Both th route LSALT and GRID LSALT are valid for this purpose. Use the one that gives you the most advantage.

Thanks.

But with this question if i was able to use the grid LSALT it would be 3000 + 500 meaning that i wouldn't require an alternate. Innisfail is just inside the grid that has 3000ft.

Innisfail isn't an aerodrome without IAP.

The images i attached explains further.

The question states that there is currently no IAP that can be flown as the NDB is unserviceable and you aren't current on GNSS.

Read the last sentence in AIP GEN 3.3-6, Para 4.1

Ok so it says, "the highest grid LSALT must be used".

So does this mean use the higher of the sector LSALT and the grid LSALT?

I'm going to need a lot more clarification here as to what each one of these is for. I'm more confused than when i started haha!

Be realistic. You have some very high mountain peaks to the North, along your route from Cairns, which has 6700ft as lsalt. All Innisfail approach plates have mda at 6500ft.

It is by pure coincidence that Innisfail is on the other side of grid border (by 1nm) where lsalt is 3000ft.

I would use grid only when flying, as pulling rulers, protractors and calculating lsalt whilst in-flight isn't wise decision. The first 3 words in the question says "you are planning".

Hope above helps.

Yea that helps a bit.

I'll check the approach plates and compare the MDA for future questions like this.

Thanks