You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a process or method of using survey-grade Global Positioning System (GPS) equipment mounted on a railroad track vehicle which will take close interval measurements of the railroad track position while being under load from the weight of the railroad track vehicle. The measurements will have horizontal and vertical positioning for each location. 
     2. Description of the Related Art 
     Using conventional methods, railroad tracks are inspected and/or surveyed by means of a survey technician utilizing a GPS receiver to locate survey features on site. In the conventional survey method, the features are located by placing the GPS receiver on the feature and taking a GPS observation for five seconds. Normally, if a railroad track is to be surveyed, the track must be shut down to traffic which creates a substantial logistical problem. Further, when several tracks are positioned adjacent to one another in close proximity, such as in a hump yard or the like, the survey technicians are exposed to dangerous conditions due to traffic on adjacent tracks. Because of these safety factors, adjacent tracks must be shut down while surveys are being conducted. Further, the conventional survey methods using GPS equipment consume extensive periods of time. Additionally, when a railroad track is surveyed using conventional GPS equipment, such a survey will not reveal or indicate deflection of the track under load as a locomotive or other track vehicles pass over the site. 
     SUMMARY OF THE INVENTION 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter. 
     The method of surveying a railroad track under load is described which comprises the steps of: (1) providing a track vehicle which may be moved along the railroad track; (2) positioning a first GPS receiver on the track vehicle; (3) positioning a second stationary GPS receiver remotely from the first GPS receiver with the stationary GPS receiver being in radio communication with the first GPS receiver; (4) moving the track vehicle along the railroad track so that the first GPS receiver receives data from a plurality of satellites relating to the horizontal position and the vertical elevation of the first GPS receiver at predetermined intervals; and (5) collecting the data received by the first GPS receiver with the height of the first receiver above the railroad track being subtracted thereto to provide the actual vertical elevation of the track at each of the predetermined intervals or locations while the track is under load. 
     In the preferred embodiment, the first GPS receiver is positioned on the track vehicle so as to be centrally positioned between the rails of the railroad track. In the preferred embodiment, the first GPS receiver is positioned on top of the track vehicle so that the signals from the GPS satellite are not blocked by passing traffic or obstacles. In the preferred embodiment, a data collector which is preferably hand-held is positioned in the track vehicle to collect data from the first GPS receiver. 
     In a second embodiment of the method, a pair of spaced-apart GPS receivers are positioned on the track vehicle so that data relating to the vertical elevation of each of the rails of the railroad track may be collected and supplied to a pair of data collectors positioned within the track vehicle. In the preferred embodiment, the track vehicle is a locomotive but the vehicle could be a high-rail vehicle or a cargo car, as well. 
     It is therefore a principal object of the invention to provide an improved method for surveying a railroad track while the track is under load. 
     A further object of the invention is to provide a method of surveying a railroad track which reduces the risk of personal injury to the survey technicians. 
     A further object of the invention is to provide a method of surveying a railroad track wherein a GPS receiver is mounted on a track vehicle with the track vehicle being moved along the track while the survey is being conducted. 
     A further object of the invention is to provide a method of surveying a railroad track which greatly decreases the time needed to survey the track. 
     A further object of the invention is to provide a method of surveying a railroad track which eliminates the need of closing down adjacent tracks as a track is being surveyed. 
     A further object of the invention is to provide a method of surveying a railroad track which provides the vertical elevation of the track as the track is being subjected to the weight or load of a track vehicle passing thereover. 
     These and other objects will be apparent to those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
         FIG. 1  is a perspective view of a locomotive moving along a railroad track having a GPS receiver mounted on the upper portion thereof which is in communication with a plurality of GPS satellites and a stationary GPS receiver located remotely of the locomotive; 
         FIG. 2  is a partial perspective view of a locomotive having a GPS receiver mounted thereon which is in communication to a data collector positioned within the locomotive; and 
         FIG. 3  is a partial perspective view of a locomotive having a pair of GPS receivers mounted thereon which are in communication with a pair of data collectors. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Embodiments are described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense in that the scope of the present invention is defined only by the appended claims. 
     In the drawings, the numeral  10  refers to a conventional railroad track having rails  12  and  14  supported on ties  16 . The numeral  18  refers to a conventional locomotive which is adapted to move along the track  10  in conventional fashion. Although it is preferred that the track vehicle  18  is a locomotive, other track vehicles such as a high-rail vehicle or a cargo car could be utilized. The primary reason for using a locomotive is that it will have a greater weight than high-rail vehicles or cargo cars so as to cause maximum deflection of the rails  12  and  14  when the locomotive passes thereover. 
