Unit Converter

The Unit Converter dialog provides quick conversion between units and values used in coordinate system parameter boxes.


  Launch the Unit Converter dialog by pressing the 123 button next to a parameter in the Coordinate System dialog or next to the Local Scale or Local Offset boxes in the Coordinate System Metrics dialog, and then choose Unit Converter.




Choose the unit of measure to be converted into the unit of measure used by the coordinate system.


Specify the number of units selected to be converted.


The converted value, in the units used by the coordinate system, of the specified number of units to be converted.


Apply the converted Result value to the box for which the Unit Converter dialog was launched.


We are working with a coordinate system, such as Orthographic, which uses meters as the units.    The metadata for the data set we are using specifies we must use X and Y local offsets of 200 US Survey feet.    We need to convert that value in US Survey feet into the equivalent number of meters.



 We press the Unit Converter button next to the Local offset X box.  



In the menu we choose Unit Converter.



The dialog launches with Meter as the unit.   From the long pull down list in the uppermost, units box we choose US Survey Foot.



We enter 200 into the Original box.   The dialog automatically converts that into 60.960... meters in the Result box.   We press OK.  



The Local offset X box is automatically populated with the computed result value of 60.960... meters.    If we want the same offset in the Local offset Y box we can either repeat the above procedure for the Y box or simply copy and paste the value from the X box.



Metrics values - Choosing a coordinate system in the main Coordinate System dialog will load the Coordinate System Metrics parameters with the correct values for the chosen system. Those are usually based on a unit of 1 meter or 1 degree, but some national coordinate systems use values like 0.9 meter. Custom values as read from a world file or entered manually will also appear.   


EPSG and SRID Overrides - EPSG and SRID coordinate systems use a numeric code to identify the coordinate system.   Metrics for EPSG and SRID coordinate systems are applied as overrides. This allows keeping the coordinate system definition as a code for readability and for easier conversion.


List all units of measure - Transform templates often provide parameter boxes that have a list of all available units of measure, and coordinate system dialogs often do as well.  However, if we would like a list of all units of measure available we can use SQL:


TABLE CALL CoordUnits();


or more elegantly, with a field that indicates if the unit of measure is an angular unit suitable for latitude/longitude coordinate systems:



  StringJsonValue([value], 'Unit', true) AS [name],

  Coalesce(StringJsonBoolean([value], 'UnitLatLon', true), false) AS [latlon]

FROM CALL CoordUnits();



See Also

Info Pane






Assign Initial Coordinate System


Reproject Component


Sub-pixel Reprojection

Map Projection


Coordinate System Metrics


Base Coordinate System


Favorite Coordinate Systems


Favorite Base Coordinate Systems


Example: Assign Initial Coordinate System - Use the Info 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


Latitude and Longitude are Not Enough