December 2-5, 2003 MGM Grand Hotel Las Vegas Autodesk Raster Design for Mapping and Land Development Professionals David Zavislan, P.E. GI12-1 Explore the new and enhanced functionality in Autodesk Raster Design for working with imagery, editing scanned maps and photos, and converting parcel, soils and topographical maps into vector data. Learn how to accurately insert georeferenced images. Insert and correlate non-referenced images. Access and manage your imagery using new image manipulation tools. Improve image display with new nonlinear tonal adjustment and palette controls. Generate surfaces from 3D polylines following breaklines and profiles drawn in scanned maps. Convert raster-to-object from scanned contour and USGS maps for use in Autodesk Land Desktop.
File Formats and Data Sources Objectives Understand the difference between raster and vector data. Understand the different types of raster files. Chapter Concepts and Terms Raster - Raster data is comprised of a series of dots, or pixels, with information about the color of each dot. The raster line shown to the right is defined by a grid of dots (bitmap) in which the dots depicting the line are colored black. Vector - Vector data is comprised of coordinate and geometric information that instructs the program how to draw the entity. As shown to the right, a vector line is defined by its two end points. Depth The amount of information stored for each pixel. Binary image Has a depth of 1 bit. Images are single color black and white. Mainly used for scanned line drawings. Grayscale image Has a depth of 8 bits. Images can have 256 shades of gray. This format is typically used to view black and white aerial photography as background information in maps and construction documents. Color image Can have a depth ranging from 4 to 24 bits per pixel. A 4-bit image will have sixteen colors and a 24-bit image will have millions of colors. Color images can be used for graphic arts, aerial photographs and mapping. An example of a mapping application is a scanned USGS quad sheet. Image resolution/density The number of dots per unit that the image was scanned or created. Image formats supported by Raster Design - Raster Design supports binary, grayscale, and up to 24-bit color images. See appendix A in the Raster Design Getting Started manual for more detailed information about supported file formats. BMP, CALS, FLIC, GeoSPOT, GIF, IG4, IGS, JPEG, PCX, PICT, PCX, PICT, PNG, RLC, TARGA, TIFF, MrSID and ECW 2
Working with Aerial Photography and Remote Sensing Objectives Import and correlate raster images. Use Land Development Desktop s point data for image correlation. Use raster data as a quick and informative means of communicating project information. Chapter Concepts and Terms A major component of Raster Design for the land development industry is the ability to insert and correlate color and grayscale digital images. This information can be used as reference data during the design process or it can be quickly incorporated into design documents and presentation graphics. Match - Correlates an image by moving, scaling and rotating the image. Matching is performed by selecting two source points on the image and two destination points in the drawing. Polynomial Rubbersheet Correlates an image by stretching and warping the image to remove distortions. At least three pairs of source and destination points are used to adjust the image. Better correlation is achieved by selecting six or more pairs of points that are distributed evenly across the image. Triangular Rubbersheet Imposes a series of triangles between the control points then applies the transformation to those areas. Because each triangular area is transformed separately, the triangular method is much more accurate than the polynomial method. However, the triangular method may result in the loss of some image data. The area to be transformed is defined by the outermost destination points. Image data outside of the transformation area is discarded. To preserve more of the image data, place control points near the extents of the image. Source point A correlation point on the image. Destination point A point in the drawing file that is selected by specifying coordinates, snapping to entities, picking on another image or by using Land Desktop point data. Change Density - the density command is used to specify an image's density value, density units, or both. Multiple images can be adjusted simultaneously if all selected images have the same density and units. Lesson 1 Inserting an aerial photo In this lesson, you will learn how to insert a non-correlated raster image. Exercise 1 Insert image Select the Image Insert Lesson 2 Image Correlation In this lesson, you will learn how to perform a multi-point rubbersheet operation using coordinate data, object snaps and Land Development Desktop point data. 3
