Abstract:
A system for measuring soil density includes a plurality of signal emitters paired with signal receivers situated within the soil and below grade (e.g. from 10 to 30 feet below grade). The emitters periodically emit the signal (e.g., ultrasonic signal), some of which is reflected back by the soil. If the soil is compact and close to the emitter/receiver, the reflected signal is received after a short delay and has high signal strength. If the soil is less compact or there is a gap between the soil and the emitter/receiver, the reflected signal is received after a greater delay and/or has lower signal strength. By making several measurements of the delay and signal strength, a baseline is established. Later, periodic measurements of the delay and signal strength are made. If the delay and/or signal strength measured differs from the baseline, the soil density has likely changed.

Description:
FIELD 
       [0001]    This invention relates to the field of soil management and more particularly to a system for measuring the soil density. 
       BACKGROUND 
       [0002]    There are many reasons to measure soil density. Besides the general geological reasons, measuring soil density is one way to detect the potential for sink hole development. 
         [0003]    A sinkhole is a collapse of soil in a particular location, typically forming a bowl-shape. It is believed that sink holes form when a void occurs under the surface and there is insufficient soil crusting to support the upper layers of soil resulting in the formation of a depression. If houses or other buildings are in the proximity of this sink hole, they are drawn into the sink hole, causing property damage and, because the depression occurs quickly, potentially bodily injury. There is typically very little warning of a sink hole forms. 
         [0004]    There are two types of sink holes. The first type is a cover-subsidence sinkhole. In such, soil transports itself into a cave in rock and the ground slowly subsides. These are not catastrophic because the soil subsides over longer periods of time, from years to maybe thousands of years. 
         [0005]    The other type of sink hole is a cover-collapse sinkhole. Cover-collapse sink holes make the news because of the destruction and injury that often results. One such sink hole opened suddenly at a resort in Clermont Fla., causing major damage to the resort, but luckily, resulting in no bodily injury. Unfortunately, a little earlier, a 20 foot sink hole opened beneath a sleeping man, killing that man. Cover-collapse sink holes tend to form in clay, because the clay holds soil together like glue. Soil leaching creates a void in the lower soil layers and the void then grows upward and, because of the clay, a bridge forms over the void. At some point, the bridge can&#39;t hold anymore and it collapses, taking with it any structures or people from above the bridged surface. 
         [0006]    Although sink holes have the potential of forming anywhere, many cover-collapse sink holes occur in Florida and Texas. To date, it has been almost impossible to predict a forming sink hole. There are little signs of a pending sink hole. Often, potential indications are fresh cracks in the foundations of houses and buildings or the skewing of a door frame making it difficult to close or open a door. Many people in areas of high risk for sink holes are required to have insurance to cover property losses due to sink holes, but insurance is meaningless when lives are lost. 
         [0007]    What is needed is a system that will effectively predict the possibility of a forming sink hole. 
       SUMMARY 
       [0008]    A system for measuring soil density includes a plurality of signal emitters paired with signal receivers (e.g., ultrasonic emitters and receivers) situated within the soil and below grade (e.g. from 10 to 30 feet below grade). The emitters periodically emit the signal, some of which is reflected back by the soil. If the soil is compact and close to the emitter/receiver, the reflected signal is received after a short delay and has high signal strength. If the soil is less compact or there is a gap between the soil and the emitter/receiver, the reflected signal is received after a greater delay and/or has lower signal strength. By making several measurements of the delay and signal strength, a baseline is established. After such, periodic measurements of the delay and signal strength are made. If the delay and/or signal strength measured is significantly different than the baseline, then the soil density has likely changed, possibly indicating a developing sink hole. 
         [0009]    In one embodiment, a soil density monitoring system is disclosed including a sensor pair having an emitting device and a receiving device. The emitting device emits a signal at a first time and the signal is reflected by soil and a reflected signal is detected by the receiving device at a second, later time. The sensor pair is positioned below grade (e.g. between 10 and 30 feet below grade) such that a signal strength of the reflected signal and a signal delay between the first time and the second time are measured as an indication of the soil density. 
         [0010]    In another embodiment, a method of determining changes in soil density is disclosed including (a) providing at least one sensor pair comprising a signal emitter and signal receiver and (b) installing the at least one sensor pair in soil below grade level (e.g. between 10 feet and 30 feet below grade). (c) One of the signal emitter is enabled to emit a signal and at least some of the signal reflects off of the soil towards the signal receiver where (d) the reflected signal is received by the signal receiver. (e) A signal strength and signal delay which is the time between the enabling and the receiving is recorded for determination of changes in soil density. 
