Calculate radar viewing angles and range vectors
Calculates the incidence angle, radar look angle and/or the range vectors for each pixel of the input elevation data. Two subcommands are available. -LINE calculates the above information based on a user defined flight path. -POINT calculates the above information based on a stationary point along a flight path. In addition to the above information, -POINT and -LINE allows calculation of the azimuth angle.
- IN
- Input image. The single band input image consisting of elevation data. Its data type may be either BYTE, INTEGER*2, INTEGER*4 or REAL*4. Window and/or band options may be specified. The elevation data is assumed to be in meters.
- LAT
- Latitude. Latitude of the point from which all calculations will be made. The latitude value is entered as degrees, minutes and seconds. South latitude values must be entered as negative degrees.
- LONG
- Longitude. Longitude of the point from which all calculations will be made. The longitude value is entered as degrees, minutes and seconds. West longitude values must be entered as negative degrees.
- ELEV
- Elevation. The elevation in meters of the aircraft or spacecraft platform. This value is assumed to be constant along the flight path.
- OUT
- Output image. The number of bands contained in the output image is based on the parameter CALCOPT. One band is created in the output image for each value set. If the output data type selected for the image is not REAL, values are rounded and truncated. The output image specifies angles in decimal degrees and range vectors in meters.
- CALCOPT(INCID,LOOK,AZM,RANGE)
- Calculation option. The list of options indicating the information to be calculated for each pixel of the input image. From one to four values may be entered for CALCOPT.
= INCID: Incidence angle. The angle defined by the surface normal vector of the current pixel of the input image and the range vector. = LOOK: Radar look angle. The angle defined by a vector at a right angle to the current platform velocity vector and the range vector. = AZM: Azimuth angle. The azimuth angle from the aircraft or spacecraft plane. = RANGE: Range vector. Distance in meters from the input pixel to the platform along the range vector.
- OFFSET(0)
- Offset value (in meters). OFFSET will be subtracted from each range vector calculation. This can be useful if the range vector values are very large (e.g. for a spacecraft platform).
- ODTYPE(R*4)
- Output data type. The data type of the output image. Specification of BYTE, I*2 and I*4 causes the rounding and truncation of data. Therefore, these data types should be used with caution since all calculations for SARTOPO are floating point calculations.
= BYTE: BYTE (8-bit unsigned integer) (0 through 255) = I*2: INTEGER*2 (16-bit signed integer) (-32768 through 32767) = I*4: INTEGER*4 (32-bit signed integer) (-2147483648 through 2147483647) = R*4: REAL*4 (32-bit signed real) (System dependent)
- IN
- Input image. The single band input image consisting of elevation data. Its data type may be either BYTE, INTEGER*2, INTEGER*4 or REAL*4. Window and/or band options may be specified. The elevation data is assumed to be in meters.
- BEGLAT
- Beginning latitude. The latitude value marking the starting point of the flight path of the aircraft or spacecraft platform. The latitude value is entered as degrees, minutes and seconds. South latitude values must be entered as negative degrees.
- BEGLONG
- Beginning longitude. The longitude value marking the starting point of the flight path of the aircraft or spacecraft platform. The longitude value is entered as degrees, minutes and seconds. West longitude values must be entered as negative degrees.
- ENDLAT
- Ending latitude. The latitude value marking the ending point of the flight path of the aircraft or spacecraft platform. The latitude value is entered as degrees, minutes and seconds. South latitude values must be entered as negative degrees.
- ENDLONG
- Ending longitude. The longitude value marking the ending point of the flight path of the aircraft or spacecraft platform. The longitude value is entered as degrees, minutes and seconds. West longitude values must be entered as negative degrees.
- ELEV
- Elevation. The elevation in meters of the aircraft or spacecraft platform. This value is assumed to be constant along the flight path.
- OUT
- Output image. The number of bands contained in the output image is based on the parameter CALCOPT. One band is created in the output image for each value set. If the output data type selected for the image is not REAL, values are rounded and truncated. The output image specifies angles in decimal degrees and range vectors in meters.
- CALCOPT(INCID,LOOK,AZM,RANGE)
- Calculation option. The list of options indicating the information to be calculated for each pixel of the input image. From one to four values may be entered for CALCOPT.