Land Desktop (LDT) point toggles When specifying start or destination points for the Match and Rubbersheet commands you may use the LDT point toggles. The toggles allow you to specify coordinates with LDT point numbers, LDT point objects or by entering northing and easting coordinate values..p - Specify point number.n - Specify Northing and Easting coordinates.g - Select LDT point object in the drawing Exercise 1 Rubber sheeting Select the Image Correlate Rubbersheet menu command. Lesson 3 Change image color depth In this lesson, you will learn how to convert a grayscale image to a color image by changing the color depth. Changing image depth Used to convert images between binary, grayscale, indexed color and true color formats. Grayscale and color images can be converted to bitonal images with the Threshold options in the Histogram command. Color images can also be converted to grayscale with the Histogram command. Color to grayscale convert color images to grayscale for better control over monochrome plotted output. Image thresholding is more predictable with grayscale images. Grayscale to color Increasing the depth of grayscale images allows areas in the image to be highlighted with different colors. This can be used as an alternative to applying hatch patterns over the image. Exercise 1 Converting grayscale image to color Select the Image Image processing Change Color Depth menu command. Lesson 4 Adjust color of image sub-region This lesson demonstrates how to adjust the color or brightness of a portion or sub-region of a raster image. The grayscale image, converted to a color depth in the previous lesson, will be modified to highlight special areas. Sub-region A user specified portion of the image which can be defined by an existing closed vector entity (circles and closed polylines), an image clip boundary, a two-point rectangular region or a multipoint polygonal region. Exercise 1 Adjusting image histogram Select the Image Image Processing Histogram menu command. Lesson 5 Change Image Density This lesson demonstrates how to change image density. 4
Density The number of pixels/dots per unit of measure. Reducing Density Reduces the size of the file. This increases AutoCAD performance and reduces the amount of hard drive space required for images. High Resolution Activate the original high resolution images for plotting or for detailed viewing. Exercise 1 Reducing image density Select the Image Image Processing Change Density menu command. Lesson 6 Save/Export image This lesson demonstrates how to save a modified raster image. Save allows you to save a modified image. Save As allows you to save an image to a new file with a new file name. Useful when the original image is a read-only file. Export allows you to save an image and create a correlation file. Correlation files a file used to position, scale and rotate a raster image when it is inserted into a drawing file. World file can be created for all exported raster file formats. It is saved in the same directory as the raster image. The world file will have the same name as the raster file but with a modified extension such as tfw for a tiff image. Exercise 1 Exporting image Select the Image Export Image menu command. Final Image 5
Using images as Reference/Background Information Objectives Identify different methods of editing scanned hard copy information. Edit raster data. Combine raster and vector data to create a hybrid document. Merge vector data into a raster image. Chapter Concepts and Terms Scanned images - Raster Design facilitates the usage of scanned hard-copy documents within AutoCAD. Scanning allows for the quick utilization of documents such as floor plans, schematics, USGS quad sheets, soils maps, older parcel and subdivision maps or hand drawn details and construction documents. Typically there are three different scenarios in which scanned documents can be used: Used as background information in raster format with no vectorization. This is a quick and inexpensive process, because the document only needs to be scanned and then correlated within the drawing. Partially edited or supplemented with vector modifications. This process is a little more costly because after the image is correlated time must be spent making modifications. Edits may be left in vector format to create a hybrid raster-vector drawing or the vector data can be converted (merged) into the raster image. The final scenario is vectorization. This process converts all of the raster information to vector entities. Once vectorization is completed, the raster image is removed from the drawing file. Vectorization requires a lot of time and is therefore the most expensive of the three methods. File format - Save scanned hard-copy, line drawings and maps as bitonal (black and white) images. Bitonal images can be used use as background drawing information or they can be converted to vector data. Resolution File size is a product of the image depth and resolutions. Bitonal images require a single bit per pixel; therefore, the file size will be determined by the number of pixels per inch at which the image is scanned. A one-inch square that is scanned at 100 dots per inch (dpi) will have an uncompressed file size of 10,000 bytes. The same image will have an uncompressed file size of 40,000 bytes when scanned at 200 dpi. File size increases with the square of the change in resolution. For bitonal images a resolution of 200 dpi is sufficient for most needs. Higher resolutions may be required for documents such as contour maps where the contours are drawn in tight groups. For bitonal images, there is no need to scan at a resolution above the physical resolution of the scanner. Lesson 1 Insert Image This lesson demonstrates the process of inserting a scanned document that does not have correlation information. Exercise 1 Insert scanned drawing image Select the Image Insert menu command. 6
