COORDINATE TRANSFORMATION
A site surveyed on a local grid, a drawing in an old datum, a client who wants everything in the national system: STREAM's Coordinate Transformation panel moves the whole project at once — points, lines, areas, measurements, text, dimensions, rasters and terrain corrections — instead of converting a point list. You build the transformation from the coordinate system definitions (EPSG), from points known in both systems, or from parameters you were given; you see the residuals and what will happen to every layer before anything is written; and you apply it in one undoable step.
A coordinate transformation converts positions from one coordinate system to another. When both systems are defined by EPSG codes, the conversion is a published operation. When one side is a local mine or site grid, or an old datum whose published transformation is only metre-level, the transformation has to be estimated from common points — the same physical points with known coordinates in both systems.
STREAM fits its models to the same common points and shows them side by side: shift, shift + rotation, similarity (rotation and scale) and affine (a separate scale in each direction), each with its root mean square error, its accuracy at independent check points and the error it would leave at a raster's corner. A better-fitting model is suggested, never selected for you.
From the coordinate system definition when both systems are in EPSG; from common points for a local grid or an old datum; or by entering a shift, rotation and scale you were given — a PROJ string can be pasted and parsed.
Take the points selected on the map, read a CSV / TXT file, or paste rows from the clipboard. Rows that carry only a name and a coordinate fill the new coordinate of the point with the same name, so the surveyor's list completes the points you picked on the map.
Every point shows its east, north and horizontal residual. Give a point the Check role for an independent accuracy figure. A point that disagrees with the rest is flagged, never removed for you; swapped easting and northing columns are detected and fixed in one click.
The Scope tab lists every layer with what will happen to it, and Calculate previews it without touching the project. A layer left out stays at its old coordinates and comes apart from the rest — the panel says how many, and Include all fixes it.
DEMs and orthophotos are placed by shift; the grid is not rotated and there is no resampling in this version. When a transformation has rotation or scale, the corner error is measured and you decide: place the raster by shift, or leave it out.
A pure shift on all layers is written as a record you switch on and off with the eye, like Offset All, and the data stays in place. Rotation, scale or a partial scope make the transformation permanent. Either way it is a single Undo step, and Undo brings your common points back.
Share Transformation copies the common point table (CSV), a PROJ string and the coefficients to the clipboard for other software. The PDF report documents the common points, residuals, parameters and the layers moved.
One point is enough for a shift, two for a similarity and three for an affine transformation. With only the minimum, residuals cannot be computed and a mistyped point goes unnoticed, so add at least one more — and give one of them the Check role.
Yes, that is the main use: enter points known in both systems and choose the similarity model. Vector data is transformed vertex by vertex. A raster cannot be rotated in this version; its corner error is measured and you choose to place it by shift or leave it out.
Only if you ask. With common points you choose Keep unchanged or Constant shift — the mean elevation difference at the common points, applied equally to the drawings and the DEM. A transformation from coordinate system definitions is horizontal only.
An imported CAD (DXF) drawing does not take part in a permanent transformation, and the panel reports how many are left behind. Line and point objects join in once you turn them into project objects with Make Editable. A pure-shift record moves everything together.
Yes. The quick choice in the status bar is unchanged; this panel does the same job with a preview, and adds common points and parameters.
Free beta for Windows x64. Works fully offline with GeoTIFF, LAS/LAZ and DXF.
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