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40 APPENDIX 4: EXTENDED SIGNALS HEALTH STATUS FILES
Appendix 4 describes the Extended Signals Health Status (ESHS) message format.
40.1 Extended Signals Health Status
The Extended Signals Health Status (ESHS) data message provides the health status
of each of the modernized civil signals (L1C, L2C, and L5) for each SV, as defined in
Table 40-I.
Table 40-I Modernized Civil Signals
Modernized Civil Signal L1C L2C L5
Reference Document IS-GPS-800 IS-GPS-200 IS-GPS-705
Applicable SV Block/Iteration III IIR-M, IIF, III IIF, III
IS-GPS-200, Section 30.3.3.1.1.2, defines the signal health of L1, L2 and L5 as follows:
“the three, one-bit, health indication in bits 52 through 54 of message type 10 refers to
the L1, L2, and L5 signals of the transmitting SV. The health of each signal is indicated
by:
0 = Signal OK,
1 = Signal bad or unavailable
The ESHS format, as shown in Figure 40-1, contains a header that identifies the
number of records (number of satellites), filename (extension .ale), and the health of
each signal as described above. The ESHS sample shown in Figure 40-1, depicts one
data record out of 28 in this sample file.
LINE
Parameter Name
1 # of Records/File Name 28 CURRENT.ALE
2 GPS Week #/GPS TOA 175 589824
3 Blank
R-1 PRN 18
R-2 SVN 054
R-3 L1/L2/L5 Health Status 0-7 in binary format (000, 001, 010, 011,
100, 101, 110, 111)
R-4 Blank
Note: The left columns are for information only and not part of the CURRENT.ALE
file. The extended health Almanac sample (CURRENT.ALE) illustrated above is a
data sample of one record out of 28 in this sample file.
Figure 40-1 Extended Signals Health Status Data Sample
Table 40-II identifies the characteristics of each parameter in the ESHS message.
40-1
ICD-GPS-870
23 June 2011