Excludes unknown-position sats from skyview displays.

In some cases, the elevation and azimuth information are missing
(i.e., reported as 0) for some satellites.  E.g., the Navika-100
receiver fails to report positions for SBAS satellites.  This change
avoids showing such satellites at the "north point" of the display.
They are *not* excluded from the textual list.

TESTED:
Ran xgps, xgpsspeed, and webgps.py against data from a Navika-100
receiver, and verified that the SBAS satellites are no longer
inappropriately shown at the top.

Signed-off-by: Gary E. Miller <gem@rellim.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/xgpsspeed b/xgpsspeed
index 30954b2a..277b575a 100755
--- a/xgpsspeed
+++ b/xgpsspeed
@@ -449,15 +449,18 @@ class NauticalSpeedometer(Speedometer):
         self.cr.set_source_rgb(r, g, b)
 
     def draw_sat(self, satsoup, radius, x, y):
-        """given a sat's elevation, azimath, SNR, draw it on the skyview
+        """Given a sat's elevation, azimuth, SNR, draw it on the skyview
         Arg:
         satsoup: a dictionary {'el': xx, 'az': xx, 'ss': xx}
         """
-        h = pi / 2 - radians(satsoup['az'])  # to xy
+        el, az = satsoup['el'], satsoup['az']
+        if el == 0 and az == 0:
+            return  # Skip satellites with unknown position
+        h = pi / 2 - radians(az)  # to xy
         self.cr.set_line_width(2)
         self.cr.set_source_rgb(0, 0, 0)
 
-        x0, y0 = NauticalSpeedometer.polar2xy(radius * (90 - satsoup['el']) // 90, h, x, y)
+        x0, y0 = NauticalSpeedometer.polar2xy(radius * (90 - el) // 90, h, x, y)
 
         self.cr.new_sub_path()
         if gps.is_sbas(satsoup['PRN']):