         [0011]    In another embodiment, a soil density monitoring system is disclosed including a computer system and at least one sensor array. The sensor array(s) are located (or positioned) within the soil below a grade (e.g., from 10 feet to 30 feet below grade). Each sensor array includes one or more pairs of emitting devices and receiving devices. The emitting devices emit a signal at a first time (T 0 ), the signal is reflected by soil, and a reflected signal strength is detected by the receiving device at a second, later time (T 1 ). A signal delay is the difference between the first time and the second time. The pairs of the emitting devices and the receiving devices are operatively connected (e.g. wired, wireless) to the computer system. Software executing in a tangible memory of the computer system reads the reflected signal strengths and the signal delays. The reflected signal strengths and delays are related to a density of the soil in vicinity of each of the pairs of the emitting devices and the receiving devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: 
           [0013]      FIG. 1  illustrates a schematic view of a soil density detection system. 
           [0014]      FIG. 2  illustrates a second schematic view of the soil density detection system. 
           [0015]      FIG. 3  illustrates a perspective view of a sensor array of the soil density detection system. 
           [0016]      FIG. 4  illustrates a schematic view of a typical placement of sensor arrays for soil density detection system. 
           [0017]      FIG. 5  illustrates a schematic view of a system for soil density detection system. 
           [0018]      FIG. 6  illustrates a flow chart of software of the soil density detection system. 
           [0019]      FIG. 7  illustrates a second flow chart of software of the soil density detection system. 
           [0020]      FIG. 8  illustrates a third flow chart of software of the soil density detection system. 
           [0021]      FIG. 9  illustrates an exemplary histogram chart as read by sensors of the soil density detection system. 
           [0022]      FIG. 10  illustrates a second exemplary histogram chart as read by sensors of the soil density detection system. 
           [0023]      FIG. 11  illustrates a schematic view of a typical computer system of the soil density detection system. 
           [0024]      FIG. 12  illustrates a schematic view of an exemplary controller of the soil density detection system. 
           [0025]      FIG. 13  illustrates a schematic view of an exemplary wired sensor array of the soil density detection system. 
           [0026]      FIG. 14  illustrates a schematic view of a second exemplary wireless sensor array of the soil density detection system. 
           [0027]      FIG. 15  illustrates a schematic view of an exemplary wireless sensor array of the soil density detection system. 
           [0028]      FIG. 16  illustrates a schematic view of an exemplary notification transmission of the soil density detection system. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures. 
         [0030]    Referring to  FIG. 1 , a schematic view of a soil density detection system is shown. The soil density detection system includes one or more sensor arrays  10  embedded in the soil and a controller or computer  40  for processing signals from the one or more sensor arrays  10 . The controller  40  is preferably housed within a structure  1  (e.g. a house  1 ). In  FIG. 1 , all of the sensor arrays  10  connect to the controller  40  through a wireless transmission within a housing  6  (see  FIG. 2  for details). In some embodiments, a conduit (e.g. PCV pipe)  5  provides for wiring to the sensor array  10 . Wireless signals from the sensors sensor array  10  and wireless transmitter  30  (see  FIG. 2 ) are received on one or more antenna  42  and then processed by the controller  40 . In other embodiments (as will be shown), some or all of the sensor arrays  10  are connected by wire(s) connecting the sensor arrays  10  to the controller  40 . 
         [0031]    Referring to  FIG. 2 , a second schematic view of the soil density detection system is shown. In this example, more details of the sensor arrays  10  are shown. One sensor array  10  is directly connected to the controller  40  through a cable  20 , while another sensor array  10  is connected to a wireless transmitter (or transceiver)  30  and antenna  32  by one or more wires  20 . In the later, data regarding the individual sensors  12 / 14 / 16  (see  FIG. 3 ) is communicated between the sensor array  10  and the wireless transmitter (or transceiver)  30  on one or more wires, either by direct connection, sequenced connection, a bus architecture, or any other connection known. The wireless signal is transmitted from the antenna  32  to a second antenna  42  interfaced to a receiver within the controller  40  (not shown). Note, although a radio frequency wireless transmission is shown, any type of wireless transmission is anticipated, including wireless transmission using light, sound, etc. 
         [0032]    It is anticipated, but not required, that the transmitter  30  be housed in a covered box  6 , either on, at, or below grade. Since the transmitter  30  is preferably battery powered, it is also preferred that the box  6  have a removable cover  7  for battery replacement. In a preferred embodiment, a section of conduit  5  (e.g. PVC pipe) provides a channel for the wire(s)  20 . In embodiments in which there is a direct connection of the sensor array  10  to the controller  40  by wires  20 , it is anticipated, though not required, that a cover  8  be installed at the upper end of the conduit  5 , either removable or fixed. 
