I study historical NDVI data sets of wetland vegetation from 1985 to the present for a certain region. Since Landsat 5 TM stopped sending data in 2011, I am using Landsat 7 data to fill in the information of the last decade. However, NDVI values seem to be slightly higher for L7 than L5. This might affect my interpretation of the landscape. I would like to know how are other researchers dealing with this problem. I have the feeling I need to adjust the NDVI values from L7 before comparing the data with L5. I can't find the right literature pointing out this issue.
Thank you very much in advance.