34.11. PRF: Classic Platform Location/Orientation Data

The flight profile (PRF) file contains a series of records that indicates the platform's position and orientation as a function of time. It assumes that there will be a record for each scan that the instrument makes. The SCAN_RATE in the section will be overridden by the time interval in the PRF file. Essentially, each entry in this file specifies the location of an instrument capture. If there are N entries in this file, then there will be N instrument capture events. For example, if there are N entries in the file, there will be N lines in the final image if the instrument has is 1D array. A PRF file is a standard input file and therefore may contain comment lines. The first non-comment line must be the DIRSIG_PRF marker. The remaining lines in the file consist of flight records that use the format described in Table 34-4.

The platform orientation angle conventions are illustrated in Figure 34-1. The roll angle uses a right-hand rule along the mean flight line. The pitch angle is in reference to the Earth surface and is positive if the nose of the platform pitches up. The yaw angle is positive for angles clockwise from the mean flight line. The following PRF file example was extracted from the jitter.prf file in the distributed fighter scene.

DIRSIG_PRF
#
# Flight data generated for flyover of the DIRSIG fighter scene.
#
-2.5500 -12240.0000  0.0000  12000.0000  0.00068079  0.0000  0.0000
-2.5400 -12192.0000  0.0000  12000.0000  0.00083888  0.0000  0.0000
-2.5300 -12144.0000  0.0000  12000.0000  0.00078790  0.0000  0.0000
.
. [middle lines deleted for documentation purposes]
.
2.5400  12192.0000  0.0000  12000.0000  0.00407840  0.0000  0.0000
2.5500  12240.0000  0.0000  12000.0000  0.00429313  0.0000  0.0000
2.5600  12288.0000  0.0000  12000.0000  0.00429965  0.0000  0.0000
    

As of Release 3.2, the user can also supply a flight profile with a FRAMING_ARRAY type instrument. If the user sets the PROFILE_FILENAME , than the instrument will acquire a full image at each location in the flight record. This allows the user to simulate image frames acquired during the approach of the sensor, produce stereo image pairs, etc. The images will be stored to individual image files using the same approach and naming scheme as the GENERATE_IMAGE_PER_SCAN option in the section. The format file has the same format except that the platform orientation angles use the following definitions: The following flight profile demonstrates a potential use. This file will produce 7 separate images as the platform closes in on the origin (0.0, 0.0, 0.0 ) along a 45 degree downward flight path. If the user set the IMAGE_FILENAME variable to example.img , the 7 output image files will be example0000.img , example0001.img ... example0006.img .

1.00 0.0 1750.0 1750.0 0.0 -45.0 0.0
2.00 0.0 1500.0 1500.0 0.0 -45.0 0.0
3.00 0.0 1250.0 1250.0 0.0 -45.0 0.0
4.00 0.0 1000.0 1000.0 0.0 -45.0 0.0
5.00 0.0  750.0  750.0 0.0 -45.0 0.0
6.00 0.0  500.0  500.0 0.0 -45.0 0.0
7.00 0.0  250.0  250.0 0.0 -45.0 0.0