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Philosophy question for discussion: What coordinates and range to use in a database for scanner+GPS operation?

For a simple conventional channel (Podunk Town PD), you get to choose coordinates -
a) Base/Repeater
b) Center of RF coverage area
c) Center of jurisdiction
- and range -
1) to ensure you're listening before you get in range (cover the RF fringe)
2) to ensure adequate signal before you tune it (cover inside the fringe)
3) to cover the entire jurisdiction

It's a step more complicated with a trunking system. The talkgroup coordinates probably get treated like a conventional channel, but when do you turn adjacent sites on and off? Where is a simulcast site "located"?

M) Use site lat/long and actual coverage range
N) Use site lat/long and pick ranges to ensure the circles overlap properly
O) Pick lat/longs and ranges to better match true RF coverage
P) Pick lat/longs and ranges to generate system coverage without holes but with minimum overlap
Q) Pick lat/longs and ranges that account for biases in the way talkgroups show up.
zz) and for any of the above, split into two or more locations to better cover a non-circular area (I hear the database admins groaning).

Your thoughts?

Location of tower.

On good band days or when ducting is going on, the signal travels for miles outside of it's normal range and makes it hard to draw a solid conclusion as to what the actual range of the repeater is. When one knows the physical location of the tower, they would then be able to go from there. Same for simulcast sites, physical location for those as well.

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Conventional:

c) Center of jurisdiction
- and range -
3) to cover the entire jurisdiction

Trunked:

N) Use site lat/long and pick ranges to ensure the circles overlap properly (lat/lon center appropriately adjusted for non-omni sites)
+ above rules for talkgroup center/range


The reasoning is simple. If I wanted to listen past jurisdictional boundaries then I'd put the scanner in search mode and be done with it. The advantage of location-based scanning is the scanner can give me local content without manually having to select/deselect banks every time I cross a jurisdictional boundary.

Agreed, I tend to go for jurisdictions on conventional and talkgroups.

Ignoring simo for the moment, I've found that using site coordinates leads to excessive overlap with flaky coverage. For instance, to get KC/VC Grass Mtn to cover Greenwater to Buckley without going too far into PierceCo, I've shifted the site a little bit NW, and also moved MacDonald north to get the transitions to work out. Remember that most of the time I'm on the main roads, so putting the boundary at the right spot on my route is more important than worrying that the circle isn't covering some area that has good RF but no roads.

For simulcast, you can't use transmitter coordinates unless you create a site for each simo tower - too much hassle for me, and you still wind up with the issues of overlapping sites described above. I just pick a circle (or two) that give the appropriate result, like getting EPSCA to turn on and off when crossing the floating bridges yet not going too far into Renton or Kangley.