensor information can be recorded along with GNSS data to later compensate for mis-leveling of the antenna. 
     Handheld GNSS device  100  may further include a distance sensor (not shown) to measure a linear distance. The distance sensor may use any range-finding technology, such as sonar, laser, radar, and the like. Such distance sensors are well-known by those of ordinary skill in the art and any such device may be used. 
       FIG.  4    illustrates a bottom view of the handheld GNSS device  100  according to embodiments of the invention. The handheld GNSS device  100  may be mounted on a tripod, or some other support structure, by a mounting structure such as three threaded bushes  114 , in some embodiments of the invention. 
       FIG.  8    illustrates an exploded view of the handheld GNSS device  100 . When assembled, GNSS antenna  802  is covered by the GNSS antenna cover  104 , and the communication antennas  806  are covered by the communication antenna covers  106 . 
       FIG.  9 A  illustrates an exemplary view  900  of display  112  for positioning handheld GNSS device  100 . In one example, display  112  may display the output of camera. In this example, the display of the output of camera lens  116  or  110  includes point of interest marker  902 . As shown in  FIG.  9 A , point of interest marker  902  is a small circular object identifying a particular location on the ground. In the examples provided herein, we assume that the location to be measured is located on the ground, and that the point of interest is identifiable by a visible marker (e.g., point of interest marker  902 ). The marker may be any object having a small height value. For instance, an “X” painted on the ground or a circular piece of colored paper placed on the point of interest may serve as point of interest marker  902 . 
     In another example, display  112  may further include virtual linear bubble levels  904  and  906  corresponding to the roll and pitch of handheld GNSS device  100 , respectively. Virtual linear bubble levels  904  and  906  may include virtual bubbles  908  and  910 , which identify the amount and direction of roll and pitch of handheld GNSS device  100 . Virtual linear bubble levels  904  and  906  and virtual bubbles  908  and  910  may be generated by a CPU  1108  and overlaid on the actual image output of the camera. In one example, positioning of virtual bubbles  908  and  910  in the middle of virtual linear bubble levels  904  and  906  indicate that the device is positioned “horizontally.” As used herein, “horizontally” refers to the orientation whereby the antenna ground plane is parallel to the local horizon. 
     In one example, data from horizon sensors may be used to generate the linear bubble levels  904  and  906 . For instance, sensor data from horizon sensors may be sent to CPU  1108  which may convert a scaled sensor measurement into a bubble coordinate within virtual linear bubble levels  904  and  906 . CPU  1108  may then cause the display on display  112  of virtual bubbles  908  and  910  appropriately placed within virtual linear bubble levels  904  and  906 . Thus, virtual linear bubble levels  904  and  906  may act like traditional bubble levels, with virtual bubbles  908  and  910  moving in response to tilting and rolling of handheld GNSS device  100 . For example, if handheld GNSS device  100  is tilted forward, virtual bubble  908  may move downwards within virtual linear bubble level  906 . Additionally, if handheld GNSS device  100  is rolled to the left, virtual bubble  908  may move to the right within virtual linear bubble level  904 . However, since virtual linear bubble levels  904  and  906  are generated by CPU  1108 , movement of virtual bubbles  908  and  910  may be programmed to move in any direction in response to movement of handheld GNSS device  100 . 
     In another example, display  112  may further include planar bubble level  912 . Planar bubble level  912  represents a combination of virtual linear bubble levels  904  and  906  (e.g., placed at the intersection of the virtual bubbles  908  and  910  within the linear levels  904  and  906 ) and may be generated by combining measurements of two orthogonal horizon sensors (not shown). For instance, scaled measurements of horizon sensors may be converted by CPU  1108  into X and Y coordinates on display  112 . In one example, measurements from one horizon sensor may be used to generate the X coordinate and measurements from a second horizon sensor may be used to generate the Y coordinate of planar bubble level  912 . 
