Resulting Imagery Location

Destination File wizard page specifies resulting raster imagery format and location on a disk:

Import Map wizard Destination File page

This wizard page provides following options:

Image destination path - enables you to paste-in or select resulting imagery path on a disk.
Image format - indicating selected image format during specifying destination path.
Image path type - defines the image's XRef path type in AutoCAD.
Create image georeferencing file - enables creating a "world" georeferencing file along the image.

It also provides following navigation buttons:

Previous - returns to Raster Imagery Post-processing wizard page.
Next - proceeds to Imported Raster Imagery wizard page.
Cancel - exits this wizard and closes the dialog.
Help - displays this help page.

Imagery Destination Path

Initially, destination image name is set to random string, while destination imagery path is set to temporary Windows folder: You can change it by clicking on button next to the destination file name - the Select location to export Raster image file opens:

Raster imagery Save File dialog

Besides selecting target folder and file name, you also need to define output raster format. Default file format is TIFF (Tagged Image File Format), also enabling creating image georeferencing ("World") file accompanying output raster file - if this option is checked in wizard. Please note that not all formats provide creating image georeferencing file.

Please note that if you specified mosaicking image tiles, each image tile results in separate raster file. Thus each file on disk will have numerical suffix after specified file name.

Supported Image Formats

Following output image file formats are supported by TopoPlanner:

Extension	World File	Format Description
TIF	TFW	Tagged Image File Format
BMP	BPW	Windows Bitmap Format
GIF	-	Graphics Interchange Format
PNG	PGW	Portable Network Graphics Format
JPG	JGW	Joint Photographic Expert Group Format
ECW	-	ERDAS Compressed Wavelets Format

Image Compression

An important concept which distinguishes many image types is whether they are compressed. Compressed files are significantly smaller than their uncompressed counterparts, and fall into two general categories: "lossy" and "lossless". Lossless compression ensures that all image information is preserved, even if the file size is a bit larger as a result. Lossy compression, by contrast, can create file sizes that are significantly smaller, but achieves this by selectively discarding image data. The resulting compressed file is therefore no longer identical to the original. Visible differences between these compressed files and their original are termed "compression artifacts."

Image Path Type

Running either IMAGE or EXTERNALREFERENCES command in AutoCAD opens up an External References docker with the list of raster images currently referenced in active drawing. AutoCAD supports following path types for inserted raster imagery:

Full path option provides complete path to the output raster image, as displayed in Saved Path field of the External References AutoCAD docker. This option somewhat prevents user to further move image away from specified path, otherwise AutoCAD may not be able to "find" it afterwards.

Resulting saved path using Full path option

Relative path option deploys relative path to the output raster image, with regards to the active drawing path, as displayed in Saved Path field of External References AutoCAD docker. This option is accessible only if active drawing is already saved (newly opened, non-saved DWG drawings will prevent this option from showing up in first place).

Resulting saved path using Relative path option

Image Georeferencing File

Image georeferencing (or "World") file is a plain text computer data file used by geographic information systems to georeference raster map images. This file can be used by both AutoCAD Map 3D's via MAPIINSERT command to automatically georeference inserted image, and also many other GIS packages like ESRI ArcGIS. Below is displayed the contents of a sample world file using EPSG:31370 coordinates:

0.375786317197

0.0000000

-0.376292235547

155420.068430997000

201221.089997690000

The generic meaning of world file parameters are:

Line 1: A: pixel size in the x-direction in map units/pixel
Line 2: D: rotation about y-axis
Line 3: B: rotation about x-axis
Line 4: E: pixel size in the y-direction in map units, almost always negative
Line 5: C: x-coordinate of the center of the upper left pixel
Line 6: F: y-coordinate of the center of the upper left pixel

Graphical view of above described world files parameters and computed values of the four first upper left pixels of an image:


Case 1: Square pixels, no rotation	Case 2: Square pixels, with rotation


Case 3: Rectangular pixels, no rotation	Case 4: Rectangular pixels, with rotation

Please keep in mind that world file does not support any raster clipping or coordinate system information. That is - clipping boundary information (if selected during picking area of interest operation) is lost, only original rectangular image boundary is retained. The name of the resulting world file is equal to raster image file name, while file extension of the world file is based on the raster file's extension, as described in supported file formats above.