GBDX

ENVI® RPC Orthorectification

This task orthorectifies an image georeferenced with a rational polynomial coefficient (RPC) sensor model or a replacement sensor model (RSM) using a DEM and optional GCPs.

GBDX Registered Name: ENVI_RPCOrthorectification
Provider: Harris Geospatial Solutions

Imagery Examples

Before: input IKONOS image that has not been orthorectified

Before: input IKONOS image that has not been orthorectified

After: Output raster image after running ENVI RPC Orthorectification

After: Output raster image after running ENVI RPC Orthorectification

Quickstart

This is a workflow example for basic processing.

# Quickstart Example running the task name.

# Initialize the Environment.
from os.path import join, split
from gbdxtools import Interface
gbdx = Interface()

tasks = []
output_location = 'ENVI/RPCOrthorectification'

#Ikonos Imagery See. https://gbdxdocs.digitalglobe.com/docs/ikonos
cat_id = '2000032417393810000010101359'
img_meta = gbdx.catalog.get(cat_id)
ikonos_path = join('s3://',
                   img_meta['properties']['bucketName'],
                   img_meta['properties']['bucketPrefix'],
                   '{0}_{1:0>7}'.format(img_meta['properties']['bucketPrefix'], img_meta['properties']['components']-1),
                   '')

# Orthorectify the imagery
envi_RPCO = gbdx.Task("ENVI_RPCOrthorectification")
envi_RPCO.inputs.input_raster = ikonos_path
envi_RPCO.inputs.input_raster_band_grouping = 'multispectral'
envi_RPCO.inputs.input_raster_format = 'ikonos'
envi_RPCO.inputs.dem_raster_filename = 'GMTED2010.jp2'
tasks += [envi_RPCO]

workflow = gbdx.Workflow(tasks)
workflow.savedata(
    envi_RPCO.outputs.task_meta_data, location=output_location
)

workflow.execute()

Inputs

The following table lists all ENVI_RPCOrthorectification inputs.
Mandatory (optional) settings are listed as Required = True (Required = False).

Name Required Default Valid Values Description
file_types False N/A string GBDX Option. Comma seperated list of permitted file type extensions. Use this to filter input files -- Value Type: STRING[*]
input_raster True N/A See ENVIRASTER input type Specify a raster that has a RPC sensor model or a replacement sensor model (RSM) to orthorectify. -- Value Type: ENVIRASTER
input_raster_format False N/A See ENVIRASTER input type Provide the format of the image, for example: landsat-8. -- Value Type: STRING
input_raster_band_grouping False N/A See ENVIRASTER input type Provide the name of the band grouping to be used in the task, ie - panchromatic. -- Value Type: STRING
input_raster_filename False N/A See ENVIRASTER input type Provide the explicit relative raster filename that ENVI will open. This overrides any file lookup in the task runner. -- Value Type: STRING
input_raster_raw_output False False See ENVIRASTER input type Provide True to output an ENVI Binary instead of a tif. -- Value Type: STRING
dem_is_height_above_ellipsoid False N/A string Set this property to true if the DEM is already expressed as the height above the ellipsoid and no geoid offset is required. -- Value Type: BOOLEAN
output_subset False N/A string Use this property to define a spatial subset from the input image that will apply to the output from ENVIRPCOrthorectificationTask. The output will be a rectangular subset that encompasses the the extent of the input subset. If you set this property, the output extent will be larger than that of the input subset, but the output may contain background pixels. Also, you do not need to specify the ENVIGCPSet::ApplyOffset method to adjust the position of ground control points (GCPs). Set this property to a four-element array expressing the spatial range (in pixels) of the input image. The array is of the form [x1, y1, x2, y2]. Pixel coordinates are zero-based. -- Value Type: INTARRAY
input_gcp False N/A See ENVIGCPSET input type A set of ground control points (GCPs). -- Value Type: ENVIGCPSET
grid_spacing False 10 string Grid spacing to use. -- Value Type: INT -- Default Value: 10
dem_raster False N/A See ENVIRASTER input type Specify a digital elevation model (DEM) raster. A DEM raster is only required if the input raster has a RPC sensor model. If you do not have a DEM file readily available, you can use the global DEM named GMTED2010.jp2 that is provided with your ENVI installation under the Harris/envixx/data folder. The Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) dataset has a mean resolution of 30 arc seconds. -- Value Type: ENVIRASTER
dem_raster_filename False N/A string Provide the explicit relative raster filename that ENVI will open. This overrides any file lookup in the task runner. -- Value Type: STRING
geoid_offset False N/A string Set this property to a floating-point value (in meters) of a geoid offset if the DEM is referenced to mean sea level. -- Value Type: DOUBLE
resampling False "bilinear" string Specify the resampling method. Nearest Neighbor: Uses the nearest pixel without any interpolation. Bilinear: Performs a linear interpolation using four pixels to resample, Cubic Convolution: Uses 16 pixels to approximate the sinc function using cubic polynomials to resample the image. -- Value Type: STRING -- Default Value: "Bilinear"
output_pixel_size False N/A string Set this property to a two-element array indicating the output X and Y pixel size, in meters. The default value is the pixel size of the input image. -- Value Type: DOUBLEARRAY
output_raster_uri_filename False N/A string Specify a string with the fully-qualified path and filename for OUTPUT_RASTER. -- Value Type: STRING

Outputs

The following table lists all ENVI_RPCOrthorectification outputs.
Mandatory (optional) settings are listed as Required = True (Required = False).

Name Required Default Valid Values Description
task_meta_data False N/A directory GBDX Option. Output location for task meta data such as execution log and output JSON
output_raster_uri True N/A directory Output for OUTPUT_RASTER. -- Value Type: ENVIURI

Output structure

The output_raster_uri file will be written to the specified S3 Customer Account Location.

Issues

This algorithm provides the ability to orthorectify IKONOS imagery available on the GBDX platform as level OrthoReady-2A data products. In order to orthorectify all other DigitalGlobe imagery on GBDX as level Basic-1B data products from QuickBird, GeoEye-1 or WorldView-1/2/3 sensors we recommend using the Advanced Image Preprocessor algorithm instead since it automatically uses a very high resolution DEM for elevation source during the orthorectification process which can improve terrain correction.

Background

For additional background information on this task please refer to the Harris Geospatial ENVI documentation and
ENVI® RPC Orthorectification.

Contact

If you have any questions or issues with this task, please contact gbdx-support@digitalglobe.com.