[Manifold-l] Distance calculations

[Lorne]

> the gist of the problem is that there are several ways to measure
distances
> and while we could always take steps to make it easier to measure
distances
> in some default way (eg, over an ellipsoid), the fundamental problem of
> choosing the exact type of distance you want to use will not go away
> any time soon.

Just a comment Adam... all personal opinion.

I 'suspect' that large numbers of Manifold users are not formally trained in
GIS. This would be the result of low product price and the fact that
Manifold directly targets high-end Office users.  I believe (rightly or
wrongly) that most of the non-GIS professionals using Manifold will want to
work in non-projected space.  There are also situations that force that
approach - I once had managers who wanted all maps in Lat/Long. Lat/Long
also makes more sense in some cases.  For example, when you are looking at
large distances in meteorology you generally want to work with Lat/Long
positions. Trying to set a storm position at x:3495827, y:492883 doesn't do
it and flipping back and forth from projected to non-projected space is not
in the cards for more limited users (although that little x/y toggle on the
coordinates dialog is great!).  Most meteorologists using the standard
Meteorological Service of Canada Polar Stereographic maps will not know that
the native map unit is metres not degrees since they are always working with
the graticule that is overlaid on the map.  When one moves into GIS from
disciples such as this, one of the biggest hurdles is coordinate systems and
projected space.

I have never understood why Manifold makes working with unprojected space so
difficult. This is one area where lower level software works well for many.
There would be no requirement to have separate SQL functions to calculate
distances in Mapinfo - there would only be one function such as

   SELECT Distance(Geom ([ID]),NewPoint(-77.0770,38.9657),"mi")FROM [Usps 2
Table]

If the drawing is Lat/Long, then ellipsoid distances are returned
automatically (which is what a meteorologist would want anyway :-)

I always find the typical exchange below puzzling in the sense that it is a
standard newbie question in Manifold and a problem that could be
circumvented (although I know there are all sorts of technical
considerations).

GeoReference Tread:
http://69.17.46.171/Site/Thread.aspx?id=26643&ti=632924946083230000

mikereed at 8/29/2006 9:58 AM (17 hours ago) (#26644) 
I am a newbie to Manifold and have not been able to find a solution to the
following: My goal is to create 30 mile buffers around points........... 

artlembo at 8/29/2006 1:38 PM (14 hours ago) (#26659) 
use SQL for that.
select distance(d1.id,d2.id,"mi") from d1,d2

adamw at 8/29/2006 8:57 PM (6 hours ago) (#26670) 
It is possible once you project the drawing you want to use from lat/lon to,
say, Mercator.

This has been discussed elsewhere, but I guess this is one of those
difficult Manifold development team problems. How to reconcile the main aim
of creating the world's best GIS where professional opinions hold great sway
with the wants of the many lower functioning users drawn to the product
because of low cost and the MS Office user marketing. (I'm one of those
"lower functioning" types so no offense intended :-)

I know that Manifold representatives actively promote the idea that Manifold
may be too much software for many users and that they might want to consider
simpler solutions.  This will not stop large numbers of people coming to
Manifold because the the price :-)

Lorne