Geodesic for measuring; Planar for analysis

[Craig_Eissler_Iceman]

Measure tool: Geodesic vs. Planar: The Help page indicates "Geodesic" is always more accurate.

OK, but, why do they also indicate that projected coordinate systems are more suited for analysis -- which includes measuring, of course?

In fact, in the Calculate Geometry menu tool (but NOT the ArcGIS toolbox tool) is grayed out, when attempting to measure in geographic coordinates ..this, I understand. How it relates to the other observations, I do not.

Thanks, CCE

[DanPatterson]

Perhaps you can use this as an example for Tech Support

LL corner  300,000, 5,000,000

UR corner 300, 010, 5,000,010

MTM zone 9  (NAD_1983_CSRS_MTM_9)

[Craig_Eissler_Iceman]

Thanks again for sharing. Accuracy, or measurement result differences, wasn't my original concern on this Post. However, now I'm starting to see some differences within the same measurement mode and projected coordinate system -- similar to what you illustrated. Also see my results below between the Measure tool and the Shape_geometry fields. ...Close, but not exact. Why not? ...Ok, I'll submit a Case to Esri Support to see what they say.