Feature group

Feature

Sigma

Cableless systems with only shootblind capability

Cableless systems with some data return capability

Benefit of feature and related issues

GPS timing

Internal to ground unit

Mostly internal to ground unit

Some systems rely on distributed timing

GPS reception cannot be guaranteed everywhere. Alternatives may be essential.

Ground unit shape

Virtually impossible to tip over

Some systems easy to tip, may lose GPS signal

Some systems easy to tip, may lose GPS signal

High stability internal clock

Yes

Not usual

Not usual

VHF sync

Option

Not possible

Not possible