Tutorial5_Remapping_and_Video.md

Tutorial 5: Remapping and timelapse generation

Besides correcting disparity maps, the polynomial fit can also be used to remap secondary images to a common reference and obtain more precisely coregistered images. These can for example be used to create a timelapse of the monitored landslide.

Step 1: Matchmaking

As a first step, generate a matchfile that matches all scenes in a directory to a common reference. Use the match_to_one_ref() function from the preprocessing tools for that purpose. This will take all images from one folder and match it with the oldest acquisition.

import preprocessing_functions as preprocessing

work_dir = "./tutorial/L3B"
matches = preprocessing.match_to_one_ref(work_dir)

Step 2: Apply polynomial fit and remap

To remap the secondary images according to the polynomial fit and thus improve the co-registration between reference and secondary image, again use the apply_polyfit() function and make sure to set the save_remapped_sec option to True. After disparity map generation (if not already present) and polynomial fitting, the pixels in the secondary image will be shifted according to the disparity fit and then interpolated using bilinear interpolation. All remapped secondary images will be saved in your working directory with the file extension *_remap.tif.

import optimization_functions as opt

dmaps_pfit = opt.apply_polyfit(matches, prefix_ext= "_L3B", order = 2, demname = cop_dem, save_remapped_sec = True)

Step 3: Create video

From the remapped images (or also original PlanetScope scenes) you can create a nice timelapse of the landslide motion:

import postprocessing_functions as postprocessing

postprocessing.make_video(matches, video_name = "timelapse_remapped.mp4", ext = "_remap", crop = 300)

This function will find the reference and remapped secondary images and create a video (timelapse_remapped.mp4) and a GIF (timelapse_remapped.gif) out of these images. Histogram matching is applied to have similar brightness values and the date of acquisition is placed in the upper left corner. Use the crop option to discard pixels along the image margins and zoom in on the scene center. If you would like to create a timelapse from the original PlanetScope scenes, set the file extension to "".

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