Patent Publication Number: US-2010131237-A1

Title: Laser distance measuring grade rod

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/200,151, filed Nov. 24, 2008 (Nov. 24, 2008). 
    
    
     SEQUENCE LISTING 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     THE NAMES OR PARTIES TO A JOINT RESEARCH AGREEMENT 
     Not applicable. 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to grade rods used in the construction and survey industry. More specifically the present invention relates to grade rods integrated into a laser distance measuring system. 
     2. Discussion of Related Art Including Information Disclosed Under 37 CFR 1.97, 1.98 
     Laser alignment systems have been used in construction and surveying for years. Typically, a remote laser transmitting device is used to create a reference plane or reference cone, and at least one remote laser light detector is used to locate the position of the plane or cone. The laser light detector is typically attached with a friction clamp to a grade rod and uses a photodetector to provide visual and or audio indicators in the form of up/down arrows and/or tones to assist in centering the laser plane at a predetermined and fixed reference position on the laser light detector, generally referred to as the “on grade” position. After the laser light detector has been positioned on the grade rod such that the laser plane is centered on the on grade position, markings aligned with this position that are on the friction clamp transfer this on grade position to the grade rod which then gives a measure of distance between the laser plane and given point on the target surface. The typical grade rod used to enable this procedure is simply an elongated member with markings spaced evenly, a predetermined distance apart that coincide with a given units and scale. 
     Prior art grade rods used in construction and survey industry contain several disadvantages. One inherent disadvantage is the need to loosen the frictional guide mount to allow the laser receiver to be slid up and down the grade rod in order to align the laser receiver with the reference plane. Often the laser receiver is brought out of alignment as the frictional mount is tightened as the laser receiver is not concentric with the grade rod and any loosening or tightening of the mount causes the laser receiver to rock about the mounting point. This effect is exasperated due to the fact current laser receivers offer sensitivities up to +/− 1/32″. The situation becomes even more difficult if the laser plane is outside arm&#39;s reach (if the user is in a depression such as a hole or ditch.) In this case the laser light detector must be approximately placed on the graduated rod and lifted into the laser plane and if centering is not achieved the graduated rod is lowered in order to adjust the position of the laser light detector and lifted back into the laser plane. This process is repeated until centering is achieved. This is a time consuming process that requires adjusting the laser light detector up and down the graduated rod while monitoring the audio and visual aids until centering is achieved. 
     Another disadvantage of prior art grade rods is they require the user to obtain several grade rods to handle the numerous units (English, Metric) and scales ( 1/10″, 1/16, mm, cm, etc. . . . ) used in the construction and survey industry. 
     Another disadvantage prior art grade rods is the human error that often occurs in estimating and transferring the reference position onto the grade rod. This can result in considerable expense and frustration for the user. 
     Another disadvantage of prior art grade rods stems from their geometry, which makes them long, cumbersome, and inconvenient to transport to specific areas on the site. For example, with concrete flatwork it is often desirable to use a laser light receiver to verify tolerances while the concrete is being placed. In this situation, use of a graduated rod is difficult since there is nowhere to place the rod when not in use, and walking through wet concrete is highly undesirable. 
     Another disadvantage of prior art grade rods is the limitations in the maximum distance they are able to measure between the laser plane and a given surface. This is because at some point a graduated rod becomes too long to be manageable. 
     Another disadvantage in prior art grade rods is the difficulty involved in measuring the distance between the laser plane and a given surface located above the laser plane. Measuring the distance between the laser plane and a given surface above the laser plane is desirable to verify whether ceilings, beams, pipes or other construction members located above the laser plane are level or have a predetermined slope. This is made difficult by prior art grade rods since they require holding the grade rod in the air while adjusting the laser light detector up and down the graduated rod in order to center the laser plane on the reference position. In many cases the target surface is located too far above the reference beam for a grade rod to be used. 
     Another disadvantage of prior art grade rods is their inability to provide relative measurements and mathematically manipulate current measurements in relation to past measurements. In the construction and survey industries, it often more desirable to know the relative distance (i.e., the differences in heights between two points on the target surface) rather than a sequence of measurements that provide the distance between the laser plane and various points on the target surface. 
     Still another disadvantage of prior art grade rods is that they must be held plumb in order for an accurate vertical height measurement to be determined. 
     The foregoing background discussion reflects the current state of the art of which the present inventor is aware. Reference to, and discussion of, the prior art methods and systems is intended to aid in discharging Applicant&#39;s acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. However, it is respectfully submitted that none of the known art discloses, teaches, suggests, shows, or otherwise renders obvious the invention described and claimed herein. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, it is a principal purpose of the present invention to provide a grade rod integrated into a laser distance measuring system, which provides a measure of distance from the on grade position of an external laser receiver to a user-defined target point without requiring the use of a pole or rod to adjust the position of the external laser receiver on the grade rod or to interpret measurements. 
