Which messages work better in city environment, MSM4 or MSM7 ?

Q&A forumWhich messages work better in city environment, MSM4 or MSM7 ?
dskumher asked 4 months ago

I use MSM4 messages 1074.1084,1094,1124 which give instant fix in open sky conditions but in city ,most of the time I do not get RTK fix. Shall I use MSM7 messages
for getting fix ? Byte size should not be too high as I use RTCM3 output only from the base.

3 Answers

[…Messages 1097 (GALILEO), 1107 (SBAS), 1117 (QZSS), 1127 (BeiDou) are MSM7 (Multiple Signal Messages). MSM7 are high precision messages which contains a complete set of RINEX observations with extended resolution. That means that you should turn on only one message of choosen system to get all data about it.
Remember, that you can not use GLONASS and BeiDou systems together.
Use 1117 QZSS message if you are located in East-Southeast Asia and Australia.
Use 1107 SBAS message if you are located in Noth America, Europe, North Africa, Near East, South Asia and East Asia, Russia
Use 1127 BeiDou message if you are located in Asian region and Australia……]
Anyway, you should not turn off important messages, especially MSM messages. Instead, you can set the cycle to update messages at 1 to 2 Hz to reduce data bandwidth.
 

skypuppy answered 4 months ago

You mean SBAS is supported now?

clive1 replied 4 months ago

No, that you pick either MSM4 or MSM7 messages across all constellations to have consistency, other providers might have SBAS as an option from their Base Station or RTK Network.

skypuppy answered 4 months ago

Um, isn’t “SBAS” named only in the GPS constellations (US?)

clive1 replied 4 months ago

The MSM messages are passing observation/ranging data, not “what” the SBAS satellites are sending in the data payloads. Same with the QZSS.
RTK is about applying rigid geometry, you’ve got a reference station bolted to a known location, and a common view of a bunch of points in space, frozen in an instant.

clive1 replied 4 months ago

They are not “corrections” in the “differential” sense.