# ComputePolylineFeatureFromImage

## Brief Description

This application compute for each studied polyline, contained in the input VectorData, the chosen descriptors.

## Tags

Feature Extraction

## Long Description

The first step in the classifier fusion based validation is to compute, for each studied polyline, the chosen descriptors.

## Parameters

- [param] -in <string> An image to compute the descriptors on.. Mandatory: True. Default Value: ""
- [param] -vd <string> Vector data containing the polylines where the features will be computed.. Mandatory: True. Default Value: ""
- [param] -elev <string> This group of parameters allows managing elevation values. Supported formats are SRTM, DTED or any geotiff. DownloadSRTMTiles application could be a useful tool to list/download tiles related to a product.. Mandatory: True. Default Value: "0"
- [param] -expr <string> The feature formula (b1 < 0.3) where b1 is the standard name of input image first band. Mandatory: True. Default Value: ""
- [param] -field <string> The field name corresponding to the feature codename (NONDVI, ROADSA...). Mandatory: True. Default Value: ""
- [param] -out <string> The output vector data containing polylines with a new field. Mandatory: True. Default Value: ""
- [param] -inxml <string> Load otb application from xml file. Mandatory: False. Default Value: ""
- [param] -outxml <string> Save otb application to xml file. Mandatory: False. Default Value: ""

## Limitations

Since it does not rely on streaming process, take care of the size of input image before launching application.

## Authors

OTB-Team

## See Also

## Example of use

- in: NDVI.TIF

- vd: roads_ground_truth.shp

- expr: "(b1 > 0.4)"

- field: NONDVI

- out: PolylineFeatureFromImage_LI_NONDVI_gt.shp