ST_GEOMETRY function to remove M and/or Z values

[Bud]

Could a function be added to ST_GEOMETRY to remove the M-dimension from a geometry?

Similar to SDO_GEOMETRY's CONVERT_TO_STD_GEOM function:

SDO_LRS.CONVERT_TO_STD_GEOM
Converts an LRS geometric segment to a standard SDO_GEOMETRY line string by removing measure information.

[Bud]

We also need to be able to remove the Z dimension from ST_GEOMETRY.

Related post here: 

I need to remove Z dimension on spatial column (ST_GEOMETRY) with Esri on Oracle using the PL/SQL pa...

[Bud]

For anyone who doesn’t want to wait for this to be implemented, here are some ideas for a temporary workaround:

Convert the ST_GEOMETRY to WKT, manipulate the WKT ordinates, convert back to ST_GEOMETRY.

Note: We might lose some information from the SHAPE if we did that, such as losing true curves, since true curves are only stored in the shape blob, not in the ST_GEOMETRY portion of the SHAPE column. What column is true curve data stored in? (SDE.ST_GEOMETRY for Oracle)
In other words, the ST_GEOMETRY constructor function that we’d use to update the SHAPE would replace the entire SHAPE value, so the shape blob with true curves info would be lost.

Links:

• Remove third ordinate from string of 3 ordinates
• In a string, replace third number in each set with new number
• Or convert to SDO_GEOMETRY, remove the Ms or Zs using Oracle Spatial functions, and then convert back to ST_GEOMETRY.
  • Idea: Function to remove Z, but not M, from SDO_GEOMETRY
  • Remove Z dimension
  • Convert M-enabled SDE.ST_GEOMETRY to SDO_GEOMETRY using SQL

I haven’t had a chance to test those ideas.