     Another object and advantage of the present invention is to provide a grade rod integrated with a gravity reference device, such that the grade rod need not be held plumb over the user-defined target in order to determine the vertical distance between the on grade position of the external laser receiver and the target point. 
     It is yet another object of the present invention to provide a grade rod integrated into a communications device, which will allow an external laser receiver with compatible communication abilities to send a command signal to capture a measurement when the laser receiver&#39;s on grade position is aligned with a laser plane; then, if the external laser receiver is of the kind that is able to substantially determine a measure of the distance the on grade position is either above or below the laser plane at substantially the same time that the command signal is sent, then this distance value will be relayed to provide a corrected distance, wherein the corrected distance is substantially equal to a measure of the distance from the point at which the laser receiver detected the laser plane (at the time the capture command was sent) to the user-defined target point. 
     Additional advantages and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with practice of the invention. 
     To achieve the foregoing and other advantages, and in accordance with a first preferred embodiment of the present invention, a grade rod is provided that comprises: a reference position aligned with the on grade position of an external laser receiver; a housing configured to accept the external laser receiver and to allow the external laser receiver&#39;s on grade position to be aligned with the reference position on the housing; a distance measuring device that uses a laser light receiver and at least one laser light photosensor, the distance measuring device used to substantially determine a first distance between the laser light photosensor and an external predetermined target point, the laser light photosensor generating a first signal if receiving reflected laser light energy from the laser light photosensor; a processing circuit that receives the first signal; and a display device to display measured distance values. 
     In a second preferred embodiment of the present invention, a grade rod is provided that comprises: a reference position aligned with the on grade position of an external laser receiver; a housing configured to accept the external laser receiver and to allow the external laser receiver&#39;s on grade position to be aligned with the reference position on the housing; a distance measuring device that uses a laser light receiver and at least one laser light photosensor, the distance measuring device used to substantially determine a first distance between the laser light photosensor and an external predetermined target point, the laser light photosensor generating a first signal if receiving reflected laser light energy from the laser light photosensor; a gravity sensor that generates a second signal that is substantially indicative of the housing&#39;s angular orientation with respect to gravity; a processing circuit that receives the first signal and the second signal; and a display device to display measured distance values. 
     In a third preferred embodiment of the present invention, a grade rod is provided that comprises: a reference position aligned with the on grade position of an external laser receiver; a housing configured to accept the external laser receiver and to allow the external laser receiver&#39;s on grade position to be aligned with the reference position on the housing; a distance measuring device that uses a laser light receiver and at least one laser light photosensor, the distance measuring device used to substantially determine a first distance between the laser light photosensor and an external predetermined target point, the laser light photosensor generating a first signal if receiving reflected laser light energy from the laser light photosensor; a communications device that generates a second signal when receiving a third signal from the external laser receiver; a processing circuit that receives the first signal and the second signal; and a display device to display measured distance values. 
     In a final, and fourth preferred, embodiment of the present invention, a grade rod is provided that comprises: a reference position aligned with the on grade position of an external laser receiver; a housing configured to accept the external laser receiver and to allow the external laser receiver&#39;s on grade position to be aligned with the reference position on the housing; a distance measuring device that uses a laser light receiver and at least one laser light photosensor, the distance measuring device used to substantially determine a first distance between the laser light photosensor and an external predetermined target point, the laser light photosensor generating a first signal if receiving reflected laser light energy from the laser light photosensor; a gravity sensor that generates a second signal that is substantially indicative of the housing&#39;s angular orientation with respect to gravity; a communications device that generates a third signal when receiving a fourth signal from the external laser receiver; a processing circuit that receives the first signal, the second signal, and the third signal; and a display device to display measured distance values. 
     Other advantages of the present invention will become apparent to those skilled in this art from the following description and drawings wherein there is described and shown a preferred embodiment of this invention in one of the best modes contemplated for carrying out the invention. As will be realized, the invention is capable of other modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 
     Other novel features characteristic of the invention, as to organization and method of operation, together with further objects and advantages thereof will be better understood from the following description considered in connection with the accompanying drawings, in which preferred embodiments of the invention are illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration and description only and are not intended as a definition of the limits of the invention. The various features of novelty that characterize the invention are pointed out with particularity in the claims annexed to and forming part of this disclosure. The invention does not reside in any one of these features taken alone, but rather in the particular combination of all of its structures for the functions specified. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The invention will be better understood and objects and advantages other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, wherein: 
         FIG. 1  is a front view of a distance measuring grade rod as constructed according to the principles of the present invention. 
