If I may add some comments to OS's comprehensive post..
(a) MUST make full analysis of all obstacles in the Takeoff path until reaching 1500 feet, or a higher altitude if dictated by obstacles.
It is a great concern that many operators don't worry too much about this ... ie there is some good fortune associated with the reliability of modern aircraft.
(b) In Australia this is mandated in the AIP, but surprisingly, not in the applicable performance regulations, CAO 20.7.1B.
The operational implementation (20.7.1B) of the airworthiness requirement (101.5/6 - now long gone) made inference of such a requirement. The AIP words were introduced quite some years ago by a Canberra operations chap motivated by the best of honorable intentions but not much background understanding of the realities of the engineering. The amendment was made to require the GA pilot to play operations engineer with his light twins in a manner roughly similar to what the airlines did with their far greater resources. After considerable argument I got agreement from higher up the chain to rescind the amendment (which I thought was a bit onerous and impracticable) .. however, as often happens, behind the scenes backroom manoevring saw that squashed and I eventually gave up .. however, I did frame the letter so that I could have the occasional giggle over the whole matter ...
(b) will often exceed 30 miles.
For a critical twin OEI operation, 50 miles is a useful ROM for the distance to a useful height (we all used to cite the Diesel 9 as being the archetypical example of this ..
but a necessity if we are to stay within 25 nm.
The alternative is to do a lot of obstacle work yourself for those difficult places ..
(c) A certain Obstacle Analysis provider
If I am inferring who OS is referring to correctly, I would say that, on the basis of an audit I did quite some years ago, they do a good job in what they do .. but, as cited by OS, there is a gap between that and what would be nice (necessary ?) to have for the operation. There were reasons for their policy and, if I am reading OS correctly, I am surprised that they haven't varied the approach as we had some detailed discussions on just this sort of problem.
(d) Australia is the exception with good Public Domain Obstacle GRADIENT data from Supplementary Takeoff Distances
As the surveys normally are done in the conventional manner, rather than being a strict inclinometer survey, the published gradients are calculated from the (x,y,z) triplets .. so, if you ask the right person .. you can get the specified obstacle data.
(e) So what to do? First, obtain data
And if you still don't have adequate data, you throw a theodolite over the shoulder and go bush for the time it takes to run a check survey to satisfy yourself that the data you propose to use is OK.
(f) Now, what do you want to do? Aim it and go, hoping for the best, or insist that your operator spend a few (quite a few) bucks on getting proper airport analysis and EOSID development?
This is an underlying consideration that OS, Mutt and I keeping trying to push in these sort of PPRuNe threads .. while there is no reason why a non-engineer pilot who knows the ropes can't do the work (and Tee Emm, in the previous post, is an example I could cite) the majority of pilots don't have the training or knowledge to do so. Far too often we hear tales from pilot colleagues (more so in the corporate/GA sector, but sometimes with the scheduled carriers) involving eyeballing a departure rather than doing the sums in a rational and constructive manner. It just doesn't work that way unless you are driving an F18 or similar triumph of thrust over aerodynamics .. The fact that we don't see CFITs day in day out is a reflection of aircraft engine reliability more than anything else.
Tee Emm's example is not atypical and that worthy gentleman can cite quite a few other operator instances of less than desirable policies from his very lengthy experience with a variety of airlines ...