         [0033]    In the example shown in  FIG. 2 , a typical placement of the sensor arrays  10  is shown. In this example, the conduit  5  is pushed into the soil to a distance d 2 , and then the conduit is retracted so a bottom rim of the conduit  5  is at a lesser distance into the soil, d 1 . In this way, the sensor arrays  10  sit within the soil in a location deeper than d 1  but shallower than d 2 , thereby the sensor arrays  10  are not blocked by the conduit  5 . Any system of placement is anticipated and the present invention is in no way limited to any placement mechanism or conduit system. 
         [0034]    As will be shown in  FIG. 3 , the sensor arrays  10  have sensors  12 / 14 / 16 , a first part of the sensors  12 / 14 / 16  being an emitter  12  that emit signals (e.g. ultrasonic sound) and a second part of the sensors  12 / 14 / 16  being a detector  14  that provides an electrical signal indicative of the timing and strength of reflections of the emitted signal back from the surrounding soil. The more dense the soil, the quicker the reflections are received and the greater magnitude of the reflections. In some embodiments, the sensor arrays  10  include a humidity/moisture sensor  16  that provides an electrical signal indicative of the moisture content of the surrounding soil. 
         [0035]    As an example of an installation, for one certain water table depth, the conduit  5  is sunk 21 feet, and then pulled back one foot, leaving the sensor array  10  at approximately just under 21 feet beneath the surface. 
         [0036]    Although there is no restriction on depth, it is anticipated that there is no need to place the sensor array  10  more than 18-20 feet beneath the surface because, typically, 18-20 feet of soil is self-supportable, in that, that much soil thickness will hold a typical home even if there is a total void below the 20 foot depth. This does not preclude installation at depths greater than 20 feet, such as 30 feet. 
         [0037]    In locations with high water tables, it is anticipated, but not required, that the sensor array  10  is placed at depths that are above the average water table depth so that any density readings are not skewed by the sensor array  10  being surrounded by water, though it is also anticipated to install the sensor array  10  at any depth. In some embodiments, one or more sensor arrays are positioned below the water table, etc. 
         [0038]    Referring to  FIG. 3 , a perspective view of a sensor array  10  of the soil density detection system is shown. Although shown as a particular  6 -sided shape, the sensor array  10  is not limited to any specific size or shape. In this example, density sensor pairs  12 / 14  are located on four sides (90 degrees apart from each other) of the sensor array  10  (only two are visible), providing readings from four different directions. In other embodiments, more or less pairs of sensors  12 / 14  are utilized to provide greater coverage or lesser coverage, as needed. As shown with the sensor pair  12 / 14  to the right of this view, the emitter  12  emits a signal (e.g. an ultrasonic noise burst) and the detector  14  receives a reflected signal, converts the reflected signal to an electrical signal that is relayed to the controller  40  through the wire(s)  20  and/or the transmitter  30 . The electrical signal is used to determine the time delay and signal strength of that reflected signal. The greater the soil density, the shorter the delay and/or the greater the signal strength of the received reflected signal. For example, if a sink hole begins to form next to this sensor pair  12 / 14  of the sensor array  10 , there will be a void next to the sensor  12 / 14  and the reflected signal will have a lower strength. Also, the signal will have to travel farther before it is reflected; hence the delay between transmission and reception will increase. 
         [0039]    Many types of density sensor pairs  12 / 14  are anticipated. The preferred density sensor pairs  12 / 14  include an ultrasonic emitter  12  and an ultrasonic detector  14  as used, for example, in electronic yard sticks, fish finders, sonar, etc. Although this type of density sensor pairs  12 / 14  is preferred, other density sensor pairs  12 / 14  are anticipated including density sensor pairs  12 / 14  that use non-ultrasonic sound, radio frequencies, light, etc. 
         [0040]    In a preferred embodiment, though not required, a moisture/humidity sensor  16  is employed to measure the soil moisture content in the vicinity of the sensor array  10 . When present, the moisture/humidity sensor  16  detects moisture and converts the amount of moisture into an electrical signal. The electrical signal representative of moisture content from the moisture/humidity sensor  16  is relayed to the controller  40  to adjust readings that may vary due to, for example, excess rain. In times of high rain, rain water leeches through the soil and surrounds the sensor arrays  10 , changing the signal strength and time delay of the signals even though no soil movement occurs. 
         [0041]    Referring to  FIG. 4 , a schematic view of a typical placement of sensor arrays  10  for soil density detection system is shown. In this example, one sensor array  10  is set roughly at each corner of the building  1  and one extra sensor array  10  is set between two corners of the building  1 , as obstacles such as trees, decks, porches, etc., permit. In some installations, one or more sensor arrays  10  are set beneath the building  1 , depending upon the size of the building  1 . It is known how to place objects beneath a building  1  (or other obstruction such as decks, trees, porches, etc.) by drilling or planting on angle or in an ‘S’ fashion, often known as directional drilling. Additionally, for certain structures  1 , it is also anticipated that there is access to the grade beneath the structure  1  through crawl spaces, etc., through which the sensor arrays  10  are then set. 