         FIG. 2A  is a top view of a distance measuring grade rod as constructed according to the principles of the present invention. 
         FIG. 2B  is a bottom view of a distance measuring grade rod as constructed according to the principles of the present invention. 
         FIG. 2C  is a rear view of a distance measuring grade rod as constructed according to the principles of the present invention. 
         FIG. 2D  is a perspective view of a distance measuring grade rod as constructed according to the principles of the present invention 
         FIG. 3  is a front view of a distance measuring grade rod in use with an external laser receiver and its associated clamp as constructed according to the principles of the present invention. 
         FIG. 4  is a top plan view of a distance measuring grade rod in use with an external laser receiver and its associated clamp as constructed according to the principles of the present invention. 
         FIG. 5  is an upper right front perspective view of a distance measuring grade rod combined with a extendable pole in use with an external laser receiver and its associated clamp, as constructed according to the principles of the present invention. 
         FIG. 6  is a block diagram of the major internal electronics of a distance measuring grade rod as constructed according to the principles of the present invention. 
         FIG. 7  is a block diagram of the major internal electronics of a distance measuring grade rod as constructed according to the principles of the present invention. 
         FIG. 8  is a block diagram of the major internal electronics of a distance measuring grade rod as constructed according to the principles of the present invention. 
         FIG. 9  is a block diagram of the major internal electronics of a distance measuring grade rod as constructed according to the principles of the present invention. 
         FIGS. 10-13  are operational flowcharts showing use of the first through fourth preferred embodiments of the distance measuring grade rod of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to  FIGS. 1-9 , wherein like reference numerals refer to like components in the various views, there is illustrated therein a new and improved laser distance measuring grade rod, generally denominated  10  herein. 
       FIGS. 1-5 , collectively, show that the inventive apparatus  10  includes a housing  12  typically fabricated from molded plastic and configured such that it is accessible to an external laser receiver  40  and to allow the on grade position of external laser receiver  40  to be aligned with reference line  14  as shown in  FIG. 3 . This configuration is enabled by constraining the width of housing  12  about reference line  14  to that of the maximum clamp capacity of a typical laser receiver clamp  42 . This is approximately 2.25″. This configuration may also be accomplished using a mounting bracket with threaded holes for securing the laser receiver to the distance measuring grade rod apparatus  10 . The external laser receiver  40  is then attached to the bracket such that its on grade position is aligned with reference line  14 . Those with skill will immediately appreciate the many well-known ways of providing this structural configuration. 
     An annular upper pole mount  18  and an annular lower pole mount  20  are located on the top and bottom of housing  12  to allow the option of mounting apparatus  10  to an extendable pole  38 . One or more openings  24  may be disposed on any of a number of locations on the housing or in upper pole mount  18  to allow for an acoustical output device, such as the audio device  130 , shown schematically in  FIGS. 6-9 . A user interface with a set of user input keys  22  are located below these openings, allowing the user to apply power, input data, and to access certain functions of apparatus  10 . 
     Located above the user input keys is a display  16 , preferably a liquid crystal display (LCD), used to output measurements and provide useful system information, such as battery life, mode, acoustical output volume, units, and the like. A reference line  14  is located directly below display  16  and is used to properly align external laser receiver  40  with apparatus  10  such that accurate measurements from the on grade position of the external laser receiver  40  to a user-defined target point may be made. 
     Referring now especially to  FIG. 2B , a bottom view of the apparatus  10  is shown. In this view there is shown the lower pole mount  20  in which are disposed a first aperture  26  for allowing egress of transmitted energy, and a second aperture  28  for receiving reflections of the transmitted energy. It will be understood that the geometry and size of the lower pole mount  14  and the apertures  26  and  28  may be altered to enhance the ability to transmit and receive such energy. It will be further noted that the extendable pole  38  mounted to apparatus  10  using pole mounts  18 / 20  will be substantially hollow and without internal obstructions such that the transmitted energy may flow unimpeded through it. It will also be noted that apertures  26  and  28  may be located outside lower pole mount  14 . However locating the apertures within the circumference of the lower pole mount at  26 / 28  allows the transmitted energy to be reflected off the bottom of the hollow extendable pole  38  (if used), which will be advantageous in referencing surfaces with small areas such as the top of a grade stick. In addition, the use of an extendable pole will allow measurements to be easily retained by locking the length of the pole. The housing  12  and user input keys  22  can also be seen. 
       FIG. 2C  is a rear view of the apparatus  10  showing housing  12  and a battery compartment door  34 . Regular, rechargeable, or solar cells may be used as the power source for the electronic circuits contained within housing  12 . If solar cells are used, an aperture may be provided on housing  12  to receive solar energy. The upper and lower annular pole mounts,  18  and  20 , respectively, can also be seen. 
