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# iamap
[Documentation](https://iamap.readthedocs.io/en/latest/)
[Gitlab reop](https://forge.ird.fr/amap/iamap)
[Gitlab repo](https://forge.ird.fr/amap/iamap)
## Rationale
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docs/source/_static/examples/classif_1950.png

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docs/source/_static/examples/classif_2022.png

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docs/source/_static/examples/classif_2022_old.png

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docs/source/_static/examples/landcover_change.png

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docs/source/_static/examples/landcover_change_old.png

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......@@ -83,4 +83,60 @@ And with pre-processing:
```
<!-- ## Mapping Land Cover in La Réunion -->
## Mapping Land Cover change in La Reunion island
The objective is to characterize land cover change in La Reunion island based on the analysis of aerial IGN ortho-photography from 1950 and 2022.
Data :
- The collection of historical Orthophotos (1950) is accessible from the following website : https://geoservices.ign.fr/bdorthohisto
The historical map is divided into a mosaic of 130 grayscale tiles, i.e. in a 1-band rasters, ranging from 0 to 255 to represent the light intensity.
The resolution of each image is 50cm/pixel.
- The collection of recent Orthophotos (2022) is accessible from the following website : https://geoservices.ign.fr/bdortho
The recent map is divided into a mosaic of 130 color tiles, i.e. in RGB (Red, Green, Blue) 3-bands rasters where each band uses pixel value ranging from 0 to 255 to represent the corresponding color intensity. The resolution of each image is 20cm/pixel.
- Preliminary step : a data transformation for the comparison 1950 / 2022 :
The recent images resolution (2022) is transformed from 20cm/pixel to 50cm/pixel using QGIS in order to obtain the same resolution as the historical images (1950) . In addition, a conversion from color (RGB or 3-bands) to grayscale (1-band) is applied using QGIS plugin OTB (OTB > feature extraction > radiometric indices >set band 3 2 1 and choice Bi index (Brightness index) . Thanks to these two steps the comparison between both maps can be done pixel by pixel.
- Method
Each image is fed through a ViT base DINO encoder before fitting a random forest (RF) classifier on the obtained features.
- The Land Cover classes :
A photo-identification is achieved on 30 randomly selected tiles for each dataset. The variability inherent to each class is accounted for by the identification of 10 polygones per landcover class.
The different landcover classes are the following :
- Agricultural
- Low vegetation
- Forest
- Shade
- Urban
Here is the figure showing the classification results for 1950
```{image} ./_static/examples/classif_1950.png
:alt: Image 1
:class: centered-image
:width: 600px
:align: center
```
Here is the figure showing the classification results for 2022
```{image} ./_static/examples/classif_2022.png
:alt: Image 2
:class: centered-image
:width: 600px
:align: center
```
Here is the figure showing the land cover changes between 1950 and 2022
```{image} ./_static/examples/landcover_change.png
:alt: Image 3
:class: centered-image
:width: 600px
:align: center
```