Lesson 2 Correlate image This lesson demonstrates how to adjust a scanned detail drawing to the correct scale within the AutoCAD drawing. Match - Correlates an image by moving, scaling and rotating the image. Matching is performed by selecting two source points on the image and two destination points in the drawing. Exercise 1 Match image to correct scale Select the Image Correlate Match menu command. Lesson 3 REM edit image This lesson demonstrates how to use Raster Design s REM editing tools to modify data within a raster image. REM Raster Entity Modification REM Objects are used to select raster entities to be modified. REM objects can be modified with REM editing commands and AutoCAD commands, such as MOVE, SCALE, COPY and MIRROR. Three types of REM objects can be created: Region Enhanced bitonal region Primitive REM Region - includes all the pixels within the user-specified region. Regions can be specified by selecting polygonal, rectangular, diagonal or circular regions. Additionally, regions can be defined from existing vector entities. REM regions can be created from bitonal, grayscale and color images. Enhanced bitonal region a REM object that includes complete raster entities within the region. Enhanced bitonal regions can not be generated from grayscale and color images. Primitive a distinct raster line, arc or circle. Primitive REM objects can not be generated from grayscale and color images. Exercise 1 Options Select the Image Options menu command. Select the REM tab and the Raster Entity Detection tab. Exercise 2 Creating REM Region Select the Image Raster Entity Manipulation Create Region Rectangular menu command. Exercise 3 Editing or copying REM Region Select the REM object, right-mouse-click and select Copy from the menu. Select the Edit Paste menu command to create a copy of the REM object. Edit REM object with AutoCAD commands. Exercise 4 Merging REM Region back into image Select the Image Raster Entity Manipulation Merge to Raster Image menu command. 7
Lesson 4 Vector edit image This lesson demonstrates how to create a hybrid document using both raster images and vector drawing information. Raster data can be erased either by deleting REM objects or by using the Image Remove menu commands. Exercise 1 Rub or Erase raster data Select the Image Remove Rectangular Region menu command. Exercise 2 Draw new edits AutoCAD Draw commands. Lesson 5 Merge vector into raster This lesson demonstrates how to combine AutoCAD entities into a raster image. Pen settings assign thickness to raster lines based on the color of the AutoCAD vector entity. Pen settings are applied when using the Merge Vector command. Line weights assigned to entities or layers in AutoCAD are not used when merging. Merge Vector creates a raster image of vector entities. Create precise geometry with AutoCAD commands, and then convert them to raster format. Converting entities to raster will result in a single raster file, instead of having a hybrid raster and vector document. Entities can be merged into existing or new raster images. Exercise 1 Options Select the Image Options menu command. Select the Vector Merge tab. Exercise 2 Draw new edits AutoCAD Draw commands. Exercise 3 Merge pen settings Select the Image Merge Configure Raster Pens menu command. Exercise 4 Merge vector into image Select the Image Merge Vector into Raster menu command. 8
Vectorization (Digitizing) Objectives Generate Land Desktop (LDT) ready entities directly in Raster Design Quickly convert raster data to AutoCAD entities with Raster Design s enhanced vectorization tools. Generate MTEXT with Raster Design s Text Recognition command. Chapter Concepts and Terms Vectorization the process of converting raster images into AutoCAD vector entities. Bitonal images are required for the raster snap, and line following conversion functions. Lesson 1 Insert rectified USGS quad sheet This lesson shows how to insert a raster image that has a companion world file. Exercise 1 Insert Image Select the Image Insert menu command. Lesson 2 Convert image to bitonal In this lesson, you will learn how to convert a color image into a bitonal image. The color image of a USGS quad sheet needs to be converted to bitonal so that the vectorization commands can be used to digitize contour and breakline entities. Color Palette The Palette Manager dialog box displays color tables representing the values in the image