       FIG. 2A  is a top view of apparatus  10  showing housing  12  and the upper pole mount  18  with a geometry substantially equal to the lower pole mount  20 . 
       FIG. 2D  is a perspective view showing the inventive apparatus  10  mounted to extendable pole  38  that illustrates one possible geometry of housing  12  which has rounded corners and is sized to be comfortably held in one hand. While not shown in the above figures, a level vial can be positioned on housing  12  to assist the user in maintaining a plumb alignment during the measuring process. In addition, the above description applies to all of the various embodiments described below as they only differ in their internal electronics which are described in the block diagrams and in their functionality as described in the operation flowcharts. 
       FIGS. 6-9  are block diagrams depicting the functional units and operational elements of the internal electronics of first through fourth preferred embodiments of the present invention,  100 ,  200 ,  300 , and  400 , respectively. All of the embodiments employ a laser distance measuring device  110  that uses a laser light photosensor and laser light source to determine a first distance from the laser light photosensor to a user-defined target spot. There will also be a predetermined second distance defined as the distance from the laser light photosensor to reference line  14 . A third distance is the sum of the first distance and the second distance and will be substantially equal to the distance from the on grade position of an external laser receiver to the user-defined target spot when the on grade position is aligned with reference line  14 . 
     The laser distance measuring device may be configured to account for this fixed second distance in order to provide the third distance; alternatively microprocessor  120  may perform this task. There are many types of commercially available laser distance measuring devices. While some use a direct measurement of time of flight, most systems modulate a laser beam of light electronically and measure the degree of phase shift between the transmitted and reflected light. Avalanche photo diodes are typically used as photosensors to receive the reflected light due to their sensitivity to light which allows them to measure distant or dim objects or work without a special reflective target. The design of laser distance measuring device may take many forms known in the art, including those shown in U.S. Pat. Nos. 6,624,881 and 7,023,531, the disclosures of which are incorporated in their entirety by reference herein. 
     The third and fourth embodiments, shown in  FIGS. 8-9 , use a communications device  150 , which allows the transfer of data and command signals between an external laser receiver with compatible communication abilities and microprocessor  120 . This communication may be over a wire (i.e. serial, parallel) or wireless (i.e. infrared, Bluetooth, radio, etc.) taking many forms known in the art. If communication functionality is provided via wired means, then a cable receiver such as a phone or network jack may be provided on housing  12 . 
     The second and fourth embodiments, shown in  FIGS. 7 and 9 , use a gravity sensor  140  that determines the angular orientation of the apparatus with respect to gravity. Typically, gravity sensors are accelerometers that determine the magnitude of a force along three mutually orthogonal axes. An exemplary accelerometer is found in the Analog Devices ADXL330. The gravity sensor  140  may be placed in housing  12 . A suitable option is to locate the gravity sensor  140  at the base of extendable pole  38 , as it would be less prone to spurious lateral acceleration in this location, thereby allowing it to stabilize more quickly. The user could be made aware of the gravity sensor  140  condition in relation to its stability by providing audio feedback. For example, a unique sound such as a beep could be produced at an increasing frequency as the gravity sensor  140  became more unstable and could be stopped when within tolerances. This feedback would alert the user if he/she were moving the device too quickly, thus indicating when it was possible to take an accurate measurement. 
       FIG. 6  is a block diagram illustrating the principal electronic units of a first preferred embodiment of the present invention. A laser distance measuring device  110  produces a first signal, indicative of a measured distance, which is sent to microprocessor  120 . Operator keys  22  are also connected to microprocessor  120  and allow the user to capture a measurement, input data, and enable certain functions of device  10 , typically via voltage loads. Upon receipt of the first signal and user inputs via operator keys  22 , microprocessor  120  drives an acoustical output device  130  (typically a piezo electric speaker) and outputs a measured distance value to a display device  16  (typically a liquid crystal display). Microprocessor  120  will also process user inputs via user keys  22  to drive the audio device  130  if erroneous information is entered and will output system information to display  16 , such as battery level, volume, mode, and so forth. 
       FIG. 7  is a block diagram illustrating the functional electronic units of a second preferred embodiment  200  of the present invention. A laser distance measuring device  110  produces a first signal, indicative of a measured distance, which is sent to microprocessor  120 . A gravity reference device  140  produces a second signal indicative of the angular orientation of housing  12  with respect to gravity, and this signal is also sent to microprocessor  120 . Microprocessor  120  combines the first and second signals and calculates the vertical measured distance value (i.e., the measured distance value if device  200  were held substantially plumb with respect to gravity over the target point). Operator keys  22  are also connected to microprocessor  120  and allow the user to capture a measurement, input data, and enable certain functions of device  200 . Upon receipt of the first signal and second signal, and in response to user inputs, microprocessor  120  drives an acoustical output device  130  and outputs a measured distance value to display  16 . Microprocessor  120  will also process user inputs via user keys  22  to drive the audio device  130  for example if erroneous information is entered and output system information to display  16  such as battery level, volume, mode, the so forth. 
