Abstract:
A system and method for maintaining a desirable depth of snow on a ski slope, on which a plurality of snowmaking apparatuses are stationed to produce artificial snow. The system and method obtain the position of a snow compressing vehicle, and calculate the snow depth at the point by comparing the snow compressing vehicle&#39;s position against geographical information when there is no snow. The system and method evaluate the necessity for supplementing snow at the point, and output the necessary amount of snow for the point via the snowmaking apparatuses. Based on the need for supplementing snow at each point, the system further calculates an operating rate suitable for each snowmaking apparatus to achieve optimum efficiency.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a system and a method for maintaining a ski slope using snowmaking apparatuses. 
     2. Description of the Related Art 
     In general, it is necessary to evenly press down freshly fallen snow in order to maintain the ski slope. This is done by pressing down fresh snow and uniformizing the snow surface over a large area using a snow compressing vehicle. 
     When using the snowmaking apparatus, it is also required to spread and compress snow produced by snowmaking apparatus in a way similar to one described above. That is, when artificial snow is supplied by the snowmaking apparatus due to natural snow shortage, the produced artificial snow needs to be spread over a desired area or, especially, transported to areas where snow is scarce since the artificial snow is distributed unevenly on the ski slope. 
     Traditionally, whether or not the snowmaking apparatus should be operated is determined based on a human&#39;s visual check on snow coverage or on actual snow coverage measurement at selected points. Often, ski slope maintenance itself is performed by a snow compressing vehicle operator who maintains the snow surface while visually checking the snow condition. 
     However, this method produces inconsistent results depending on experiences and skills of each maintenance worker. Also in some cases, efficiency of ski slope maintenance may become compromised due to unnecessary operations of the snowmaking apparatus and the snow compressing vehicle. 
     SUMMARY OF THE INVENTION 
     A purpose of the present invention, created in consideration of the above circumstances, is to provide a system and a method which are capable of producing consistent results in the ski slope maintenance regardless of experiences and skills of ski slope maintenance workers. 
     A more specific purpose of the present invention is to provide a method and a system which enable efficient operation of a snowmaking apparatus and a snow compression machine. 
     To attain the above objectives, according to a first aspect of the present invention, there is provided a system for maintaining a ski slope with a plurality of snowmaking apparatuses, comprising: means for obtaining a geographical position of a snow compressing vehicle which is used for maintaining the ski slope; means for comparing said geographical position of the snow compressing vehicle and geographical information of a snowless ski slope to thereby calculate snow coverage at each position of the ski slope; means for determining snow supplement necessity based on the snow coverage at each position of the ski slope and outputting a required snow supplement amount in association with each position; and means for calculating a required operating rate for the snowmaking apparatus based on the required snow supplement amount for each portion of the ski slope. 
     According to a structure described above, it is possible to precisely measure the snow coverage at each position of the ski slope and operate each snowmaking apparatus at an optimum operating rate. Thus, it is possible to perform consistent and efficient maintenance of the ski slope. 
     According to one embodiment of the present invention, the aforesaid snow compressing vehicle position obtaining means obtains the snow compressing vehicle position through a GPS (Global Positioning System) which is installed on this snow compressing vehicle. 
     According to another embodiment, the aforesaid snow supplement necessity determination means calculates an average value of the snow coverage in a predetermined range and calculates the snow supplement necessity and the required snow supplement amount for each position of the ski slope based on the aforesaid average value. 
     According to still another embodiment, the aforesaid snowmaking apparatus operating rate calculation means sums the required snow supplement amount for positions which belong to a range covered by each snowmaking apparatus and calculates the required operating rate for each snowmaking apparatus. 
     According to yet another embodiment, the aforesaid snowmaking apparatus operating rate calculation means calculates the required operating rate for the aforesaid snowmaking apparatus in addition to the aforesaid required snow supplement amount based on a snow melting amount. 
     According to still another embodiment, the aforesaid snowmaking apparatus operating rate calculation means receives temperature, humidity and wind velocity data for positions where each snowmaking apparatus is installed and estimates the aforesaid snow melting amount based on the aforesaid temperature, humidity and wind velocity data. 
     According to yet another embodiment, the aforesaid snowmaking apparatus operating rate calculation means issues an operating command to each snowmaking apparatus based on a calculated operating rate. 
