Abstract:
An arrangement and appertaining method utilizing the arrangement provides a cost effective way to implement an accurate and cost effective satellite positioning differential augmentation system. This hybrid system integrates a network of Ground Based Augmentation Systems (GBAS) with a Satellite Based Augmentation System (SBAS), permitting the high integrity features of the GBAS to be utilized with the much broader coverage area of the SBAS system without requiring significant expenditures that would be required for upgrading either of the systems independently.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to satellite based positioning systems such as GPS and more specifically to the measurement and monitoring of the signals transmitted by differential satellite augmentation systems. 
     2. Description of Related Art 
     A satellite based positioning system is used to determine a position of a receiver and typically includes a plurality of satellites, the receiver, and one or more ground stations. Each of the satellites transmits a signal that contains a code and certain prescribed information useful to the receiver in determining its position. 
     The receiver synchronizes itself to the codes of at least four satellites and uses the information in the signals from these satellites in order to perform a triangulation-like procedure so as to determine its coordinates with respect to a reference, such as the center of the Earth and the GPS standard time. The receiver is not constrained to a specific location and, therefore, represents a variable position. The purpose of the satellite based positioning system is to make it possible for the receiver to determine its position regardless of the location of the receiver. 
     The accuracy of the position determined by the receiver is adversely affected by conditions that are common to all receivers in a given area. A ground station containing a receiver in a fixed location is used to monitor the signals transmitted by the satellites and determines corrections to the transmitted satellite signal. The ground station notifies the receiver of any necessary signal corrections to allow the receiver to make more accurate position calculations. This arrangement is referred to as differential positioning. 
     Since the mobile receiver completely relies on the corrections transmitted from the ground station as being correct, any condition that is inconsistent between the satellite measurements made at the mobile receiver and the ground station will cause a an undetected error in the mobile receiver. To protect the mobile receiver, the ground station monitors the signals transmitted by the satellites in order to detect faults within the satellites that would affect the mobile receiver. This function of detecting faults is referred to as providing integrity for the corrections that the ground station sends to the mobile receiver. For GPS, these faults include signal power, code signal deformation, code and carrier divergence, radio frequency interference, signal acceleration and erroneous ephemeris data. 
     The ground station system is also referred to as an augmentation system, since it augments both the accuracy and integrity of the original navigation satellite signals. There are two classes of augmentation systems: (1) Satellite Based Augmentation System (SBAS) that provides differential positioning across a wide area like the continental US, and (2) Ground Based Augmentation System (GBAS) that provides differential positioning to a smaller area, up to about 200 miles. 
     Satellite-Based Augmentation System (SBAS) 
     The known SBAS architecture used for wide-area coverage is shown in FIGS. 1 and 2. In the SBAS architecture  10 , a network of receivers  14  is used to collect satellite data  120 , and perform measurements  110 , from the navigational satellites  20  over a satellite to receiver communication path  214  and determine augmentation data  132 , which includes differential corrections, ionospheric delay errors, and accuracy of the navigation satellite signals at the receivers&#39;  14  location. 
     This measurement data  110  is transferred from the receiver  14  to one or more master stations  12  via a receiver to master station communication path  232 . The master stations  12  are centralized data processing sites used to determine differential corrections and integrity of the augmentation  110  over the SBAS Area of Coverage  16 . The processed SBAS correction and integrity data  132  is then sent to an SBAS satellite  18  via a master station to satellite communication path  212 . This SBAS satellite  18 , that generally functions as a communications repeater, then broadcasts the correction and integrity data  132  via a satellite to SBAS user communication path  218  to any user  23  within the area of coverage  16 . This structure is illustrated in more detail in FIG.  2 . 
     Ground-Based Augmentation System (GBAS) 
     According to FIG. 3, the Ground Based Augmentation System (GBAS)  30  contains GBAS receivers  32  that measure navigation satellite data  120  provided by the satellite  20  via a satellite to GBAS receiver communication path  240 . These receivers  32  communicate satellite data and ranging measurements  150  to a GBAS processor  34  that determines the differential corrections and integrity of the satellite signals. The processor  34  communicates these corrections and integrity data  152  through a local area transmitter  36  to a GBAS user receiver  38  within the GBAS coverage area. Typically the area of coverage for a GBAS is 30 to 50 miles. This smaller coverage volume allows the GBAS to provide greater levels of accuracy and integrity than the SBAS. 
     The greater levels of accuracy and integrity lend the GBAS to precision airplane approach applications. Due to the strict integrity requirements of precision approach applications, current GBASs, such as those defined by the FAA in FAA Specification FAA-E-2937A (“FAA-E-2937A”), herein incorporated by reference, contain monitors for detecting the integrity of the satellite signal waveform as well as the integrity of the ranging measurement from the satellites. Use of these monitors and other requirements allow the accuracy, continuity and integrity of GBAS to be much greater than that of SBAS. 
     Known Solutions 
     Allowing for more complex operations like precision approach in the SBAS coverage volume requires a greater level of integrity and monitoring than is provided by current SBAS implementations. Two known solutions for addressing enhanced integrity on SBAS have been previously considered. 
     The first solution applies additional SBAS reference receivers  14  to provide additional sampling points within the coverage area  16 . The measurements from these additional receivers  14  develop a more detailed differential and ionospheric correction. Unfortunately, additional receivers  14  add cost for the receivers  14  and communication links  232 ,  234 . 
     The second solution includes, in the SBAS receivers  14 , satellite signal monitors similar to that required per FAA-E-2937A. These monitors would increase the integrity of the measurements made by the receivers by monitoring for the types of anomalies defined in FAA-E-2937A. However, this solution also requires additional costs to update the numerous current receivers  14  that exist with these new monitors. 
     SUMMARY OF THE INVENTION 
     The present invention utilizes the resources of the GBAS station to supplement the measurement and integrity requirements of the of the SBAS station receivers. This is accomplished by an inventive rigorous communication link between the GBAS stations and the SBAS master station and the necessary processing, translation and storage of related information. The present invention also improves the functionality of the GBAS stations by exchanging data between the various GBAS stations on the communication link. 
     In its most rudimentary form, the GBAS passes raw measurements, corrections, integrity measurements, and integrity monitoring results to the SBAS station via this rigorous link. The SBAS station can utilize this data to produce corrections and monitoring consistent with the same level of rigor as the GBAS system and thereby increasing the SBAS stations integrity. This communication function and master station function mitigate the hazardous and misleading effects that can be caused on the SBAS user by the SBAS receiver. Thus the SBAS receiver can be can be developed to a lower level of certification or potentially completely removed. 
     Individual GBAS stations can use the data collected from other GBAS stations on the communication link to improve the functionality and integrity of the corrections produced over those produced by the GBAS system alone. The functionality is increased since the GBAS network can produce wide area corrections similar to the known SBAS implementation and could as such replace the SBAS receivers with a GBAS system that would also provide local area service. The integrity of the GBAS system can improved with the GBAS network data by using measurements from other GBAS systems to monitor effects of satellite signals that vary only over long distances such as ionospheric effects. These effects are challenging for GBAS to monitor since the effect is difficult to isolate with measurements made over the short distances between the GBAS receivers. Using measurements from other GBAS stations a greater distance away makes these determinations simpler to perform with greater integrity. 
     Specifically, the invention relates to a ground based augmentation system (GBAS) network, comprising: a navigation satellite; an interconnecting system communication network; at least a first GBAS and a second GBAS, each GBAS comprising: a GBAS receiver that is configured to receive navigation satellite data from the navigation satellite and covert it into GBAS raw augmentation data; a GBAS processor that is configured to receive GBAS raw augmentation data from the GBAS receiver and to format it into formatted GBAS differential correction and integrity data; and a GBAS transmitter configured to send GBAS differential correction and integrity data to the interconnecting system communication network; the GBAS processor of the first GBAS being configured to receive GBAS differential correction and integrity data produced by the second GBAS and to include this data in its own formatted GBAS differential correction and integrity data. 
     The invention also relates to an integrated satellite based augmentation system (SBAS)-GBAS comprising: a navigation satellite; an interconnecting system communication network; one or more GBASs, each GBAS comprising: a GBAS receiver that is configured to receive navigation satellite data from the navigation satellite and covert it into GBAS raw augmentation data; a GBAS processor that is configured to receive GBAS raw augmentation data from the receiver and to format it into formatted GBAS differential correction and integrity data; and a GBAS transmitter configured to send GBAS differential correction and integrity data to the interconnecting system communication network; the integrated SBAS-GBAS system further comprising: an SBAS, comprising: an SBAS satellite that is configured to transmit SBAS correction and integrity data to a user; an SBAS receiver that is configured to receive navigation satellite data from the navigation satellite and convert it into SBAS augmentation data; an SBAS master station that is configured to receive the SBAS augmentation data from the receiver, to receive GBAS differential correction and integrity data from the interconnecting system communication network, and to transmit processed SBAS correction and integrity data that includes the received GBAS differential correction and integrity data to the SBAS satellite. 
