Dear Researchers,
We are aware of the advantages and limitations of both Satellite-based Remote Sensing and Aerial Photogrammetry. However, when we are analyzing the land-use land cover (LULC) changes induced as a result of a natural disaster, such as forest-fire, floods, etc., which method, according to your experience, will be more significant than other to conduct the aforesaid analysis? Why?
Regards,
Aman Srivastava
Dear Arman,
Obviously, to obtain images of an area before suffering a natural disaster, it is most common to adquire them from satellite images (due to their periodicity of capture). Once a catastrophic event has occurred, both options can be taken.
The selection of the acquisition system will depend on several factors, such as the need to obtain images in a short period of time of the affected area, the level of accuracy of the image (spatial resolution), the analyses to be applied, etc.
From my point of view, if the satellite images available prior to the natural disaster have enough resolution to be useful for your analysis, it is preferable to use the same platform. This will facilitate the temporal studies, as well as the possible methods applied because the same wavelengths will be used for each of the spectral bands.
I understand that when you refer to aerial photographs, you are also referring to UAVs, in this case, if you have any of them, it is always convenient to take images (of higher resolution) to support the spectral images.
I hope it helps. Regards
The answer is contextual. What is the purpose of the images? What access to equipment and analysis software exists? Are images being taken anyway to be shared or is this task specific to one researcher's needs? Could multiple methods be used in order to compare them?
Note that fires and floods are natural hazards, not necessarily disasters, if we have prepared for them. Consequently, we prefer to avoid the phrase "natural disaster":
1. Book https://global.oup.com/academic/product/disaster-by-choice-9780198841340
2. Paper https://doi.org/10.1016/j.pdisas.2019.100008
3. Commentary https://www.psychologytoday.com/blog/disaster-choice/202005/does-nature-play-disaster-games
Hello,
I would recommend a combined method, using both satellite and UAV based imagery. You can obtain high quality satellite imagery from ESA. Moreover, you can use SAR imagery (TerraSAR-X has 1m resolution). Tutorials can be found on the official page of ESA or on YouTube (RUS Copernicus Training). If you use the combined method, you can cross-validate your results, hence your analysis will be more reliable.
Best,
Anna
Dear @Aman,
The answer is very subjective, it's depending on your application and accuracy requirements. If you're aiming for wide area coverage, of course satellite images are better. But, if you require high resolution images, you can acquire the aerial photos according to your own settings which focusing on the specific area.
In most of the senario, satellite images are the best way to yield pre-event's historical information, while UAV/aircraft based camera are mobilize to obtain the current features on site. In fact, both are applicable to assess the pre- and post- event changes.
As long as the method (satellite or aerial) has sufficient resolution to determine your land cover types of interest and you can get frequent enough imagery to monitor the course of the changes you are interested in, it then comes down to a question of accuracy. When performing change detection of one land cover class to another, the accuracy of the initial classifications in both images is important, and accuracy in the classifications depends on the quality of those images.
Satellite images tend to undergo some form of atmospheric compensation, a necessity especially over natural disasters that involve heavy haze from smoke and fire. There is also the possibility of using short-wave infrared (SWIR) bands to see through the smoke. These may not be the case with the aerial images you acquire, raising the possibility that the satellite imagery may yield improved results.
Thank you, Dr. Pedro Perez Cutillas, Dr. @Ilan Kelman, Dr. Dahl Clark Winters, Dr. Kelvin Kang Wee Tang, Dr. M. Kamraju, Dr. Anna Hajnalka Kerekes, for providing your valuable insights to the question. I can now firmly conclude, with the help of your opinions, that given the advantages and limitations of both Satellite-based Remote Sensing and Aerial Photogrammetry, both these techniques can be employed for analyzing the land-use land cover (LULC) changes induced as a result of a natural disaster in view of their accuracy in image classification, resolution of the study area, quickness of yielding results, and the type of the research question needed to be addressed. Hence, their applications are circumstantial and expertise is required for employing the same.
Hi Dr Aman Srivastava . I agree with Dr M. Kamraju that both methods should be recommended as a precaution.
It depends on your work and the accuracy needed. Normally use satellite images to detect the changes. Atmospheric conditions are the major limitation in the satellite images.
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