Kestrel 4000 set up (take 2)

[nheninge]

I am working on validating the numbers my K4000 is spitting at me and need some help, specifically with regards to BARO and ALT settings.

I want the unit to give me station pressure, so I set the ref ALT to 0 on the BARO screen, and all is well. (SP = 29.54)

On the ALT screen my true altitude is showing correctly for the area (225 feet verified by topo map), but the reference BARO pressure on this screen is 29.82. My actual station pressure is 29.5 and the BARO pressure is likely about 30.05. Adjusting this number only inflates or deflates my altitude falsely. Why is the unit using a number somewhere in between my SP and BARO readings?

In the BARO calibration screen I decreased the pressure to reflect my current altitude at the Station pressure.

I realize THIS data reflects small changes, but I have a high altitude hunt coming up and I want to understand where these numbers are coming from, and make sure my unit setup is OK.

Thanks ahead

[Mikecr]

Originally Posted by nheninge

I want the unit to give me station pressure, so I set the ref ALT to 0 on the BARO screen, and all is well. (SP = 29.54)

This is right

Originally Posted by nheninge

On the ALT screen my true altitude is showing correctly for the area (225 feet verified by topo map), but the reference BARO pressure on this screen is 29.82

This should be as much needed

Originally Posted by nheninge

Why is the unit using a number somewhere in between my SP and BARO readings?

I 'Think' the ref BARO reading on the Altitude screen is SL adjusted pressure(not station)

Originally Posted by nheninge

In the BARO calibration screen I decreased the pressure to reflect my current altitude at the Station pressure.

Again, I 'think' you now have all calibrated correctly

It's been a couple years since I calibrated mine, as it still holds correctly. Easy quick check for me because I'm exactly 10' above sea level. My user screen is TEMP, PRESSURE, and HUMIDITY. That's it. Need to jog my memory..

So how does it look now on your pressure and altitude screens? Is it showing station pressure and ~225' correctly?

[nheninge]

All looks well, except...

Altitude seems to be all over the place (100' to 300' feet) (constant actual 225' without moving the unit). I guess I can just adjust altitude (by adjusting the reference BP on the altitude screen) when a known altitude is encountered? If the altitude function does not affect Kestrel's station pressure calculation, then maybe it doesn't matter. Altitude can be determined on my garmin.

My user screen setup is the same as yours. Second user screen with wind, altitude, and density altitude. Projected elevation/windage values when compared to field data was excellent to 1000 yards plus (here in texas)(, but it is hard to verify drop with a change in altitude during the trip. I suspect this is a problem for most. A few test shots on arrival should do the trick.


What do you mean by SL? Too many acronymns!

[Mikecr]

SEA LEVEL adjusted. That's what I think BARO represents on the altitude screen.
Altitude wiggles with pressure, and will always because it's not actually measured, but calculated by a Krestel -using pressure, which wiggles.
It's the station pressure that's needed for ballistics, so you could turn off altitude from the menu, as well as wind chill, wet bulb, etc.
GPS measures actual altitude, if for some reason you ever want it.

[nheninge]

Gotcha! My thoughts exactly.

From the manual:

Barometric Pressure and Altitude Adjustment
The Kestrel 4000 will measure station pressure in order to calculate barometric pressure and altitude. Changes in either air pressure or altitude will affect these readings, so it's important to make adjustments as necessary.

Sounds like station pressure is pretty solid and everything else is based on this measurement.

Thanks for the advice.