     The invention also relates to an integrated SBAS-GBAS system comprising: a navigation satellite; an interconnecting system communication network; one or more GBASs, each GBAS comprising: a receiver that is configured to receive navigation satellite data from the navigation satellite over a navigation satellite to GBAS receiver communication path and convert the navigation satellite data into GBAS raw augmentation data; a processor that is configured to receive GBAS raw augmentation data over a receiver to processor communication path, the processor comprising: a network input connected to a GBAS to interconnecting system communication network communication path that is configured to receive formatted integrated system data from the communication network; a receiver input connected to a GBAS receiver to GBAS processor communications path that is configured to receive the raw augmentation data from the receiver; an augmentation data database; a Local Area Augmentation System (LAAS) message receiver that is configured to receive the formatted integrated system data from the network input, convert the integrated system data, and store it in the augmentation data database; a GBAS receiver augmentation data receiver that is configured to receive the raw augmentation data from the receiver input, convert the raw augmentation data, and store it in the augmentation data database; an integrity monitor checker that is configured to read data from the augmentation data database; a receiver status database that is configured to store receiver status data; an LAAS message formatter that is configured to accept information from at least one of the augmentation data database, the integrity monitor checker and the GBAS receiver status database, and is configured to create at least one of LAAS messages for output; a network output that is configured to accept LAAS messages from the LAAS message formatter and output them to the GBAS to interconnecting system communication network communication path; a transmitter/user output that is configured to accept LAAS messages from the LAAS message formatter and output them to at least one of a local transmitter and user; the integrated SBAS-GBAS system further comprising: an SBAS, comprising: an SBAS satellite that transmits SBAS correction and integrity data to a user over an SBAS satellite to SBAS user communication path; a receiver that is configured to receive navigation satellite data from the navigation satellite over a navigation satellite to SBAS receiver communication path and convert the navigation satellite data into SBAS augmentation data; a master station that is configured to receive the SBAS augmentation data from the receiver over an SBAS receiver to SBAS master station communication path, the master station further comprising: a network input connected to an SBAS to interconnecting system communication network communication path that is configured to receive formatted integrated system data from the communication network; a receiver input connected to an SBAS receiver to SBAS master station communications path that is configured to receive SBAS augmentation data from the receiver; an augmentation data database; an SBAS LAAS message receiver that is configured to receive the formatted integrated system data from the network input, convert the integrated system data, and store it in the augmentation data database; an SBAS receiver augmentation data receiver that is configured to receive the SBAS augmentation data from the receiver input, convert the SBAS augmentation data, and store it in the augmentation data database; an SBAS integrity processor that is configured to receive the SBAS augmentation data that is stored in the augmentation data database and configured to process integrity data; a correction processor that is configured to receive augmentation data from the augmentation database and the integrity data and produce SBAS correction and integrity data; an output that is configured to accept the SBAS correction and integrity data from the correction processor and output them to the SBAS satellite via the SBAS master station to SBAS satellite communication path. 
     The invention also relates to a method for operating a networked GBAS system, comprising: receiving navigation satellite data by a first GBAS; formatting navigation satellite data by the first GBAS into formatted GBAS differential correction and integrity data; transmitting the formatted GBAS differential correction and integrity data to an interconnecting system communication network; receiving the formatted GBAS differential correction and integrity data from the interconnecting system communication network by a second GBAS; formatting navigation satellite data by the second GBAS into further formatted GBAS differential correction and integrity data, utilizing the received formatted GBAS differential correction and integrity data from the first GBAS; transmitting the further formatted GBAS differential correction and integrity data to at least one of the interconnecting system communication network and a GBAS user. 
     The invention also relates to a method for transmitting SBAS correction and integrity data to an SBAS satellite, comprising: producing, by a GBAS processor, formatted integrated system data comprising GBAS raw augmentation data; receiving, by an SBAS master station, SBAS augmentation data from an SBAS receiver and the formatted integrated system correction and integrity data from a communication network; formatting, by the SBAS master station, SBAS correction and integrity data using the SBAS augmentation data and the GBAS differential correction and integrity data; and transmitting the SBAS correction and integrity data to an SBAS satellite by the SBAS master station. 
     Finally, the invention also relates to a method for operating an integrated SBAS-GBAS system that comprises a GBAS and an SBAS, the method comprising: receiving navigation satellite data by a GBAS receiver and an SBAS receiver; formatting GBAS raw augmentation data from the navigation satellite data by the GBAS receiver; transmitting, by the GBAS receiver, GBAS raw augmentation data to a GBAS processor; formatting GBAS raw augmentation data into formatted GBAS differential correction and integrity data by the GBAS processor; transmitting the formatted GBAS differential correction and integrity data to an interconnecting system communication network; formatting SBAS augmentation data from the navigation satellite data by the SBAS receiver; transmitting, by the SBAS receiver, SBAS augmentation data to an SBAS master station; receiving, by the SBAS master station, formatted GBAS differential correction and integrity data from the interconnecting system communication network; formatting, by the SBAS master station, SBAS correction and integrity data using the SBAS augmentation data and the GBAS differential correction and integrity data; and transmitting the SBAS correction and integrity data to an SBAS satellite by the SBAS master station. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The invention is explained in greater detail below with reference to the drawings. 
     FIG. 1 is a pictorial diagram illustrating the known SBAS architecture; 
     FIG. 2 is a dataflow schematic illustrating the known SBAS system; 
     FIG. 3 is a dataflow schematic illustrating the known GBAS system; and 
     FIG. 4 is an interconnect diagram illustrating the inventive hybrid system; 
     FIG. 5 is a dataflow schematic illustrating the inventive hybrid system; 
     FIG. 6 is a dataflow schematic showing a preferred embodiment for the inventive GBAS processor; and 
     FIG. 7 is a dataflow schematic showing a preferred embodiment for the inventive SBAS processor. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 4 illustrates the basic architecture of the overall inventive integrated GBAS/SBAS  40  architecture in which the SBASs  10  and GBASs  30  are integrated. This integration is structured around a communication network  250  and protocol that transfers satellite measurement, correction and integrity data  120  determined at the GBAS stations  30  to other systems  12 ,  30  in order to gather and disseminate formatted integrated system data  170  that contains accurate and reliable correction and integrity data for users over a wide area (as in the SBAS system). This provides the benefit of having more accurate and reliable data obtained in the traditional GBAS architecture with the widespread coverage obtained in the traditional SBAS architecture. 
     As illustrated in FIG. 4, there are many GBASs  30  across a given region providing satellite corrections and integrity to users within their GBAS local coverage area. Each GBAS  30  is connected via a communications network  250  to other GBASs  30  as well as SBAS master stations  12 . The GBAS stations  30  formulate messages  170  containing: 
     1. the raw measurements made by the GBAS station for each ranging source on each receiver contained in the GBAS system; 
     2. differential correction data for each ranging source available to the GBAS system; 
     3. raw measurements of signal integrity parameters for each satellite on each reference receiver; and 
     4. the results of integrity monitors performed by the GBAS on ranging sources, receivers and the GBAS system itself. 
     The GBAS  30  station obtains additional functionality once this information  170  is received from other GBASs  30 . The additional data  170  is used to compute corrections and monitor integrity over a wide area, similar to SBAS. The GBAS  30  can also use the additional data to perform monitoring functions for the local area function that require a long separation between receivers  32 . An example of this is the determination of the effect due to erroneous ephemeris data being transmitted from the satellite. The additional data received also supports the native integrity monitoring functions by providing additional data to isolate the root cause of any integrity failure between the a ranging source and a receiver. 
     The SBAS master station  12  can utilize the additional data  170  in a manner similar to the GBASs  30 . The SBAS station  12  generates its correction and integrity data for its users from the data  170  received via the network  250 . The raw measurements and correction data are used to determine the effect of observables that are required for the SBAS wide area system  10  to provide valid data to its users. Examples of these observables are ionospheric effects and Radio Frequency Interference (RFI). The SBAS master station  12  can also use the raw integrity measurement or integrity monitor results to determine if a given ranging source has lost integrity. 
     Communication Network and Protocols 
     The network  250  used for transfer of data may include any standard multiple access or point to point communication network used as standard industry practice. RS-232, IEEE 802.3, and EIA X.25, can be used as physical communication mechanisms in the current embodiment. TCP/IP and PPP may be used as transport mechanisms; with these transport mechanisms, socket technology may be employed over the TCP/IP and PPP transport protocols. The specifications defining these protocols are herein incorporated by reference. 
     The message protocol used to send data  170  across the communication network  250  in the current embodiment may be based on the LAAS (Local Area Augmentation System) signal in space application data protocol defined in the RTCA DO-246A Specification (“DO-246A”), herein incorporated by reference, Sections 2.3.5, 2.3.6 and 2.3.7 and illustrated in Table 1. Any suitable protocol known in the art may be used at each of the communication layers, however, and the invention is not limited to the utilization of those expressly listed. 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Format of a LAAS Message Block 
               