     According to still another one embodiment, this system further has means for issuing a snow compressing command to the aforesaid snow compression vehicle for each position of the ski slope based on the snow supplement necessity and the required snow supplement amount for each position of the ski slope. 
     According to a second aspect of the present invention, there is provided a method for maintaining the ski slope provided with a plurality of snowmaking apparatuses, comprising the steps of: obtaining the snow compressing vehicle position for the snow compressing vehicle used for maintaining the ski slope; comparing the snow compressing vehicle position, the snow compressing vehicle position obtained by snow compressing vehicle position obtaining means, and geographical information of the snowless ski slope to thereby calculate snow coverage at each position of the ski slope; determining the snow supplement necessity for each position of the ski slope and outputting the required snow supplement amount in association with each position; and calculating a required operating rate for the aforesaid snowmaking apparatus based on the required snow supplement amount, the aforesaid required snow supplement amount determined by snow supplement necessity determination means. 
     Other characteristics and marked effects of the present invention will become apparent to those skilled in the art upon referring to explanations of the following specification when taken in conjunction with the accompanying drawings explained below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram showing an entire ski slope according to one embodiment of the present invention; 
     FIG. 2 is a schematic structural view showing a monitoring system provided at a central monitoring station of a skiing area; 
     FIG. 3 is a schematic structural view showing a snowmaking apparatus; 
     FIG. 4 is a schematic diagram showing a range of coverage for each ice crushing system for the entire ski slope; and 
     FIG. 5 is a schematic diagram showing a method for measuring snow coverage. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 
     FIG. 1 is a schematic diagram showing an entire ski slope  1  of a ski resort A. 
     In this example of the ski resort A, ten snowmaking apparatuses  2   a - 2   j  are placed along the ski slope  1  with a predetermined interval. Here, each of these snowmaking apparatuses  2   a - 2   j  is an ice crushing system (hereafter, referred to as “ice crusher”), which produces snow by crushing ice flakes. All ice crushers  2   a - 2   j  are connected to a central monitoring station  4 , with two-way communication through wiring  3 , which is preferably made of optical cables. 
     At a place such as near an upper end of a ski lift, where it is convenient to look over the ski slope  1 , there is installed a Global Positioning System (hereafter, referred to as “GPS”) standard station  5 , which is in radio communication with a snow compressing vehicle, shown as  6  in FIG.  1 . This snow compressing vehicle  6  is equipped with a GPS moving station  7 , which is capable of receiving radio waves from a GPS satellite and detecting its own three-dimensional position. A detected position of the GPS moving station  7  and, therefore, of the snow compressing vehicle  6  is transmitted to the GPS standard station  5  by radio and, then, to the central monitoring station  4  through wiring, shown as  8  in FIG. 1, which is preferably made of optical fibers. 
     FIG. 2 is a functional block diagram explaining details of the ice crusher  2   a  (for simplicity, ice crushers  2   b - 2   j  are not illustrated), the snow compressing vehicle  6 , the GPS standard station  5  and a control system of a monitoring system  9 , which is installed at the central monitoring station  4 . Each of these components will be described in detail below in accordance with this FIG.  2  and other drawings. 
     Ice Crusher 
     First, the aforesaid ice crusher  2   a  has an ice crusher control section  14  for controlling the ice crusher  2   a . This ice crusher control section  14  is connected to the monitoring system  9  through a predetermined transponder  19 . An exemplary structure of the ice crusher  2   a  will be described below in accordance with FIG.  3 . 
     As shown in FIG. 3, the ice crusher  2   a  is broadly defined by a water tank  11 , which contains water  10  for snowmaking, and a snowmaking section  13  for generating and crushing ice flakes to thereby produce artificial snow  12 . 
     This snowmaking section  13  has a cooling plate  15  for freezing the water  10 , which is supplied from the aforesaid water tank  11 , a cooling apparatus  16  for cooling the cooling plate  15 , a blower  17 , which is connected to the aforesaid cooling plate  15 , for conveying ice flakes  18  produced by this cooling plate  15  at a predetermined air blast pressure, and a crushing machine  20 , which is connected to one edge of the blower  17 , for finely crushing the ice flakes  18  to thereby generate the artificial snow  12 . 
