Feature Representation

All SLF features contain the slf_type attribute. The value for this attribute is set identically to the value of the feature’s feature type.

Attribute Name	Contents
slf_type	Specifies what type of data the feature represents. Range: slf_segment | slf_point | slf_linear | slf_areal | slf_txt | slf_dsi Default: No default

Segments

slf_type: slf_segment

The SLF segments contain the coordinate sequence that make up the SLF point, linear, and areal features.

These attributes are specific to the segment features.

Attribute Name	Contents
slf_seg_segment	This is the unique identification number given to the segment.
slf_seg_feature_count	A segment can be referenced by various features. This number keeps a count of the number of features referencing the segment.
slf_seg_point_count	The number of coordinates contained in this segment.

Points

slf_type: slf_point

The slf_point features do not have any coordinate. An slf_point feature is allowed to reference more than one segment. That is, an slf_point may be a collection of points having all attributes in common except for their geographical location.

The following table lists the attributes common to all slf_point, slf_linear, and slf_areal features.

Attribute Name	Contents
slf_fea_feature_id	This is the unique identification number given to the feature.
slf_fea_feature_ header_block_count	The slf_feature_header is made up of a sequence of 40 byte blocks. This attribute counts the number of 40 byte blocks that make up the slf_feature_header. For ITD data, the value of this attribute is 7.
slf_feature_header	Contains descriptive information for the feature. In the case of ITD data, the length for the value of this attribute is 280 bytes.
slf_fea_segment_count	Counts the number of segments that make up the feature.
slf_segmentID{#}.id	A list of unique segment IDs that make up the feature.

Linear

slf_type: slf_linear

Linear features output by the SLF reader do not have any coordinates. The attributes for linear features are identical to the attributes found for slf_point features.

Areal

slf_type: slf_areal

Areal1An areal feature is just a polygon. The SLF‘s specification always refers to these features as areal features therefore, to assist those readers familiar with the SLF, it is referred to as areal throughout this section. features output by the SLF reader do not have any coordinates. The attributes for areal features are identical to the attributes found for slf_point features.

Text

slf_type: slf_txt

At this time, only the TXT records for ITD data are recognized and processed. If the SLF data set is not ITD, then the TXT record is ignored.

The SLF reader outputs two types of slf_txt features when reading ITD data, distinguishable by the value of their slf_txt_type attribute. The slf_txt_type attribute may contain the following values:

• misc_or_not_eval—these are features output when processing the Miscellaneous/Not Evaluated TXT record
• surface_material—these are features output when processing the Surface Roughness Information TXT record

The following table lists the attributes for txt features having misc_or_not_eval as the value of their slf_txt_type attribute.

Attribute Name	Contents
slf_txt_feature_type	Indicates whether the feature is a miscellaneous feature (9D010) or a not evaluated feature (9D020). There is no default.
slf_txt_feature_id	This is the feature slf_point, slf_linear, or slf_areal to which this slf_txt feature is referred.
slf_txt_ feature_description	This is where you find descriptive information about this feature.

The following table lists the attributes for txt features having surface_material as the value of their slf_txt_type attribute.

Attribute Name	Contents
slf_srq_value	Surface roughness quality value
slf_srq_description	Description of surface roughness type

DSI

slf_type: slf_dsi

There is exactly one feature of this type for every SLF file processed. The slf_dsi feature contains no geometry. It is a place holder for all descriptive information common to all data. The data is contained in the DSI record of the SLF file.

The following table lists the attributes that the slf_dsi feature contains. Values for some attributes listed may be blank. This is dependent on the actual information contained in the DSI record. Only relevant DSI attributes, as described in Appendix M, Implementing Interim Terrain Data (ITD) in 2-D SLF, of the MIL-STD-2413 document, are listed here.

Tip: Tip: Any DSI fields not listed in the following table are still attributes in the slf_dsi feature. A log of the feature shows all attributes that the feature contains.

