Frsky Mavlink Passthrough - MSL truncated?

@Eric_Stockenstrom wrote:

Hi Guys

I'm using Frsky pasthrough telemetry for my personal tracker, and Altitude msl appears to be one order of magnitude too small and truncated/rounded, or am I missing something?

True altitude here is 1466m msl (yes very high!)
Altitude msl contained in GPS Status frame (Data ID 5002) is binary 15.

Actual data frame = 0xFC011B7

I understand that the stated unit of measure is decimetres, and power = 2, but how do we end up with 15? The granularity is way too course to be useful.

I see the Arducopter code looks like this:

// Altitude MSL in dm
const Location &loc = _ahrs.get_gps().location();
gps_status |= prep_number(roundf(loc.alt * 0.1f),2,2)<<GPS_ALTMSL_OFFSET;
return gps_status;

Maybe the roundf(loc.alt * 0.1f) is the culprit?

Eric

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