Georeferencing – Should I Update or Rectify?

Once you have finished choosing and evaluating your links, you are ready to persist your results. There are 2 options to choose from: Update Georeferencing and Rectify.

Update Georeferencing

  • Only updates your files- no redundancy created
  • Update are almost immediate

Rectify

  • A new raster dataset is created and the original file is left unaltered
  • Choose many options: such as file format, cell size, resampling technique, and NoData value.
  • This is the only option for some files: such as GRID and other files that cannot be updated (e.g. read-only files)

Depending on your workflow, both Update Georeferencing and Rectify have their advantages.

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3 Comments

  1. gionette says:

    We’ve found that if you are making an image catalogue with the georeferenced images, you need to rectify or else if doesn’t work properly. Also I find that rectifying is necessary if you might need to use that image in another map document, because I’ve found that sometimes when I’ve updated the georeferencing, I’ve had visibility issues when I’ve tried to bring it into another arcmap document. On the other hand, after Version 9.0, we’ve found that a big annoying , pain in the behind, black box gets added to rectified rasters. Now if you can get rid of that you did in earlier ArcMap versions a lot of users would be thrilled!!!

  2. Simon Woo says:

    If you meant raster catalogs (within a geodatabase), did you create a managed, or unmanged raster catalog? Referenced (Unmanged) raster catalogs should be able to pick up the new georeferencing image georeferencing. A Managed raster catalog on the other hand stores the rasters in the geodatabase, so you would actually have to modify those rasters, not the original.

    If you meant DBF style image catalog, then those are always referenced (unmanaged). However those image catalogs required you to specify the minimum bounding rectangle for the rasters in advance, so any update to the source georeferencing will not matter. You should update the georeferencing first, and then create the image catalog (with the new proper extents).

    In regards to the black border, if you specify a NoData Value while you Rectify (i.e. 0), or if you specify Grid as your output format, your output should not have a black background. I believe previously we automatically output your data to a Grid format. ArcGIS 9.x uses IMG and TIFF as the default output formats.

  3. gionette says:

    the only problem with the grid is that it’s pretty much useless anywhere else BUT I do a lot georeferecing of black and white documents and If I set no data to 0 it makes it all black but If i set no data to 1, OMG it makes it wonderfully perfect!!! Thanks so much for the tip. I’ve been looking and have asked a few people *cough* tech support *cough* and never got this answer! You have saved us a lot of arcscan work!!! Thanks Simon!!