What would the reason be that the DA on a Kestrell is different from what FFS calculates

[TheGerman]

It's not a huge difference, but still 500-700 DA off between the two.

If I have the Kestrel running (its on all defaults, haven't messed with it) and use the temperature, baro and humidity readings, enter them exactly into FFS - I get a difference in DA where the Kestrel is 500-700 DA higher than whatever FFS calculates.

I've checked everything. Made sure station what checked in FFS and that it didn't have some conflicting data anywhere; but why would it be different?

 

[JohnsMyName]

I have no idea, but will be checking back for the answer. Anyone?

 

[Lowlight]

Usually, it's a bad setting but if everything is default it should be fine, the Kestrel uses pressure so that changes the actual number because the altitude is actually wrong a bit.

Actually, 500ft is not that much as DA is better rounded to the nearest 1000ft. You don't need the inbetween numbers.

 

[TonyC]

I'm just Pre reading the manual as I switch from colbore to FFS and came across this :-

[Note: When using a Kestrel connected to the program, do not expect the Density Altitude as calculated by the Kestrel unit to necessarily agree with the program’s calculation. The problem is that the Kestrel does not send the actual pressure, temperature and humidity to the program; rather, it sends rounded off values. For example, when the program calculates the pressure at sea level, it calculates it as 29.92115526565 in. Hg., uses that value in its calculations but displays the rounded figure of 29.92. The use of rounded figure for calculation purposes will result in a slight error in density altitude. When using the Kestrel, pressure is rounded to two significant digits, temperature and humidity values are rounded to one significant digit, and then these values are sent to the program. The program will use the rounded values, but the resulting density altitude calculation will not match that of the Kestrel which is using values of greater precision internally.]

 

[MACHTECH]

Nice catch Tony! I just purchased a Trimble and FFS and am in the process of reviewing the manual before I start programming. My PLRF15C arrived a few days ago. I'm just waiting on my 4500NV and all the mounting hardware for my RRS tripod. Can't wait to get it all clicking!

Todd

 

[TheGerman]

Figured it was something like what LL and Tony mentioned. Was just curious as it bothered me, even if it was an insignificant change.

 

[Petrov]

Make sure your reference altitude is set at 0 feet on kestrel