Appendix A: Data Descriptor Record

DDR Integer Fields

nl Number of lines in image

ns Number of samples in image

nbands Number of bands in image

dtype Data type of samples:

=1: unsigned char

=2: short

=3: long

=4: float

master_line Line relative to master image

master_sample Sample relative to master image

valid[0] => projection code flag

valid[1] => zone code flag

valid[2] => datum code flag

valid[3] => projection coefficients

valid[4] => ground units

valid[5] => ground distance

valid[6] => corner coordinates

valid[7] => line/sample increments

NOTE: The flags can have the value of:

=0: INVALID

=1: VALID

=2: UNKNOWN

proj_code GCTP projection code

zone_code UTM or State Plane zone

datum_code Code for the datum/ellipsoid. Represents ellipsoid ONLY if less than 100.

DDR Character Fields

system[12] Computer system data is on

proj_units[12] Projection units(GCTP units+other)

last_used_date[12] Last access date. NOTE: All ddr dates are stored as "ddmmm-yy". For example, a date of December 31, 1986 is stored as: "31dec86" with month in lower case.

last_used_time[12] Last access time. NOTE: All ddr times are stored using a twenty- four hour clock. Seconds are separated by a colon. Example: 1:05:55 pm is stored as 1305:55

DDR Double Precision Fields

proj_coef[15] Projection parameters. Refer to GCTP documentation for field definitions

upleft[2] Corner coordinates entered in latitude/longitude

loleft[2] or projection coordinates (y,x) in northing/

upright[2] easting order

loright[2]

pdist_y Projection distance/pixel (y)

pdist_x Projection distance/pixel (x)

line_inc Line increment for sampling

sample_inc Sample increment for sampling. NOTE: The line/sample increments are the values applied to the original image to obtain this image. If resampling or subsampling was not applied, the value contained in these fields is 1.0

Band DDR Integer Fields

bandno Band number

valid Validity flag for min/max

=0: INVALID

=1: VALID

=2: BOUNDED

Band DDR Double Precision Fields

minval Minimum intensity value

maxval Maximum intensity value

Band DDR Character Fields

source[32] Source of data

instrument[32] Type of sensor

direction[64] Direction of the capture process

date[10] Capture date (See date format previously listed)

time[8] Capture time (See time format previously listed)

Refer to the LAS 7.1 Programmer's Guide for the manner in which each LAS module updates the DDR.