Entering Georeferencing Information for the Document

Georeferencing options are complex; what works for architectural workflows may not be suitable for GIS workflows. Different regions of the Earth have different geographical requirements.

Since the earth is not a perfect sphere, it is not a straightforward process to project a map onto the earth’s surface, or transfer an object onto the surface. Projections are mathematical formulas that translate the shape of the earth onto a 2D page. Because the translation loses data, different projections represent the longitudinal and latitudinal coordinates of the non-uniform sphere on the page.

When georeferencing is enabled, each design layer stores information that describes the mapping of that layer’s Cartesian coordinate system onto a geographic coordinate system of latitude and longitude. The origin offset determines how the projection relates to the internal origin (the center of the drawing in the Vectorworks file); this offset can be turned off at the document level or at the layer level for GIS workflows.

If all or most design layers will have the same georeferencing information, use the Georeferencing command to set the parameters for the document. After the default document georeferencing is set, edit each design layer to enable georeferencing, and to customize the settings for individual layers, if needed.

Layers without georeferencing will be assumed to be in the Equirectangular projection, which maps latitude and longitude directly onto the X-Y axis. The origin will represent 0°, 0°, and the scale will be equal to that of the Earth’s scale of latitude and longitude at the Equator. Some georeferencing tools do not work properly on design layers that are not georeferenced.

To set georeferencing for a document:

1. Select File > Document Settings > Georeferencing.

The Document Georeferencing dialog box opens.

►    Click to show/hide the parameters.

Parameter	Description
Adjust origin and orientation of georeferenced data to match document coordinates	Offsets the location of the georeferenced data so that it matches the way that the projection relates to the drawing’s internal origin. Normally, enable the option for architectural documents which center and orient around geographical latitude/longitude coordinates; deselect the option when working with raw GIS data (shape files), when no offset is needed, and the center of the data set is also considered to be the center of the projection.
Latitude/Longitude	Specifies the latitude and longitude at the document origin (0,0); enter decimal degrees, or degrees/minutes/seconds (for example, 39.18, 39° 10’ 32”, or 39d 10m 32s) preceded by a minus (-) sign when appropriate
Angle to True North	Specifies which direction is north from the document origin; use an azimuth degree measurement (0° is along the Y axis, 90° is along the positive X axis)
Projection	Select the appropriate projection type, based on the drawing’s scale and purpose; additional parameters that are required to map to the selected projection display in the area below this field. See Projection Options for details about projections. Alternatively, select the WKT (Well Known Text) option and specify any other projection or coordinate system that is supported by GDAL (Geospatial Data Abstraction Library) in the WKT markup language.
Ellipsoid	Select the appropriate reference ellipsoid used to create the projection (applies to all projections except State Plane Coordinate System NAD83 and NAD27)
UTM Grid Zone/Hemisphere	For the Universal Transverse Mercator (UTM) projection, select the UTM grid zone and UTM hemisphere that apply to this drawing
State/Zone	For a State Plane Coordinate System (NAD83 or NAD27) projection, select the state and zone that apply to this drawing
Center Latitude/Longitude	Specify the latitude and longitude of the center of the selected projection (applies to Equirectangular, Azimuthal Equidistant, Transverse Mercator, Cassini-Soldner, Gnomonic, or Stereographic projections)
Scale	For the Transverse Mercator projection, specify the scale factor along the central longitude; for the Stereographic projection, specify the scale factor at the central point
Standard Parallel 1/2	For the Lambert Conformal Conic projection, enter the two standard parallels to use for the projection
Text	For WKT (Well Known Text) projection, allows you to create a projection and save it for future use. Click Save or Delete to add/remove an item in the Projection list; specify a unique CRS Name when saving if you do not want to replace the existing data.
CRS LookUp	For WKT (Well Known Text) projection, opens the CRS LookUp dialog box that displays all the coordinate reference systems supported in the Vectorworks software. Select the desired reference system and click OK. The relevant text displays in the Text field. Enter text from the EPSG code or CRS name in the Filter field to filter the list and assist with selection.
Transformation mode	Select the appropriate option for transforming the layer objects when the layer’s projection type is changed: ●    Do not transform this layer’s geometry: Layer objects will not be transformed when the layer’s projection is changed ●    Transform all geometry individually: Best for projecting geographic data, such as municipal boundaries, roads, rivers, and locations on a map ●    Move and rotate all geometry as a group: Best for projecting non-geographic drawing objects, such as architectural plans
Transform images to match layer’s projection (Landmark required)	For layers that are set to be georeferenced, ensures that the image pixels are at the correct latitude and longitude to match the layer’s projection; when selected, image objects are also transformed if the Transformation mode is changed
Reset	Discards any edits made and returns all fields to their former values

2. Click OK to save the georeferencing settings.

3. Enable georeferencing for each design layer that requires it, as described in Entering Georeferencing Information for a Design Layer.

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