PIDF IMAGE DEFINITION BLOCK

UDF definitions which contain data that can be mapped onto a sphere should contain an image definition block in their PIDF especially if the mapping coordinates (laitiude and longitude) are returned as separate UDF measurements (either in the sensor or ancillary data blocks). The primary purpose of the image block is to point an application to the locations of the mapping coordinates in the UDF definition and to specify how they are defined relative to the image pixels.

A PIDF image definition block consists of a single structure which contains the image information fields. It has the generalized form:

struct Image {
   char   format = 'Entry';
   char   type = 'Entry';
   char   bin_type = 'Entry';
   string storage = "Entry";
   int    num_lat_longs = Entry;
   struct LatLongN {
       char   lat_loc = 'Entry';
       int    lat_num = Entry;
       int    lat_unit = Entry;
       string lat_def = "Entry";
       char   long_loc = 'Entry';
       int    long_num = Entry;
       int    long_unit = Entry;
       string long_def = "Entry";
   };
};

Not all of the above structure fields need be present in the image defintion. Only those which are applicable to the image being defined need be included. Default values are supplied for any unspecified field.

KEYWORD: format

A flag which indicates if an image has a starting row of pixels and if so how to find it in the data. The recognized options are:

This is a char field which if not included in the Image structure is defaulted to a dash (-).

KEYWORD: type

The pixel depth. The recognized options are:

This is a char field which if not included in the Image structure is defaulted to a dash (-).

KEYWORD: bin_type

The method to use in establishing the pixel edges in the image. Pixels are considered to be rectangular in shape. The recognized options are:

This is a char field which if not included in the Image structure is defaulted to a N.

KEYWORD: storage

A flag indicating what longititude and latitude data sets are returned within the UDF. A UDF may contain multiple sets of latitude and longitude data each of which is associated with one of 9 fixed positions within an image pixel. The defined pixel postions include: the pixel center, the four pixel corners, and the four pixel edge centers. These are shown below together with their common acronyms:

This is a char field which if not included in the Image structure is defaulted to a dash (-).

KEYWORD: num_lat_longs

The number of defined LatLong structures in the Image structure. If there are no defined LatLong structures then this field should be set to 0. This field must occur above the first LatLong structure definition. It is an int field.

KEYWORD: lat_loc

A flag indicating the UDF data class under which the latitude data is stored. The recognized options for this field are:

pidf v2_SAIC {
$*********************************************************************
    struct Image {
$********************IMAGING INFO*************************************
        char format = 'S';                           $$ Snapshot
        char type = '1';                             $$ 1-D capability
        int num_lat_longs = 1;                       $$ lat/long pairs
        struct LatLong0 {                            $$ lat/long def
            char lat_loc = 'S';                      $$ lat in sensor 
            int lat_num = 2;                         $$ sen number
            int lat_unit = 7;                        $$ lat unit num
            string lat_def = "C";                    $$ center lat
            char long_loc = 'S';                     $$ long in sensor
            int long_num = 1;                        $$ sen number
            int long_unit = 8;                       $$ long unit num
            string long_def = "C";                   $$ center long
        };                                           $$ end lat/long
        string storage = "C";                        $$ center only
    };
$*********************************************************************
};