     As shown in  FIG.  9 A , display  112  may further include central crosshair  914 . In one example, central crosshair  914  may be placed in the center of display  112 . In another example, the location of central crosshair  914  may represent the point in display  112  corresponding to the view of front camera lens  110  along optical axis  242 . In yet another example, placement of planar bubble level  912  within central crosshair  914  may correspond to handheld GNSS device  100  being positioned horizontally. Central crosshair  914  may be drawn on the screen of display  112  or may be electronically displayed to display  112 . 
     Display  112  may be used to aid the user in positioning handheld GNSS device  100  over a point of interest by providing feedback regarding the placement and orientation of the device. For instance, the camera output portion of display  112  provides information to the user regarding the placement of handheld GNSS device  100  with respect to objects on the ground. Additionally, virtual linear bubble levels  904  and  906  provide information to the user regarding the orientation of handheld GNSS device  100  with respect to the horizon. Using at least one of the two types of output displayed on display  112 , the user may properly position handheld GNSS device  100  without the use of external positioning equipment. 
     In the example illustrated by  FIG.  9 A , both point of interest marker  902  and planar bubble level  912  are shown as off-center from central crosshair  914 . This indicates that optical axis  242  of camera lens  110  or  116  is not pointed directly at the point of interest and that the device is not positioned horizontally. If the user wishes to position the device horizontally above a particular point on the ground, the user must center both planar bubble level  912  and point of interest marker  902  within central crosshair  914  as shown in  FIG.  9 B . 
       FIG.  9 B  illustrates another exemplary view  920  of display  112 . In this example, virtual linear bubble levels  904  and  906  are shown with their respective virtual bubbles  908  and  910  centered, indicating that the device is horizontal. As such, planar bubble level  912  is also centered within central crosshair  914 . Additionally, in this example, point of interest marker  902  is shown as centered within central crosshair  914 . This indicates that optical axis  242  of front camera lens  110  is pointing towards point of interest marker  902 . Thus, in the example shown by  FIG.  9 B , handheld GNSS device  100  is positioned horizontally above point of interest marker  902 . 
     The bottom camera lens  116  or front camera lens  110  can be used to record images of a marker of a known configuration, a point of interest, placed on the ground. In one application, pixels and linear dimensions of the image are analyzed to estimate a distance to the point of interest. Using a magnetic compass or a MEMS gyro in combination with two horizon angles allows the three dimensional orientation of the GNSS handheld device  100  to be determined. Then, the position of the point of interest may be calculated based upon the position of the GNSS antenna  802  through trigonometry. In one embodiment, a second navigation antenna is coupled to the housing  102  of the GNSS handheld device  100  via an external jack  804  ( FIG.  8   ). The second navigation antenna can be used instead of magnetic compass to complete estimation of full three-dimensional attitude along with two dimensional horizon sensors. 
     Estimation of a distance to a point of interest can be estimated as described in U.S. patent application Ser. No. 12/571,244, which is incorporated herein by reference for all purposes. The bottom camera lens  116  may also be used. 
     If the optical axis of the camera is not pointing directly at the point of interest, the misalignment with the survey mark can be recorded and compensated by analyzing the recorded image bitmaps. 
       FIG.  10    illustrates an exemplary process  1000  for using a GNSS device and total station automatically together. A total station is an optical system to measure angle and distance from a known point to determine the location of the object targeted by the total station optical system. An encoder on the total station measures an angle, and in some cases, is calibrated to a known azimuth. 
     At block  1002 , a tripod and tribrach, or other supports, are setup at the “Occupation Point” (OP). The total station is fit into the tribrach, for example by fitting the total station&#39;s legs in the tribrach. In one example, the GNSS device is fitted on top of the total station, for example using alignment legs to have your “Total Solution” station that combines the GNSS device and the total station. This is depicted in  FIGS.  13 A- 13 E , which depict various views of a GNSS device with a total station, such as GNSS device  100 . 
