Re: Graph Plotting - Reprise

[brian whatcott <inet@INTELLISYS.NET>]

At 19:11 8/16/00 -0600, you wrote:
> > Try out Tecplot, it said. And I did. 6 MBytes of download.
>
> TX for the tip Brian -- This sounds like just what I need, but .........
>
> $1295!!!!!!!!
>
> Jim Green
> mailto:JMGreen@sisna.com
> http://users.sisna.com/jmgreen


Sounds pretty steep to me Jim. But then again - this morning I was
pondering an attack on an intermittant problem.

 A simulator sometimes crashes into an invisible obstruction while
 flying at several thousand feet.

A representation of surface terrain is provided by the random x,y,z
 co ordinates of navaids. (Actually it's a lat,lon,elevation triplet
to place on the reference geoid. This is replaced by a close polygonal
grid of coordinates when a custom airfield boundary region is entered,
 so that the day visual scene is reflected appropriately by radar
altimeter etc. at close quarters.)

The simulator host interpolates between the nearest navaids in a local
radius to provide a current terrain elevation, and if the navaids are
too sparse, it assumes it may have flown over a coast, and begins to
slope the effective terrain elevation towards sea level.

 This situation is not helped when the digital database (such as
Jeppeson provides) allows some navaids to be listed as 0 elevation
when their precise data is not available.

The problem occurs (I surmise) when an airfield comes into range,
over high terrain with sparse navaids and the elevation data again
 become profuse, or at least available.
 This presents a step discontinuity - a glass mountain.

Wouldn't it be nice, I ponder, to represent the navaid elevations
in the area of interest as a scattered plot, which Tecplot could
then interpolate on a grid as elevation contours? (Visualization
is such a powerful sensory mode...) Then if I positioned a circle
around the landscape contours of interest to locate a hole in the
 navaid coverage, it would not be unreasonable to add to the
appropriate database an elevation marker - a dummy navaid with
no other purpose than relay its elevation, if you will.

Hmmm...all I need is a $1300 purchase request approved then?
...Probably not!

brian whatcott <inet@intellisys.net>  Altus OK
                Eureka!