Create an image containing atmospheric correction values.
Create an image containing atmospheric correction values. The image will be the same size and in the same projection as the input image. One to nine bands will be created depending on input parameters. The bands can be: water vapor, elevation, ozone, quality control, satellite zenith angle, solar zenith angle, relative azimuth angle or geographic line and sample.
- IN
- Input image. A LAS image of AVHRR data that has an associated ADDR file or a LAS image with valid projection information in the DDR.
- OUT
- Output image. The output image is a one to nine band image the same size and in the same projection as the input image.
- ELEV(--)
- Elevation image. A single band image containing elevation in kilometers. The image must be in geographic projection with units of degrees.
- OZONE(--)
- Ozone image. A single band image containing ozone values in centimeters. The image must be in geographic projection with units of degrees.
- WATER(--)
- Water vapor image. A single band image containing water vapor values in centimeters. The image must be in geographic projection with units of degrees. This image is associated with the QC image (see User Note 3).
- QC(--)
- Quality Control band image. A single band image of qualitiy control flags. The image must be in geographic projection with units of degrees. This image is associated with the WATER image (see User Note 3).
- ANGFLG(YES)
- Generate angles bands flag. If this flag is specified as YES, solar zenith, satellite, zenith and relative azimuth angles are calculated and written to the output image (see User Note 5).
- INTERPFLG(NN)
- Interpolation flag. Indicates the type of interpolation desired. Two types of interpolation are available (see User Notes 1 and 6):
NN = nearest neighbor BL = bi-linear
- LINEGRID
- Line gridsize. The line sub-sampling interval for the input image.
- SAMPGRID
- Samples gridsize. The sample sub-sampling interval for each sub-sampled line in the image.
- LSBFLG(NO)
- Line Sample band flag. If this flag is set to YES, the line and sample bands are created. These values are for a 180 by 360 image in Geographic projection.
- ANGSCALE(NONE)
- Angles scale. Scaling method used to store ANGLES. The data type indicated in the image's DDR will be used to determine the scaling factors and offset values to use when unscaling the data.
= GLOBAL: Global scaling = NONE: No scaling = US: US scaling
A 7-band image ah14060399123456atm is created using the model information from ah14060399123456 and values from the images: wv14060399, wv14060399qc, ozone and gtopo30. The three angles bands are created since the ANGFLG defaults to YES. The input images are sampled at every 30 lines and samples.
A 3-band image us_232245atm is created using the projection information from the DDR of image us_232245 and the values from the gtopo30 image. The three angles bands will not be created (see User Note 5). The input image is sampled at every 40 lines and every 50 samples.
GETATM uses a sub-sampling technique to create an output image the same size and in the same space as the input image. This is done to reduce the number of times the AVHRR satellite model or the GCTP routines are used to compute latitude and longitude. The sub-sampling intervals are variable so that the user can arrive at a good compromise between computation time and output image accuracy.
The TAE parameters are retrieved and input images are opened. An attemp is made to open the image ADDR. If successful, the satellite model is initialized, otherwise the image DDR is opened and the projection parameters are checked for validity. At the specified gridpoints the latitude and longitude, as well as the angles, are calculated. The corresponding line and sample are computed for each input image and values at those locations are obtained. The pixels between the gridpoints are filled in with interpolated values to create the output image. Two types of interpolation are used: nearest neighbor and bi-linear interpolation (see User Note 1 and 6).
The input image did not have a valid ADDR or the ADDR was not present. If angles are desired, insure the ADDR exists and rerun the process.
An error was encountered allocating memory. If the error persists, contact the system administrator.
No bands were specified for the output image. Insure that at least one of the following is specified: WATER, OZONE, or ELEV images, or that ANGFLG=YES.
An error occurred updating the DDR for the specified band. Check that the user has write priveledges and that sufficient disk space is available.
An error occurred while trying to read the image DDR. Insure the DDR exists and rerun the process.
The projection information was not in the DDR. If the user intended to use DDR projection information, insure the DDR is valid. If the ADDR was to be used, see error message [getatm-getaddr].
The projection code for the XXX image was not geographic. Insure the image is in geographic projection.
The projection units in the DDR did not match any of the accepted units that the GCTP routines expect. Make sure the units are one of: radians, feet, meters, seconds of arc, degrees of arc or packed DMS.
An error occurred initializing the GCTP projection transformation routine. The error message preceding this one indicates the specific error encountered.
The projection units for the XXX image was not in degrees. Insure the image projection units are degrees.
A fatal error was encountered. The error message displayed immediately preceding this message is the specific error encountered. Processing terminates.
QC - a bi-linear interpolation on the flags would corrupt their vaues and invalidate their meaning. WATER - the QC flags indicate where the water vapor values originated so water values must be interpolated in the same manner as the flags. ELEVATION - the invalid value flags in the image would bias the interpolation. LINE - the invalid value flags in the image would bias the interpolation. SAMPLE - the invalid value flags in the image would bias the interpolation.
Water Vapor Elevation Ozone Quality Control Satellite Zenith Solar Zenith Relative Azimuth Geo Line Geo SampleBands not specifed by the user are omitted from the list e.g. if an elevation image is specified and LSBFLG=YES, the 3-band output image would be:
Band 1 - Elevation Band 2 - Geo Line Band 3 - Geo Sample