User's Guide ______________________________________________________________________
66 __________________________________________________________________ M210482EN-B
Telegram Structure Remarks
a.
Spaces (20 hex) always appear with the following bytes: 5,
7, 11, 20, 26, 32, 38, 44, 49, 54, 59, 65, 71, 76, 79, 82, 91.
The only other byte that may contain a <SPACE>, is byte
78, provided that the dimension is in meters.
Numbers are always given with the leading zeros as in
bytes 27 to 31 in the example.
b.
NODET (and NODT) indicates that the value in question
has not been detected because there was only one cloud
layer or no cloud layer at all, for example.
Like any measured value, NODET also contains
information about the result of the measurement.
NODET may appear instead of cloud layers, minimum
vertical extensions of clouds, and vertical visibility.
c.
When bytes 83 to 90 signal an CL31 alarm, all cloud
detection values within the telegram are replaced by minus
signs (-, 2D Hex). For example:
----- is shown instead of bytes 27 to 31.
d.
All values given are height above the runway level;
Ceilometer CL31 itself might be located above or below
the runway level. Therefore, byte 72 must always contain
a sign byte, or -.
Failure and Warning Messages
Bytes 83 to 89 of the LD40 standard telegram inform about warnings
and errors. A '0' signifies that no error of that error group has
happened.
An alarm will lead to data telegrams to contain invalid data. A
warning status does not cause invalid data.
The following tables describe how CL31 is mapped to the LD40 error
groups. Table 9 below shows the definition of the different error
groups.
