Kestrel Compass issues

[jaybic]

Hello all,
I have a Kestrel function issue. I have both a 4500 with AB and a 5700 with AB and have to recalibrate the compass all the time. I will calibrate the compass(not sure if I should use TRUE or Magnetic), test it against a real compass...reads 0 degrees/North properly. get a target DOF by capturing of say....139 degrees. then capture the wind speed and direction and get something like 20 degrees...and the wind is damn near blowing straight at my back and towards the target. I spent enough time in the USMC in land nav courses and then in the desert and all over the globe to know that is not correct so any ideas? Am i doing something wrong in the kesrel setup? does the Kestrel need to have the compass calibrated every time it is used? and if so, why is it wrong even after it has just been calibrated?

Thanks for the insight ladies and gents,

Jamie

 

[_Windrider_]

Hello all,
I have a Kestrel function issue. I have both a 4500 with AB and a 5700 with AB and have to recalibrate the compass all the time. I will calibrate the compass(not sure if I should use TRUE or Magnetic), test it against a real compass...reads 0 degrees/North properly. get a target DOF by capturing of say....139 degrees. then capture the wind speed and direction and get something like 20 degrees...and the wind is damn near blowing straight at my back and towards the target. I spent enough time in the USMC in land nav courses and then in the desert and all over the globe to know that is not correct so any ideas? Am i doing something wrong in the kesrel setup? does the Kestrel need to have the compass calibrated every time it is used? and if so, why is it wrong even after it has just been calibrated?

Thanks for the insight ladies and gents,

Jamie

Do u have the plastic strip between the batteries?

 

[jaybic]

on the 4500, yes...the 5700 does have that.

 

[_Windrider_]

on the 4500, yes...the 5700 does have that.

Ok last thought. Yes u need to calibrate every time, at least I do. And second, be sure you have the magnetic deviation set for your longitude. You should calibrate in magnetic.

 

[KestrelMeters]

Hey Jamie,
I think the issue here is that you may be expecting both DOF and Wind direction to be absolute values but Wind Direction is not absolute, it is relative to the DOF.

For example, suppose you capture your DOF as 90 degrees (shooting East). The wind is blowing from the South (180 degrees). When you do your capture the DOF will show as 90 degrees (absolute) BUT the wind direction will also show as 90 degrees (relative to DOF). The wind is coming from 90 degrees in relation to the target.

So if you are showing a wind direction of 20 degrees, that IS pretty much a downwind wind direction. 0 degrees would be a perfectly downwind wind and it doesn’t matter what your DOF is, a perfect downwind will always be captured at 0 degrees.

Typically we tell people to just to use Magnetic North and they should be fine. You shouldn’t have to calibrate the compass every time they use it, but it is good practice to calibrate any time they go to a different location to shoot.

I’ve attached something that helps people manually enter numbers, maybe this will help explain it.
You can also see this post I put up for you:
https://kestrelmeters.com/blogs/news/compass-calibration-dof-magnetic-vs-true

 

[_Windrider_]

Hey Jamie,
I think the issue here is that you may be expecting both DOF and Wind direction to be absolute values but Wind Direction is not absolute, it is relative to the DOF.

For example, suppose you capture your DOF as 90 degrees (shooting East). The wind is blowing from the South (180 degrees). When you do your capture the DOF will show as 90 degrees (absolute) BUT the wind direction will also show as 90 degrees (relative to DOF). The wind is coming from 90 degrees in relation to the target.

So if you are showing a wind direction of 20 degrees, that IS pretty much a downwind wind direction. 0 degrees would be a perfectly downwind wind and it doesn’t matter what your DOF is, a perfect downwind will always be captured at 0 degrees.

Typically we tell people to just to use Magnetic North and they should be fine. You shouldn’t have to calibrate the compass every time they use it, but it is good practice to calibrate any time they go to a different location to shoot.