             
          
           
               
                   
                 Message Block 
                 Bits 
                 Bytes 
               
               
                   
                   
               
               
                   
                 Message Block Header 
                 48 
                 6 
               
               
                   
                 Message 
                 up to 1696 
                 up to 212 
               
               
                   
                 Message Block CRC 
                 32 
                 4 
               
               
                   
                   
               
               
                   
                 The Message Block Header is defined in DO-246A Section 2.3.6. This header contains message structure, Station ID, message type and length fields.  
               
               
                   
                 The Message is specific to the type of message.  
               
               
                   
                 The Message Block CRC is defined in DO-246A Section 2.3.7. The CRC provides message integrity against communication disruptions.  
               
             
          
         
       
     
     In the preferred embodiment that uses the LAAS protocol, at least six specific message types are sent across this network link  250 . These messages  170  are transmitted from each GBAS station on the network and the messages are received on each of the GBAS stations  30  and the master SBAS station  10 . 
     Three of these message types (1, 2 and 4) are defined in DO-246A, and three of these message types (48-50) are inventively provided. Although the messages are defined by the structures illustrated below, it should be understood that these definitions are only exemplary in nature and that the invention should not be limited to these precise structures but rather could include structures that contain similar data that could be operated upon in a similar manner. These messages include: 
     1. the known LAAS Type 1 message defined in DO-246A Section 2.4.3; the LAAS Type 1 message is used to communicate the differential corrections transmitted by each ranging source and integrity parameters on those corrections; 
     2. the known LAAS Type 2 message defined in DO-246A Section 2.4.4; the LAAS Type 2 message contains information on GBAS related data such as the GBAS position and accuracy designator among other parameters; 
     3. the known LAAS Type 4 message defined in DO-246A Section 2.4.6; the LAAS Type 4 message contains information on the identification and usable state of approaches to the GBAS; 
     4. a newly defined LAAS Type 48 message for a Raw Measurement Message illustrated in Table 2; 
     5. a newly defined LAAS Type 49 message for a Receiver Status Message illustrated in Table 3; and 
     6. a newly defined LAAS Type 50 message for an Integrity Monitor Message illustrated in Table 4. 
     The newly defined Raw Measurement Message may utilize the LAAS Message Type 48 (which is currently undefined in DO-246A) to communicate the raw measurement parameters for each ranging source and each receiver on the GBAS system. These parameters may include, as illustrated in Table 2, pseudorange and carrier measurements, satellite position data, signal to noise levels, and other relevant data. This message type may also include raw integrity measurements such as signal quality measurements that are made along the correlator function and carrier lock discriminators. 
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Structure of the Receiver Status 
               
