Assign Initial Coordinate System

Accessed in the Component pane by clicking the coordinate system picker button for the component.  Appears in the dropdown menu only when the coordinate system is shown in red color, the Manifold indication the initial coordinate system has not yet been assigned.

 

Modern formats designed to store spatial data will automatically specify the coordinate system to be used for the data they provide.   Data from such sources will import seamlessly into Manifold with the initial coordinate system automatically assigned.  In the Component pane the coordinate system for the component will appear in black text, indicating the initial coordinate system has been assigned and the component is ready to go.

 

If we import or link data only from modern formats designed for spatial data storage we might never see this command or need to use it.  It appears as an option only for those components that do not yet have an initial coordinate system assigned.  That usually happens for components that were imported or linked from formats that failed to specify the initial coordinate system, or that were created manually or through programmatic means without specifying the initial coordinate system.

When Manifold shows the coordinate system in black color, as in the Latitude / Longitude coordinate system seen above left,  that tells us the component the component has been imported from a format that specifies the coordinate system to use, or that the component has been created manually or programmatically with initial coordinate system specified.

 

If the coordinate system is shown in red color, as in the illustration below, we must click the coordinate system picker button and choose Assign Initial Coordinate System.  

 

  

 

Red color tells us the component has been created without specifying the coordinate system or it has been imported from a format that does not specify projection information.   

 

That often happens when acquiring data from older formats or from sources, such as CAD or photography formats, not designed to store spatial data.   In such cases Manifold uses Pseudo-Mercator in red color as a placeholder, until we can assign the correct initial coordinate system.

 

Assigning an initial coordinate system is easy: Click the coordinate system picker button in the Component pane and under Assign Initial Coordinate System unfolds a menu that allows easy specification of the desired coordinate system.

 

 

(Favorites List)

A list of favorite coordinate systems.  Factory defaults are Pseudo-Mercator and Latitude / Longitude.  Add or delete favorites as desired.

More...

Launch the full Coordinate System dialog that allows a choice of thousands of systems.

Favorites

Add, delete, or modify favorite coordinate systems.

Paste

Paste a coordinate system from the Windows Clipboard.

Paste without Metrics

Paste a coordinate system from the Windows Clipboard, but do not apply the Coordinate System Metrics it specifies.

 

Used Once

When we must use this command, we only use it once after initial import or linking of a component.  After it is used once the command will no longer appear.   If we make an error applying this command, we can repair the error by using the Repair Initial Coordinate System command that thereafter will be available.

 

For a step-by-step illustrated example using the Assign Initial Coordinate System command, see the Example: Assign Initial Coordinate System topic.

Notes

No changes to data - Assigning an initial coordinate system does not change the coordinate numbers embedded in a drawing's geometry and it does not change pixels in images.   It only tells Manifold what coordinate system to assume when interpreting that data.   The only change is to the coordinate system property for the data.

 

Difficulties - There are two difficulties using Assign Initial Coordinate System:

 

Knowing what to assign - People publish projected data all the time in spatially brain-dead formats which do not convey projection information, and then they fail to tell users what projection they  used.    

 

The red text along with a choice limited to Assign Initial Coordinate System warns us that the source of the data failed to specify the coordinate system, but if we do not know from other means (such as reading a description of the data on a web site) what coordinate system should be used we cannot manually assign it using the command.

 

We might get lucky through trial and error.   We could, try Latitude / Longitude, and discover the data looks OK against a "known good" layer like Bing.   But that is fake luck in many circumstances because we will not know if a default datum choice like WGS84 is the right one, and not NAD27 or some other datum that also would produce a visually close alignment.    

 

The best approach is to sharpen our detective skills, to carefully search the website from which we downloaded the data and to carefully review any accompanying metadata files to see if we can find an authoritative statement of what coordinate system was used.

 

Keeping the careless at bay - People who do not read instructions may misuse Assign Initial Coordinate System by thinking it is used to change a coordinate system that has already has been correctly assigned.   The result is total chaos because first, the initial coordinate system has now been wrongly assigned, and second, the red text that was used to warn that the coordinate system was probably wrong will now be replaced with black text, giving the impression that the (probably wrong) coordinate system is correct.  

 

Instead of changing the projection, such errors take a perfectly good image or drawing that was ready to be made useful through intelligent use of Assign Initial Coordinate System, and instead assign the wrong coordinate system to that data.  

 

Mangers should prevent this problem by teaching beginners to pause when they see red text and the sole choice of Assign Initial Coordinate System.  They should not do anything further without consulting somebody who knows what they are doing.   Forbid untrained users from using Assign Initial Coordinate System until their work can be reviewed by a knowledgable user, or until they have learned enough not to misuse the command.

 

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.

 

Trust Manifold - If the coordinate system readout for a component appears in red text in the Component pane and Manifold allows only the choice of Assign Initial Coordinate System from the coordinate system picker button, we should not argue with the system, no matter how sure we are that the data that was imported or linked came with a specification of initial coordinate system.   Believe the initial coordinate system was not specified and use the command to specify it manually.

 

Data that is thought to contain coordinate system info frequently does not.   People forget to include necessary files, files get damaged when edited by the wrong software (see the commentary on killing GeoTIFFs in the TIF topic) and sometimes people publish data assuming everybody on Earth will by default use exactly the same coordinate system they do, so they do not include info required for those who do not base all thought upon Universal Transverse Mercator Zone 42 (S).

 

See Also

Component Pane

 

Coordinates

 

Projections

 

Repair Initial Coordinate System

 

Reproject Component

 

Map Projection

 

Coordinate System

 

Base Coordinate System

 

Favorite Coordinate Systems

 

Favorite Base Coordinate Systems

 

Example: Convert a 0 to 360 Degree Projection - We often encounter data, both images and drawings, using latitude and longitude degrees that appears to be in Latitude / Longitude projection but which has longitude values from 0 degrees to 360 degrees and latitude values from 0 degrees to 180 degrees, instead of the usual arrangement of -180 degrees to 180 degrees for longitude centered on the Prime Meridian, and -90 degrees to 90 degrees for latitude centered on the Equator.  This example shows how to utilize such data by assigning the correct projection.

 

Example: Assign Initial Coordinate System - Use the Component pane to manually assign an initial coordinate system when importing from a format that does not specify the coordinate system.

 

Example: Change Projection of an Image - Use the Reproject Component command 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.

 

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

 

About Coordinate Systems

 

Projections Tutorial