Initial Projection

Do NOT use this dialog if you have not carefully read the Projections topic.   

 

To re-project a drawing or image into a different projection, use Edit - Change Projection.   Do NOT use Edit - Initial Projection in an attempt to re-project a component.

 

The Initial Projection dialog is used to correct errors when a drawing or image is brought into Manifold with the wrong coordinate system specified.  It is used just once to assign the correct coordinate system to the component.  It should never be used again for that component.  

 

Use Only Once to Correct Errors

il_initial_proj_danger.png

Never Use This Dialog Otherwise

 

Using Edit - Initial Projection is easy: Choosing that menu command launches the Coordinate System dialog to allow us to choose one of the thousands of coordinate systems in the  Standard or EPSG lists or to specify a Custom coordinate system to use.    Choose a coordinate system, press OK and we are done.    

 

See the Coordinate System topic for details on using that dialog.

 

There are three difficulties using Initial Projection:

 

 

 

 

Notes

Synonyms -  The terms projection and coordinate system are used as interchangeable synonyms in Manifold.  Cartographers favor the term projection while programmers seem to prefer coordinate system.  This documentation uses the two terms interchangeably, with the term projection tending to be used more in GIS or display contexts and the term coordinate system tending to be used more when discussing programming, SQL or standards.

 

Why not hide the command?  - If Edit - Initial Projection is frequently misused by the careless, why not hide it deep in the menu structure where only a more experienced user will be able to find it?  It may come to that.   The problem is not inconveniencing careful users who frequently need to use the command.    Spatial data is so often published with the wrong coordinate system assigned or with slightly-wrong coordinate systems assigned or in formats that do not convey the coordinate system that using Initial Projection to assign a coordinate system to newly-imported data is a frequent task.  It is easy to do and no big deal to accomplish safely and successfully.

See Also

Coordinates

 

Projections

 

Change Projection

 

Map Projection

 

Coordinate System

 

Base Coordinate System

 

Favorite Coordinate Systems

 

Favorite Base Coordinate Systems

 

Example: Change Projection of an Image - Use the Change Projection dialog to change the projection of an image, raster data showing terrain elevations in a region of Florida, from Latitude / Longitude to Orthographic centered on Florida.

 

Example: Adding a Favorite Coordinate System - Step by step example showing how to add a frequently used coordinate system to the Favorites system.

 

Example: Detecting and Correcting a Wrong Projection - A lengthy example exploring projection dialogs and a classic projection problem.  We save a drawing into projected shapefiles and then show on import how a projection can be quickly and easily checked and corrected if it is wrong.

 

Re-Projection Creates a New Image - Why changing the projection of an image creates a new image.

 

About Coordinate Systems

 

Projections Tutorial