               
                 Message Application Data (Type 49) 
               
             
          
           
               
                   
                 Units or 
                   
                   
                 Number of 
                 Byte 
               
               
                 Parameter 
                 Fixed Value 
                 Range 
                 Resolution 
                 Bytes 
                 Number 
               
               
                   
               
             
          
           
               
                 Synchronization Character 1 
                 2A hex 
                 N/A 
                 N/A 
                 1 
                 1 
               
               
                 Synchronization Character 2 
                 2A hex 
                 N/A 
                 N/A 
                 1 
                 2 
               
               
                 Number of Bytes (fixed length; 
                 99 decimal 
                 N/A 
                 N/A 
                 1 
                 3 
               
               
                 includes bytes 4 through 102) 
               
               
                 Reference Receiver 
                 none 
                 N/A 
                 N/A 
                 1 
                 4 
               
               
                 Ranging Source 
                 ref. LGR-28516 
                 0 to 255 
                 1 
                 1 
                 5 
               
               
                   
                 and children 
               
               
                 Status 
                 ref. LGR-28523 
                 N/A 
                 N/A 
                 3 
                 6-8 
               
               
                   
                 and children 
                   
                   
                   
                 (LSB . . . MSB) 
               
               
                 Narrow Band Received Power 
                 dB 
                 0 to 128 
                 1 + 2 9   
                 2 
                  9-10 
               
               
                   
                   
                 see note #3 
               
               
                 Wide Band Received Power 
                 dB 
                 0 to 128 
                 1 + 2 9   
                 2 
                 11-12 
               
               
                   
                   
                 see note #3 
               
               
                 Pseudorange 
                 meters 
                 ±268,435,456 
                 1 + 2 7   
                 5 
                 13-17 
               
               
                   
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {4 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded) 
               
               
                 Accumulated Delta Range 
                 meters 
                 ±2 31   
                 1 
                 4 
                 18-21 
               
               
                 (Integer part) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                 Accumulated Delta Range 
                 meters 
                 0 to 1 
                 1 + 2 9   
                 3 
                 22-24 
               
               
                 (Fractional part) 
                   
                 See note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {4 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded, sign 
               
               
                   
                   
                   
                   
                   
                 bit always 0} 
               
               
                 Current IODE 
                 none 
                 0 to 255 
                 1 
                 1 
                 25 
               
               
                 Current Ephemeris CRC 
                 calculated 
                 N/A 
                 N/A 
                 2 
                 26-27 
               
               
                   
                   
                   
                   
                   
                 (LSB . . . MSB) 
               
               
                 Satellite X Position 
                 meters 
                 ±67,108,864 
                 1 + 2 8   
                 5 
                 28-32 
               
               
                 (current IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {5 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Satellite Y Position 
                 meters 
                 ±67,108,864 
                 1 + 2 8   
                 5 
                 33-37 
               
               
                 (current IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {5 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Satellite Z Position 
                 meters 
                 ±67,108,864 
                 1 + 2 8   
                 5 
                 38-42 
               
               
                 (current IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {5 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Satellite Correction 
                 meters 
                 ±2,097,152 
                 1 + 2 10   
                 4 
                 43-46 
               
               
                 (current IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                 Previous #1 IODE 
                 none 
                 0 to 255 
                 1 
                 1 
                 47 
               
               
                 Previous #1 Ephemeris CRC 
                 calculated 
                 N/A 
                 N/A 
                 2 
                 48-49 
               
               
                   
                   
                   
                   
                   
                 (LSB . . . MSB) 
               
               
                 Satellite X Position 
                 meters 
                 ±67,108,864 
                 1 + 2 8   
                 5 
                 50-54 
               
               
                 (previous #1 IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {5 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Satellite Y Position 
                 meters 
                 ±67,108,864 
                 1 + 2 8   
                 5 
                 55-59 
               
               
                 (previous #1 IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {5 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Satellite Z Position 
                 meters 
                 ±67,108,864 
                 1 + 2 8   
                 5 
                 60-64 
               
               
                 (previous #1 IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {5 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Satellite Correction 
                 meters 
                 ±2,097,152 
                 1 + 2 10   
                 4 
                 65-68 
               
               
                 (previous #1 IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                 Previous #2 IODE 
                 none 
                 0 to 255 
                 1 
                 1 
                 69 
               
               
                 Previous #2 Ephemeris CRC 
                 calculated 
                 N/A 
                 N/A 
                 2 
                 70-71 
               
               
                   
                   
                   
                   
                   
                 (LSB . . . MSB) 
               
               
                 Satellite X Position 
                 meters 
                 ±67,108,864 
                 1 + 2 8   
                 5 
                 72-76 
               
               
                 (previous #2 IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {5 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Satellite Y Position 
                 meters 
                 ±67,108,864 
                 1 + 2 8   
                 5 
                 77-81 
               
               
                 (previous #2 IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                 {5 lsb zero 
               
               
                 padded} 
               
               
                 Satellite Z Position 
                 meters 
                 ±67,108,864 
                 1 + 2 8   
                 5 
                 82-86 
               
               
                 (previous #2 IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {5 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Satellite Correction 
                 meters 
                 ±2,097,152 
                 1 + 2 10   
                 4 
                 87-90 
               
               
                 (previous #2 IODE) 
                   
                 see note #3 
                   
                   
                 (LSB . . . MSB) 
               
               
                 SQM data: 
                 height of an ideal 
                 ±0.125 
                 1 + 2 14   
                 1.5 
                 91-92 
               
               
                 0.025 chip early in-phase 
                 correlation peak 
                 see note #3 
                   
                   
                 lsb = byte 88, 
               
               
                   
                   
                   
                   
                   
                 bit 0 
               
               
                   
                   
                   
                   
                   
                 msb = byte 89, 
               
               
                   
                   
                   
                   
                   
                 bit 3 
               
               
                 SQM data: 
                 height of an ideal 
                 ±0.125 
                 1 + 2 14   
                 1.5 
                 92-93 
               
               
                 0.025 chip late in-phase 
                 correlation peak 
                 see note #3 
                   
                   
                 lsb = byte 89, 
               
               
                   
                   
                   
                   
                   
                 bit 4 
               
               
                   
                   
                   
                   
                   
                 msb = byte 90, 
               
               
                   
                   
                   
