NavCom StarUtil-3000 Rev.G - Manual (Page 78)

StarUtil 3000 User Guide – Rev G
4-76
GEOIDAL99 Format
The GEOIDAL99 database file must be a binary file. It has a header plus a data section,
described below.
Table 3 : GEOIDAL99 Header Format
Data Item Data Type Units Bytes
Header
SLAT – Southernmost latitude R64 Degrees 8
WLON – Westernmost longitude R64 Degrees 8
DLAT – Distance interval in latitude R64 Degrees 8
DLON – Distance interval in longitude R64 Degrees 8
NLAT – Number of rows of latitude U32 4
NLON – Number of columns of longitude U32 4
IKIND – Data type
The value always should be 1 (=> real *4)
U32 4
The data section of the GEOIDAL99 database file follows immediately after the header. Table 4
displays the format, in which “a” represents a R32 Data Type, R = Row and C = Column. For
example, “a
R3C2
” = 4 bytes (real number) of data at Latitude Row 3, Longitude Column 2.
The data is variable length. NLAT is the total number of rows. NLON is the total number of
columns. (Table
3 defines NLAT and NLON.)
Table 4 : GEOIDAL99 Data Format (variable length)
1 2 3 4 NLON
1 a
R1C1
a
R1C2
a
R1C3
a
R1C4
… a
R1CNLON
2 a
R2C1
a
R2C2
a
R2C3
a
R2C4
… a
R2CNLON
3 a
R3C1
a
R3C2
a
R3C3
a
R3C4
… a
R3CNLON
4 a
R4C1
a
R4C2
a
R4C3
a
R4C4
… a
R4CNLON
… … … … …
NLAT a
RNLATC1
a
RNLATC2
a
RNLATC3
a
RNLATC4
a
RNLAT/CNLON
The data section is stored in the file beginning with the Westernmost (WLON)/Southernmost
(SLAT) point. In Table
4 , this is the first point in Row 1: “a
R1C1
”. Row 1 (row-major) is stored:
“a
R1C1
”, “a
R1C2
”, “a
R1C3
”, “a
R1C4
”, etc. Then Row 2 is stored: “a
R2C1
”, “a
R2C2
”, “a
R2C3
”, “a
R2C4
”, etc.
This is continued sequentially for each row until the Easternmost/Northernmost point,
“a
RNLAT/CNLON
”, is stored. Each row creates a list of 4-byte real values NLON long, with DLON
longitudinal intervals along the row of latitude.