Whilst agreeing with everything you put forth, I have been in the GIS business for over 13 years. The problem with GIS is NOT getting the terminology scientifically correct; the problem is getting the terminology into a format the pointy-haired bosses can understand well enough to approve a budget.
John D. Haynes Director Geodata Consultants, Inc. 1-800-838-6661 ex.10 [EMAIL PROTECTED] www.geodataconsult.com ----- Original Message ----- From: "Quantitative Decisions" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, September 18, 2002 3:49 PM Subject: Re: Sum: MI-L Taking bearings - terminology > At 11:12 AM 9/18/02 -0800, Declan Troy wrote: > >There were four suggestions for the proper terminology for a line > >projected from a starting point and a bearing; ... > >rhumb: a line or course on a single bearing > >strike: the direction of the line of intersections of a horizontal plane > >with an uptilted geological stratum; a distance > >transect: a line along which a survey is made > >vector: a course or compass direction especially of an airplane > > "Strike," "vector," and "bearing" all refer to a direction, not a line or > curve. A "rhumb line," or "loxodrome," is a curve on the earth's surface > whose bearing is constant from point to point. A "geodesic" is a curve on > the earth's surface that locally realizes the shortest distance between its > points. Geodesics are the (straight) "lines" of Riemannian geometry. > > (The bearings of most geodesics vary from point to point (geodesics lying > along the equator and along meridians are the exceptions). For spherical > earth models, a loxodrome will appear straight in a Mercator projection and > all geodesics through a given point will appear straight in a polar > projection centered at the point; otherwise, projections of loxodromes and > geodesics tend to be noticeably curved. Conversely, portions of > (euclidean) lines on a map usually correspond to curved routes on the > earth's surface. Thus, the question has multiple answers depending on > whether you mean "line" to be straight and whether by "projected from ... a > bearing" you mean straight on the earth's surface, straight on a map, or of > constant bearing.) > > Trivial matters like this are fascinating because they expose both the > richness and the frailties of our shared interest: multiple terminology > reflects not only multiple points of view but also the convergence and > collaboration of multiple disciplines, a decided strength of GIS; however, > lack of common terminology, and--far worse--the pandemic tendency to use > terms in a loose and ill-defined way, expose GIS as a young area without > (as yet) a solid professional or scientific grounding. > > Cheers, > Bill Huber > Quantitative Decisions > > > --------------------------------------------------------------------- > List hosting provided by Directions Magazine | www.directionsmag.com | > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > Message number: 3116 > > > --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 3117
