4

I have six overlapping NDVI images derived from atmospherically corrected SPOT5 images, all from the same date. How can I mosaic the images perfectly without seeing any differences between the same class but from different images? Please see picture below for illustration. The images have all been re-scaled to 0-1 (min-max) values.

enter image description here

7

Your best bet would be to mosaic the raw red band and near infrared band images from which the NDVI images are derived. There are techniques for creating seamless mosaics for images, e.g. through the use of histogram matching and feathering techniques. For areas of overlap, the feathering method will calculate the output value as a weighted combination of the two input pixel values from the overlapping bands, where the weights are derived from the squared distance of the pixel to the edge of the data in each of the input raster files. Therefore, less weight is assigned to an image's pixel value where the pixel is very near the edge of the image. The result of this feathering method is that the output mosaic image should have very little evidence of the original image edges within the overlapping area. Histogram matching can be performed on one of the input images (i.e. the 'Append' image) to force its radiometric properties (contrast) to match that of the 'Base' image. The best results will be from combining histogram matching and feathering.

Once you're satisfied with the mosaics, you can then derive the larger NDVI image (NDVI = (NIR - Red) / (NIR + Red)). This will likely result in a more satisfactory mosaic than trying to match the NDVI images directly.

  • thank you for your advice and suggestion, however i have one slight problem, i created a segmentation in eCognition, thereafter, i extracted the NDVI from the segemnted images. to run one SPOT image in eGoctionion takes a little bit over 24 hours as the pan-sharpened images are about 12 GB, so if i mosaic all six scenes, it might take forever. Is there no other way to mosaic the NDVI images without having to mosaic the bands? – Mokhine Motswaledi Sep 15 '14 at 20:09
  • I am not only deriving NDVI, but other indices as well. so i cant only mosaic the near infrared and red band only – Mokhine Motswaledi Sep 15 '14 at 20:25
  • @MokhineMotswaledi If the images have been segmented, then I can't see any way that you can mosaic the image without having the images edges apparent. I'm afraid that really you need to go back to the raw images to do this properly. – WhiteboxDev Sep 15 '14 at 20:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.