         [0042]    Note that the present invention is not limited to any particular configuration or quantity of sensor arrays  10 . 
         [0043]    It is anticipated that each sensor array  10  have identification such as a serial number, sequence number, etc. During installation, the installation process preferably includes mapping of such identification to a sensor array number and/or an individual sensor  12 / 14 / 16  within the sensor array  10 . The sensor array number and/or individual sensor number is then used in communications such as notifications  131  (see  FIG. 16 ) to identify with sensor array  10  or sensors  12 / 14 / 16  have detected an issue. 
         [0044]    Referring to  FIG. 5 , a schematic view of a system for soil density detection system is shown. In the center of this exemplary configuration is a controller (or computer)  40 . In other configurations more or less components are present, as required. The controller  40  is coupled to one or more sensor arrays  10 , for example, directly coupled to several density sensors  12 / 14  and humidity sensors  16 . Several other density sensors  12 / 14  and humidity sensors  16  are indirectly coupled to controller  40  through one or more transmitters  30  or transceivers  30  communicating to one or more receivers  260  or transceivers  260  connected to the controller  40 , through respective antennas  30 / 42 . Again, any combination of wired or wireless sensor arrays  10  is/are interfaced to the controller  40 . 
         [0045]    Note that the wireless connection is required to be at least in one direction, that is, from the sensor array&#39;s  10  transmitter  30  to the controller&#39;s receiver  260  so that data from the sensors  12 / 14 / 16  is transmitted to the controller  40 . In some embodiments, there is a two-way communication instead of a one-way communication and the sensor array  10  and the controller both have transceivers  30 / 260 . In this way, the controller  40  has the ability to signal the sensor array  10  to initiate a reading, to send results, etc. 
         [0046]    It is also anticipated that other data be communicated between the sensor array  10  and the controller  40  such as battery status, identification numbers (e.g., in some embodiments, each sensor array  10  and/or each pair of density sensors  12 / 14  has a unique serial number to map sensor array  10  locations to transmitted signals, etc.). 
         [0047]    In this example, two datasets  44 / 46  are interfaced to the controller  40 , preferably stored in non-volatile memory such as a hard disk or solid state memory  240  (see  FIG. 11 ). The first data set  44  is collected density data  44  and thresholds. Each time a sensor array  10  reports any density or humidity data, the data is stored in the collected density data  44 , for example in an array representing a histogram over time (see  FIGS. 9 and 10 ). As will be described, an initial set of readings are read from the sensors  12 / 14 / 16  and stored in the collected density data  44 , creating a baseline (or thresholds) from which, later readings are compared to determine if any issues or potential emergencies exist. 
         [0048]    In steady-state operation, the controller collects data from the sensor arrays  10  and determines if the data is indicative of a potential sink hole development. In addition, in some embodiments, the controller  40  is connected to a network (e.g. the Internet)  100  and the controller  40  has the ability to extract information from external sources of data  110  such as weather services, news services, etc. In such embodiments, the controller  40  augments data from the sensor arrays  10  with weather, news, etc., to better understand the data from the sensors  12 / 14 / 16 . For example, if the locale in which the sensor arrays  10  are located has had constant rain for many days, certain thresholds are modified slightly, or if the weather includes frost that requires farmers to spray their fields to prevent freezing of fruit, more frequent scanning of the sensors  12 / 14 / 16  is made, etc. 
         [0049]    Having a connection to this network  100  provides the controller  40  with a path to the cellular network  130 , through which optional alerts are transmitted to, for example, an assigned cellular phone  132 . To facilitate notification, contact data  46  is maintained and administered (e.g. edited, changed) by the controller  40 . The contact information  46  includes, for example, how to notify the correct person when a change occurs, when a building issue is occurring, or when a catastrophic situation is predicted, etc. 
         [0050]    Having a connection to this network  100  also provides the controller  40  with a path to a remote computer  111 , such as a remote computer  111  that is part of a service provider. In some embodiments, the controller  40  sends a transaction to a remote computer  111 , encoded with, for example, an identification of the building, an identification of the sensor array  10  and/or sensor  12 / 14 / 16 , some amount of data for analysis, an indication of severity, etc. From this transaction, the remote computer  111  optionally analyzes the data and takes appropriate action, including, but not limited to, dispatching technicians, notifying emergency personnel, notifying a contact for the building, etc. 
         [0051]    Referring to  FIG. 6 , a flow chart of software of the soil density detection system is shown. In this, a self-test  300  is optionally performed to make sure all sensors  12 / 14 / 16  and sensor arrays  10  are functioning and connected, and the first sensor  12 / 14 / 16  is addressed  300 . Now, a loop is started to read  302  the current sensor and store  304  the data from that sensor in the density data  44 . If more sensors are in the current configuration  306 , the next sensor is addressed  308  and the loop continues. If there are no more sensors in the current configuration  306 , then, a preferable, though optional, delay is taken  310  then the first sensor is again addressed  312 . If initialization is not done  314 , the reading  302  and storing  304 , etc. is repeated until enough data is collected and the initialization is done  314 , at which time the density study process begins (see  FIGS. 7 and 8 ). 
