Setting station min. elevation or filtering - two different outcomes

SatNOGS Software
#1

When I edit my station, I can set “Minimum horizon (Your station minimum observation elevation)”. Let’s say I set it to 45° and save. Now, when I click “Calculate future passes”, I get three observations (max. elevations 89°, 68° and 80°).

If I go back and edit my station to set minimum horizon to 0° and save, and then click “Calculate future passes”, of course I get a lot more. But if I click the filter, and set “Max. elevation” to 45°, I get 63 (!) observations - many higher than 80° elevation.

Why this discrepancy - shouldn’t these two methods yield at least approximately the same results?

1 Like
#2

Indeed it is a little confusing and there is something hidden in there.

Minimum horizon means that observations will be scheduled from the minimum horizon to the max elevation and down again to min horizon. What’s hidden is that there is a minimum duration of one observation, if I remember well is 2min. So in this case you have observation that goes 45° -> max elevation -> 45° and have duration more than 2min.

In the second case you have observations 0° -> max elevation -> 0° and you set the Elevation filter which filters the observations by their maximum elevation. So, if you set the elevation filter from 45° to 90° you will see all the 0° -> max elevation -> 0° observations where max elevation is between 45° and 90°.

To make it more clear, if you set min horizon at 45° and set max elevation between 50° and 80° that means that you will get all the observations beginning from 45°, going to max elevation and ending at 45°, last more than 2 minutes and their maximum elevation is between 50° and 80°.

Let me know if that’s clear, any suggestion on renaming or having better interface are always welcome. :slight_smile:

2 Likes
#3

Ah, well, that certainly does explain it! Thank you! I’m not sure if there is a better way of explaining it in the interface, but it certainly makes sense :slightly_smiling_face:

#4

For my station, 488, I have min elevation set to 30 degrees due to terrain masking from north through southeast. However I see stations scheduling observations with a max el of 9 degrees! It’s frustrating to watch my rotor pointing into the hills and trees. It appears the “min elevation” setting has no effect. Likewise for Target Utilization.

#5

In some special events like deployments, ARISS Contacts etc, in most cases it works better (more chances to receive) to schedule from 0 to 0 degrees as either you don’t have the exact TLE that describe the orbit and/or satellite is transmitting so powerful signal that station can receive it bellow the min horizon. There are plans to implement a way to outline better the min horizon and improve performance of stations instead of using one value for 360 degrees.

About the Target Utilization, currently it is not a strict limit but anyone who schedules should try to follow it. In 488 I see that the target utilization is 50% which means that in a day it could be utilized up to 12h. I’ve checked the last month and it has an average of 30 observations per day with ~10min per observation that means ~5h/day which is ~20% utilization.

I understand that 20% can feel a lot in some cases, so please adjust the target utilization to the best value, but as I said, have in mind that this hasn’t been a strict limit yet. Just let me add here that as station owner you have always the right to remove or alter observations on your station if needed, in such a case a message to the scheduler (via pm here in community) would be nice (but not necessary) in order to be informed.

#6

Thanks Fredy, appreciate the explanation.

1 Like