Orient ОС-201 [166/244] Sbas18ionospheric grid point masks

Orient ОС-201 [166/244] Sbas18ionospheric grid point masks
COMNAV OEM BOARD REFERENCE MANUAL
Chapter 4. Logs Messages
ComNav Technology Ltd.
147
CNT-OEM-RM001, Rev 1.8
Supported Format
ASCII
Reply (ASCII)
Field#
Field Type
Format
Binary
Byte
Binary Offset
1
SBAS17
header
H
0
2
PRN
ULong
4
H
3
#ents
Ulong
4
H+4
4
Data ID
Ushort
2
H+8
5
Entry PRN
Ushort
2
H+10
6
Health
Ushort
4a
H+12
7
X
Long
4
H+16
8
Y
Long
4
H+20
9
Z
Long
4
H+24
10
X vel
Long
4
H+28
11
Y vel
Long
4
H+32
12
Z vel
Long
4
H+36
13
Next entry
H+8+(#ents x 32)
4+#ents*9
t0
Ulong
4
H+8+ (#ents x32)
5+#ents*9
xxxx
Hex
4
H+12+(#ents x32)
6+#ents*9
[CR][LF]
-
-
-
4.2.10.11 SBAS18 Ionospheric Grid Point Masks
Description
The ionospheric delay corrections are broadcast in SBAS Message Type 18 as vertical delay
estimates at specified ionospheric grid points (IGPs), applicable to a signal on L1. In order to
facilitate flexibility in the location of these IGPs, a fixed definition of densely spaced IGP
locations is used, resulting in a large number of possible IGPs. The predefined IGPs are
contained in 11 bands (numbered 0 to 10). Bands 0-8 are vertical bands on a Mercator
projection map, and bands 9-10 are horizontal bands on a Mercator projection map.
The density of these predefined IGPs, is dictated by the possible large variation in the
ionosphere vertical delay during periods of high solar activity, especially at lower latitudes.

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