         [0052]    Referring to  FIG. 7 , a second flow chart of software of the soil density detection system is shown. A sufficient sample of data has been collected from the sensors  12 / 14 / 16 , over some amount of time (see  FIG. 6 ), and various thresholds are set  400 . Since the density in front of each sensor pair  12 / 14  may be different due to the location of the sensor within the soil and/or the soil density to that side of the sensor array  10 , etc., it is anticipated, but not required, that each density sensor pair  12 / 14  have a unique threshold that is maintained so that, each time that density sensor pair  12 / 14  is read, the value read is compared to the unique threshold for that density sensor pair  12 / 14 . 
         [0053]    Now the first sensor is addressed  402  and a loop is started. 
         [0054]    The first step of the loop is optionally a test  404  to make sure the sensor  12 / 14 / 16  and/or transmitter is connected and operational. Next, the sensor  12 / 14 / 16  is read  406  and the data from that sensor  12 / 14 / 16  is compared to a threshold  408 , preferably a threshold specific to that sensor  12 / 14 / 16 . If the data is within expected limits  408 , the next sensor is addressed  412  and the loop continues. 
         [0055]    If the data is not within expected limits  408 , variances are calculated  420  to determine how significant the current reading has changed with respect to the data stored in, for example, density data  44  in histograms or other structure. If the variance is significant  422  (e.g. an impeding sink hole is predicted), an alarm is made or transmitted  424 . This consists of any notification mechanism known, including, but not limited to, sounding a sound device, lighting a light emitting device, making vibrations, sending an email, sending a text message  131  (see  FIG. 16 ), making a pre-recorded voice call, and sending a transaction to a service computer  111 . In the latter, it is anticipated that there be a service similar to that of alarm companies that receive potential sink hole indications and take action, including notifying occupants. In such, it is also anticipated that the service have access to prior sensor readings to better understand what is happening under the grade and to gain an understanding of the true severity of the situation. In some embodiments, the histogram data is uploaded to a larger computer (not shown) and further analyzed for potential problems. 
         [0056]    If the current reading is above the threshold, but the severity is not deemed significant  422 , then the issue is logged  426 . In some embodiments, the logs are checked for some number of entries that imply some type of activity below the grade. 
         [0057]    Referring to  FIG. 8 , a third flow chart of software of the soil density detection system is shown. This flow is similar to that of  FIG. 7 , except the histograms (or other data structures and thresholds) are further updated by subsequent data read from the sensors  12 / 14 / 16 . Once sufficient samples of data has been collected from the sensors  12 / 14 / 16  over some amount of time (see  FIG. 6 ), various thresholds are set  400 . Since the density in front of each sensor pair  12 / 14  may vary due to the location of the sensor within the soil and/or the soil density to that side of the sensor array  10 , etc., it is anticipated, but not required, that each density sensor pair  12 / 14  have a unique threshold that is maintained so that, each time that density sensor pair  12 / 14  is read, the value read is compared to the unique threshold for that density sensor pair  12 / 14 . 
         [0058]    Now the first sensor is addressed  402  and a loop is started. 
         [0059]    The first step of the loop is optionally a test  404  to make sure the sensor  12 / 14 / 16  and/or transmitter is connected and operational. Next, the sensor  12 / 14 / 16  is read  406  and the data from that sensor  12 / 14 / 16  is compared to a threshold  408 , preferably a threshold for that sensor  12 / 14 / 16 . If the data is within expected limits  408 , the thresholds are updated  410  and the next sensor is addressed  412  and the loop continues. In this example, the thresholds are updated  410  to allow for gradual shifting of the soil density from, for example, compacting from weight, vibration from vehicles, rain percolation, etc. 
         [0060]    If the data is not within expected limits  408 , variances are calculated  420  to determine how significant the current reading has changed with respect to the data stored in, for example, density data  44 , as, for example, in histograms. If the variance is significant  422  (e.g. an impeding sink hole is predicted), an alarm is made or transmitted  424 . This consists of any notification mechanism known, including sounding a sound device, lighting a light emitting device, making vibrations, sending an email, sending a text message, making a pre-recorded voice call, and sending a transaction to a service. In the latter, it is anticipated that there be a service similar to that of alarm companies that receive potential sink hole indications and take action, including notifying occupants. In such, it is also anticipated that the service have access to prior sensor readings to better understand what is happening under the grade and to gain an understanding of the true severity of the situation. In some embodiments, the histogram data is uploaded to a larger computer (not shown) and further analyzed for potential problems. 
