Command: project

Syntax

project { <elist> ... } | <points>

Description

Apply mapping projections to entities or points.

Parameters

• <elist>
  A group/entity list defining which entities are to be projected. If omitted, the current contents of the these group are projected.

• <points>
  A point identifier (scalar or array) whose co-ordinates are to be projected.

Switches

• -b
  Treat <points> as 2 opposite corners of a rectangle defining a bounding box. The rectangle will be transformed and returned in "minimum maximum" order. Because rectangles do not necessarily transform orthogonally into other projections, the operation will ensure that all points along the perimeter of the original rectangle lie within the transformed rectangle. The array length of <points> must be 2. This switch is ignored when transforming entities.

• -ef=<filter>
  A filter to be applied to all entities within <elist>, further qualifying which entities are to be projected. If omitted, the filter current_filter is used.

• -from=<projection>
  A projection defining the current projection of the entities (or points). If omitted, the current projection mapping is used. Use the phrase -from=ll_proj to convert from longitude/latitude.

• -fu=<units>
  The units for the entities/points to be transformed. If this is omitted then the current value of units is assumed, or "ll" if the -from projection is a Long/Lat projection.

• -r
  Treat <points> as 2 opposite corners of a rectangle. The rectangle will be transformed and returned in "minimum maximum" order. Because rectangles do not necessarily transform orthogonally into other projections, the result will be that a reverse transformation on the new rectangle would return the original rectangle, although this may result in loss of coverage at the extremities. The array length of <points> must be 2. This switch is ignored when transforming entities.

• -to=<projection>
  A projection defining the new projection for the entities (or points). If omitted, the current projection mapping is used. Use the phrase -to=ll_proj to convert into longitude/latitude.

• -tu=<units>
  The units for the resulting entity/point transformations. If this is omitted then the current value of units is assumed, or "ll" if the -to projection is a Long/Lat projection.

Notes

If either the -from or -to projection is null, this command does nothing.

If the -from and -to projections are identical, but the corresponding units values are different, this command will merely perform an appropriate scale operation.

The from projections must be ones with inverse procedures, i.e. with the ability to transform from Cartesian to longitude/latitude and vice-versa.

Sub-entities of compounds may be manipulated in isolation from their parent entities.

Examples

Project all entities in the these group.

project -from=amg55, -to=amg56

Project two entities into the current projection.

project fred, my.face, -from=merc_10

Read from file and project an array of points.

point pps[]
pfile myfile.dat,-op=pps
project pps,-from=ll_proj,-to=ukng

Project window corners into a new bounding box.

point corns[] = mywin.corners
project corns,-from=ll_proj,-to=ukng,-b

See Also