       FIG. 8  is a block diagram illustrating the principal electronic elements of a third preferred embodiment  300  of the present invention. A laser distance measuring device  110  produces a first signal, indicative of a measured distance, which is sent to microprocessor  120 . A communications device  150  connected to microprocessor  120  produces a third signal in the form of data and command signals sent from an external compatible laser receiver. If the external compatible laser receiver has the ability to pass data in the form of an offset value (which is a measure of distance the laser plane is above or below the laser receiver&#39;s on grade position at the time the capture command was sent), then microprocessor  120  will use the offset value to compute and output a “corrected first distance” value, wherein the corrected first distance is substantially equal to a measure of distance from where the laser receiver detected the laser plane (at the time the capture command was sent) to the user-defined target point. If the laser receiver has the ability to pass command signals, such as a “capture measurement” command, then microprocessor  120  will treat the command signals as it does with equivalent user commands. Operator keys  22  are also connected to microprocessor  120  and allow the user to capture a measurement, input data and enable certain functions of device  300 . Upon receipt of the first and third signals, and at times user inputs via operator keys  22 , microprocessor  120  drives an acoustical output device  130  and outputs a measured distance value to display  16 . Microprocessor  120  will also process user inputs via user keys  22  to drive the audio device  130 , such as when erroneous information is entered, and will produce an output of selected system information to display  16 , including such information as battery level, volume, mode, and so forth. 
       FIG. 9  is a block diagram illustrating the principal electronic elements of a fourth preferred embodiment  400  of the present invention. A laser distance measuring device  110  produces a first signal, indicative of a measured distance, which is sent to microprocessor  120 . A gravity reference device  140  produces a second signal indicative of the angular orientation of housing  12  with respect to gravity, and it sends this second signal to microprocessor  120 . Microprocessor  120  combines the first and second signals to calculate the vertical measured distance value (again, the measured distance value if device  400  were held substantially plumb with respect to gravity over the target point). A communications device  150  connected to microprocessor  120  produces a third signal in the form of data and command signals sent from an external compatible laser receiver. If the laser can pass data in the form of an offset value, as defined above, then microprocessor  120  will use the offset value to compute and output a corrected first distance value. If the laser receiver can pass command signals, then microprocessor  120  will treat the command signals as it does equivalent user commands. Operator keys  22  are also connected to microprocessor  120  and allow the user to capture a measurement, input data and enable certain functions of device  400 . Upon receipt of the first through third signals, as well as user inputs, microprocessor  120  drives an acoustical output device  130  and outputs a measured distance value to display  16 . 
     It will be understood that the precise circuits depicted in the above block diagrams, and discussed in this specification, could be modified to perform similar, although not exact, functions and mathematical operations without departing from the principles of the present invention. 
       FIGS. 10-13  are schematic flow charts showing the method steps employed in using the above-described first through fourth preferred embodiments of the inventive apparatus. 
       FIG. 10  is a flowchart showing the operation of the first preferred embodiment of the present invention. Apparatus  10  with electronics  100  ( FIG. 6 ) is turned on at  160 . At  162  the user attaches an external laser receiver  40  to outer housing  12  such that the on grade position of the external laser receiver  12  is aligned with reference line  14  (see also  FIGS. 1-5 ). In this configuration the distance from the reference line  14  to the target point will substantially equal the distance from the on grade position of the laser receiver  40  to the target point. The user then determines if the laser plane is outside arm&#39;s reach at  164 . 
     If the laser plane is outside arm&#39;s reach, the user next attaches  166  the extendable pole  38  to lower pole mount  20  and plumbs  168  the extendable pole by placing the base of extendable pole  38  over a given target point. Due to the thickness of the platform or base on extendable pole  12  is placed, the user will enter a mode via a key press or combination of key presses of user keys  22  that will inform microprocessor  120  to compensate for the base thickness in its measurements. Magnetic sensors can be provided to automatically detect the pole presence and relieve the user of the need to manually enter this mode. While maintaining a plumb alignment, the housing is placed into the laser plane  170  until audio or visual indicators on the laser receiver confirm that an on grade position has been achieved. The pole length is then locked  172 . 