         [0061]    If the current reading is above the threshold, but the severity is not deemed significant  422 , then the issue is logged  426 . In some embodiments, the logs are checked for some number of entries that imply some type of activity below the grade. 
         [0062]    Referring to  FIG. 9 , an exemplary histogram chart as read by sensors of the soil density detection system is shown. In these exemplary histograms, data for six sensors are shown numbered  1  through  6 . The readings are taken over time periods T 1  through T 9 . Any time period is anticipated such as hourly, daily, twice per day, weekly, etc., depending upon, perhaps, battery capacity, storage capacity of the controller  40 , local area ground activity, water table activity, historical data, etc. For this example, assume the time period represent days. In this example the data recorded for the first day, T 0 , is similar to the second day, T 1 , and is similar to all days with minor variations. Therefore, there is a reasonable expectation that the subsoil is intact and there is no sink hole development. 
         [0063]    Referring to  FIG. 10 , a second exemplary histogram chart as read by sensors of the soil density detection system is shown. In this example, the data recorded for the first day, T 0 , is similar to the second day, T 1 , but as days go by, significant reductions in soil density are found. For example, starting at T 6 , the overall soil density from the first sensor (sensor  1 ) has dropped significantly and drops even more at T 8  and T 9 , while the data from sensor  6  (humidity) remains substantially constant, meaning that there has been no significant change in soil water content. Therefore, there is a reasonable expectation that there is sink hole development. For example, what might be detected is a cavern forming in front of the first sensor, sensor  1 , but not yet large enough to be well detected by the other sensors ( 2 - 5 ). In such, as described prior, this significant change in density will exceed the threshold and initiate an alarm notification. For example, such a change will initiate an email or text message to a homeowner or a transaction to a watch service. In the latter, it is expected that the homeowner (building owner) is notified and technicians are dispatched to the building to further server the situation. By knowing which sensor array or arrays  10  have experienced significant density reading changes, the technician is better able to pinpoint the potential sink hole and to further probe to understand the severity of the situation and, possibly take precautionary and repair measures such as evacuation, backfilling the cavity, injecting foaming polyurethane into the cavity, etc. 
         [0064]    The above examples of histograms are for example only and are in no way limiting the data that is maintained and/or the format and structure of the data. For example, in a most minimal system, the data is only maintained until a threshold is determined, then subsequent readings are compared to that threshold, reducing the amount of data storage required. In a more robust system, every time the data is read, a time stamp and the data is stored in, for example, an array and the array is available for future study and analysis. 
         [0065]    Referring to  FIG. 11 , a schematic view of a typical computer system  40  of the soil density detection system is shown. The example computer system  40  represents a typical controller or computer system  40  with interfaces for the sensor arrays  10 . Although no keyboard or display is shown, such elements are well known in the industry. The example computer system  40  is shown in a simple form, having a single processor  210 . Many different computer architectures are known that accomplish similar results in a similar fashion and the present invention is not limited in any way to any particular computer system  40 . The present invention works well utilizing a single processor system as shown in  FIG. 11 , a multiple processor system where multiple processors share resources such as memory and storage, a multiple server system where several independent servers operate in parallel (perhaps having shared access to the data or any combination). 
         [0066]    A processor  210  executes or runs stored programs that are generally stored for execution within a memory  220 . The processor  210  is any processor or a group of processors, for example an Intel Pentium-4® CPU, controllers such as 80C51, or the like. The memory  220  is connected to the processor by, for example, a memory bus  215  and the memory  220  is any memory  220  suitable for connection with the selected processor  210 , such as SRAM, DRAM, SDRAM, RDRAM, DDR, DDR-2, etc. Also, as shown, but not required, connected to the processor  210  is a system bus  230  for connecting to peripheral subsystems such as a network interface  280 , a hard disk or other non-volatile storage  240  (e.g. flash), a disk drive (e.g. DVD, CD)  250 , all of which are optional. 
         [0067]    In general, the hard disk  240  is used to store programs, executable code and data persistently, while the disk drive  250  is used to load CD/DVD/Blue ray disk having programs, executable code and data onto the hard disk  240 . These peripherals are examples of input/output devices, persistent storage and removable media storage. Other examples of persistent storage include core memory, FRAM, flash memory, etc. Other examples of removable media storage include CDRW, DVD, DVD writeable, Blueray, compact flash, thumb drives, other removable flash media, floppy disk, ZIP®, etc. In some embodiments, other devices are connected to the system through the system bus  230  or such are connected with other input-output connections/arrangements as known in the industry. Examples of these devices include printers; graphics tablets; joysticks; and communications adapters such as modems and Ethernet adapters. 
