- Go to the Baro screen and set your actual reference altitude. ( http://www.whatismyelevation.com/ )
- Note the barometric pressure shown on that screen.
- Go to the altitude screen and set the reference barometric pressure to that shown on your baro screen.
- Now go back to the Baro screen and set your reference altitude to zero.
Important note: You should have Sync Baro or Sync Alt set to OFF when you are doing this or else you will be changing both references each time you make a change.
Kestrel 3500 Note:
It is the same procedure for the 3500. You don't have to worry about sync alt. The 3500 acts like the 4000 series with sync alt/baro permanently off.
You will always get station pressure from performing one single step, setting the Ref alt to zero. Everything else I've mentioned is how to set the altitude correctly when the kestrel is set to station pressure, since you no longer have the barometric pressure shown on the kestrel anymore.
This way you are getting the barometric pressure from the Kestrel to use for the Altitude and then reverting back to Station pressure on the Baro screen.
More on Station Pressure.
Really, the only people asking us about these are those using ballistic software...
Basically you need station pressure for ballistic calculations. Many applications assume though that you only know barometric pressure from the weather channel. So they want you to input the barometric pressure and your altitude. The program then calculates the station pressure from that. So if the customer’s program asks for both pressure and altitude, they most likely want the barometric pressure and altitude and then the customer would have to adjust for each time they move locations.
Typically for shooting, you will want your station pressure, not the barometric pressure. Station pressure is the pressure felt at that spot, without being adjusted for altitude. This is the same pressure being felt by the bullet when traveling in the air. When you adjust station pressure for your altitude, this is now Barometric pressure and typically only used to track weather patterns. In order to get the Kestrel to read station pressure, you should set your reference altitude to ZERO. This will then show you station pressure, every time, and there would be no need to adjust it if you move locations.
Unfortunately station pressure is not readily available if you do not have a Kestrel. Therefore many ballistics programs have the user enter their barometric pressure AND altitude. The ballistics calculator then calculates station pressure from this for the ballistics solution. This is because barometric pressure is widely produced by the local weather stations and easily obtainable. If your ballistics programs requires you to enter the barometric pressure and altitude, then you will need to adjust your reference altitude each time you change locations. You will also need to keep updating your reference barometric pressure on the altitude screen to ensure your altitude is correct.
If there is an option in the ballistics calculator that you are using to enter the station pressure vice barometric pressure, then please select this option and set your reference altitude to zero. If not, then you will need to enter your reference altitude each time you move locations to get the barometric pressure. Use this barometric pressure as your reference barometric pressure for the altitude and use those numbers for your ballistics solution.