     In one embodiment, a conventional GPS receiver  20  is secured to the top of the locomotive  18  so that it may receive data from a plurality of satellites  22  in an unobstructive fashion. Preferably, the GPS receiver  20  is centrally positioned with respect to the rails  12  and  14  to provide data for the center of the track  10 . The height of the GPS receiver  20  above the rails  12  and  14  will be determined in conventional fashion so that the data received by the GPS receiver  20  may be adjusted to subtract the height of the receiver  20  above the rails  12  and  14  from the data received from the GPS satellites  22 . In other words, the data received from the satellite  22  may indicate that the GPS receiver  20  has an elevation of 1,500 feet. The distance between the upper end of the rails  12  and  14  and the GPS receiver may be 15 feet so the data will be adjusted to indicate that the rails  12  and  14  are at an elevation of 1,485 feet. 
     The numeral  24  refers to a stationary GPS receiver which is positioned remotely of the GPS receiver  20  and which is in communication with the satellites  22  and which is in radio communication with the GPS receiver  20  with both of the receivers observing the same satellite signals thereby increasing the accuracy of the data. If a Virtual Reference Station (VRS) network system is available in the area of the track being surveyed, it will not be necessary to utilize the stationary GPS receiver  24 . The receiver  20  in communication with a hand-held data collector  26  within the locomotive  18  which is being held by a survey technician. The fact that the survey technician may ride inside the locomotive  18  increases the safety factor since the technician does not have to be physically present on the track  10  to locate features. The technician will be able to monitor the GPS satellite quality from the data collector  26 . The data collector  26  is preferably a hand-held device that logs the GPS survey data from the GPS receiver  20 . The data collector  26  communicates with the GPS receiver  20  by connecting a cable  27  between the receiver  20  and the data collector  26  or by using a radio connection. The technician can place descriptions on the GPS observations being logged into the data collector  26 . The technician can also set the parameters of the GPS system to log data at certain intervals. The track vehicle may be moving and the survey observations can be logged and recorded. The vehicle does not have to be stopped in order to log an observation. Logging the data while the locomotive or track vehicle  18  is moving gives the ability to collect a dense amount of data in a small amount of time. The technician may set the parameters to log observations in five foot intervals, which is ten times more dense than the traditional survey requirements. If the track vehicle is traveling at five miles per hour, 1,056 observations can be made at five foot intervals in a one mile stretch, in a 12 minute time frame. 
     If it is desired to determine the position of each of the rails  12  and  14 , a pair of GPS receivers  20  are placed on the track vehicle  18  with each of the receivers  20  being positioned directly above one of the rails  12  and  14  ( FIG. 3 ). This situation will normally be used where one rail is higher than the other such as in super elevations through curves for example. In this case, an individual data collector  26  will be used for each receiver as seen in  FIG. 3 . Both receivers  26  will log data at the same time to compare the difference in elevation on each rail. 
     Thus it can be seen that a novel method has been provided for surveying a railroad track  10  which provides maximum safety to the survey technician since the survey technician may be positioned within the locomotive or other track vehicle. Further, the survey data is gathered as the locomotive  18  is moved along the track  10  which greatly decreases the time required to complete the survey. The fact that the receiver  20  is located on the top of the track vehicle ensures that the GPS signals will not be blocked by passing traffic, obstacles, etc. Receiver  20  may be secured to the top of the track vehicle  18  in any means as long as it is mounted in a manner that eliminates any movement of the GPS receiver once in place. For example, magnetic mounts may be used, suction cups may be used or the mount for the GPS could be welded to the vehicle  18 . 
     An extremely important feature of this system is that the elevation of the track may be measured when the track is under load of the weight of the track vehicle which will indicate unstable conditions beneath the track. It can therefore be seen that the invention accomplishes all of its stated objectives. 
     Although the invention has been described in language that is specific to certain structures and methodological steps, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific structures and/or steps described. Rather, the specific aspects and steps are described as forms of implementing the claimed invention. Since many embodiments of the invention can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.

Summary:
A method of inspecting or surveying a railroad track under load is described wherein a GPS receiver is mounted on top of the track vehicle such as a locomotive, high-rail vehicle or cargo car with data being collected at predetermined intervals to provide horizontal and vertical data for each location.