Today Jeff and I had a first look at the LANDSAT data provided to us by Stéphane. That data consists of two sets of images, one from 1990 taken by the LANDSAT 4 and 5 satellites and one from 2000 taken by LANDSAT 7. There are some images missing from the 1990 set. I would say, glancing quickly at the mosaic of images, that +/- 5% of the area of the island is missing. There are three bands in the images. We don’t have extensive descriptions of the files we’ve been given, but we’re guessing that the bands are green, red and near infrared. The pixel size is 28.5m * 28.5m. It is coarse, but we can recognize shapes. For instance, we can see roads and barren land is easily identifiable. As far as vegetation is concerned, we can see shapes of different shades of green. Therefore, we should be able to do a classification to map the plantations and the forest. However, it is bound to be challenging as there are factors that will complicate the task at hand. For instance, the land that is to be mapped is hilly and that creates shadows. The area of the island is quite large and the altitude of the terrain varies. The broad range of climatic conditions will translate in different types of vegetation with their own spectral signatures. Furthermore, the different growth stages of various oil palm plantations will mean that different plantations don’t show up the same way on the images.
The classification will require the identification of valid training sites. To figure out which sites may be used, we are going to have to make use of various resources. For instance, we plan on using hi resolution areal photographs publicly available online (through Google Earth, Virtual Earth, World Wind…) where we can easily identify plantations. Today, we looked at was available through Google Earth. Unfortunately, hi resolution aerial photographs where only available for a very small fraction of the island of Borneo, emphasizing the need to find other sources of information to find training sites. One of those might be the concessions for palm oil plantation maps from the WWF.
Since a picture is worth a tousand words... :
Here is forest (on the left) and a palm plantation (on the right), identified with a hi resolution photo from Google Earth:
If we zoom in a little, we can see the distinct pattern of the palm plantations contrasting with the forest:
And this is what the area looks like on the LANDSAT images from 2000 that Stéphane gave us:
As can be seen, the difference between forest and plantation is obvious to the human eye, let's hope our classification software feels the same way...
The classification will require the identification of valid training sites. To figure out which sites may be used, we are going to have to make use of various resources. For instance, we plan on using hi resolution areal photographs publicly available online (through Google Earth, Virtual Earth, World Wind…) where we can easily identify plantations. Today, we looked at was available through Google Earth. Unfortunately, hi resolution aerial photographs where only available for a very small fraction of the island of Borneo, emphasizing the need to find other sources of information to find training sites. One of those might be the concessions for palm oil plantation maps from the WWF.
Since a picture is worth a tousand words... :
Here is forest (on the left) and a palm plantation (on the right), identified with a hi resolution photo from Google Earth:
If we zoom in a little, we can see the distinct pattern of the palm plantations contrasting with the forest:
And this is what the area looks like on the LANDSAT images from 2000 that Stéphane gave us:
As can be seen, the difference between forest and plantation is obvious to the human eye, let's hope our classification software feels the same way...
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