Category: Navigation

This seems odd.  Yesterday the FAA issued a Flight Advisory — PDF here — warning that during a period of “GPS testing” starting today aircraft transiting the large area diagrammed above could find that “the GPS signal may be unreliable or unavailable.”  WTF?  But never mind sites like Engadget which immediately assumed that “anyone planning on using GPS in the southeastern US for the next month or so will likely want to make sure they have a fallback option.”  If you read the Advisory carefully you’ll see that whatever is being tested — which sure seems like jamming to me — will apparently be more effective at high altitudes than on the levels most of us travel…

So that’s the Garmin GMR 604 xHD open array radar I installed last May painting a crowded harbor on the screen of a GPSMap 7212 in late July.  Gizmo was headed southwest at the time — the GPS heading, or COG, is meaningless because she’s tied up to a float — and so you have to twist your brain a bit to see how well the radar is imaging the details of Jonesport’s Sawyer Cove, and hence that the long straight target at the upper left is the famously uncharted steel and concrete breakwater there.  And I think if you make the comparison you’ll agree that the true color target display really helps to understand what the radar is doing.  Those light blue and green returns at upper left, for instance, are almost certainly some sort of noise created the breakwater’s heft and hardness.  I could have turned the gain down to eliminate that noise, but then I might not have seen the light blue at lower left — which is an emerging mud flat, I think — and similarly difficult targets once I got underway.  True color returns is indeed my favorite feature of the xHD/7212 combination…

It’s about to be Thanksgiving here in the states, and — aside from the normal family stuff (which is huge) — I surely am thankful for being the custodian of a wonderful boat, for living in a beautiful corner of the oceans, and for getting to fool with some great technology.  Above is Gizmo’s lower helm, the Fall 2010 edition, and while there’s a lot here that I haven’t written about yet, I’m going to focus today on that little Garmin GPSMAP 740 on the chart table…