 |
 |
 |
 |
|
 |
 |
SAE J2735-Draft-Rev26 [issued: 09-18-08]
-
218 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
Remarks: Some message sets allow a request of other relevant messages by use of this ID, some others do
not. Some messages do not yet support this ID and force the message receiver to sort the recovered
message to align event geographically. This is expected to be an area of harmonization. Developers should
also note that data from different source agencies can vary with the numbering used as well.
8.4 Data Element: DE_MAYDAY_Heading_number [ATIS]
Use: The value of heading. This element is used to convey the heading of the device when moving. Units
are in 360/254 degrees where the value of 0x00 is taken to be due north, 0x01 is taken to be slightly east of
north.
ASN.1 Representation:
Heading ::= INTEGER (0..255)
-- Vaild Encoding rules , an unsigned 8 bit value
-- 0 = due north, larger going clockwise (east of north)
-- (0..253) 360/254 degrees per bit
-- 254 = no heading at all (stationary)
-- determined by
-- examining the velocity DE
-- 255 = heading not known
XML Representation:
<xs:simpleType name="Heading" >
<xs:annotation>
<xs:documentation>
Vaild Encoding rules , an unsigned 8 bit value
0 = due north, larger going clockwise (east of north)
(0..253) 360/254 degrees per bit
254 = no heading at all (stationary)
determined by
examining the velocity DE
255 = heading not known
</xs:documentation>
</xs:annotation>
<xs:restriction base="xs:unsignedByte"/>
</xs:simpleType>
Used By: This entry is directly used by the following 4 other data structures in this standard (record type,
descriptive name, ASN.1, and XML name (if present) of each):
DF
DF
DF
MSG
In addition, this item may be used by data structures in other ITS standards.
Formula: Encode as an unsigned 8 bit value with 0 = due north, increasing going clockwise (east of north)
and (0..253) 360/254 degrees per bit. Use values of 254 = no heading at all (stationary) and 255 = heading
not known.
Remarks: No accuracy requirement known. Note that magnetic north can vary from giod north
considerably and in the presence of local objects. This element was originally defined in J2313. From
Section 8.12 "Heading."
8.5 Data Element: DE_MAYDAY_Location_quality_code [ATIS]
Use: A value representing the "goodness" of the position estimate (accuracy). The element is used to
convey the relative quality of a GPS generated location. This quality value is enumerated as shown, as
follows below.
 |