negative elevation

[hextejas]

I have inherited a satellite tracking program and told to make it work. Well, I am forging ahead but this is my 1st time into amateur radio (KG5TKY) and radio satellites.
Anyhow, the tracking software has an azimuth and elevation. What I dont understand is how the elevation can be a negative from where I am.
Houston, TX, essentially sea level.
That's a puzzle.
Thanks

 

[kruser]

Anything below the horizon would be negative given the crafts and your altitude.

 

[hextejas]

Anything below the horizon would be negative given the crafts and your altitude.

Thank you kruser, I am still trying to figure all this out and you have been a big help.

 

[RFI-EMI-GUY]

That's common and many programs have a setting to announce Aquisition of Signal AOS when the elevation becomes positive or above a user set minimum elevation. You might not have AOS below a certain EL because of trees or surrounding terrain.