                   
                   
                 bit 7 
               
               
                 SQM data: 
                 height of an ideal 
                 ±0.125 
                 1 +2 14   
                 1.5 
                 94-95 
               
               
                 0.050 chip late in-phase 
                 correlation peak 
                 see note #3 
                   
                   
                 lsb = byte 91, 
               
               
                   
                   
                   
                   
                   
                 bit 0 
               
               
                   
                   
                   
                   
                   
                 msb = byte 92, 
               
               
                   
                   
                   
                   
                   
                 bit 3 
               
               
                 SQM data: 
                 height of an ideal 
                 ±0.125 
                 1 + 2 14   
                 1.5 
                 95-96 
               
               
                 0.075 chip late in-phase 
                 correlation peak 
                 see note #3 
                   
                   
                 lsb = byte 92, 
               
               
                   
                   
                   
                   
                   
                 bit 4 
               
               
                   
                   
                   
                   
                   
                 msb = byte 93, 
               
               
                   
                   
                   
                   
                   
                 bit 7 
               
               
                 SQM data: 
                 height of an ideal 
                 ±0.125 
                 1 + 2 14   
                 1.5 
                 97-98 
               
               
                 0.100 chip late in-phase 
                 correlation peak 
                 see note #3 
                   
                   
                 lsb = byte 94, 
               
               
                   
                   
                   
                   
                   
                 bit 0 
               
               
                   
                   
                   
                   
                   
                 msb = byte 95, 
               
               
                   
                   
                   
                   
                   
                 bit 3 
               
               
                 SQM data: 
                 height of an ideal 
                 ±0.125 
                 1 + 2 14   
                 1.5 
                 98-99 
               
               
                 0.125 chip late in-phase 
                 correlation peak 
                 see note #3 
                   
                   
                 lsb = byte 95, 
               
               
                   
                   
                   
                   
                   
                 bit 4 
               
               
                   
                   
                   
                   
                   
                 msb = byte 96, 
               
               
                   
                   
                   
                   
                   
                 bit 7 
               
               
                 PLL Discriminator sigma 
                 degrees 
                 0-63.75 
                 1 + 22 
                 1 
                 100  
               
               
                 CRC-16 (bytes 1 thru 100) 
                 Calculated at Tx. 
                 N/A 
                 N/A 
                 2 
                 101-102 
               
               
                   
                   
                   
                   
                   
                 (LSB . . . MSB) 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Structure of the Receiver Status 
               
               
                 Message Application Data (Type 49) 
               
             
          
           
               
                   
                 Units or 
                   
                   
                 Number of 
                 Byte 
               
               
                 Parameter 
                 Fixed Value 
                 Range 
                 Resolution 
                 Bytes 
                 Number 
               
               
                   
               
             
          
           
               
                 Synchronization Character 1 
                 2A hex 
                 N/A 
                 N/A 
                 1 
                  1 
               
               
                 Synchronization Character 2 
                 2A hex 
                 N/A 
                 N/A 
                 1 
                  2 
               
               
                 Number of Bytes (fixed 
                 89 decimal 
                 N/A 
                 N/A 
                 1 
                  3 
               
               
                 length; includes bytes 4 
               
               
                 through 92) 
               
               
                 Reference Receiver 
                 16 hex 
                 N/A 
                 N/A 
                 1 
                  4 
               
               
                 GNS Receiver Mode 
                 (ref. LGR-28494) 
                 N/A 
                 N/A 
                 1 
                  5 
               
               
                   
                   
                   
                   
                   
                 {bits 0, 1, 2} 
               
               
                 Receiver Initialization 
                 (ref. LGR-28495) 
                 N/A 
                 N/A 
                   
                 5 
               
               
                 Message Validated 
                   
                   
                   
                   
                 {bit 3} 
               
               
                 Time Integrity Monitor Status 
                 (ref. LGR-35063) 
                 N/A 
                 N/A 
                   
                 5 
               
               
                   
                   
                   
                   
                   
                 {bits 4, 5} 
               
               
                   
                   
                   
                   
                   
                 {2 msb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Almanac/Ephemeris 
                 meters 
                 0 to 2 16  − 1 
                 1 
                 2 
                 6-7 
               
               
                 Comparison Threshold 
               
               
                 Ephemeris Consistency 
                 meters 
                 0 to 2 16  − 1 
                 1 
                 2 
                 8-9 
               
               
                 Threshold 
               
               
                 Number of Satellite 
                 (ref. LGR-28496) 
                 0 to 255 
                 1 
                 1 
                 10 
               
               
                 Measurements 
                   
                 [valid = 0 to 18] 
               
               
                 Satellite Visible &amp; Healthy 
                 (ref. LGR-28497) 
                 0 to 255 
                 1 
                 1 
                 11 
               
               
                 S/W Part Number 
                 (ref. LGR-28498) 
                 N/A 
                 N/A 
                 4 
                 12-25 
               
               
                   
                   
                   
                   
                   
                 (LSB . . . MSB) 
               
               
                 Compatibility Number 
                 (ref. LGR-28499) 
                 N/A 
                 N/A 
                 7 
                 26-32 
               
               
                   
                   
                   
                   
                   
                 (LSB . . . MSB) 
               
               
                 Spare 
                 reserved 
                 N/A 
                 N/A 
                 7 
                 33-39 
               
               
                 GPS Week Number 
                 weeks 
                 0 to 2 16  − 1 
                 1 
                 2 
                 40-41 
               
               
                   
                   
                 (valid = 0 to 5218) 
                   
                   
                 (LSB .. MSB) 
               
               
                 GPS Measurement Time 
                 seconds 
                 0 to 2 31  − 1 
                 1 + 2 
                 4 
                 42-45 
               
               
                   
                   
                 (valid = 0 to 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                 604799.5) 
               
               
                 Receiver Latitude 
                 degrees 
                 ±90 deg 
                 8.38E-8 deg 
                 4 
                 46-49 
               
               
                   
                   
                 (+ = North) 
                 (180/2 31 ) 
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                   
                   
                   
                 {max data 
               
               
                   
                   
                   
                   
                   
                 range ±90} 
               
               
                 Receiver Longitude 
                 degrees 
                 ±180 deg 
                 8.38E-8 deg 
                 4 
                 50-53 
               
               
                   
                   
                 (+ = East) 
                 (180/2 31 ) 
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                 see note #3 
               
               
                 Receiver Attitude 
                 feet 
                 +2 17   
                 1 + 2 3   
                 3 
                 54-56 
               
               
                 (with respect to msl) 
                   
                 (+ = up) 
                   
                   
                 (LSB . . . MSB) 
               
               
                   
                   
                 see note #3 
               
               
                   
                   
                   
                   
                   