Attribute Name	Contents	# of Bytes
slf_dsig_product_type	Specifies the product type. Possible values are: Digital Interim Terrain Data/Tactical (DITDT) or Digital Interim Terrain Data/Planning (DITDP).	5
slf_dsig_data_set_id	This is the data set identification. Range: String	20
slf_dsig_edition	Edition number of the data set. For a new data set, the edition number is 1. Range: 1..999	3
slf_dsig_compilation_date	Date the data set was compiled. Range: YYMM	4
slf_dsig_maintenance_date	Date the data set was updated. Set to 0000 for new data. Range: YYMM	4
slf_dsig_SLF_version_date	Date of the SLF version that applies to the data set. Range: YYMMDD	6
slf_dsig_DMAFF_version_date	The Defense Mapping Agency Feature Format (DMAFF) version date that applies to the data set. Range: YYMMDD	6
slf_dssg_security_ classification	This is the security classification code. Range: T (Top Secret) S (Secret) C (Confidential) F (For Official Use Only) R (Restricted) U (Unclassified)	1
slf_dssg_security_release	Security control and release code based on source and ancillary materials.	2
slf_dssg_downgrading_ declass_date	Downgrading and declassification date. Range: DDMMYY |OADR (originating agency’s determination required)| blank spaces	6
slf_dssg_security_handling	Security handling description.	21
slf_dspg_data_type	The data type is set to GEO for ITD. Range: GEO (geographic coordinate data)	3
slf_dspg_horizontal_units_of_ measure	Measuring system for the horizontal coordinates. Range: SEC (geographic seconds)	3
slf_dspg_horizontal_ resolution_units	Number of units of measure that constitute the least count of the horizontal coordinate system. Range: 0.010 (for 1:50,000 scale ITD) | 0.020 (for 1:250,000 scale ITD)	5
slf_dspg_geodetic_datum	Reference system code for horizontal positions. Range: World Geodetic System 1984 (WGE) or a local datum from Appendix B, Datums, of MIL-STD_2413 when no conversion to WGE exists.	3
slf_dspg_ellipsoid	Ellipsoid to which the horizontal datum is referenced. Range: WGE | Ellipsoid codes from Appendix E, Ellipsoids of MIL-STD-2413	3
slf_dspg_vertical_resolution_units	Number of units of measure that constitute the least count of the vertical coordinate system. Range: b.bbb (where b is a blank)	5
slf_dspg_vertical_reference_ system	Set to Mean Sea Level (MSL) for ITD. Range: MSL	4
slf_dspg_latitude_of_origin	Latitude to which all geographic coordinates in the data set are referenced. Range: DDMMSSSSH	9
slf_dspg_longitude_of_origin	Longitude to which all geographic coordinates in the data set are referenced. Range: DDDMMSSSSH	10
slf_dspg_latitude_of_SW_ corner	Southernmost latitude of the data set. Range: DDMMSSSSH	9
slf_dspg_longitude_of_ SW_corner	Westernmost longitude of the data set. Range: DDDMMSSSSH	10
slf_dspg_latitude_of_ NE_corner	Northernmost latitude of the data set. Range: DDMMSSSSH	9
slf_dspg_longitude_of_ NE_corner	Easternmost longitude of the data set. Range: DDMMSSSSH	10
slf_dspg_total_number_of_ features	The total number of features in the data set. Range: Integer >= 0	6
slf_dspg_number_of_point_ features	The total number of point features in the data set. Range: Integer >= 0	6
slf_dspg_number_of_linear_ features	The total number of linear features in the data set. Range: Integer >= 0	6
slf_dspg_number_of_areal_ features	The total number of areal features in the data set. Range: Integer >= 0	6
slf_dspg_total_number_of_ segments	The total number of segments in the data set. Range: Integer >= 0	6
slf_dshg_edition_code	The first two digits of the edition code is the recompilation code. The third digit is the revision count. The edition code is set to 000 for first-time coverage of a geographic area.	3
slf_dshg_project	Project Specification. Range: String	15
slf_dshg_spec_date	Product specification date. Range: YYMM	4
slf_dshg_spec_amendment_ number	Product specification amendment number. Range: 1..999	3
slf_dshg_producer	Producer of the data. Range: String	8
slf_dshg_digitizing_system	The system used to digitize the data set. Range: String	10
slf_dshg_processing_system	The system used to process the data set. Range: String	10
slf_dshg_data_generalization	The data generalization code is set to 0 for ITD.	1
slf_dshg_north_match_merge_ number	Number of times that this data set has merged with the adjacent data to the north side The value is zero-filled for new data. Range: Integer	1
slf_dshg_east_match_merge_ number	Number of times that this data set has merged with the adjacent data to the east side. The value is zero-filled for new data. Range: Integer	1
slf_dshg_south_match_merge_ number	Number of times that this data set has merged with the adjacent data to the south side. The value is zero-filled for new data. Range: Integer	1
slf_dshg_west_match_merge_ number	Number of times that this data set has merged with the adjacent data to the west side. The value is zero-filled for new data. Range: Integer	1
slf_dshg_north_match_merge_ date	North match merge date. The value is zero-filled for new data. Range: YYMM	4
slf_dshg_east_match_merge_ date	East match merge date. The value is zero-filled for new data. Range: YYMM	4
slf_dshg_south_match_merge_ date	South match merge date. The value is zero-filled for new data. Range: YYMM	4
slf_dshg_west_match_merge_ date	West match merge date. The value is zero-filled for new data. Range: YYMM	4
slf_dshg_yy_mm_of_earliest_ source	Year and month of the earliest source material. Range: YYMM	4
slf_dshg_yy_mm_of_latest_ source	Year and month of the latest source material. Range: YYMM	4
slf_dshg_data_conversion_code	Set to 001 for ITD (1:50,000 scale). Otherwise, it is null.	3