     The aforesaid water tank  11  functions to filter and store the water  10  such as city water, rain water, snowmelt and the like, and supplying this water  10  to the cooling plate  15  while controlling the water flow using a flow control valve  22 . The cooling plate  15  is, for example, drum-shaped and its surface is cooled to a temperature of, for example, −15 ° C. by the aforesaid cooling apparatus  16 . Therefore, the water  10  supplied into this cooling plate  15  freezes and attaches on the surface of this cooling plate  15  as ice. 
     The aforesaid cooling apparatus  16  has a refrigerant pipe  24 , which is fixed to the aforesaid cooling plate  15 , and performs a heat exchange between a refrigerant, which is flowing in the refrigerant pipe  24 , and the water  10  to thereby generate the ice flakes  18 . The cooling apparatus  16  has a compressor  26  for compressing the refrigerant which passes through the cooling plate  15 , a condenser  27  (heat exchanger) for condensing the refrigerant which passes through the compressor  26 , and a expansion valve  28  for adiabatically expanding the refrigerant which passes through the condenser  27 , and creates a cooling cycle to circulate the refrigerant in the above order. 
     Here, the aforesaid compressor  26  may be of any type such as a vortical type, a scroll type and the like, and is driven by, for example, a motor  30 . This motor  30  is connected to a power source  32  through a driver  31 . 
     The ice frozen on and attached to the aforesaid cooling plate  15  is scraped by a knife-shaped blade, an impeller vane or the like, or peeled off by hot gas with a temperature 70° C.-80° C. supplied through the cooling plate  15 , and reshaped into the ice flakes  18  with a predetermined size. Next, these ice flakes  18  generated as above are sent into the aforesaid blower  17 . This blower  17  has a function of sending the ice flakes  18  towards the aforesaid crushing machine  20  using the air blast pressure generated by an air blaster  40 . 
     The crushing machine  20  has a casing  44 , whose ice flake inlet  43  is connected to the aforesaid blower  17 , crushing blades  45  installed in this casing  44  with a free rotation for crushing the ice flakes  18  to thereby produce the artificial snow  12 . A rotational motor  46  drives the crushing blades  45  at a high speed rotation along arrows B. An artificial snow outlet  47  discharges the produced artificial snow  12  via a snow ejection pipe  48 . 
     The ice flakes  18 , which are sent to the crushing machine  20  by the blower  17 , are crushed into small pieces by the crushing blades  45  rotating at a high speed and sent to the artificial snow outlet  47  as the artificial snow  12 . Then, this artificial snow  12  is supplied onto the ski slope  1  through the snow ejection pipe  48 , which is connected the artificial snow outlet  47 . 
     Also, in order to detect ambient conditions, an air temperature sensor  50 , a humidity sensor  51 , an aerovane sensor  52  and a pluviometeric sensor  53  are installed on this ice crusher  2   a.    
     These sensors  50 - 53  and drivers for the motor  30  and the rotational motor  46  are all connected to the aforesaid ice crusher control section  14 . This ice crusher control section  14  controls each section to thereby produce the artificial snow  12  according to values detected by the sensors  50 - 53  and commands from external systems. According to this embodiment, commands for this ice crusher control section  14  are issued from the aforesaid monitoring system  9 . 
     Snow Compressing Vehicle and GPS Standard Station 
     As shown in FIG. 2, the aforesaid snow compressing vehicle  6  has a communication interface  60  for communicating with the aforesaid GPS standard station  5 . The communication interface  60  is connected to an instruction apparatus  61  for giving a driving instruction to a driver of the snow compressing vehicle  6 , and to the aforesaid GPS moving station  7 . The GPS moving station  7  has a function for receiving signals from at least three GPS satellites  62   a - 62   c  using a GPS elliptic antenna  64 , which is installed at a predetermined position on the snow compressing vehicle  6 , and calculating a position of this GPS elliptic antenna  64  based on the above signals. 
     Position data of the GPS elliptic antenna  64  is transmitted to the monitoring system  9  of the aforesaid central monitoring station  4  via the GPS standard station  5 , and used for calculating snow coverage at each position on the ski slope  1  as described in detail below. Also, as described in detail below, the aforesaid monitoring system  9  issues a moving command to the snow compressing vehicle  6  according to the snow coverage at each position on the ski slope  1 . The moving command is sent to the snow compressing vehicle  6  through the GPS standard station  5  and displayed at the aforesaid instruction apparatus  61 . 