                 {3 lsb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 GDOP 
                 unitless 
                 0-25.5 
                 0.1 
                 1 
                 57 
               
               
                 Almanac Space Vehicle 
                 n/a 
                 0-63 
                 N/A 
                 1 
                 58 
               
               
                 Identification (SVID) 
                   
                 (VALID RANGE = 
                   
                   
                 {2 MSB ZERO 
               
               
                   
                   
                 0-32) 
                 PADDED} 
               
               
                 Eccentricity (ε) 
                 dimensionless 
                 0-(1 + 2 5 ) 
                 1 + 2 21   
                 2 
                 59-60 
               
               
                 Time of Applicability (t oa ) 
                 seconds 
                 0-2 20   
                 2 12   
                 1 
                 61 
               
               
                   
                   
                 (VALID RANGE = 
               
               
                   
                   
                 0-602,112) 
               
               
                 Orbital Inclination (δ i ) 
                 semi-circles 
                 ±(1 + 2 4 ) 
                 1 + 2 19   
                 2 
                 62-63 
               
               
                   
                   
                 SEE NOTE #3 
               
               
                 Rate of Right Ascension 
                 semi-circles/sec 
                 ±(1 + 2 23 ) 
                 1 + 2 38   
                 2 
                 64-65 
               
               
                 (OMEGADOT) 
                   
                 see note #3 
               
               
                 Space Vehicle Health 
                 n/a 
                 N/A 
                 N/A 
                 1 
                 66 
               
               
                 Status Discretes (SV 
               
               
                 Health) 
               
               
                 Square Root of the Semi- 
                 meters 1/2   
                 0-2 13   
                 1 + 2 11   
                 3 
                 67-69 
               
               
                 Major Axis (√A) 
               
               
                 Longitude of Ascending 
                 semi-circles 
                 ±1 
                 1 + 2 23   
                 3 
                 70-72 
               
               
                 Node of Orbit Plane at 
               
               
                 Weekly Epoch (Ω 0 ) 
                   
                 see note #3 
               
               
                 Argument of Perigee (ω) 
                 semi-circles 
                 1 + 2 23   
                 3 
                 73-75 
               
               
                   
                   
                 see note #3 
               
               
                 Mean Anomaly at 
                 semi-circles 
                 ±1 
                 1 + 2 23   
                 3 
                 76-78 
               
               
                 Reference Time (M 0 ) 
                   
                 see note #3 
               
               
                 Satellite Clock Correction 
                 seconds 
                 ±(1 + 2 10 ) 
                 1 + 2 20   
                 2 
                 79-80 
               
               
                 Bias (a f0 ) 
                   
                 see note #3 
                   
                   
                 {5 msb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Satellite Clock Correction 
                 sec/sec 
                 ±(1 + 2 28 ) 
                 1 + 2 38   
                 2 
                 81-82 
               
               
                 Rate (a f1 ) 
                   
                 see note #3 
                   
                   
                 {5 msb zero 
               
               
                   
                   
                   
                   
                   
                 padded} 
               
               
                 Almanac Week Number 
                 weeks 
                 0-255 
                 1 
                 1 
                 83 
               
               
                 (WNa) 
               
               
                 Spare 
                 reserved 
                 N/A 
                 N/A 
                 7 
                 84-90 
               
               
                 CRC-16 (bytes 1 thru 90) 
                 Calculated at Tx 
                 N/A 
                 N/A 
                 2 
                 91-92 
               
               
                   
                   
                   
                   
                   
                 (LSB . . . MSB) 
               
               
                   
               
               
                 Table Notes:  
               
               
                 1. Where multiple bytes are required for a parameter, “LSB . . . MSB” means least-significant byte to most-significant byte.  
               
               
                 2. The terminology “X lsb zero padded” means the X least significant bits are padded with zeros and “X msb zero padded” means the X most significant bits are padded with zeros. No data is contained in the pad bits -- they must be shifted out prior to applying lsb weighting.  
               
               
                 3. The actual maximum value is the positive range value minus the least significant bit weight (lsb). The lsb weight is the resolution.  
               
             
          
         
       
     
     The newly defined Integrity Monitor Message may utilize the LAAS Message Type 50 (which is currently undefined in DO-246A) to communicate the status of integrity monitor checks executed by the GBAS system. These data may include elements illustrated in Table 4. 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 BYTES 
                 RANGING SOURCES 
               
               
                   
                   
               
             
             
               
                   
                  1 
                 Signal Deformormation-Evil Waveform 
               
               
                   
                  2 
                 Signal Deformormation-Cross Correlation 
               
               
                   
                  3 
                 Signal Deformation-Multipath 
               
               
                   
                  4 
                 RFI 
               
               
                   
                  5 
                 Signal to Noise Level 
               
               
                   
                  6 
                 Signal to Noise Cross Correlation 
               
               
                   
                  7 
                 Code Carrier 
               
               
                   
                  8 
                 Acceleration 
               
               
                   
                   
                 Corrections 
               
               
                   
                  9 
                 Pseudorange Spikes 
               
               
                   
                 10 
                 Filter Spike Restart 
               
               
                   
                 11 
                 Filter Restart 
               
               
                   
                 12 
                 Not Converged at Mask Angle 
               
               
                   
                 13 
                 Excessive PRC 
               
               
                   
                 14 
                 Excessive RRC 
               
               
                   
                 15 
                 Excessive Sigma pr gnd   
               
               
                   
                 16 
                 Excessive B-Values 
               
               
                   
                 17 
                 RRC Exclusion 
               
               
                   
                 18 
                 RRC Anomaly 
               
               
                   
                 19 
                 PRC Exclusion 
               
               
                   
                 20 
                 PRC Anomaly 
               
               
                   
                 21 
                 PRC Failure IMON Warning 
               
               
                   
                 22 
                 PRC Failure IMON Fail 
               
               
                   
                 23 
                 PRC Anomaly IMON Warning 
               
               
                   
                 24 
                 PRC Anomaly IMON Fail 
               
               
                   
                 25 
                 Sigma PRC Warn 
               
               
                   
                 26 
                 Sigma PRC Fail 
               
               
                   
                 27 
                 Sigma PRR Warn 
               
               
                   
                 28 
                 Sigma PRR Fail 
               
               
                   
                 29 
               
               
                   
                 30 
                 Accumulated Delta Range Failure 
               
               
                   
                 31 
                 Position Data Stale Failure 
               
               
                   
                 32 
                 Position Data Stale Warning 
               
               
                   
                 33 
                 Navigation Warning 
               
               
                   
                 34 
                 Navigation Failure 
               
               
                   
                 35 
                 Time Integrity Failure 
               
               
                   
                 36 
                 Minimum Common Failure 
               
               
                   
                 37 
                 Minimum Common Warning 
               
               
                   
