Compute Polyline Feature From Image¶

Detailed description¶

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

Parameters¶

This section describes in details the parameters available for this application. Table [1] presents a summary of these parameters and the parameters keys to be used in command-line and programming languages. Application key is ComputePolylineFeatureFromImage .

Input Image An image to compute the descriptors on.

Vector Data Vector data containing the polylines where the features will be computed.

Elevation management 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.

• DEM directory: This parameter allows selecting a directory containing Digital Elevation Model files. Note that this directory should contain only DEM files. Unexpected behaviour might occurs if other images are found in this directory.
• Geoid File: Use a geoid grid to get the height above the ellipsoid in case there is no DEM available, no coverage for some points or pixels with no_data in the DEM tiles. A version of the geoid can be found on the OTB website (http://hg.orfeo-toolbox.org/OTB-Data/raw-file/404aa6e4b3e0/Input/DEM/egm96.grd).
• Default elevation: This parameter allows setting the default height above ellipsoid when there is no DEM available, no coverage for some points or pixels with no_data in the DEM tiles, and no geoid file has been set. This is also used by some application as an average elevation value.

Feature expression The feature formula (b1 < 0.3) where b1 is the standard name of input image first band.

Feature name The field name corresponding to the feature codename (NONDVI, ROADSA...).

Output Vector Data The output vector data containing polylines with a new field.

Load otb application from xml file Load otb application from xml file.

Save otb application to xml file Save otb application to xml file.

Example¶

To run this example in command-line, use the following:

otbcli_ComputePolylineFeatureFromImage -in NDVI.TIF -vd roads_ground_truth.shp -expr "(b1 > 0.4)" -field NONDVI -out PolylineFeatureFromImage_LI_NONDVI_gt.shp

To run this example from Python, use the following code snippet:

#!/usr/bin/python

# Import the otb applications package
import otbApplication

# The following line creates an instance of the ComputePolylineFeatureFromImage application
ComputePolylineFeatureFromImage = otbApplication.Registry.CreateApplication("ComputePolylineFeatureFromImage")

# The following lines set all the application parameters:
ComputePolylineFeatureFromImage.SetParameterString("in", "NDVI.TIF")

ComputePolylineFeatureFromImage.SetParameterString("vd", "roads_ground_truth.shp")

ComputePolylineFeatureFromImage.SetParameterString("expr", "(b1 > 0.4)")

ComputePolylineFeatureFromImage.SetParameterString("field", "NONDVI")

ComputePolylineFeatureFromImage.SetParameterString("out", "PolylineFeatureFromImage_LI_NONDVI_gt.shp")

# The following line execute the application
ComputePolylineFeatureFromImage.ExecuteAndWriteOutput()