It seems to me that there is a lot of discussion about the altitude variation of the missing 777 without any verification of how the Malaysian military made that determination. A land based radar would only get primary returns over the ocean out to about 250 miles (maybe) but the radar would only show position, not altitude. Altitude is reported via the transponder, which was supposedly turned off. So how did the military determine the aircraft altitude? A ship based radar might have some chance of estimating altitude from a position near the aircraft, but even that’s doubtful. So, how credible is the assertion of the Malaysian military absent any qualifying information?
If I’m off base on this, someone please set me straight.
I have no idea. Does the following help answer that?
Because the plane stopped transmitting its position about 40 minutes after takeoff, military radar recorded only an unidentified blip moving through Malaysian airspace. (...) That is in part because the data is based on signals recorded by two radar stations, at the Royal Malaysian Air Force’s Butterworth base on the peninsula’s west coast, near Penang, and at Kota Bharu, on the northeast coast. Two radars tracking a contact can significantly increase the reliability of the readings.
Still, Ravi Madavaram, an aerospace engineer at the consulting firm Frost & Sullivan, based in Kuala Lumpur, said the accuracy of ground-based radars in determining a plane’s altitude diminishes the farther away the plane is. When Flight 370 lost contact with ground controllers, it was more than 100 miles from Kota Bharu and 200 miles from Butterworth, distances that he said could degrade accuracy. But the altitudes measured as the plane crossed the peninsula would be more reliable, he said.