palette. You can select individual colors in the color table to get information on their color values, frequency, and index values. By selecting one or more colors from the color table, you can also change their color values, combine colors, assign transparency, and delete colors from the palette. Color palette editing can be used to combine colors and simplify and image for digitizing purposes. In this example, all of the unwanted pixel colors will be converted to white, leaving behind only the desired linework. Thresholding a process of converting a color or grayscale image to a bitonal (single bit) image. A pixel color number is selected as the threshold value. All pixels with a color number less than the threshold number are changed to black. All pixels with color numbers greater than the threshold value become white. Inverting reverses the color order of a raster image. For bitonal images, black pixels become white and white pixels become black. For color and grayscale images, negatives can be converted to positive, or visa versa. Often the thresholding process will create a bitonal image where the linework is generated in the background color. These images will need to be inverted before any of the vectorization commands can be applied. Exercise 1 Adjust Color Palette Select the Image Image Processing Palette Manager menu command. Exercise 2 Histogram Select the Image Image Processing Histogram menu command. 9
Exercise 3 Invert Image Select the Image Cleanup Invert menu command. Lesson 3 Vectorize contours This lesson demonstrates the vectorization tools in Raster Design used to create vector entities from raster images. Contours will be created from a USGS quad sheet image. Raster Snap snaps AutoCAD crosshairs to raster linework in bitonal images Quick Bar toolbar menu with buttons to turn on and off Raster Snap and to set Raster Snap modes. Contour Raster Design can generate Land Desktop s (LDT) contour entity with the Contour Follower command. LDT applies styles to contour objects to control their appearance and how they are labeled. Contours are also used to generate data used for building digital terrain models. Exercise 1 Option Select the Image Options menu command. Select the VTools General tab and the VTools Follower tab. Exercise 2 Digitize contours Select the Image Vectorization Tools Contour Follower menu command. Exercise 3 Label contours Select the Terrain Contour Labels Group Interior menu command. This is a LDT command. Lesson 5 Vectorize breaklines This lesson demonstrates how to digitize breakline data from a raster contour map. This data can be used with the contours, digitized in the last exercise, to build a digital terrain model. Breakline 3D Polyline used in terrain modeling to define grade breaks. Raster Impact Points Points where the vector line intersects a raster entity. Exercise 1 - Options Select the Image Options menu command. Select the VTools Follower tab. Exercise 2 Digitize breaklines Select the Image Vectorization Tools 3D Polyline Follower menu command. Exercise 3 View breaklines in 3D Select the Utilities Object Viewer menu command. This is a LDT command. 10
Lesson 6 Text Recognition This lesson demonstrates how to convert text using the Text Recognition command in Raster Design. Text Recognition Using the Recognize Text command you can select raster text in your drawing and convert it to TEXT or MTEXT. The settings entered in the Text Recognition Setup dialog box determine the search parameters for the text recognition engine and the display of the recognized text in the Verify Text window. Exercise 1 - Settings Select the Image Text Recognition Recognize Settings menu command. Select the VTools Follower tab. Exercise 2 Convert Text Select the Image Text Recognition Recognize Text menu command. Recognize Settings Window 11
About the Speaker: David Zavislan is the corporate CADD manager at Nolte Associates, Inc. He supports Nolte s engineering and document delivery processes, developing and implementing CADD tools, training, and standards. A licensed civil engineer, David has also been an independent CADD consultant, specializing in civil engineering, surveying, and mapping. During his career he has worked as a structural engineer, staff engineer for a municipal public works www.nolte.com department, project engineer, project manager, and as a software trainer and consultant for a software reseller. David earned a B.S. in Civil Engineering at Colorado State University in 1985. For additional information on the materials covered in this class or information about services available from David Zavislan and Nolte Associates, please email David at: david.zavislan@nolte.com The expanded version of this handout and the sample files used in this presentation can be downloaded from www.nolte.com. Go to the [client access] page. (You may be required to install an FTP utility for your browser). Enter the file name GI12-1-long.zip in the download box, and then click the download button. This download will be available through the end of January, 2004. 12