         [0068]    In embodiments having a network connection, a network interface  280  connects the processor  210  to the network  100  through a link  285  which is, for example, a high speed link such as a cable broadband connection, a Digital Subscriber Loop (DSL) broadband connection, a T1 line or a T3 line, a wireless Wi-Fi connection, etc. Such a network interface is used as described with  FIG. 5  to send notification signals to, for example, a cellular phone  132 . 
         [0069]    In some embodiments, a local alarm  255  is also included. Upon detection of a possible sink hole forming, the local alarm is activated, for example, making noise, light, vibrations, or signaling a local wireless device of the impending danger. 
         [0070]    Any combination of wired or wireless sensor arrays  10  is anticipated. For wireless sensor arrays  10 , the sensors  12 / 14 / 16  are interfaced to a wireless transmitter or transceiver  30  through, optionally, signal conditioners  57 . The wireless transmitter/transceiver  30  wirelessly connects to a wireless receiver or transceiver  260 , which in turn connects to the processor  210  through, for example, the bus  230 . For wired sensor arrays  10 , the sensors  12 / 14 / 16  are interfaced to one or more optional send/receive signal conditioners which in turn connects to the processor  210  through, for example, the bus  230 . 
         [0071]    Although not required, it is preferred that the sensor pairs  12 / 14  be sequenced, such that, one sensor pair  12 / 14  on a sensor array  10  is activated, then another, then another, and so on. In this way, there is less interference between sensor pairs  12 / 14 . 
         [0072]    Referring to  FIG. 12 , a schematic view of an exemplary controller  40  of the soil density detection system is shown. Show is a minimal controller  40  having a processor  210  (other components from  FIG. 11  are not shown for clarity reasons). A stored program in the processor communicates with a receiver or transceiver  260  to receive data from the sensor arrays  10  which is received/transmitted on an antenna  42 . In some embodiments, the processor  210  disables the transceiver when not in use. In some embodiments, in which there is a transceiver  260 , in addition to reading data from the individual sensors  12 / 14 / 16 , the processor has transmit capability to instruct individual sensors  12 / 1416  to initiate density/humidity readings (e.g. polling), etc. In this, once a situation is detected (e.g. possibility of a sink hole), software running on the processor  210  has the ability to change the polling cycle and gather more data to better determine the severity of the issue and/or determine if other sensors  12 / 14 / 16  are becoming effected. Otherwise, in a non-polling configuration (one-way), each sensor array  10  controls when readings are made, making changing of the inter-reading interval difficult. In a polling configuration, it is anticipated that the processor have or have access to a timer  59  for initiating polling, etc. 
         [0073]    In embodiments in which the controller  40  communicates with a network, a network interface  280  is provided. The network interface  280  provides wired or wireless connection to, for example, a Wi-Fi network, a wide area network (cellular), a local area network. When present, the network interface  280  communicates data, notifications, etc. In configurations in which the network is wireless, an antenna  282  is also provided, operatively coupled to the network interface  280 . As above, the processor preferably has the ability to enable/disable the network interface  280  to, for example, save power. 
         [0074]    Power  98  is provided and distributed to the components of the controller  40 , for example an AC power supply  98 , battery power  98 , rechargeable battery power  98 , AC power with battery backup  98 , etc. 
         [0075]    Referring to  FIG. 13 , a schematic view of an exemplary wired sensor array  10  of the soil density detection system is shown. Show is a minimal controller  40  having a processor  210  (other components from  FIG. 11  are not shown for clarity reasons). A stored program in the processor  210  communicates with the sensors  12 / 14 / 16  through, optionally, a signal conditioner  57  which properly drives/terminates the sensors  12 / 14 / 16  and or multiplexes the signals to/from the sensors  12 / 14 / 16  over a number of wires  20 . The processor  210  instructs individual sensors  12 / 14 / 16  to initiate density/humidity readings through the optional signal condition  57  and cables/bus  20 . Software running on the processor  210  has the ability to change/adjust the polling cycle and gather more data to better determine the severity of an issue and/or determine if other sensors  12 / 14 / 16  are becoming effected. It is anticipated that the processor have or have access to a timer  59  for initiating polling, etc. 
         [0076]    Although two density sensor pairs  12 / 14  and one moisture/humidity sensor  16  is shown, any number of sensors  12 / 14 / 16  connected to the processor  210  is anticipated. 
         [0077]    In embodiments in which the controller  40  communicates with a network such as a Wi-Fi network, wide area network (cellular), local area network, etc., a network interface  280  is provided to communicate data, notifications, etc. In configurations in which the network is wireless, an antenna  282  is also provided, operatively coupled to the network interface  280 . As above, the processor preferably has the ability to enable/disable the network interface  280  to, for example, save power. 
         [0078]    Power  98  is provided and distributed to the components of the controller  40 , for example an AC power supply  98 , battery power  98 , rechargeable battery power  98 , AC power with battery backup  98 , etc. 
