Example: Assign Initial Coordinate System

We use the Component tab of the Info pane to manually assign an initial coordinate system, when importing from a format that does not specify the coordinate system.



Consider a project where we have created a new map using the OpenStreet Maps imageserver as a base layer.



We open the map, and then we zoom into a view of Monaco.



In the Component tab of the Info pane we can see the coordinate system used by the map is Pseudo-Mercator, the default offered by Manifold when creating new components.  Because that coordinate system is reported in black text we know that the coordinate system has been automatically provided by the OSM data source.   


Likewise, the coordinate system the Map uses is also in black text because the coordinate system for the map was defined when we created the map, using default Pseudo-Mercator.


When using an undocked Info pane set to the narrowest width, the pane does not have enough room to show the full values and units for Pixel size.   If we are curious what those are for OSM (no need for this example, but to indulge our curiosity), we can drag the right border of the undocked pane to widen the pane:


That lets us see that the pixel size of the image used to convey OSM is approximately 0.3 meters by 0.3 meters.


To continue on with this example, we next  import a shapefile to create a drawing, and then we add that drawing to the map.



We import a shapefile that shows buildings in Monaco.  


However, the shapefiles we have imported to create the buildings drawing did not include a ,prj file that specifies the coordinate system to use.     Most shapefiles will have a .prj with them and thus will automatically import using the correct coordinate system, but every now and then we encounter a shapefile that does not.  Ouch.   No problem, as that is easy to deal with in Manifold.



When we drag and drop the buildings drawing into the map it does not appear in Monaco.   



The Component tab of the Info pane immediately shows us what is wrong so we can fix it, showing the coordinate system for the buildings layer as Pseudo Mercator in red text color.


It shows Pseudo Mercator as the coordinate system because that is the default which is assigned to any component created from a source that does not specify a coordinate system.  It is just a placeholder, and indicated as such by the red text used to display it.  The red text tells us the coordinate system is unverified, it may be wrong, and we must specify the correct coordinate system by manually assigning the initial coordinate system.


 To do that we click on the coordinate system picker button.   



Because the buildings component was brought into the project without a coordinate system being specified, Manifold only allows one action, assigning the initial coordinate system.  Choosing Assign Initial Coordinate System unfolds a menu that allows one of three choices:





In this example we know that the buildings drawing uses Latitude / Longitude projection.   That choice is used so often that it is one of the built-in favorites.   We choose Latitude / Longitude as the initial coordinate system for the buildings drawing.


As soon as we do that, two things happen:



First, the read out for the buildings layer coordinate system in the Component tab immediately switches to Latitude / Longitude in black text.   The use of black text indicate the coordinate system has been assigned and is no longer just a placeholder that may or may not be accurate.



Second, the buildings layer immediately snaps into correct position in the map, showing that the buildings illustrated are indeed in Monaco.



If we click on the coordinate picker button again we can see the available options have changed, now that the coordinate system has been assigned.    We now have the two options that are allowed for a drawing that has had an initial coordinate system assigned:





Latitude / Longitude? - How do we know the buildings drawing used Latitude / Longitude? The web site from which we obtained the drawing said so.


See Also

Info Pane: Component






Assign Initial Coordinate System


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: 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