topic Re: ArcMap-SPCS Zone Edge Distortions in Coordinate Reference Systems Questions

ArcMap-SPCS Zone Edge Distortions

ChuckTurlington — Wed, 04 Oct 2017 11:51:52 GMT

Hello,

I am using ArcMap 10.4.1.

I am still reviewing the basics of map projections and came across the concept of planar projections not fully touching at edges, due to distortion, if for example, the globe was projected using a planar stereographic type Planar Projection. However, I it seems to me that none of the State Plane zones would likely "stich" together seamlessly at the edges either. But I also thought one of the advantages of the State Plane System was that it offered continuity between large areas that are projected. So I have to ask, do the State Plane projections between states touch seamlessly at edges, or can one expect a distorted miss-alignment along zone edges ?

Re: ArcMap-SPCS Zone Edge Distortions

DanPatterson_Retired — Wed, 04 Oct 2017 12:04:49 GMT

can't speak for state plane, but in older UTM maps in Canada at scales of 1:50,000, there used to be vertical shifts along the edges of map sheet adjacent polygons. I would suspect/hope that such artifacts would be 'corrected' in digital versions. As a test, crank 2 adjoining map sheet up and have a look

Re: ArcMap-SPCS Zone Edge Distortions

MelitaKennedy — Wed, 04 Oct 2017 16:26:51 GMT

Hi Chuck,

Most projections will not "stitch together" on the edges. Polyconic is one that will, normal cylindricals (not transverse or oblique Mercator) as well. A state plane zone is designed for the zone's area, not whether it will match up with neighboring zones.

I hadn't heard that state plane zones were designed for continuity for large areas (except within a zone). Instead, I think it was to define a coordinate reference system with overall linear distortion no worse than one part in 10000.

Melita