                 37 
                 RR Mode Change 
               
               
                   
                 38 
                 Absent Satellite 
               
               
                   
                 39 
                 Less than 4 Satellites 1 RR 
               
               
                   
                 40 
                 Less than 4 Satellites all RR 
               
               
                   
                 41 
                 Type 1 Message Failure 
               
               
                   
                   
                 Navigation Data 
               
               
                   
                 42 
                 Invalid Parity 
               
               
                   
                 43 
                 Bad IODC 
               
               
                   
                 44 
                 HOW Bit 18 
               
               
                   
                 45 
                 NAV is 0 
               
               
                   
                 46 
                 Bad Preamble 
               
               
                   
                 47 
                 Ephm CRC change, not IODE 
               
               
                   
                 48 
                 Sat Unhealthy 
               
               
                   
                 49 
                 Ephem Alm Miscompare 
               
               
                   
                 50 
                 Ephem Alm Miscompare 
               
               
                   
                 51 
                 Ephem Ephem Miscompare 
               
               
                   
                 52 
                 Ephem Ephem Miscompare 
               
               
                   
                 53 
                 Inconsistent NAV Data Sets 
               
               
                   
                 54 
                 Ephemeris Transition Failure 
               
               
                   
                 55 
                 Ephemeris Transition Failure 
               
               
                   
                 56-59 
                 Time of applicability 
               
               
                   
                 60-61 
                 16 bit CRC 
               
               
                   
                   
               
             
          
         
       
     
     Each byte is composed of the following: 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Bit Definition 
               
             
          
           
               
                   
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
               
               
                   
                   
               
             
          
           
               
                   
                 Fault 
                 Recovery 
                 Alert 
                 Don&#39;t Care 
               
               
                   
                   
               
               
                   
                 0 = Not present  
               
               
                   
                 1 = Present  
               
             
          
         
       
     
     A more detailed description of the integrated system can be seen in FIG.  5 . As can be seen in the integration, the GBAS processor  34  transmits the formatted integrated system data  170  in the form of LAAS formatted message types to the SBAS master station  12  over the interconnecting system communication network  250 . This information is then processed by the SBAS correction processing  24  and the SBAS correction and integrity data  132  is transmitted to the SBAS satellite  18  over an SBAS master station to SBAS satellite communication path  212 . 
     GBAS Structure and Function 
     FIG. 6 illustrates the inventive GBAS structure in which the GBAS processor  34  has a network input  56  from the communication network  250  for receiving formatted integrated system data  170 , such as the LAAS formatted message types described above, over a communication path  270 . The network input  56  provides the data  170  to an LAAS message receiver  64  that translates received message data and stores it in an augmentation data database  52 . The LAAS message receiver  64 . 
     The processor  34  also has a receiver input  58  for receiving raw augmentation data  150  from the GBAS receiver  32  over a communication path  242 . The GBAS receiver message receiver  66  translates received data  150  and sends data for each receiver to the GBAS augmentation function  52 . The GBAS receiver message receiver  66  may contain hardware elements and/or software elements for performing this translation and storage operation. This message receiver function produces the LAAS Type 48 and Type 49 information and sends that information to the LAAS Message formatter  62  for creation of these messages. 
     In a preferred embodiment, the LAAS message formatter  62  utilizes the GBAS Augmentation function  52  data, the GBAS Integrity Function  68  data and GBAS Receiver Message Receiver to format LAAS Type 1, 2, 4, 48, 49 and 50 messages. The LAAS Message Formatter  62  then can output these formatted messages  170  to the communication network  250  using a processor network output  60  and a communication path  244 . The LAAS message formatter  62  can output the formatted GBAS data  152  to a user  38  using a user output  59  to a local area transmitter  36  and a communication path  244  to the user  38 . 
     The inventive GBAS has two primary functions: (1) output the messages consistent with the above-described LAAS protocol, and (2) utilize the received inputs to enhance the current computations. 
     Generation of the actual LAAS formatted Type 1, 2 and 4 messages for the LAAS signal in space is well known and defined in the link protocol according to DO-256A and DO-245. The additional Type 48 and Type 49 messages are generated from the raw augmentation (observable and configuration) data  150  determined at each receiver  32  in the GBAS. The Type 50 message contains the result of integrity monitors  68  executed on the ranging source signals  120  received by the GBAS system from the Navigation Satellite  20 . 
     Each GBAS  30  on the network also receives the same set of messages (Types 1, 2, 4 and 48-50) from each of the other GBASs  30  on the network. This information is used for: (1) long base-line monitoring, and (2) development of corrections with integrity over a wide area. 
     Performance at the mobile receiver decreases as the distance (or baseline) between the GBAS and the mobile receiver increases. To protect the integrity of the mobile user, the GBAS monitors phenomena that vary over long distances. These phenomena include ionospheric effects, RFI interference, and Navigation Satellite ephemeris errors. GBAS receivers are placed in close proximity to each other. This proximity makes the effects of these long baseline phenomena difficult to observe and monitor since the observable effects over the short distance of separation are small. By using the receiver measurement data from other GBASs via the communication network (utilizing the Type 48 and 49 messages) the baseline is extended to the distance between GBAS systems and thereby the effects of the long baseline phenomena are more observable and can be monitored in a simpler and more robust manner. 
     The long baseline created by the use of data from other GBAS stations allows the GBAS to produce corrections with integrity over a wide area. The GBAS station would create these corrections from the Type 1 and 2 messages received. The resulting corrections can be transmitted on the GBAS local transmitter. The collection of GBAS systems interconnected over a large area would produce a similar function to the SBAS but without the satellite link. 
     SBAS Structure and Function 
     FIG. 7 illustrates the inventive SBAS structure. The SBAS  10  receives the LAAS Messages (Type 1, 2 48, 49 and 50) from GBAS systems  30  on the communication network  270  with an SBAS network message receiver  84 . The messages received are decoded and the data is passed to the SBAS Augmentation function  24  and SBAS Integrity Function  22 . The SBAS Augmentation function combines the data from the network along with the data from the SBAS receivers  110  received via an SBAS receiver communication input  232  to create corrections with a higher accuracy than the original SBAS system. The accuracy of the SBAS is dependent on the number and geographical dispersion of the measurements. Using the data from the GBAS systems received on the network increases both of these factors. 
     The SBAS integrity Monitor Function  22  may also use the measurement (Type 48, Type 49) and/or the correction data (Type 1, Type 2) as a mechanism to monitor the integrity of the corrections produced by the SBAS augmentation Function  24  from measurements made by the SBAS Receivers. Using the inventive GBAS Network data  170  to supplement the SBAS integrity has a distinct advantage. When there are GBAS geographically dispersed around the SBAS receivers, an additional and dissimilar collection of measurements is provided to the SBAS integrity function without the addition of more SBAS receivers. With this additional system of measurements corrections can be constructed (Using the Type 48 and 49 messages or Type 1 and 2 message) over the wide are of SABS coverage and then compared to the corrections generated by the SBAS Augmentation Function  22 . Additionally, the GBAS systems have a higher level of integrity than a SBAS system because the GBAS is used for precision approach applications where the requirements are stricter. The inventive SBAS, using the GBAS measurements with greater integrity realize the benefit of increasing the integrity of the SBAS corrections  132  since the data used to check the integrity is of higher integrity than was possible with SBAS alone. 
     The preferred embodiments illustrated in the drawings, and specific language above are illustrative of the purposes of the invention. No limitation of the scope of the invention is intended by this specific language, and the invention should be construed to encompass all embodiments that would normally occur to one of ordinary skill in the art. 
     The present invention may be described in terms of functional block components and various processing steps. Such functional blocks may be realized by any number of hardware and/or software components configured to perform the specified functions. For example, the present invention may employ various integrated circuit or optical components, e.g., memory elements, processing elements, logic elements, look-up tables, and the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. Similarly, where the elements of the present invention are implemented using software programming or software elements the invention may be implemented with any programming or scripting language such as C, C++, Java, assembler, or the like, with the various algorithms being implemented with any combination of data structures, objects, processes, routines or other programming elements. Furthermore, the present invention could employ any number of conventional techniques for electronics configuration, signal processing and/or control, data processing and the like. 
     The particular implementations shown and described are illustrative examples of the invention and are not intended to otherwise limit the scope of the invention in any way. For the sake of brevity, conventional electronics, control systems, software development and other functional aspects of the systems (and components of the individual operating components of the systems) may not be described in detail. Furthermore, the connecting lines, or connectors shown in the various figures presented are intended to represent exemplary functional relationships and/or physical or logical couplings between the various elements. It should be noted that many alternative or additional functional relationships, physical connections or logical connections may be present in a practical system. Moreover, no item or component is essential to the practice of the invention unless the element is specifically described as “essential” or “critical”. Numerous modifications and adaptations will be readily apparent to those skilled in this art without departing from the spirit and scope of the present invention. 
     LIST OF REFERENCE CHARS 
     
