• State Suggested Answer
  • Replies 7 replies
  • Answers 2 answers
  • Subscribers 114 subscribers
  • Views 1190 views
  • Users 0 members are here

Different Geographic Projections from Two Files are Slightly Offset From Each Other

David Hollner
Offline

Hello forum!

I have two survey files.  One older survey uses an older state projected geographic coordinate system and the newer survey uses a newer projected GCS.  When both are referenced into a mutual file (both Geographic-Reprojected), all points are 1.5–2 feet off from each other, give or take.  Using any other projection on one doesn't come much closer.

Is there a way to adjust a setting somewhere to make them fall closer together, since reprojected references aren't allowed to be moved?  Or, is this the closest they can get?

  • Assume I cannot have one's survey coordinates rerun under the other's coordinate system.
  • See attached image.  (I work for a company that may not allow me to attach design files.)
  • Changing "Reference Reprojection Settings" to Yes or If Spatially Large, or the method to AEC Transform, appears to make no difference.

Coordinate System Projections (North America > USA > New York > ...):

  • Older survey:  "NY-E - NAD27 New York State Planes, East Zone(3101), US Foot" -- 2nd from the top for me.
  • Newer survey:  "NY83-EF - NAD83 New York State Planes, East Zone, US Foot" -- 6th from the top for me.  Project files will use this projection.  I am working about 1,025,000+ feet from global origin.

Working Units/Accuracy Settings:

  • Survey Feet (SF) Master Units
  • Resolution:  1000 per Distance Survey Foot
  • Working Areas:
    • Total:  1,705,912,362 Miles
    • Solids:  813.442402 Miles (4.29497 e-5 SF accuracy)

Using MicroStation V8i SS10, v. 08.11.09.919

Thank you!
-- Dave

Parents
  • 0 Offline

    I read this: Depending on where you are in North America, NAD27 and NAD83 may differ in tens of meters for horizontal accuracy. The average correction between NAD27 and NAD83 is an average of 0.349″ northward and 1.822″ eastward

    But you could try EPSG:32015 for NAD27 as it has slightly different scale factor.

  • 0 Offline in reply to Oto
    Oto said:
    The average correction between NAD27 and NAD83 is an average of 0.349″ northward and 1.822″ eastward

    Hmm, that seems like it would make up most the difference.  Question is now, is there a way to move the reference of the older survey that distance while keeping it as "Reprojected"?

    I think ultimately I'll have to just make it Coincident to the original and reproject it manually.  Thanks for the quote about the correction distance.

    Oto said:
    But you could try EPSG:32015 for NAD27 as it has slightly different scale factor.

    I tried all other NY East projections that were in feet before posting.  None made too much of a difference.  One (probably that one) moved a fraction of an inch it seemed; not two feet.

Reply
  • 0 Offline in reply to Oto
    Oto said:
    The average correction between NAD27 and NAD83 is an average of 0.349″ northward and 1.822″ eastward

    Hmm, that seems like it would make up most the difference.  Question is now, is there a way to move the reference of the older survey that distance while keeping it as "Reprojected"?

    I think ultimately I'll have to just make it Coincident to the original and reproject it manually.  Thanks for the quote about the correction distance.

    Oto said:
    But you could try EPSG:32015 for NAD27 as it has slightly different scale factor.

    I tried all other NY East projections that were in feet before posting.  None made too much of a difference.  One (probably that one) moved a fraction of an inch it seemed; not two feet.

Children
Communities
Support and Services
Training and Learning
Social Media