topic Re: Projection changes Spatial Reference but not X and Y. in ArcObjects SDK Questions

Projection changes Spatial Reference but not X and Y.

IanHern — Thu, 03 Feb 2011 20:56:38 GMT

Hey Guys,

I am calling Project on IGeometry (its an IPoint) and its updating the Spatial Reference but not the X and Y. Any ideas on what could be causing this?

Point X, Y, and SpatialReference.Name before projection:
-111.500208333333
52.7583416666666
GCS_North_American_1927

and after projection:
-111.500208333333
52.7583416666666
NAD_1927_UTM_Zone_5N

This is what I expect to see after the projection:
3040679.65085327
6998991.0570187
NAD_1927_UTM_Zone_5N

Cheers,
Ian

Re: Projection changes Spatial Reference but not X and Y.

MelitaKennedy — Thu, 03 Feb 2011 22:28:19 GMT

Hey Guys,

I am calling Project on IGeometry (its an IPoint) and its updating the Spatial Reference but not the X and Y. Any ideas on what could be causing this?

Point X, Y, and SpatialReference.Name before projection:
-111.500208333333
52.7583416666666
GCS_North_American_1927

and after projection:
-111.500208333333
52.7583416666666
NAD_1927_UTM_Zone_5N

This is what I expect to see after the projection:
3040679.65085327
6998991.0570187
NAD_1927_UTM_Zone_5N

Cheers,
Ian

Hi Ian,

The point's too far away from zone 5, which has a central meridian of -153. We set a limit of 45 degrees of longitude from the central meridian in ArcGIS. If a point falls outside the horizon, it's unchanged. I can project the point in the underlaying projection engine directly, but I don't get those exact values (3214331.2658 6691441.5288). There aren't many transverse Mercator implementations which could take those XY values and return back the given lat/lon values.

-111.5 is in zone 12N.

Melita

Re: Projection changes Spatial Reference but not X and Y.

IanHern — Fri, 04 Feb 2011 15:34:41 GMT

I tried using zone 12N and the X Y didn't convert, in fact I am getting some super weird behavior.

So I have this point from a Feature Layer and I want to project it to a projected coordinate system (from a geographic one with the same datum).

When I project the point the Spatial Reference updates to be correct but the X and Y values aren't changed.

HOWEVER if I create a new Point and set the X Y and Spatial Reference to be the same as my first point, then when I project this new point the X, Y, and Spatial Reference all update. I have spent lots of time comparing the original point and my created point and can not see any differences between them.

And ideas?

Cheers,
Pooh