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» Online Classroom   »   » Public Discussion of Marine Radar   » Geographic Radar Range calculation

Author Topic: Geographic Radar Range calculation

 - posted June 27, 2008 05:00 PM      Profile for TomD           Edit/Delete Post 

I have the following question from the RADAR workbook, question 1-4. "Your scanner is 16 ft high, a large target is 36 feet high, how far off might you first see this target?"

My calculations are 1.22 X (SQRT antenna height) + 1.22 X (SQRT target height) = 12.2 nm.

The correct answer in the workbook is 10 nm.. Where did I go wrong?

From: Oregon
David Burch

 - posted June 27, 2008 05:06 PM      Profile for David Burch           Edit/Delete Post 
Good question. You have done the geographic range properly, but at this distance off just the very tip of the target is just on the visible horizon. There would be no radar target showing to send reflections back from till it gets a bit closer and some target is above the horizon.

the question reads "how far off might you first see this target?" and the only reasonable answer is 10 nmi... ie a bit closer than the geographic range. ie it did not ask for the geographic range.

other choice was 6, way closer than needed, and another was 24, below horizon, etc.

From: Starpath, Seattle, WA

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