About Correlating an Image During Insertion

You can set the following options when inserting an image:

• Correlation source
• Insertion point (georeferencing correlation information)
• Rotation
• Scale
• Density
• Units for insertion point and density
• Color

If you modify the correlation settings, AutoCAD Map 3D saves the changes with the drawing.

Correlation Settings

• Correlation Source — Displays available correlation sources. (See the Correlation Sources section, following.) If a source is not listed, it may not be in the same directory as the image file or, if it is a resource (.res) file, it may not be on the specified resource file path.
  Note: To specify the path for resource (.res) files, at the Command prompt, enter mapioptions. Select the Paths tab.
• Insertion Point — The insertion point is the lower left corner of the image before any rotation is applied.

  The insertion point values on the Source tab of the Image Insertion dialog box use the unit specified at the bottom of the Source tab. The insertion point values on the Insertion tab are translated to the current AutoCAD Map 3D drawing unit.

  You can edit the settings or select an insertion point in the drawing by clicking Pick on the Insertion tab and then picking a location in the drawing.

• Rotation — Rotation is in degrees or in the units set by the AUNITS variable. The image is rotated around the insertion point.
• Scale — If the image you insert contains correlation information, the image is inserted at the scale specified by that information. Otherwise, the image is inserted at a scale factor of 1 image unit of measurement to 1 AutoCAD Map 3D unit of measurement. You can change the scale to align the image with the vector geometry in the drawing. For example, if your raster image has a scale of 1 inch equals 50 feet or 1:600, and your AutoCAD Map 3D drawing has a scale of 1 unit equals 1 inch, enter 600 as the scale on the Insertion tab.
• Density — For bitmaps, the density unit used in the image may be in dots per inch. For satellite photos, the density may be in miles. This unit is also used for the insertion point.

To see how your correlation settings translate to AutoCAD Map 3D units, select the Insertion tab. To preview the settings in the drawing, click Apply.

Correlation Sources

When you insert an image, AutoCAD Map 3D searches for correlation files for the image and displays them in the Correlation Source list of the Image Correlation dialog box. You may see the following sources listed.

• World File (Various file extensions)
• Resource File (.res) — You can specify an alternate location for resource files. See To Set the Resource Files Directory.
• Tab File (.tab)
• Image File — For certain types of images, correlation data can be saved as part of the image file. These file types include RLC, IG4, IGS, GeoTags in GeoTIFF, or HDR File in GeoSPOT.
• Default — The values that you set on the Image Defaults tab of the Raster Extension Options dialog box.