Description
A processing block that segments an image at a provided scale into image objects and exports them as segmented polygons in a Shapefile.
See this block on the marketplace.
How it works
Use this block as an initial processing step in landcover, vegetation, water, urban area analysis, and change detection workflows.
This block uses an iterative algorithm that merges pairwise objects starting from individual pixels. It merges these objects until the specified homogeneity criteria is reached, and then fits polygons to match these objects.
- Input: a projected GeoTIFF image with 3–4 spectral bands (RGB+).
- Output: a Shapefile with 2D+ polygons describing identified image objects with geocoded coordinates.
| Parameter | Overview |
|---|---|
VAR_SP | integer / required The scale parameter sets the homogeneity criteria. It is a combination of color and shape criteria. Use a higher parameter value to outline larger objects of interest, and vice versa. There is no input range, and the default value is 42. |
VAR_SIMP | integer / required The simplification parameter sets how the polygons will be drawn around the segmented objects. The value can range as follows:
1. |
VAR_Shape | float / required The shape parameter determines the weighting given to shape of objects over their color during segmentation. Use a higher parameter value to increase the influence of shape and lower the influence of colors. The value can range as follows:
0.1. |
VAR_Compactness | float / required The compactness parameter determines the weighting given to compactness of objects over their smoothness during segmentation. Use a higher parameter value to increase the compactness and lower the smoothness of objects. It can range from:
0.5. |
To find more about these parameters, see the eCognition website.
Compatibility
This processing block is a powerful tool that can be used as part of an image processing workflow.
Different object types can be segmented by manipulating the parameters. The objects are exported as Shapefiles. Shapefiles are a geospatial vector data format that can be imported to most GIS software.
The objects can then be reshaped, classified and analyzed.
Example
An example is shown below that identifies image objects using Pléiades catalog data from storage as a data source.
{
"up42-processing-from-storage:1": {
"asset_ids": ["d86b5212-e3c3-4807-8715-324171a79833"]
},
"ecognition_mrs:1": {
"VAR_SP": "100",
"VAR_SIMP": "1",
"VAR_Shape": "0.1",
"VAR_Compactness": "0.5"
}
}
Capabilities
Input
raster
| up42_standard | |
|---|---|
bands | {
"or": [
[
"red",
"green",
"blue"
],
[
"red",
"green",
"blue",
"nir"
],
[
"red",
"green",
"blue",
"nir",
"pan"
]
]
} |
dtype | {
"or": [
"uint16",
"uint8"
]
} |
format | GTiff |
sensor | {
"or": [
"Pleiades",
"SPOT",
"Sentinel2",
"Landsat8",
"Hexagon"
]
} |
resolution | {
"or": [
0.15,
0.3,
0.5,
1,
1.5,
10,
15
]
} |
processing_level | {
"or": [
"l2",
"l3"
]
} |
Output
vector
| up42_standard | |
|---|---|
format | Shapefile |
geometry_type | Polygon |