Projections: Difference between revisions
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Projection refers to a map projection like [http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system UTM]. In XMS software, | Projection refers to a map projection like [http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system UTM]. In XMS software, projections are associated with the project and individual data objects. | ||
Starting with SMS 11.1 and GMS 9.1, the XMS software works on the concept of a "Display Projection". This is the projection being worked in. Each geometric object loaded into the XMS package, such as a Scatterset, DEM, grid or mesh, also has an associated projection. These two projections may not be the same. If the two projections are compatible (i.e. it is a viable option to convert from one projection to the other), the XMS package will convert the data from the object projection to the display projection, just for display purposes. This is referred to as "Project on the fly". The data itself maintains the values associated with the object projection so when the XMS package saves a project, the data files are not modified. | Starting with SMS 11.1 and GMS 9.1, the XMS software works on the concept of a "Display Projection". This is the projection being worked in. Each geometric object loaded into the XMS package, such as a Scatterset, DEM, grid or mesh, also has an associated projection. These two projections may not be the same. If the two projections are compatible (i.e. it is a viable option to convert from one projection to the other), the XMS package will convert the data from the object projection to the display projection, just for display purposes. This is referred to as "Project on the fly". The data itself maintains the values associated with the object projection so when the XMS package saves a project, the data files are not modified. | ||
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==Display Projection== | ==Display Projection== | ||
[[File: | [[File:WMS DisplayProjections.png|thumb|350 px|Example of the ''Display Projection'' dialog.]] | ||
The display projection, or the projection currently associated with the project, can be specified via the ''Display'' | '''Display Projection''' menu command. This setting controls how the XMS application displays (or interprets) data. Data defining objects with a specified projection are converted to the display projection (if it is different from the object projection) for display purposes only. This is referred to as "projection on the fly". The data saved to files as part of a project, or exported for a simulation are exported in the object projection. Display projection only affects the display. | The display projection, or the projection currently associated with the project, can be specified via the ''Display'' | '''Display Projection''' menu command. This setting controls how the XMS application displays (or interprets) data. Data defining objects with a specified projection are converted to the display projection (if it is different from the object projection) for display purposes only. This is referred to as "projection on the fly". The data saved to files as part of a project, or exported for a simulation are exported in the object projection. Display projection only affects the display. | ||
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===Global Projection === | ===Global Projection === | ||
[[File: | [[File:HorizontalProjections.png|thumb|400 px|The ''Select Projection'' dialog.]] | ||
Data referenced to a global projection can be easily correlated and used with other applications that utilize projections including GIS and CAD. When the display projection is specified as a global projection, the XMS application can export georeferenced images, shapefiles, and KMZ files that may be directly imported to other applications. | Data referenced to a global projection can be easily correlated and used with other applications that utilize projections including GIS and CAD. When the display projection is specified as a global projection, the XMS application can export georeferenced images, shapefiles, and KMZ files that may be directly imported to other applications. | ||
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===Reproject on the Fly=== | ===Reproject on the Fly=== | ||
When data from multiple projections are loaded into | When data from multiple projections are loaded into an XMS application, without a defined projection, they do not overlay and the display shows data clusters at two distinct locations. With project on the fly, if the data object has a defined projection (such as a *.prj file), this data would be reprojected on the fly to the display projection. | ||
If data does not line up due to incorrect or incomplete projection specification, specify different object projections to attempt to align the data correctly. Object projection is specified by right-clicking on the object in the project explorer. | If data does not line up due to incorrect or incomplete projection specification, specify different object projections to attempt to align the data correctly. Object projection is specified by right-clicking on the object in the project explorer. | ||
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===Reproject object=== | ===Reproject object=== | ||
This command is done on a specific geometric object (grid, mesh, scatter set, ...) by right-clicking on the entity in the Project Explorer and | This command is done on a specific geometric object (grid, mesh, scatter set, ...) by right-clicking on the entity in the Project Explorer and selecting '''Reproject...'''. If the object does not have a specified projection, this command is not available. It can be accessed by selection the '''Projection...''' command for the object in the same right-click menu and defining a projection for the object. | ||
When the object has a projection, this command reprojects from one projection to another. The command brings up a dialog with a "from" projection specified on the left and a "to" projection specified on the right. The "from" projection is defaulted to the object projection. The "to" projection is defaulted to the display projection. | When the object has a projection, this command reprojects from one projection to another. The command brings up a dialog with a "from" projection specified on the left and a "to" projection specified on the right. The "from" projection is defaulted to the object projection. The "to" projection is defaulted to the display projection. | ||
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===Single Point Reprojection=== | ===Single Point Reprojection=== | ||
'''Single Point Reprojection''' command is found in the ''Display'' menu and allows entering the XYZ coordinates for a point in one projection and see what the new coordinates would be if the point was reprojected to a different projection. It also allows creating a feature point at the new location. | '''Single Point Reprojection''' command is found in the ''Display'' menu and allows entering the XYZ coordinates for a point in one projection and see what the new coordinates would be if the point was reprojected to a different projection. It also allows creating a feature point at the new location. | ||
[[File:ReprojectSinglePoint. | [[File:ReprojectSinglePoint.png|thumb|none|600 px|Example of the ''Reproject Single Point'' dialog.]] | ||
===Restrictions=== | ===Restrictions=== |