[alma-config] topographic constraints

[John Conway]

On Fri, 11 Feb 2000, Min Yun wrote:

> 
> Peter Napier just reminded me that we need more progress on 
> incorporating the topographic constraints on the existing
> strawperson designs.  I have not heard from anyone whether 
> anyone else tried to use Bryan's digital mask or creating
> your own.  I would like this to be the top agenda item for
> the next telecon on the 23rd.  Please give this some thought
> and communicate any progress or comments to A. Webster or me.
>

A had a quick look at 
the 5 degree gradient mask; it is certainly a lot more restrictive than
the 10 degree mask. Its useful to have these standard 
masks (I guess to make people try to optimise with similar 
restrictions). However given that the amount of available area 
in the SW for placing telescopes changes so much between 5 and 10 degrees
gradient perhaps we could also have a FITS map with just the gradient in 
every pixel (maybe it exists somewhere but I couldn't see 
it on Bryans web page). There seems to be contributions to the 
total gradient due to a general slope plus local details, given this 
maybe if one went to a cutoff of say 7 degrees the amount of available
land dramaticlly increases, but with just the binary masks is hard to
tell.

It would be nice also to have some idea of what maximum 
gradient we can manage and what the tradeoffs are with the
transporter costs - can Peter Napier or someone else 
comment on this? Clearly its a vital question for deciding which
geometries are possible.

    John