[GRASSLIST:1159] distance on ellipsoid?

[Deuchler, Christoph]

Hi,

for the question on which reference body/coordinate system to choose for a
GIS it would be great if some of the GRASS experts could confirm or comment
the following assumptions:


(1) when working in a projected location (e.g. UTM) all distance
measurements are done according to Pythagoras (file distance.c in the source
code)

(2) when working in a Lat/Lon location the distances are measured along a
great circle on the surface of the ellipsoid (file geodist.c, I don't have
the book on hand which is mentioned in the comments)

similar for area measurements: 

(3) in projected locations areas are measured in the plane (file area.c)

(4) in Lat/Lon locations the surface of the ellipsoid/sphere is returned
(files area_ellipse.c and area_sphere.c)

Every reply is greatly appreciated.

Christoph