performance specification digital terrain elevation data

MIL-PRF-89020Bconsisting of 2700 ASCII characters. Each character is represented by 1 byteor 8 bits. The record allows for up to nine accuracy sub regions within theproduct should the accuracies of various portions of this product differ.Each sub region may consist of up to fourteen coordinate pairs to accuratelyportray the outline. Coordinates are input clockwise. Unused coordinatepairs are blank filled.Note: Numeric values shall be right justified with leading zeros. Alphaand alphanumeric characters shall be left justified.3.13.5.1 Accuracy sub region description. A sub region descriptioncontains the sub region accuracies, the number of sub region coordinate pairsand the actual coordinate pairs which define the sub region area. Unused subregions and/or unused coordinate pairs within a sub region will be blankfilled. The sub regions will be organized as follows:a. The first coordinate pair of the first sub region must be thesouthwest corner of the bounding rectangle.b. The first coordinate pair of each sub region must be the mostsouthern and western point in the sub region. Southern takes precedence overwestern.c. The first coordinate pair of each sequential sub region mustbe arranged in a clockwise direction starting with the first sub region. Subregions which contain at least part of a degree line will take precedence andbe numbered clockwise, starting in the SW corner and proceeding around thefour bounding degree lines. Remaining sub regions will be numbered in a southto north, west to east manner based on initial point within each sub region.d. Coordinate pairs within a sub region must be arranged in aclockwise direction.e. Each sub region coordinate pair must be located on or withinthe bounding rectangle.f. Each coordinate pair in the bounding rectangle must berepresented as a sub region coordinate pair.g. Sub region areas must not overlap or leave gaps. The entirearea defined by the bounding rectangle must be covered by sub region areas(i.e. the sum of the sub regions must equal the 1° product area).h. The first and last coordinate pairs of a sub region shall notbe the same. Closure of the sub region area is implied.i. A sub region can only be generalized if all of the sub regiondescriptions have been used.j. Sub region format:Field Length CharacterSub region Number in Characters Start1 284 582 284 3423 284 6264 284 9105 284 11946 284 14787 284 17628 284 20469 284 233034