     If the laser plane is not outside arm&#39;s reach at decision block  174 , then the user has the option of not using the extendable pole at  174 . Often it will be more convenient to use the extendable pole as it helps in stabilizing housing  12  and accessing target points with small surface areas, such as the top of grade stakes. (Pointing a laser beam at such a small target is difficult.) However, in some circumstances such as when determining if large expanses of wet concrete are on grade, using the extendable pole is difficult. In these situations the user will choose “NO” at  174  and proceed to block  184  where the user will aim device  10  at a given target point. Laser distance measuring devices often include a visual marking device that produces an easily seen beam of light to aid the user in aiming the device at a given target point. At  186  the user carefully plumbs housing  12  over the given target point. At  188  the user moves housing  12 , while still being careful to maintain a plumb alignment and to assure that the visual marker is still pointing at the given target point. The user continues moving the housing until it is in the laser plane and the on grade position is confirmed by audio or visual indicators on laser receiver  40 . The measurement is captured via user input keys  22  at block  190 , and this value is displayed at  192 . 
     Still referring to  FIG. 10 , if the user chooses YES at  174 , the user attaches the extendable pole  12  to lower pole mount  20  and at block  176  attaches the pole the pole base over a given target point. The user will also enable a mode that compensates for the thickness of the base of extendable pole  38 , as noted above. Care is taken to plumb this arrangement over the target point at  178 . At block  180  the user begins moving housing  12  into the laser plane, while taking care to maintain a plumb alignment until audio or visual indicators on laser receiver  40  confirm its on grade position. The user then locks the length of the extendable pole  38  and presses the Capture button at block  182 . This will retain the measurement as noted above. However, since the laser plane is in reach the user will also have the option of depressing one of the user keys  22  to capture and retain a measurement. The measurement is then displayed at  192 . 
       FIG. 11  is a flowchart showing operation of the second embodiment of the present invention. Apparatus  10 , with electronics  200  ( FIG. 7 ) is turned on at  260 . At  262  the user attaches an external laser receiver  40  to outer housing  12  such that the on grade position of the external laser receiver  12  is aligned with reference line  14 . In this configuration the distance from the reference line  14  to the target point will substantially equal the distance from the on grade position of the laser receiver  40  to the target point. The user then determines if the laser plane is outside arm&#39;s reach at  264 . 
     If the laser plane is outside arm&#39;s reach, at block  266  the user attaches the extendable pole  38  to lower pole mount  20  and places the base of extendable pole  38  over a given target point. Due to the thickness of the base of extendable pole  12 , the user will enter a mode via a key press or combination of key presses of user keys  22  that will inform microprocessor  120  to compensate for the base thickness in its measurements. In contrast to the first preferred embodiment, the user is not required to hold the assembly plumb because gravity reference device  140  detects the angular orientation of housing  12  and supplies this data to microprocessor  120 . Microprocessor  120  combines this data with data received from laser distance measuring device  110  to mathematically determine what the measured distance value (distance from reference line  14  to the target point) would be if the assembly were held substantially plumb over the target point. At block  270  the user begins moving housing  12  into the laser plane until audio or visual indicators on laser receiver  40  confirm that the on grade position is aligned with the laser plane. At block  272  the user then locks the length of the extendable pole  38 . This will retain the measurement, since the output of laser distance measuring device  110 , in this arrangement, will only change if the length of extendable pole  38  varies. The measurement is then displayed at  292 . 
     If the laser plane is not outside arm&#39;s reach at decision block  264 , then the user has the option of not using the extendable pole at decision block  274  and NO is entered via user inputs and the user proceeds to block  284  where the user will aim device  10  at a given target point. At block  288  the user begins moving housing  12  while ensuring that the visual marker is still pointing at the given target point. The user continues moving the housing in the laser plane until audio or visual indicators on laser receiver  40  confirm that its on grade position is aligned with the laser plane. The measurement is captured via user keys  22  at  290  and this value is displayed at  292 . 
     Still referring to  FIG. 11 , if the user chooses YES at decision block  274 , at block  276  the user attaches the extendable pole  12  to lower pole mount  20 , places the base of extendable pole  12  over a given target point, and enables a mode that compensates for the thickness of the pole base. Again, in contrast to the first preferred embodiment, the user is not required to hold the assembly plumb due to the inclusion of gravity reference device  140 . At block  280  the user begins moving housing  12  into the laser plane until audio or visual indicators on laser receiver  40  confirm that its on grade position is aligned with the laser plane. The user then locks the length of the extendable pole  38  and presses the Capture button at block  282 , which will retain the measurement as noted above. However, since the laser plane is in reach, the user will also have the option of depressing one of the user keys  22  to capture and retain a measurement. The measurement is then displayed at  292 . 
