Handbook for Predicting Stream Meander Migration and Supporting Software (2004)

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D-1 In order to use the Channel Migration Predictor, it is neces- sary to have banklines in Shapefile format (*.shp) for at least two historical conditions. This information may already be available in some other format that is compatible for use with the GIS software, such as CAD file formats (DWG, DXF, DGN, etc). However, it is more likely that a collection of his- torical aerial photographs is available in a variety of formats. Some may be digital and georeferenced, some may be digital but not georeferenced, and others may be paper copies. Once these various photo sources have been assembled, the main task becomes extracting banklines, transferring them into a common reference system, and finally bringing them into the ArcView Shapefile format. There are multiple ways to accomplish this task. One way is to manipulate the aerial images digitally so that they are all rotated, stretched, and aligned to a common coordinate system. Once they have been manipulated, they can simply be brought into ArcView, and the banklines can be traced directly into Shapefiles. This method requires some fairly expensive soft- ware that is probably not readily available to the average user. Examples of such software include the Image Analysis exten- sion for ArcView, Descartes Image Manager for MicroStation, and AutoDesk Land Development Desktop. There is another method that can be accomplished with more readily available software tools. This method is illus- trated below. In this example, Microsoft PowerPoint and Jasc Paint Shop Pro are used in addition to ArcView. Paint Shop Pro is one of many affordable image-manipulation software packages. The following example uses the two images shown in Figure D.1. Both images show a reach of the Minnesota River that has a history of active migration. One photo is from 1991 and was downloaded from TerraServer (see Appendix A). It has a World File defining its geospatial reference (e.g., Universal Transverse Mercator (UTM) coordinates, Zone, NAD83, and meters). The other photo is a scan from a paper copy showing conditions for the year 1968. Notice that the scanned image has no orientation and is at a different scale than the image obtained from TerraServer. STEP 1—GETTING PHOTOS IN DIGITAL FORMAT The first step is to get both photos into digital format. As mentioned previously, the 1991 photo came from TerraServer and has a World File associated with it. This image was cre- ated by stitching together multiple smaller files. Because the World File references the upper left corner of the overall image, only the World File for the upper-left-most image was used. This file can be brought directly into ArcView using the “Add Data” button, selecting “Image Data Source” as the file type, and browsing for the image. This image will be added as a new theme, and the banklines can be directly traced into a new Shapefile. The other photo (1968 photo) is a scanned image acquired from a paper copy and saved as a TIFF or “Tagged Image File Format” (*.tif) file. STEP 2—TRANSFERRING BANKLINES TO THE REFERENCE PHOTO Both images were brought into PowerPoint either on sepa- rate pages or side by side on the same page, as shown in Fig- ure D.1. The banklines for a selected bend on the scanned image were traced using the drawing tools in the PowerPoint software. Three registration points common to both pho- tographs were also marked using a simple graphic such as a circle, as shown in Figure D.2. After the banklines and regis- tration features for the 1968 photo were drawn, they were grouped together using the “group” tool and copied to the 1991 image. The 1991 image is the reference image because its coordinate system and orientation are known. Before proceeding, the aspect ratio for the grouped set of 1968 features was locked. This was accomplished by right- clicking on the graphic set and selecting “Format Object.” In the form that appears, there is a “Lock Aspect Ratio” check box on the “Size” tab. With the aspect ratio locked, the 1968 features may now be resized and rotated so that the registration points are aligned on the 1991 reference photo as shown in Figure D.3. Next, a box is drawn around the exact limits of the 1991 reference photo. This “georeference” box will be used to help create an image file of the 1968 banklines that will be georeferenced to the same coordinates as the georeferenced 1991 image. STEP 3—BRINGING THE BANKLINES INTO ARCVIEW Next, the 1991 photo was removed from the newly aligned bankline data, registration points, and the georeference box as shown in Figure D.4. This page was turned into a TIFF file by selecting “Save As” under the “File” pull-down menu in PowerPoint and selecting TIFF as the file type. Only the page that is being viewed will need to be saved as a TIFF file. The new TIFF file is then opened in Paint Shop Pro and cropped to the limits of the georeference box. A file with the 1968 banklines is created that covers the same area as the APPENDIX D TIPS FOR DELINEATING BANKLINES FROM HISTORIC AERIAL PHOTOS FOR USE WITH THE CHANNEL MIGRATION PREDICTOR

D-2 1991 reference photo. In order to bring this new image file into ArcView, the TIFF has to be the same size in number of pixels as the 1991 reference photo. The 1991 reference photo is 400 by 400 pixels, so the 1968 bankline image file is con- verted to the same size. Once the 1968 bankline image file is the same size, the World File (*.tfw) for the 1991 photo can be used to locate it in ArcView. This is done by simply copy- ing the World File to a file with the same name as the new bankline image file. The 1968 bankline image file can then be brought into ArcView as described in Step 1 above, using the “Add Data” button. The file should open in the same location as the 1991 reference photo that is already loaded. Using the 1968 bank- line image as a reference, a second set of 1968 banklines can be traced into a new Shapefile. After the second set of 1968 banklines have been digitized, the 1968 image can be deleted, leaving the 1991 reference aerial photo and the 1968 bankline set as shown in Figure D.5. This procedure can be repeated for any additional historic photographs that need to be brought into ArcView. Once the banklines are in Shapefile format, the user is ready to begin using the Data Logger and Channel Migration Predictor tools in ArcView. Figure D.1. Two historical photos used in the meander migration analysis. 1968 Photo — Scanned 1991 Photo — from TerraServer Figure D.2. Banklines (green) and registration features (red) delineated on the scanned 1968 photo.

D-3 Figure D.3. Banklines (green) and registration features (red) from the 1968 photo rotated and stretched to match the 1991 reference photo. 1968 Photo — Scanned 1991 Photo — from TerraServer Figure D.4. Banklines (green), registration features (red), and georeference box (red) to be exported as a TIFF file.

D-4 Figure D.5. 1968 banklines after being turned into a Shapefile and superimposed on the 1991 reference photo.