I think that's saying it's only seeing one satellite (number 18):

GSV - GPS Satellites in View

The number of satellites in view, together with each PRN (SV Id), elevation and azimuth, and C/No (Signal/Noise Ratio) value. Only four satellite details are transmitted in one message. There are up to 4 messages used as indicated in the first field NoMsg.

$GPGSV,NoMsg,MsgNo,NoSv,{,sv,elv,az,cno}*cs<CR><LF>
Name
ASCII String
Units
Description
Format
Example

$GPGSV
string
$GPGSV

 

Message ID
GSV protocol header
NoMsg
1 digit
3

 

Number of Messages
Total number of GPGSV messages being output
MsgNo
1 digit
1

 

Message Number
Number of this message
NoSv
numeric
10

 

Satellites in View

 

sv
numeric
23

 

Satellite ID
SV ID (GPS: 1-32, SBAS 33-64 (33=PRN120))
elv
numeric
38
degree
Elevation
Maximum 90
az
numeric
230
degree
Azimuth
Range 0 to 359
cno
numeric
44
dBHz
C/No
Range 0 to 99, null when not tracking
...

 

 

 

...
Data of 2nd, 3rd Satellite (same as above)
sv
numeric
29

 

Satellite ID
SV ID (Range 1 to 32)
elv
numeric
71
degree
Elevation
Maximum 90
az
numeric
156
degree
Azimuth
Range 0 to 359
cno
numeric
47
dBHz
C/No
Range 0 to 99, null when not tracking
...

 

 

 

...

 

cs
hexadecimal
*7F

 

Checksum

 

 

 

 

 

<CR> <LF>
End of message

C


On Aug 7, 2007, at 10:13 AM, Michael Caughey wrote:

$GPGSV,1,1,01,18,,,27*74