Class Name: Regular Axis

Superclass - <Axis>

Subclasses

Definition

An instance of this DRM class is an <Axis> that uses a constant spacing between hash marks and numerical values.

Primary Page in DRM Diagram:

• 6

Secondary Pages in DRM Diagram:

• 18

Example

1. Digital Terrain Elevation Data (DTED) is sampled in a regular grid of latitude and longitude points. Accordingly, the latitude and longitude <Axes> resulting <Data Table> are <Regular Axis> instances.

2. A table of wind-chill values has axes of air temperature and wind speed. Air temperature typically starts at 0 degree Celsius and is decremented in intervals of 1 degree. Wind speed starts at calm (0 mph) and is incremented at intervals of 5 mph. Consequently, the air temperature and wind-speed axes of this table are <Regular Axis> instances.

FAQs

What is the purpose of the axis_alignment field?

The axis_alignment field provides flexibility in specifying how cells are centred with respect to middle, edge, corner, and so on.

Consider the following 4 (of 9 possible) cases for 2-D grids.

The * indicates the location where the tick mark coordinates intersect in the cell relative to the cell edges. The grid of points determined by axis tick marks represent the location of, to name a few examples, the centre, lower left corner, upper right corner, or edge, respectively, of the corresponding cell. The axis_alignment field therefore indicates the axis alignment being used.

              FACE CNTR    LR LFT CORNER   UP RT CORNER      EDGE

 Axis 1       -------        -------          ------*      -------
 ^            |     |        |     |          |     |      |     |
 |            |  *  |        |     |          |     |      *     |
 |            |     |        |     |          |     |      |     |
  --> Axis 0  -------        *------          -------      -------

Axis 0: SE_AXIS_ALNMNT_MIDDLE SE_AXIS_ALNMNT_LOWER SE_AXIS_ALNMNT_UPPER SE_AXIS_ALNMNT_LOWER
Axis 1: SE_AXIS_ALNMNT_MIDDLE SE_AXIS_ALNMNT_LOWER SE_AXIS_ALNMNT_UPPER SE_AXIS_ALNMNT_MIDDLE

Constraints

• <<Axis Type Restrictions>>

Component of (two-way)(inherited)

• zero or more <Property Grid> instances
• zero or more <Property Table> instances

Component of (two-way)

• zero or more <Mesh Face Table> instances

Inherited Field Elements

Field Elements

Notes

Fields Notes

axis_type

 This specifies the property being described by the given <Axis>.

value_unit

 This specifies the unit of measurement of the given <Axis>, which
 shall be compatible with the requirements imposed by axis_type.

 If axis_type does not require a unit of measurement (for example,
 if axis_type requires a value type of STRING), then value_unit
 shall be set to EUC_UNITLESS.

value_scale

 This specifies the scale applicable to value_unit.

 If axis_type does not require a unit of measurement (for example,
 if axis_type requires a value type of STRING), then value_scale
 shall be set to ESC_UNI.

axis_value_count

 This is the number of "hash marks" along the given <Axis>.

interpolation_type

 This allows the data provider to indicate how best to interpolate
 the data to points that are in-between grid points on the axis.
 When a <Data Table> has more than one axis, the order of the
 interpolations is in the order of axis definitions.

first_value

 This specifies the first numeric value on the axis.

spacing

 This specifies the distance between tick marks.

 For SE_SPACING_TYP_ARITHMETIC, spacing is the
 arithmetic difference between tick marks, such
 that Tick(N) = first_value + (N * spacing)

 For SE_SPACING_TYP_GEOMETRIC, spacing is the
 difference between tick marks such
 that Tick(N) = first_value * (spacing^N)

spacing_type

 This indicates how the spacing value is used to
 compute tick marks.

axis_alignment

 This indicates the position of the axis with respect
 to the axis interval. Note that 'lower' and 'upper'
 refer to the axis INDEX; e.g., 'lower' means
 'aligned to the side with the lower index'.