     At block  1004 , the GNSS device determines the accurate position of the OP and collects other relevant information from the user (e.g., setup and/or configuration data). This position is stored and optionally displayed on the screen (e.g., see  FIG.  14 E ). 
     At block  1006 , the GNSS device is moved (e.g., by lifting and carrying the GNSS device) to the “Back Point” (BP) while the camera of the total station robotically follows the “+” sign on the back of the GNSS device (see  FIG.  17   ). The total station transmits the image data to GNSS device for optional display on the screen of the GNSS device. In some cases, the total station camera automatically focuses on the “+” sign on the GNSS device. In some cases, manual focus may override the automatic focus. While a “+” sign is used in this example, other recognizable marks may be used. 
     At block  1008 , when the GNSS device reaches the BP, the GNSS device determines the position of the BP and the total station values are recorded. The azimuth from the OP to the BP is determined and is optionally used to calibrate the total station encoders (e.g., with 10 Sec accuracy). 
     At block  1010 , the GNSS device is optionally moved back to the total station. The combined system can be used to measure any number of target points. Optionally, the total station can laser scan the area within the user-determined horizontal and vertical angle limits and create the 3-D image of the area and objects. 
     Alternatively, process  1000  can also include automatic sun seeking and calibrating feature of the total station with just a push of a button. The total station will automatically find the sun and use the azimuth to calibrate the encoders. In this example, the BP is not needed. 
       FIG.  11    illustrates an exemplary logic diagram showing the relationships between the various components of handheld GNSS device  100 . In one example, GNSS antenna  802  may send position data received from GNSS satellites to receiver  808 . Receiver  808  may convert the received GNSS satellite signals into Earth-based coordinates, such as WGS84, ECEF, ENU, and the like. GNSS receiver  808  may further send the coordinates to CPU  1108  for processing along with position assistance data received from communication antennas  806 . Communication antennas  806  are connected to a communication board  810 . Orientation data  1112  may also be sent to CPU  1108 . Orientation data  1112  may include pitch data from pitch horizon sensors and roll data from roll horizon sensors, for example. Image data  1110  from video or still camera may also be sent along to the CPU  1108  with the position data received by the GNSS antenna  802 , positioning assistance data received by communication antenna  106 , and orientation data  1112 . Distance data from a distance sensor may also be used by CPU  1108 . CPU  1108  processes the data to determine the position of the point of interest marker and provides display data to be displayed on display  112 . 
       FIG.  12    illustrates an exemplary computing system  1200  that may be employed to implement processing functionality for various aspects of the current technology (e.g., as a GNSS device, receiver, CPU  1108 , activity data logic/database, combinations thereof, and the like.). Those skilled in the relevant art will also recognize how to implement the current technology using other computer systems or architectures. Computing system  1200  may represent, for example, a user device such as a desktop, mobile phone, geodesic device, and so on as may be desirable or appropriate for a given application or environment. Computing system  1200  can include one or more processors, such as a processor  1204 . Processor  1204  can be implemented using a general or special purpose processing engine such as, for example, a microprocessor, microcontroller or other control logic. In this example, processor  1204  is connected to a bus  1202  or other communication medium. 
     Computing system  1200  can also include a main memory  1208 , such as random access memory (RAM) or other dynamic memory, for storing information and instructions to be executed by processor  1204 . Main memory  1208  also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor  1204 . Computing system  1200  may likewise include a read only memory (“ROM”) or other static storage device coupled to bus  1202  for storing static information and instructions for processor  1204 . 
     The computing system  1200  may also include information storage mechanism  1210 , which may include, for example, a media drive  1212  and a removable storage interface  1220 . The media drive  1212  may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a CD or DVD drive (R or RW), or other removable or fixed media drive. Storage media  1218  may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by media drive  1212 . As these examples illustrate, the storage media  1218  may include a computer-readable storage medium having stored therein particular computer software or data. 