       
         
               
             
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
             
           
               
                   
               
             
             
               
                 1-99 Physical Hardware, databases, function blocks 
               
             
          
           
               
                   
                  10 
                 SBAS (satellite-based augmentation system) 
               
               
                   
                  12 
                 SBAS master station 
               
               
                   
                  14 
                 SBAS receivers 
               
               
                   
                  16 
                 SBAS area of coverage 
               
               
                   
                  18 
                 SBAS satellite 
               
               
                   
                  20 
                 navigational satellite 
               
               
                   
                  22 
                 SBAS master station integrity monitor processor 
               
               
                   
                  23 
                 SBAS user 
               
               
                   
                  24 
                 SBAS master station correction processor 
               
               
                   
                  30 
                 GBAS (ground-based augmentation system) 
               
               
                   
                  32 
                 GBAS receiver 
               
               
                   
                  33 
                 GBAS transmission to GBAS processor 
               
               
                   
                  34 
                 GBAS processor 
               
               
                   
                  36 
                 GBAS local area transmitter 
               
               
                   
                  37 
                 GBAS transmission to GBAS user 
               
               
                   
                  38 
                 GBAS user 
               
               
                   
                  40 
                 integrated SBAS/GBAS 
               
               
                   
                  52 
                 GBAS augmentation data database 
               
               
                   
                  54 
                 GBAS receiver status data database 
               
               
                   
                  56 
                 GBAS processor network input 
               
               
                   
                  58 
                 GBAS processor receiver input 
               
               
                   
                  59 
                 GBAS processor transmitter/user output 
               
               
                   
                  60 
                 GBAS processor network output 
               
               
                   
                  62 
                 GBAS LAAS message formatter 
               
               
                   
                  64 
                 GBAS LAAS message receiver 
               
               
                   
                  66 
                 GBAS receiver augmentation data receiver 
               
               
                   
                  68 
                 GBAS integrity monitor check 
               
               
                   
                  72 
                 SBAS augmentation data database 
               
               
                   
                  74 
                 SBAS master station network input 
               
               
                   
                  76 
                 SBAS master station receiver input 
               
               
                   
                  78 
                 SBAS master station output 
               
               
                   
                  84 
                 SBAS LAAS message receiver 
               
               
                   
                  86 
                 SBAS receiver augmentation data receiver 
               
             
          
           
               
                 100-199 Data/Protocol 
               
             
          
           
               
                   
                 110 
                 SBAS augmentation data (differential corrections, 
               
               
                   
                   
                 ionospheric delay errors, accuracy of navigation 
               
               
                   
                   
                 satellite signals, etc.) 
               
               
                   
                 112 
                 Processed augmentation data 
               
               
                   
                 120 
                 Navigation satellite data, including measurement data 
               
               
                   
                 132 
                 SBAS correction &amp; integrity data 
               
               
                   
                 150 
                 GBAS raw augmentation data 
               
               
                   
                 152 
                 Formatted GBAS differential correction and 
               
               
                   
                   
                 integrity data; LAAS formatted messages to the user 
               
               
                   
                 170 
                 Formatted integrated system data; 
               
               
                   
                   
                 LAAS formatted messages, types 1, 2, 
               
               
                   
                   
                 4 &amp; 48-50 to the integrated communication network 
               
             
          
           
               
                 200-299 Communication paths/network 
               
             
          
           
               
                   
                 200 
                 Integration apparatus communication network 
               
               
                   
                 212 
                 SBAS master station to SBAS satellite 
               
               
                   
                   
                 communication path 
               
               
                   
                 214 
                 Navigation satellite to SBAS receiver 
               
               
                   
                   
                 communication path 
               
               
                   
                 218 
                 SBAS satellite to SBAS user communication path 
               
               
                   
                 223 
                 Navigation satellite to SBAS user communication path 
               
               
                   
                 232 
                 SBAS receiver to SBAS master station communication path 
               
               
                   
                 234 
                 SBAS receiver to SBAS receiver relay communication path 
               
               
                   
                 240 
                 Navigation satellite to GBAS receiver communications path 
               
               
                   
                 242 
                 GBAS receiver to GBAS processor communications path 
               
               
                   
                 244 
                 GBAS local transmitter to GBAS user communication path 
               
               
                   
                 250 
                 Interconnecting system communication network 
               
               
                   
                 260 
                 SBAS to interconnecting system communication 
               
               
                   
                   
                 network communication path 
               
               
                   
                 270 
                 GBAS to interconnecting system communication 
               
               
                   
                   
                 network communication path