topic Re: Getting Landsat images to overlap in Data Management Questions

Getting Landsat images to overlap

ChrisVincent — Thu, 27 Mar 2014 19:40:25 GMT

Hi there,

I am doing study on land cover change over a period of 27 years. I have one Landsat image for each year, but as the entire area is too large, I am clipping a smaller subset in each image (these subsets will have the same coordinates in each of the 27 images). Problem is, when I try to clip these subset areas, the images don't line up between years.

I tried defining each image with the same coordinate system, but I think the problem is that the original Landsat images aren't exactly lined up. Anyone have any advice? I need these layers to line up cell by cell, as eventually I would like to do cell statistics.

Re: Getting Landsat images to overlap

NeilAyres — Sun, 30 Mar 2014 08:59:54 GMT

I tried defining each image with the same coordinate system,

Don't just "redefine" the coordinate system. If necessary, reproject the images from one coord sys to another, including a datum shift if needed.
But usually TM stuff is all on WGS84.

So decide which years worth of data will be your "master" template in terms of pixel positioning.
Then you could use the Raster Clip tool and set the environment snap raster and cell size to this master image.
This should result in each one of the images having exactly the same extent and pixel alignment.
Good luck,
Neil

Re: Getting Landsat images to overlap

DuncanHornby — Mon, 31 Mar 2014 14:27:29 GMT

When you did the clip did you ensure to have the environment setting SnapRaster set?