As part of my current project I have calculated NDVI change over time for four connected Landsat frames. Now that I have this done I was planning on mosaicking them together so I could conduct some analysis (mainly to relate NDVI change to landcover type, topography and other landscape variables).

The issue I am having is that the southern most frame is in UTM Zone 12N while the three frames north of it are in UTM Zone 11N. This causes the mosaic to shift pixels around a bit. I created a mosaic in ENVI of just the three northern frames and it worked perfectly, with pixels staying where they should be and values remaining the same.

I am looking for advice on how to proceed.

What is the best way to mosaic all four frames together that has minimal impact on my subsequent analysis (eg. not changing or interpolating new values)?

Or should I run my analysis twice (one for the UTM Zone 12N frames and another for the UTM Zone 11N frame) in order to insure the quality of my data and avoid any possible warping that reprojecting could introduce?

I would like to mosaic all four frames together if I could, but not at the cost of lowering the quality of my data.


You can reproject your images into a projection system which is not zone based, then mosaic the reprojected images. On a side note, if you have access to ArcGIS, I personally recommend you do the whole process in ArcGIS, as you’ll have a larger control. For example, by setting the Snap Raster option to an existing raster file, you can make sure the individual reprojected images still lined up nicely.

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