How does a mosaic dataset handle rasters in different projections?

The spatial reference of a mosaic dataset is specified when you create it (using the Create Mosaic Dataset tool). This spatial reference is used to manage all of the data that is ingested into your mosaic dataset. As always, re-projections are performed on-the-fly by the system.

Therefore ArcGIS handles the various projections for you.

One aspect of the spatial reference you do need to worry about it which coordinate system is specified to manage your mosaic dataset. The spatial reference or the extents of the data you are ingesting into your mosaic dataset should fall within the horizon of the mosaic datasets spatial reference extent. Any data that falls outside of the spatial reference will not display. Therefore a safe approach will be to use a spatial reference that is large- such as Mercator or WGS 1984.

Submitted by: Vinay V.

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5 Comments

  1. sibbald says:

    If the data is reprojected on-the-fly what transformation is used? How can the user find out what has been used to ensure that the most accurate one is applied? Or are you suggesting that the data must al be from the same datum, such as WGS 1984?

  2. rdunfey says:

    Good question, and on what basis is the transformation chosen?

  3. Simon Woo says:

    If you have more than 1 transformation required in the mosaic dataset, then you will need to specify the Geographic Coordinate System Transformations within the Mosaic Dataset Properties (Defaults Tab).

    I cannot post screenshots within a blog reply. Perhaps I can write up the steps to specify the Geographic Coordinate System Transformation for a mosaic dataset in next week’s blog.

    Here is the quick answer though so you are not stuck till then … In your Catalog Window, right-click your mosaic dataset and click on Properties. Click on the Defaults tab. Scroll to the bottom and click on the … to specify any Geographic Coordinate System Transformations.

  4. burwelbo says:

    I have the same problem. What I would like to khow is how to first set up a custom datum transformation and apply that? Does the custom transformation need to be on the server? If so, where do I put it? We don’t run ArcMap on the servers.
    Thanks
    Bruce Burwell

    • Simon Woo says:

      Setting up a custom datum transformation is a bit out of my scope. I do know that there is a Geoprocessing tool to create one. This question is better for a Geographic Coordinate System forum or better yet our great Support staff can find the correct analyst for you. Sounds like you also need a Server specialist since you will be serving your custom geographic transformation. I would assume that the custom transformation needs to reside on the server though.

      Sorry I am not of more help on this question. Please do call our Support staff to help you out. Thanks!