       FIG. 12  is a flowchart showing operation of the third embodiment of the present invention. Device  10  with electronics  300  ( FIG. 8 ) is turned on at  360 . At block  362  the user attaches an external laser receiver  40  to outer housing  12  such that the on grade position of the external laser receiver  12  is aligned with reference line  14 . In this configuration the distance from the reference line  14  to the target point will substantially equal the distance from the on grade position of the laser receiver  40  to the target point. The user then determines if the laser plane is outside arm&#39;s reach at decision block  364 . As this third preferred embodiment has communication functionality, the user will also attach a communications cable between the communications device  150  and external laser receiver  12  at block  362 . However, if communication is provided wirelessly, then this sub-step is not required. 
     The user then determines if the laser plane is outside arm&#39;s reach at  364 . If the laser plane is outside arm&#39;s reach, the user attaches the extendable pole  38  to lower pole mount  20  and places the base of extendable pole  38  over a given target point at block  366 . The user will also enter a mode via a key press or combination of key presses of user keys  22  that will inform microprocessor  120  to compensate for the base thickness in its measurements. Care is taken to plumb this arrangement over the target point at block  368 . At block  370  the user begins moving housing  12  into the laser plane, all the while being careful to maintain a plumb alignment. He continues this movement until audio or visual indicators on laser receiver  40  confirm that its on grade position is aligned with the laser plane. The user is not required to lock the length of extendable pole  38  as in the first and second embodiments because the communication device  150  will relay the capture command from the compatible external laser receiver to microprocessor  120 . If the compatible laser receiver is able to determine the distance the laser plane was above or below the on grade position at the time the capture command is sent, then this offset value will be sent along with the capture command. Microprocessor  120  will then use this value to compute and output a corrected first distance value, wherein the corrected first distance is substantially equal to a measure of the distance from the point the laser receiver detects the laser plane (at the time the capture command was sent) to the user-defined target point. Either way, the capture command will cause microprocessor  120  to compute the measured distance and will display it at  392 . 
     If the laser plane is not outside arm&#39;s reach at  364 , then the user has the option of not using the extendable pole at decision block  374  and responds with NO. The user will then proceed to  384  where the user will aim device  10  at a given target point. At block  386  the user is careful to plumb housing  12  over the given target point. At block  388  the user begins moving housing  12  into the laser plane while simultaneously maintaining a plumb alignment and assuring that the visual marker remains aimed at the given target point. He continues in this manner until audio or visual indicators on laser receiver  40  confirm that its on grade position is aligned with the laser plane. The user is not required to manually capture a measurement via a key press as in the first and second embodiments and the measured distance value will automatically be displayed at  392 . 
     Still referring to  FIG. 12 , if the user chooses yes at  374 , at block  376  the user next attaches the extendable pole  12  to lower pole mount  20 , places the base of extendable pole  12  over a given target point, and enables a mode that compensates for the thickness of the pole base. The arrangement is plumbed over the target point at  368 . At block  370  the user begins moving housing  12  into the laser plane, while simultaneously being careful to maintain a plumb alignment, until audio or visual indicators on laser receiver  40  confirm that its on grade position is aligned with the laser plane. Due to the inclusion of communication device  150 , the measurement will be automatically captured and displayed at  392 . 
       FIG. 13  is a flowchart showing operation of the fourth embodiment of the present invention. Apparatus  10  with electronics  400  ( FIG. 9 ) is turned on at  460 . At  462  the user attaches an external laser receiver  40  to outer housing  12  such that the on grade position of the external laser receiver  12  is aligned with reference line  14 . In this configuration the distance from the reference line  14  to the target point will substantially equal the distance from the on grade position of the laser receiver  40  to the target point. As this embodiment has communication functionality, the user will also attach a communications cable between the communications device  150  and external laser receiver  12 . However, if communication is provided wirelessly then this step is not required. 
     At decision block  464  the user next determines if the laser plane is outside arm&#39;s reach. If the laser plane is outside arm&#39;s reach, at block  466  the user attaches the extendable pole  38  to lower pole mount  20 , places the base of extendable pole  38  over a given target point, and enters a mode via a key press or combination of key presses of user keys  22  that will inform microprocessor  120  to compensate for the pole base thickness in its measurements. In contrast to the first and third embodiments, the user is not required to hold the assembly plumb as the gravity reference device  140  detects the angular orientation of housing  12  and supplies this data to microprocessor  120 . Microprocessor  120  combines housing angular orientation data with data received from laser distance measuring device  110  to mathematically determine what the measured distance value would be if the assembly were held substantially plumb over the target point. At block  470  the user begins moving housing  12  into the laser plane until audio or visual indicators on laser receiver  40  confirm that its on grade position is aligned with the laser plane. The user need not lock the length of extendable pole  38 , as is required by the first and second embodiments, because the communication device  150  will relay the capture command from the compatible external laser receiver to microprocessor  120 . If the compatible laser receiver is able to determine the distance the laser plane is above or below the on grade position at the time the capture command is sent, then this offset value will be sent along with the capture command. 