     In alternative embodiments, information storage mechanism  1210  may include other similar instrumentalities for allowing computer programs or other instructions or data to be loaded into computing system  1200 . Such instrumentalities may include, for example, a removable storage unit  1222  and an interface  1220 , such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units  1222  and interfaces  1220  that allow software and data to be transferred from the removable storage unit  1222  to computing system  1200 . 
     Computing system  1200  can also include a communications interface  1224 . Communications interface  1224  can be used to allow software and data to be transferred between computing system  1200  and external devices. Examples of communications interface  1224  can include a modem, a network interface (such as an Ethernet or other NIC card), a communications port (such as for example, a USB port), a PCMCIA slot and card, etc. Software and data transferred via communications interface  1224 . Some examples of a channel include a phone line, a cellular phone link, an RF link, a network interface, a local or wide area network, and other communications channels. 
     In this document, the terms “computer program product” and “computer-readable storage medium” may be used generally to refer to media such as, for example, memory  1208 , storage media  1218 , or removable storage unit  1222 . These and other forms of computer-readable media may be involved in providing one or more sequences of one or more instructions to processor  1204  for execution. Such instructions, generally referred to as “computer program code” (which may be grouped in the form of computer programs or other groupings), when executed, enable the computing system  1200  to perform features or functions of embodiments of the current technology. 
     In an embodiment where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into computing system  1200  using, for example, removable storage drive  1222 , media drive  1212  or communications interface  1224 . The control logic (in this example, software instructions or computer program code), when executed by the processor  1204 , causes the processor  1204  to perform the functions of the technology as described herein. 
       FIGS.  13 A- 13 E  depict various views of an exemplary total station coupled with and without an exemplary GNSS device.  FIG.  13 A  illustrates an exemplary total station  1301  (e.g. “J-Mate”). A total station is an optical system to measure angle and distance from a known point to determine the location of the object targeted by the total station optical system. In some embodiments, the total station  1301  comprises a camera  1321  that automatically identifies targets in its field of view; a laser module  1322  that measures the distance between the total station and targets by scanning and examining the areas around the intended targets to ensure reliable identification and measurement; two motors  1323  that rotate the camera portion of the total station vertically and rotate the main portion of the total station horizontally; precision encoders that measure that vertical and horizontal angles to the target; and precision level vials  1324  that indicate whether the main portion of the total station or the camera portion are level with the ground. 
     In some embodiments, the axis of the laser module  1322  (e.g., the light propagation axis) and the axis of the camera  1321  (e.g., the optical axis of the lens) need to be aligned. Conventionally, the calibration of the alignment is performed by the manufacturer of the total station unit (e.g., in a factory before the total station unit is purchased by a user). In some embodiments, the total station  1301  allows the user to calibrate the alignment after purchasing the total station unit at any time without the assistance of the manufacturer. This way, the user does not need to send the total station unit to the manufacturer for re-calibration. 
       FIG.  19    illustrates an exemplary process  1900  for calibrating the alignment between a laser module (e.g., laser module  1322 ) and a camera module (e.g., camera  1321 ) of a total station, in accordance with some embodiments of the invention. In some embodiments, the method can be triggered in response to a user input, for example, a selection of a hardware button or a software button corresponding to the calibration functionality. In some embodiments, the method can be triggered when certain conditions are met (e.g., when misalignment between the camera module and the laser module is detected). 
     At block  1902 , the total station receives a user input. In some embodiments, the user input is indicative of a selection of the calibration functionality. In some embodiments, the user input can comprise a selection of a hardware button or a software button corresponding to the calibration functionality. 
     At block  1904 , in response to the user input, the total station automatically locates a point (e.g., the center point) of an object using the camera module of the total station. For example, the total station moves the camera (e.g., using motors such as motors  1323 ) such that the point (e.g., the center point) of the object is at the center of the camera screen. The orientation information of the camera (e.g., horizontal and vertical angles) is recorded by the total station. 