I’ve attached something that helps people manually enter numbers, maybe this will help explain it.
You can also see this post I put up for you:
https://kestrelmeters.com/blogs/news/compass-calibration-dof-magnetic-vs-true

I didn’t even consider that.

 

[Nik H]

Hey Jamie,
I think the issue here is that you may be expecting both DOF and Wind direction to be absolute values but Wind Direction is not absolute, it is relative to the DOF.

For example, suppose you capture your DOF as 90 degrees (shooting East). The wind is blowing from the South (180 degrees). When you do your capture the DOF will show as 90 degrees (absolute) BUT the wind direction will also show as 90 degrees (relative to DOF). The wind is coming from 90 degrees in relation to the target.

So if you are showing a wind direction of 20 degrees, that IS pretty much a downwind wind direction. 0 degrees would be a perfectly downwind wind and it doesn’t matter what your DOF is, a perfect downwind will always be captured at 0 degrees.

Typically we tell people to just to use Magnetic North and they should be fine. You shouldn’t have to calibrate the compass every time they use it, but it is good practice to calibrate any time they go to a different location to shoot.

I’ve attached something that helps people manually enter numbers, maybe this will help explain it.
You can also see this post I put up for you:
https://kestrelmeters.com/blogs/news/compass-calibration-dof-magnetic-vs-true

Very handy to know.

Can you check the link you put up. I get a 404 error....page not found

 

[8up]

Ran into this also when I taught a Kestrel class to my guys. Nothing is wrong, as it has been explained by Kestrel themselves. If you run dof and wind off a compass azimuth reading, it's going to confuse the user. Set the wind direction to the clock method and it will match what the wind is actually doing at your firing position.

 

[jaybic]

Ok, I perhaps have a better understanding of what is going on now. And if so, nothing is actually broken or wrong other than myself interpreting the data wrong. IF I am understanding correctly and I capture the DOF first, it will give me an azimuth that is absolutely relative to NORTH(assuming the compass is correctly calibrated)...ie NORTH being 0 degrees.

My DOF being say...225 degrees...which is a perfect SW direction. and the wind is blowing right to left exactly(because wind is always exact....) 90 degrees to my DOF(putting the wind on an azimuth heading of 135 degrees relative to the compass), the kestrell would say it was 90 degrees)relative to my DOF? If so and that is correct, it appears I should just stop trying fix things that are indeed not broken it appears...

1.North= 0 degrees
2. DOF=225 degrees(relative to NORTH on compass
3. wind azimuth relative to North on compass is 135 degrees(which actuall puts it 90 degrees to my DOF?.....)
4. kestrel says 90 full value wind hold regardless of actual wind azimuth on compass?(relative to DOF as per Kestrel)

If this correct I have spent quite some time chasing my tail...

 

[V-Ref]

I think you've got it except...generally wind direction is expressed on the "heading" you'd be facing if you looked directly into the wind. Look up your local airport weather observation and stand outside and check the wind direction....it'll make sense. So in your example above if DOF is 225, and you have a right to left wind that's exactly 90 deg full value, a Weather Station would report that as 315 at 19??? knots.

You're correct in thinking from a Land Nav Mag compass perspective with your back to the above wind your compass would read 135. But wind direction reporting standards hails from Nautical and then Aviation roots, and is generally expressed in the direction you'd be pointing when facing directly into the wind.

You might be over thinking it some. I think you're on it except for this piece.

For the Kestrel...DOF=magnetic...WD=use Clock position relative to DOF (DOF=12 o'clock)...and then where the wind is FROM, not going TOO...is the Clock position.

So in your scenario above, DOF of 225, a perfect right to left full value wind would be from the 3 O Clock

Hope that helps.

 

[jaybic]

good points....I was not thinking of the wind as "the wind" but as an azimuth and not a "heading" and i do understand the difference. I guess the I have to think of it as me "flying" 105 gr bullets...but I do like the idea of using a DOF as an azimuth and the wind in an "oclock" format...I think that will simplify things...and I do have a habit of overthinking this sort of thing so...thanks again for the insight!