Unexpected shift in tile cache

[Yarrr]

Managing Tile Cache's in Arcgis Pro for use with Arcgis Online.

I've noticed a spatial shift between the original raster and the tile cache. This has occurred in multiple projects/locations- generally around 3-4 of total shift.

What can be done to prevent this shift?

[LanceCole]

@Yarrr, 

What is the coordinate system of your original data?  

Are you projecting your data to WGS84 before publishing?  If so, are you using the correct transformation(s).

AGOL basically only works with the WGS84 coordinate system and will do its best to project source data to that coordinate system.  However, with a limited number of transformations available.  For example, we store all or data in Ohio North State Plane, US FT, NAD83/86.  If I use this data in AGOL we will see a 1.5-2.0 shift in the data because it applies the NAD83 to WGS84 transformation by default.  However, if we project our data to WGS84 using the NAD83(86) to NAD83 Ohio HARN transformation first then the NAD83 to WGS84 transformation it is spot on.  Unfortunately AGOL does not currently have the ability to apply multiple transformations.

[Yarrr]

Thanks for the reply.  I assumed it was something like that- we work in State Plane also, and I noticed that the tiles were WGS84.

So you're saying the transformation is correct and accurate if done discreetly before creating the tiles?

I.e. the correct workflow is to reproject the raster from NAD83 to WGS in Arcgis Pro, then create the tile cache for export and display in AGOL?

[LanceCole]

@Yarrr,

Is this for imagery/raster or vector data?

For our imagery and raster data, we created source mosaic datasets in their original coordinate system then used the source mosaic datasets to build a reference mosaic dataset in WGS84.   This allows multiple transformations to be applied and is reprojected on the fly in publishing out data to AGOL and building tile sets. 

Source, derived, and referenced mosaic datasets

I apologize, I do not remember the exact workflow we used for the vector data.  We did get it to work dynamically.  We since moved to NAD83(2011) which AGOL can transform in a single transformation without issue.

I believe we applied a transformation on the map the feature data was published from to an intermediary coordinate system that AGOL could transform directly to WGS84.  For example, published the feature/map service from NAD83(86) to NAD83(HARN) then AGOL was able to correctly transform that to WGS84.  This workflow allowed us to keep or data in our coordinate system while dynamically publishing to AGOL with correct transformations.

Taking control of transformations with hosted feature layers

If you are generating your tile cache in Pro and exporting. It does not appear you can apply transformations as part of these geoprocessing tools.  However:

1) You can try modifying the transformation applied to the map you are generating the tiles from including a few combination transformations.  The default for WGS84 to NAD 83 is (WGS_1984_(ITRF00)_To_NAD_1983).  Try a few others such as:

• (WGS_1984_(ITRF00)_To_NAD_1983_HARN + NAD_1983_HARN_To_HARN Florida)
• (NAD_1983_HARN_To_ WGS_1984 + NAD_1983_To_HARN Florida)

2) Use the Project (Data Management) tool,  which allows the application of multiple/combination transformations to be applied, and create a temporary feature in WGS84 to generate your tiles from.  This may be the best option for you since you are generating and exporting your tile sets in Pro.

The selection of the applicable transformations really depends on the coordinate system of your original data and how to get it to WGS84.  AGOL automatically applies a single transformation to the source data and it does its best to select the correct transformation.  Currently, AGOL cannot apply multiple transformations, combination transformations (noted above) and will not apply any transformation if it cannot determine the correct one to apply.

I hope this helps and have a great evening.

[Yarrr · Accepted solution]

Thanks again for the detailed response.

The data in question is raster UAS orthophotos and DEMs.

For our "real" work with this data, it must be in NAD83(2011) US Ft as a source mosaic. 

Sharing the derived mosaic in AGOL is a bonus/visualization deliverable- though the effort/complexity/workflow required to do so is mind boggling to me.

We were able to finally create a tile cache that was correctly located by first reprojecting the mosiac to WGS84, then creating the tile cache. I did tweak the transformation from the default here as you suggested- after trying all possible options to the map before creating the tile cache unsuccessfully.

I'm puzzled as to why the transformation settings would work as anticipated in the Reproject Raster tool, but not the Manage Tile Cache tool.

Regardless, we have a solution.