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I'm using ArcGIS 10.1. When I Buffered I changed the environments to compare the two different projections. WyLAM is a statewide Lambert Conformal Conic projection used for Wyoming. State plane in Wyoming is broken into four zones and looks like it buffering is more accurate in a smaller zone.

I have a well pad that needs to be outside of a 4 mile buffer in Wyoming. I created one that is 4 miles in Wyoming East. Another person created one in wyLAM. I wanted to know why it was giving two distances.

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closed as unclear what you're asking by PolyGeo, Fezter, whuber Mar 11 at 22:45

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question.If this question can be reworded to fit the rules in the help center, please edit the question.

    
What GIS software and version are you using? What precise procedures did each person use? What is wyLAM? Can you edit your Question to revise it with these details, please? –  PolyGeo Mar 11 at 19:51
    
I'm using ArcGIS 10.1. When I Buffered I changed the environments to compare the two different projections. WyLAM is a statewide Lambert Conformal Conic projection used for Wyoming. State plane in Wyoming is broken into four zones and looks like it buffering is more accurate in a smaller zone. –  joebob Mar 12 at 15:21
    
Please edit your Question to provide such clarifications rather than tacking them on as comments. –  PolyGeo Mar 12 at 19:39
    
Please tell us more precisely how far apart those two buffers are: the answers you get will differ depending on whether the errors are a few feet or much larger than that. –  whuber Mar 12 at 20:37

1 Answer 1

up vote 3 down vote accepted

That's going to depend on where the data is located relative to the defining values of the two coordinate systems. WyLam is a statewide coordinate reference system (CRS) that uses the Lambert conformal conic map projection. The Wyoming State Plane zones use the transverse Mercator map projection. Both are conformal so they maintain shapes (angles) rather than distances or areas.

If the area of interest happens to fall near a central meridian or standard parallel, etc. of one of the CRS, that will minimize the distortions due to the projection. It could also matter if different geographic CRS were used.

Note: Depending on the software / tool that you used, the buffer may have been built using geodesic distance calculations and the results then projected into the data's CRS.

For the undistorted areas, only the central meridian and standard parallels matter in a conic projection, and only the central meridian and scale factor do in transverse Mercator.

**WyLAM**
Central Meridian = -107.5
Standard Parallel_1 = 41.0
Standard Parallel_2 = 45.0
False Easting = 500000.0
False Northing = 200000.0
Latitude Of Origin = 41.0

**Wyoming East (NAD 1983)**
Central Meridian = -105.1666666666667
Scale Factor = 0.9999375
False Easting = 200000.0
False Northing = 0.0
Latitude Of Origin = 40.5

In the State Plane zone, at 42N, 104d 18' 30"W, scale is 0.9999997, for example.

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