Create projection NAD_1983_CSRS_UTM_Zone_17N (WKID: 22617, or 22717) v6 or v7

[MelanieWawryk]

We urgently need the conversion from NAD_1983_UTM_Zone_17N (WKID: 26917) to NAD_1983_CSRS_UTM_Zone_17N (WKID: 22617 or 22717) v6 or v7 for Ontario.

This request has been logged as ENH-000171425, and while it has been marked as a long-term roadmap item, it’s critical to emphasize that the delay is not due to a lack of business justification but rather the significant development effort involved. However, this is a pressing need. NAD83 (CSRS) UTM v7 was released in March 2019, and v6 in 2017, yet Ontario—a large and key region—was somehow overlooked in earlier roadmaps.

We cannot afford further delays. Please prioritize this conversion as Ontario's operational needs are growing more urgent.

[MelanieWawryk]

Thank you! Now the difficult task of moving the geodatabase to new projection. Layers need to be recreated in a new geodatabase since you can't change the projection on an existing layer so a huge task but happy there is a way forward.

[BryanMc]

 @BojanŠavrič , we really appreciate this update for Canada!

We reviewed the Geographic Transformation documentation, and it mentions that NAD83v80vg is being used for all the CSRS transformations (v3 to v6; v3 to v7; v3 to v8).  We also tested and it does give the same coordinates when transforming to v6/7/8 (and matches documentation).  The Esri Coordinate system installer does install three NTV2 velocity files for NAD83v80VG, and NAD83v70VG, and NAD83v6VG files. However, only v80vg is in use. This means transforming from v3 to v6/7/8 gives the same results. When we use the full desktop NRCan TRX tool (not the web version), it can use the 3 different velocity grids (same 2010 epoch). This creates a bit of a variation b/w the software outputs (however v3 to v8 is the same in both software since both using v80vg).

We can see the difference in v6vg, v70vg, and v80vg is extremely small, but since they are all included with the Coordinate System installer, wondering why v60vg and v70vg aren't being used for the v6 and v7 transformations?  Should the target frame match the velocity grid (v7 using v70vg)? or better to always use latest velocity grid? Otherwise, aren't they all just v8 with v6 or v7 labels? "There is no spoon"?

Sorry if I'm misusing some terms here and appreciate any feedback you may have.

PS. If not mentioned lately, thank you to you and your fellow creators for Equal Earth PCS!

[BojanŠavrič]

Hi @BryanMc,

Thank you for your questions! Transformations to NAD83(CSRS) v6 and v7 do not use their corresponding NTv2 velocity grids because those transformations were superseded in the EPSG Geodetic Registry (see EPSG codes 10529, 10530, 10534) by new transformation variants that use the latest NTv2 velocity grid, NAD83v80VG. This is how NRCan registered these transformations. According to EPSG, users should use the latest velocity grid since transformations with previous grids are superseded.

Because NAD83(CSRS) v6, v7, and v8 share the same anchor epoch, 2010.0, transformations from NAD83(CSRS) v3 produce identical results for each. We have included all three NTv2 velocity files in the ArcGIS Coordinate Systems Data so that users who wish to work with superseded transformations can create their own custom geographic transformations and ensure possible backward compatibility with older product releases, should we later add support for those superseded transformations.

I hope this answers your questions...

Thanks,
Bojan

[BryanMc]

Thank you @BojanŠavrič ! This answers the question and has helped me get the ah-ha moment! This will definitely help us prepare for our future CSRS and NATFR2022 adventures.