Kestrel 4000

[bamawrx]

I am getting large variations in the elevations as indicated by my Kestrel 4000 nv. I inputted the reference pressure from an internet source for my local area so it can adjust its readings per the manual.

Wondered if anyone else has a similar observation, or if there might be a more accurate way to get a better reference pressure assuming that is the problem.

I get a 50' elevation deviation from the same spot day to day. Or is that as accurate as they get?

Thanks

 

[Lindy]

Re: Kestrel 4000

You must input the reference pressure every time you take a reading if you want the altitude to be accurate.

However, bear in mind that barometric pressure changes <span style="font-style: italic">about</span> 1 inch of mercury per thousand feet of elevation change.

That means that a 50 foot elevation change corresponds to about 0.05 inches of mercury - which is about the accuracy of the pressure sensor. See:

http://site.ambientweatherstore.com/specifications/kspecs.pdf

In any case, for shooting purposes, a 50 foot change in elevation is irrelevant.

If you need accuracy higher than that, for some purpose other than shooting, you need another instrument.

 

[KYpatriot]

Re: Kestrel 4000

The variance is likely from the reference pressure you are inputting...how far away is this measurement you are getting from the internet? Also, these pressures change every few minutes - could change enough to be 100' different in an hour's time. That is why aircraft get the local altimeter setting just before they land.

 

[bamawrx]

Re: Kestrel 4000

Ok thanks. I definitely misunderstood the process. Altitude applies to me only in shooting, and since I nearly always shoot at the same location I'm good. I thought that once I input a reference pressure the unit was calibrated. Not sure why I didn't realize its the difference between the reference and measured pressures that give you your altitude. Duh.. Glad I asked. Thanks for the info.

 

[mattj]

Re: Kestrel 4000

Depending on what ballistics software you are using, you can just use station pressure (which is your kestrel baro reading with altitude calibration set at zero) in place of altitude + baro.

It is nice because it is one less number to input, and you don't have to worry about calibrating the altimeter, etc.


Note: The software has to know it is using station pressure, don't just enter station pressure if it is expecting the normal altitude adjusted baro reading.