     In some embodiments, the object used in process  1900  is a QR image. Any object having a distinct view (e.g., having a clear outline such that a particular point on the object can be identified) can be used. 
     At block  1906 , in response to the user input, the total station automatically locates the same point (e.g., the center point) of the same object using the laser module of the total station. For example, the total station moves the laser module (e.g., using motors such as motors  1323 ) to bring the laser beam to coincide with the point (e.g., the center point) of the object. The orientation information of the laser module (e.g., horizontal and vertical angles) is recorded by the total station. 
     At block  1908 , the total station automatically calibrates the alignment between the camera module and the laser module based on the recorded orientation information in blocks  1904  and  1906 . Specifically, the difference between the recorded orientation information in blocks  1904  and  1906  is used for calibration and alignment (compensation) of the camera module and the laser module. Accordingly, the total station adjusts the cross-hair view of the camera to match that of the propagation axis of the laser module. 
       FIGS.  13 B- 13 D  illustrate various views of an exemplary total station coupled with an exemplary GNSS device. In some embodiments, the coupled system  1302  comprises an exemplary total station  1301  (e.g. “J-Mate”) secured on top of a tripod  1331  that stands on the ground, and an exemplary GNSS device  100  (e.g. “TRIUMPH-LS”) secured on top of the total station  1301  by registering a mounting structure such as three threaded bushes  114  from the bottom of the GNSS device  100  to the matching features on the top of the total station  1301 . The display  112  displays the view from the camera  1321 . 
       FIG.  13 E  illustrates a view  1303  of an exemplary total station coupled with an exemplary GNSS device and an exemplary plus sign target. In some embodiments, the augmented coupled system  1303  comprises the coupled system  1302  and a plus sign target  1333  attached to the GNSS device  100 . 
     In some embodiments, a user of the total station  1301  establishes its position and calibrates its vertical and horizontal encoders before measuring previously unknown points. The calibration comprises an automated process that is an improvement over processes performed in conventional total stations. Methods of calibration include: backsighting, resecting, and astro-seeking. After the total station  1301  has been calibrated, the user can optionally measure previously unknown points or perform a stakeout. 
     If GNSS signals are available at the job site of interest, the user may optionally use backsighting to calibrate the total station  1301 . During backsight calibration, GNSS measurements are taken at two locations around the job site, an occupation point (OP)  1411  and a backsight point (BP)  1413 , as shown in  FIG.  14 A . In some embodiments, a suitable choice for a backsight point is one that is in line of sight with the occupation point. 
       FIG.  14 F  illustrates an exemplary process  1450  for using a GNSS device and total station automatically together for backsight calibration. An encoder on the total station measures an angle, and in some cases, is calibrated to a known azimuth. At block  1452 , a tripod  1331  and tribrach  1331 , or other supports, are setup at the occupation point  1411 . The total station  1301  is fit into the tribrach  1331 , for example by fitting the total station&#39;s legs in the tribrach. In one example, the GNSS device  101  is fitted on top of the total station  1301 , for example using alignment legs  114  to have a “total solution” combination of the GNSS device  101  and the total station  1301 , as shown in  FIG.  14 B . This is depicted in  FIGS.  13 A- 13 E , which depict various views of a GNSS device  100  with a total station  1301 . 
     At block  1454 , the GNSS device  101  determines the accurate position of the occupation point  1411  and collects other relevant information from the user (e.g., setup and/or configuration data). In some embodiments, the RTK Survey feature of the GNSS device  100  quickly determines the accurate location of the occupation point  1411 . The user may optionally use a custom base station or any public RTN. This position is stored and optionally displayed on the screen (e.g., see  FIG.  14 E ). 