     Monitoring System 
     As shown in FIG. 2, the aforesaid monitoring system  9  has a standard station communication section  65  for communicating with the GPS standard station  5 , an ice crusher communication section  66  for communicating with the ice crusher  2   a , a ski slope map storage section  67  for storing geographical information of the ski slope  1  (ski slope map), a position obtaining section  68  for receiving the position data from the snow compressing vehicle  6  and obtaining the geographical information for the position on the ski slope  1 , a snow coverage calculation section  69  for calculating the snow coverage at the position using the position data from the snow compressing vehicle  6  and the geographical information for the position, a snow supply necessity determination section  70  for determining snow supplement necessity for the position and outputting a required snow supplement amount in association with the position, an ice crusher information storage section  71  for storing a range covered by each of the ice crushers  2   a - 2   j , an operating rate calculation section  72  for calculating an operating rate (required operation time) for each ice crusher based on the required snow supplement amount determined by the aforesaid snow supply necesity determination section  70  and the range covered by each of the ice crushers  2   a - 2   j , and issuing an operating command to each ice crusher control section  14 , and a snow compressing vehicle command section  73  for issuing a command to the snow compressing vehicle  6  in order to replenish snow to a position where snow supplement is required. 
     Each of the above components consists of computer software programs and operates when called and executed by a CPU (not illustrated) of the monitoring system  9  on RAM (not illustrated) of the monitoring system  9 . Operation of each of the above components will be described below in an order of actual ski slope maintenance procedures. 
     FIG. 4 is a schematic diagram showing a relationship between the ski slope  1  and travelling lines of the snow compressing vehicle  6 . The driver operates the snow compressing vehicle  6  so that the snow compressing vehicle  6  reciprocates on the ski slope  1  along the travelling lines, shown as  75 - 81  in FIG. 4, to thereby uniformly press down a surface of the ski slope  1 . In this example, the snow compressing vehicle  6  moves along cells, shown as  21 A,  21 B,  21 C, . . . in FIG.  4 . As the snow compressing vehicle  6  moves along these cells, a position of the GPS elliptic antenna  64 , which is installed on the snow compressing vehicle  6 , is continuously detected and sent to the aforesaid monitoring system  9  via the aforesaid GPS standard station  5 . 
     Next, the aforesaid position obtaining section  68  of the monitoring system  9  converts a coordinate of the GPS elliptic antenna  64  to another coordinate of a snow surface on which the snow compressing vehicle  6  travels (snow surface coordinate). Then, the position obtaining section  68  obtains a coordinate of a snowless ski slope surface, which corresponds to the snow surface coordinate, from the aforesaid ski slope map storage section  67 . 
     FIG. 5 is a schematic diagram explaining the above processing. 
     If a coordinate of the position of the GPS elliptic antenna  64  is (X 1 , Y 1 , Z 1 ), a coordinate on the snow surface  85 , (X 2 , Y 2 , Z 2 ), is described as below. In FIG. 5, h is a height of the snow compressing vehicle  6 , H is a height of the GPS elliptic antenna  64 , θ (theta) is an inclination angle of a travelling direction of the snow compressing vehicle  6 , and α (alpha) is an inclination angle of the ski slope width direction. Accordingly, the relationship between the positions is as follows: 
     
       
           X   2   =X   1 −( H+h )Sin θ×Cos α 
       
     
     
       
           Y   2   =Y   1 −( H+h )Sin θ×Sin α 
       
     
     
       
           Z   2   =Z   1 −( H+h )Cos θ×Cos α 
       
     
     Then, the position obtaining section  68  obtains a coordinate of the snowless ski slope surface  86  (X 2 , Y 2 , Z 0 ), which has equal x- and y-coordinate values to x- and y-coordinate values of the snow surface coordinate, from the aforesaid ski slope map storage section  67 . 
     Next, the aforesaid snow coverage calculation section  69  subtracts a z-coordinate of the snowless ski slope surface  86  from a z-coordinate of the snow surface  85  to thereby calculate the snow coverage (snow depth) S at the position of the snow compressing vehicle  6 . In other words, in this case, the snow coverage S is derived as follows: 
     
       
           S=Z   2   −Z   0 =( H+h )Cos α×Cos α− Z   0   
       
     
     In this example, the errors of measurement are 1.2 cm horizontally and 2.2 cm vertically if a distance between the GPS standard station  5  and the GPS moving station  7  is 1 km. Although these errors may increase marginally depending on a situation in actual cases, errors of about 5 cm are feasible if the distance between the GPS standard station  5  and the GPS moving station  7  is approximately 1 km. 