         [0079]    Referring to  FIG. 14 , a schematic view of a second exemplary wireless sensor array of the soil density detection system is shown. The transmitter or transceiver  30  communicates with the sensors  12 / 14 / 16 , preferably through a signal conditioner  57  which properly drives/terminates the sensors  12 / 14 / 16  and or multiplexes the signals to/from the sensors  12 / 14 / 16  over a number of wires  20 . The transmitter or transceiver  30  instructs individual sensors  12 / 14 / 16  to initiate density/humidity readings through the signal condition  57  and cables/bus  20 . For non-polled systems, it is anticipated that the transmitter or transceiver  30  have or have access to a timer  55  for initiating polling, etc. 
         [0080]    Although not required, it is anticipated that the transceiver  30  include a processor or micro-controller (not shown) for processing protocols, sequencing sensors  12 / 14 / 16 , temporary storing data, etc. 
         [0081]    Although two density sensor pairs  12 / 14  and one moisture/humidity sensor  16  is shown, any number of sensors  12 / 14 / 16  connected to the transmitter or transceiver  30  is anticipated. 
         [0082]    The transmitter or transceiver  30  communicates with the controller  40  through a wireless connection using an antenna  32 . 
         [0083]    Power  98  is provided and distributed to the components of the sensor array  10  by, for example, battery power  31 , solar power  31 , combination rechargeable battery and solar power  31 , etc. 
         [0084]    Referring to  FIG. 15 , a schematic view of an exemplary wireless sensor array  10  of the soil density detection system is shown. This wireless sensor array  10  is similar to the configuration of  FIG. 14 ; except there are three separate sets of sensors  12 / 14 / 16  controlled by one transmitter/transceiver  30  and antenna  32 . In this exemplary configuration, any number of sensors  12 / 14 / 16  is connected to each cable system  20  and to the transmitter/transceiver  30  through, for example, a signal conditioner  57 . Similarly, other sets of sensors  12 / 14 / 16  are also connected to the transmitter/transceiver  30  and antenna  32  by additional cable systems  20  and through, for example, signal conditioners  57 . In this way, any number of wireless sensor arrays  10  are wired to a central transmitter/transceiver  30  and antenna  32 . Power  31  is supplied as above. 
         [0085]    In some embodiments, the transmitter or transceiver  30  has fixed logic for selecting sensors  12 / 14 / 16 , enabling sensors  12 / 14 / 16  and transmitting data while in other embodiments, the transmitter or transceiver  30  includes a micro controller or other processing element to control operation, implement transmission protocols, select sensors  12 / 14 / 16 , enable sensors  12 / 14 / 16 , transmit data, self-test, etc. 
         [0086]    Referring to  FIG. 16 , a schematic view of an exemplary notification transmission  131  of the soil density detection system is shown. In this example, the notification transmission  131  is a text message such as a standard SMS text message shown displayed on a smart phone  132 . In alternate embodiments, the notification signal is sent by any transmission mechanism available such as email, data transactions, radio frequency modulations, data transmissions to an application running on a smart phone  132 , etc. 
         [0087]    In this exemplary notification transmission  131 , an indication of what has been detected  135  is included, such as a translation of predictions  135  based upon the rate of change of the sensor data, for example: “ground shift,” “sink hole forming,” “sink hole detected,” etc. In this example, a “ground shift”  135  was detected. Next, an identification  137  of the sensor array  10  and sensor  12 / 14 / 16  within that sensor array  10  is indicated. In this example, “sensor array  2 . 1 ” indicates the sensor  1  of the sensor array  2 . This identification  137  correlates to one of the installed sensor arrays  10  on, for example, a map of the placements of the sensor arrays  10 . Should there be a need, the serial number  139  of the sensor  12 / 14 / 16  or sensor array  10  is optionally displayed. In some embodiments, a severity  141  is displayed, for example, a severity  5  having a value of 1 indicates minor problems and a severity  5  having a value 10 indicates a severe problem and potential for loss of property and/or lives. Again, the notification message  131  shown is an example and other notification messages  131  are anticipated with more, less, and/or different content. In some embodiments, the controller  40  sends a transaction to a remote computer  111 , encoded within the transaction is, for example, an identification of the building, an identification of the sensor array  10  and/or sensor  12 / 14 / 16 , some amount of data for analysis, an indication of severity, etc. From this transaction, the remote computer  111  optionally analyzes the data and takes appropriate action, including, but not limited to, dispatching technicians, notifying emergency personnel, notifying a contact for the building, etc. 
         [0088]    Although described in the context of sink hole detection, the soil density detection system is not limited to any particular application and other uses are equally anticipated such as data gathering, seismic studies, plate shift analysis, etc. 
         [0089]    Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result. 
         [0090]    It is believed that the system and method as described and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.