COSI Corr Steps

I am working on COSI Corr an ENVI Plugin, i am using it for Landslide Displacement using UAV Imageries.

How do I select fiducial marks?

I dont know what does it mean by "X loc (pix) and Y loc (Pix) ".


Fiducial marks are the characteristic markers placed at the margins of aerial imagery. XY coord refers to the fiducial mark location (in mm) and XY loc is the image file coordinates in pixel. Remember though that fiducial marks are commonly found in photogrammetric imagery, and most UAV images don't have them.

I am assuming that you are trying to use UAV images in comparison with a previous UAV set or an image from another source. The workflow in CosiCorr for preparing ortho images (first tabs in menu) is confined only to classical aerial image frames or the specific satellite imagery formats that are supported. If your images are not in this format (or you don't have the data necessary to use this workflow) you can skip right to Correlation, after you prepare manually your images:

  1. In the case of UAV imagery, individual images have high distortions and are very difficult to process, so you need to create an orthophoto mosaic from multiple overlapping images by using any SfM workflow or software available.

  2. If your pre-event dataset is also from a UAV, repeat the same and create another orthophoto mosaic.

  3. If your other imagery is from another source, you need to either orthorectify it (satellite, aerial etc.) or crop an image file to the other image boundaries (if the image is already an orthorectified product).

  4. Prepare your two images (before and after) for CosiCorr, by resampling them in the same ground pixel resolution, to avoid artifacts and errors. Cropping in the same boundaries decreases processing time and avoids errors/artifacts near the borders. Remember both files need to be in the same projection, while the format should be any of the supported image raster formats in ENVI.

  5. Use Correlation in CosiCorr to compare pre- and post-event images. Important for this step: deselect Grided output option in Correlation properties if you haven't follow CosiCorr's image preparation workflow

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  • Dear Sir Sotiris Valkaniotis! According to tutorial fiducial marks should be available in report of UAV Data processing software. I am using PIX4D and Agisoft photoscan and non of it have any information regarding fiducial marks. I mean What and where should i put the Fiducial X and Fiducial Y (mm) values.? Jun 21 '18 at 7:35
  • Most UAV imagery that I know of doesn't include fiducial marks on the image frames, so you can't use CosiCorr's Aerial Imagery guide for UAV frames. Lens distortion and principal point offsets can be calculated (with some accuracy) by SfM software but fiducials only for classical aerial imagery formats. Jun 21 '18 at 8:22
  • Sir Sotiris Valkaniotis what do you sugggest then?. Should i directly start from correlation? Jun 22 '18 at 8:39
  • If you have UAV data, you should create orthophoto files using Pix4D, Agisoft or a similar software, then go straight to Correlation in Cosi Corr. Jun 30 '18 at 9:51
  • Sir Sotiris Valkaniotis, Please mail me at naseemkhattak02@gmail.com. You solved my problem i think we can go beyond this discussion.Thank you so much Jul 2 '18 at 3:40

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