     Next, the calculated value of the snow coverage S is sent to the aforesaid snow supply necessity determination section  70 , which calculates snow supplement necessity and a required snow supplement amount for, for example, each cell in FIG. 4 ( 21 A,  21 B,  21 C, . . .) as snow compressing vehicle  6  passes thereover. Information on the required snow supplement amount for each cell is sent to the operating rate calculation section  72 , shown in FIG. 2, and the operating rate for the corresponding ice crusher is determined as described below. 
     That is, first, the aforesaid cells are set to belong to a range covered by one of the ice crushers  2   a - 2   j . For example, in the example of FIG. 4, the ice crusher  2   a  is set to cover a range of cells defined by a solid bold line  22 . Therefore, the operating rate calculation section  72  summates required snow supplement amounts of all cells which belong to the range covered by the ice crusher  2   a  to thereby calculate the required snow supplement amount which the ice crusher  2   a  should supply. Next, this operating rate calculation section  72  receives the values detected by the sensors  50 - 53  of the ice crusher  2   a  and calculates a snow melting amount for the range covered by the ice crusher  2   a . Then, based on the required snow supplement amount and the snow melting amount, the operating rate calculation section  72  calculates an optimal operating rate (required operation time) for the ice crusher  2   a  in order to maintain the range covered by the ice crusher  2   a  on the ski slope  1 . 
     The operating rate calculation section  72  sets the operating rate for the ice crusher control section  14  of each of the ice crusher  2   a - 2   j  and operates each ice crusher based on a respective operating rate. 
     Concomitantly, the snow compressing vehicle command section  73  transmits information on the required snow supplement amount for each cell to the GPS moving station  7  through the GPS standard station  5 . The information on the required snow supplement amount for each cell is displayed at the instruction apparatus  61  of the GPS moving station  7 , for example, on a display panel. Thus, the driver of the snow compressing vehicle  6  can efficiently transport the artificial snow  12 , which is produced by the aforesaid ice crushers  2   a - 2   j , to thereby maintain the ski slope  1 . 
     According to a structure described above, it is possible to provide a method and a system capable of producing consistent results in the ski slope maintenance regardless of experiences and skills of ski slope maintenance workers. Also, according to the structure described above, it is possible to efficiently operate the snowmaking apparatus and the snow compressing vehicle when maintaining the ski slope. 
     Incidentally, the present invention is not limited to the aforesaid one embodiment and various changes and modifications can be made, without departing from the scope and spirit of the present invention. 
     For example, although the aforesaid one embodiment uses the GPS for a purpose of detecting the position of the snow compressing vehicle, the present invention is not limited to using the GPS for that purpose. For example, it is possible to calculate the snow coverage by using a reflective effect of electric or sound waves on the ground surface, which are produced by the aforesaid snow compressing vehicle. Also, the aforesaid monitoring system  9  is not limited to be installed at the central monitoring station  4  provided on the ski resort A but may also be installed at a central monitoring station, which is remotely located from the ski resort A, for monitoring a plurality of ski slopes. 
     According to the aforesaid embodiment, by using the GPS standard station  5 , data from the aforesaid snow compressing vehicle  6  is transmitted to the central monitoring station  4 . However, the present invention is not limited to this embodiment. It is possible to transmit data to the central monitoring station  4  via a relay facility which is placed independently from the aforesaid standard station  5 . 
     Furthermore, according to the aforesaid embodiment, the snow coverage S is calculated by referring to the inclination angle of the snow coverage position. However, the present invention is not limited to this embodiment. For example, there is provided a function for maintaining the angle of the aforesaid GPS elliptic antenna  64  vertical regardless of the inclination angle of the snow surface. With this function, it is possible to obtain the snow coverage amount on that position without referring to the angle of the snow surface. 
     While the invention has been described with respect to preferred embodiments, those skilled in the art will readily appreciate that various changes and/or modifications can be made to the invention without departing from the spirit or scope of the invention as defined by the appended claims.