     At block  1456 , the user slides the plus (“+”) sign target  1333  on top of the GNSS device  100 , physically separates the GNSS device  100  and plus sign target combination from the total station  1301 , and moves (e.g., by lifting and carrying the GNSS device  101 ) the combination to the backsight point  1413 , as shown in  FIG.  14 C . In some embodiments, the camera  1321  of the total station  1301  robotically follows the plus sign target  1333 . The total station  1301  transmits the image data to the GNSS device  101  for optional display on the screen  112  of the GNSS device  101 , as shown in  FIG.  14 D . In some cases, the total station camera automatically focuses on the plus sign on the GNSS device. This allows the user to confirm that the camera  1321  is following the plus sign target  1333 . In some embodiments, if the camera  1321  loses sight of the plus sign target  1333 , the user may remotely control the camera  1321  to so that the plus sign target  1333  is back in view. In some cases, manual focus may override the automatic focus. While a plus (“+”) sign is used in this example, other recognizable marks may be used in some embodiments. 
     At block  1458 , when the GNSS device  101  reaches the backsight point  1413 , the GNSS device  101  determines the position of the backsight point  1413  and the position is recorded. The azimuth from the occupation point  1411  to the backsight point  1413  is determined and is optionally used to calibrate the total station encoders (e.g., with 10-second precision). As shown in  FIG.  14 E , various information about occupation point  1411  and backsight point  1413  is displayed. 
     At block  1460 , the total station  1301  is now calibrated and ready to measure unknown locations. In some embodiments, the measurements of one of more other backsight points are made to improve the precision of the calibration. In some embodiments, if the tripod is disturbed after this calibration is complete, an LED indicator on the front of the total station  1301  will blink to show that re-calibration is required. The user may optionally replace the GNSS device  100  on top of the total station  1301  at the occupation point  1411  and proceed to measure as many target points as the job requires. In some embodiments, the GNSS device  100  is henceforth used as a controller that the user may hold in his or her hand. 
     In some embodiments, if GNSS signals are not available at the occupation point  1411 , the user may optionally use resecting to calibrate the total station  1301 . During resecting calibration, location information from two known points, point  1   1513  and point  2   1515 , and their distances and orientation from occupation point  1411  are used to establish accurate position information about the occupation point  1411  and to calibrate the encoders of the total station  1301 , as shown in  FIG.  15 A . In some embodiments, a suitable choice for a set of backsight points has both points in line of sight with the occupation point. 
       FIG.  15 D  illustrates an exemplary process  1550  for using a GNSS device  101  and total station automatically together for resect calibration. An encoder on the total station measures an angle, and in some cases, is calibrated to a known azimuth. At block  1552 , a tripod  1331  and tribrach  1331 , or other supports, are setup at the occupation point  1411 . The total station  1301  is fit into the tribrach  1331 , for example by fitting the total station&#39;s legs in the tribrach. In one example, the GNSS device  101  is fitted on top of the total station  1301 , for example using alignment legs  114  to have a “total solution” combination of the GNSS device  101  and the total station  1301 , as shown in  FIG.  14 B . This is depicted in  FIGS.  13 A- 13 E , which depict various views of a GNSS device  100  with a total station  1301 . 
     At block  1554 , the user slides the plus (“+”) sign target  1333  on top of the GNSS device  100 , physically separates the GNSS device  100  and plus sign target combination from the total station  1301 , and moves (e.g., by lifting and carrying the GNSS device  101 ) the combination to the known point  1   1513 , as shown in  FIG.  14 C . In some embodiments, the camera  1321  of the total station  1301  robotically follows the plus sign target  1333 . The total station  1301  transmits the image data to the GNSS device  101  for optional display on the screen  112  of the GNSS device  101 , as shown in  FIG.  14 D . In some cases, the total station camera automatically focuses on the plus sign on the GNSS device. This allows the user to confirm that the camera  1321  is following the plus sign target  1333 . In some cases, manual focus may override the automatic focus. While a plus (“+”) sign is used in this example, other recognizable marks may be used in some embodiments. 
