2022 09 09 Meeting Minutes

Attendees: Andre, Jack, Chris, Glen

Action items:

• Can you put a concatenated operation into a BoundCRS? Andre will ping Proj mailing list to see if anyone knows.
• BAG is specified as meters for the vertical unit? Glen will check.
  • Confirmed
• Test use of BoundCRS with GDAL. Glen will test.
  • Able to make OSR object, but to what end?
• Confirm Geographic CRS is okay in the BAG. Glen
  • Confirmed
• Convert recommendations outline to full recommendations draft. Glen

Outline of recommendations:

1. Problem statement from original position paper from last ONSWG meeting

2. Thoughts on the purpose of the CRS

   1. Clear declaration of CRS

   2. Support of datum transformations

3. Validation

   1. XML Validation

   2. CRS Validation

4. Recommendations

   1. WKT2 is allowed

   2. CompoundCRS and 3D CRS

   3. BoundCRS - Shall be compound if used

   4. EPSG in the WKT is helpful if available, but not required

   5. Direction of the vertical WKT shall be consistent with the BAG spec, which is as an Elevation (positive up).

   6. Units of measure for the vertical shall be consistent with the BAG spec, which is meters.

5. Transformations

   1. Describe the meaning of the target CRS in a BoundCRS when doing transformations

   2. Meaning and availability of information provided in a BoundCRS

      1. Storage of corrector surface in the BAG as representing the total transformation described in the BoundCRS

   3. Expected consistency in systems between vertical and horizontal, making compound or 3D

   4. Use of PROJ strings for describing the abridged transformation in the BoundCRS. Is there another option available?

   5. We expect the horizontal information in the BAG to be well known such that transformations will be supported, so additional information to support horizontal transformations isn't required in the BAG.