     Microprocessor  120  will then use the offset value to compute and output a corrected first distance value, wherein this corrected first distance value is substantially equal to a measure of the distance from the point where the laser receiver detected the laser plane (at the time the capture command was sent) to the user-defined target point. Either way, the capture command will cause microprocessor  120  to compute the measured distance and display it at  492 . 
     If the laser plane is not outside arm&#39;s reach at  464 , then the user may elect not to use the extendable pole at decision block  474  and therefore chooses NO. He then proceeds to block  484  where he aims device  10  at a given target point. At block  488  the user begins moving housing  12  into the laser plane, while simultaneously ensuring that the visual marker is still aimed at the given target point, until audio or visual indicators on laser receiver  40  confirm that its on grade position is aligned with the laser plane. The user need not manually capture a measurement via a key press as in the first and second embodiments, and the measured distance value will automatically be displayed at  492 . 
     Still referring to  FIG. 13 , if the user chooses YES at decision block  474 , at block  476  the user attaches the extendable pole  12  to lower pole mount  20 , places the base of extendable pole  12  over a given target point, and enables a mode that compensates for the thickness of the base of extendable pole. Again, in contrast to the first and third embodiments, the user is not required to hold the assembly plumb due to the inclusion of gravity reference device  140 . At block  480  the user begins moving housing  12  into the laser plane until audio or visual indicators on laser receiver  40  confirm that its on grade position is aligned with the laser plane. Due to the inclusion of communication device  150  the measurement will be automatically captured and displayed at  492 . 
     All of the above embodiments also have the ability to reference target points that reside above the reference plane. This is enabled by attaching the extendable pole  38  to upper pole mount  18  such that the transmitting laser light beam of the laser distance measuring device  110  is pointing upward. From this point, operation continues as if referencing target points below the laser plane as set out in the above-described operational flowcharts. 
     Due to the processing abilities common to the preferred embodiments, various functions or modes could be enabled as follows. One possibility is to enable an option to scan for the minimum distance measurement during a predetermined amount of time during the measuring process. Due to simple geometry this would provide the user with a measured distance value that corresponds to the extendable pole position or a transmission path that is the most plumb during the predetermined amount of time. This would apply only to horizontal laser reference planes. 
     Another possibility is to include a relative mode in which the user takes an initial measurement from some user-defined position and every subsequent measurement is the difference between that measurement and the initial reference measurement. This provides the user with the exact value needed to raise/lower a member to bring it level or to cut/fill to bring a given surface to grade without requiring the user to record or remember the measurements and then subtract grade rod measurements. 
     An offset function may be provided as well, which works as follows. There are times when there does not exist a single point on the job site that is on grade and any initial measurement point chosen in relative mode will also require an initial cut/fill value. An offset function handles this situation by allowing the user to input this initial cut/fill value, and the system will then add/subtract the value (depending on whether the initial value is a cut or a fill) to every subsequent measurement in relative mode. While this function is useful in the construction industry, the survey industry will benefit as well. One of the primary roles of a surveyor is to determine elevations. Prior art methods require a surveyor to take an initial measurement at some point with a known elevation, subtract subsequent measurements from this initial measurement and finally add this difference value to the known elevation to determine the new elevation at this point. The combination of relative mode with the offset function handles this situation quite easily as the difference values are equivalent to cut/fill values and the known elevation is equivalent to the offset value. The surveyor simply enters relative mode and inputs the known elevation as a value into the offset function. The surveyor then takes an initial measurement at the point of known elevation, and this embodiment will output the total elevation at any point the surveyor subsequently chooses. 
     Yet another option is to include GPS (Global Positioning System) and/or communication (Bluetooth, infrared, radio, etc.) functionality such that a communication link can be established with another device such as a laptop computer. 
     The above disclosure is sufficient to enable one of ordinary skill in the art to practice the invention, and provides the best mode of practicing the invention presently contemplated by the inventor. While there is provided herein a full and complete disclosure of the preferred embodiments of this invention, it is not desired to limit the invention to the exact construction, dimensional relationships, and operation shown and described. Various modifications, alternative constructions, changes and equivalents will readily occur to those skilled in the art and may be employed, as suitable, without departing from the true spirit and scope of the invention. Such changes might involve alternative materials, components, structural arrangements, sizes, shapes, forms, functions, operational features or the like. 
     Therefore, the above description and illustrations should not be construed as limiting the scope of the invention, which is defined by the appended claims.