     At block  1556 , when the GNSS device  101  reaches the known point  1   1513 , the GNSS device  101  determines the distance and azimuth from the occupation point  1411  to the known point  1   1513  and this information is recorded. At block  1558 , the user moves the combination of the GNSS device  101  and the plus sign target  1333  to the known point  2   1515 . At block  1560 , when the GNSS device  101  reaches the known point  2   1515 , the GNSS device  101  determines the distance and azimuth from the occupation point  1411  to the known point  2   1515  and this information is recorded. 
       FIG.  15 B  depicts various stages of resect calibration. As shown in  FIG.  15 C , various information about occupation point  1411 , known point  1   1513  (e.g. “first backsight point”), and known point  2   1515  (e.g. “second backsight point”) is displayed. At block  1562 , the total station  1301  is now calibrated and ready to measure unknown locations. 
     In some embodiments, the user may optionally use astro-seeking to calibrate the total station  1301 . During astro-seeking calibration, orientation information from the occupation point  1411  to the sun  1611  or from other astronomical objects is used to establish accurate position information about the occupation point  1411  and to calibrate the encoders of the total station  1301 . In some embodiments, the user first attaches a sun filter to the total station  1301 . The sun filter protects the camera  1321  from strong light. In some embodiments, a sun filter is built into the camera lens, where the lens automatically adjusts its filter when strong light is detected. As shown in  FIG.  16 C , total station  1301  automatically finds the sun  1611 , and then uses its orientation to automatically calibrate the encoders. In some embodiments, the total station  1301  automatically finds the sun by rotating the camera  1321 , detecting the strength of light, and then continuing to rotate the camera  1321  in the direction of the strongest light until light strength is at a maximum. In some embodiments, the total station stores information about the sun&#39;s relative position in the sky based on date, time, and location on earth. As shown in  FIG.  16 C , various information about occupation point  1411  and the sun  1611  (e.g. “backsight point”) is displayed. 
     After calibration has been completed, for example by backsighting, resecting, astro-seeking, or other means, the total station  1301  is ready to measure (“collect”) location information about unknown points.  FIGS.  17 A &amp;  17 B  illustrate various information being displayed during a collection phase using a GNSS device and total station. 
     After calibration has been completed, for example by backsighting, resecting, astro-seeking, or other means, the total station  1301  is ready to stakeout a region in some embodiments. The functions and features of the total station  1301  stakeout are very similar to the conventional GNSS stakeout. In a conventional GNSS stakeout, RTK solutions guide the user to the stake points, but with the system disclosed herein, the camera  1321  follows the plus sign target  1333  and then the encoders and laser measurements provide guidance to the stakeout features like visual stakeout and other types of stakeout.  FIGS.  18 A- 18 D  depicts various stages of a stakeout of a region using a GNSS device and total station. 
     In some embodiments, total station  1301  is also a camera-aided smart laser scanner. The camera  1321  identifies redundant points that do not need to be scanned but instead copies or interpolates from other readings without loss of information. For example, if the camera  1321  identifies a completely uniform area, it only scans the four corners of the area and interpolates in between. This feature can increase the effective speed of the scanner to be much higher than its native 10 points per second speed. This feature can also be used to find items such wires, poles, and “closest-in-view” items and measure them automatically. 
     In some embodiments, the total station  1301  scans around an intended target to measure the distance to the target and ensure that the target is found and measured reliable. The total station  1301  scans a circle around the target and shows the minimum and maximum distance from the total station  1301  to ensure that it is not measuring a wrong point, especially around the edge of a wall. 
     It will be appreciated that, for clarity purposes, the above description has described embodiments with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processors, or domains may be used. For example, functionality illustrated to be performed by separate processors or controllers may be performed by the same processor or controller. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization. 
     Furthermore, although individually listed, a plurality of means, elements, or method steps may be implemented by, for example, a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather the feature may be equally applicable to other claim categories, as appropriate. 
     Although a feature may appear to be described in connection with a particular embodiment, one skilled in the art would recognize that various features of the described embodiments may be combined. Moreover, aspects described in connection with an embodiment may stand alone.