= INCID: Incidence angle. The angle defined by the surface normal vector of the current pixel of the input image and the range vector. = LOOK: Radar look angle. The angle defined by a vector at a right angle to the current platform velocity vector and the range vector. = AZM: Azimuth angle. The azimuth angle from the aircraft or spacecraft plane. = RANGE: Range vector. Distance in meters from the input pixel to the platform along the range vector.
- OFFSET(0)
- Offset value (in meters). OFFSET will be subtracted from each range vector calculation. This can be useful if the range vector values are very large (e.g. for a spacecraft platform).
- ODTYPE(R*4)
- Output data type. The data type of the output image. Specification of BYTE, I*2 and I*4 causes the rounding and truncation of data. Therefore, these data types should be used with caution since all calculations for SARTOPO are floating point calculations.
= BYTE: BYTE (8-bit unsigned integer) (0 through 255) = I*2: INTEGER*2 (16-bit signed integer) (-32768 through 32767) = I*4: INTEGER*4 (32-bit signed integer) (-2147483648 through 2147483647) = R*4: REAL*4 (32-bit signed real) (System dependent)
In this example, the user has input the beginning and ending latitudes and longitudes of the flight path. The elevation value entered is assumed to be in meters and is assumed to be constant over the flight path. The output REAL*4 image created by SARTOPO will contain 3 bands. The first band will contain the incidence angles (in decimal degrees), the second band will contain the radar look angles (also in decimal degrees), the third band will contain the azimuth angles (in decimal degrees) and the fourth band will contain the lengths (in meters) of the range vectors.
In this example, the user has input the beginning and ending latitudes and longitudes of the flight path. The elevation value entered is assumed to be in meters and is assumed to be constant over the flight path. The output REAL*4 image created by SARTOPO will contain a single band. This band will contain the lengths (in meters) of the range vectors. The OFFSET value of 5000 will subtracted from each output value.
In this example, the user has input the latitude and longitude of a stationary point from which all subsequent calculations are made. The elevation value entered is assumed to be in meters. The output INTEGER*2 image created by SARTOPO will contain 4 bands. The first band will contain the incidence angles (in decimal degrees), the second band will contain the radar look angles (in decimal degrees), the third band will contain the azimuth angles (in decimal degrees) and the fourth band will contain the lengths (in meters) of the range vectors.
SARTOPO is used to calculate radar viewing angles as well as range vectors using the input elevation image. For each pixel of the input image, the user may choose to have the inicidence angle, the radar look angle and/or the range vector calculated. If either subcommand is chosen, the azimuth angle may also be calculated. All information for the point mode is calculated from a stationary point along the flight path which is input by the user as a latitude/longitude value. If the subcommand -LINE is chosen, the position along the user input flight path which is the shortest distance from which the current pixel can be seen is calculated. The viewing angles and range vectors are then calculated from this position. The range vector calculation is actually the length of the vector whose end points are the current pixel location and the aircraft/spacecraft position. The parameter OFFSET can be used to scale this value. This is especially useful if calculations are being made for a spacecraft platform since these values can become quite large. The incidence angle is the angle defined by the range vector and the surface normal vector of the current pixel. The normal vector of the current pixel (a vector perpendicular to the current pixel) is the average of 4 normal vectors calculated using 4 points surrounding the current pixel. The radar look angle is the angle defined by the perpendicular to the flight path plane (aircraft) or the orbital plane (spacecraft) and the range vector. The azimuth angle is measured from the north pole and is calculated based on the user input position and the current pixel location.
A nonfatal error was encountered during processing. The image data is probably valid and therefore saved. The error message that is displayed immediately preceding this message is the specific error that was encountered. Processing continues.
A fatal error was encountered during processing. The error message that is displayed immediately preceding this message is the specific error that was encountered.
SARTOPO works with elevation data. Therefore, only 1 band of image data is allowed. Enter either a single band image or use the band specification syntax to select 1 band from a multi-band image for the IN parameter.
An error was encountered while attempting to dynamically allocate memory. The user may have reached the memory limits of the system. Contact the system manager for more information.