Register Image    _______________________  From Spatial Transformation
Sold through www.spatial-online.com. 
Register an image in ArcView.

Table of Contents

Overview

Register Image enables the user to register an image in ArcView. The image is not modified, but the World File is defined and/or set to place the image as precisely as possible in ArcView. This allows shifting and scaling independently in the X and Y directions. For higher order image transformations, Spatial Transformation provides products Stretch Image and Warp Image.

A transformation is defined by a set of control points, matching positions on the image to the desired position on the map. From these points, a best origin and scale in X and Y directions is determined using a least squares fit.

Register Image provides interactive functionality to establish the control points. When the control points have been established, a button will instantly move the image. It also provides a dialog with more information. The resultant transformation is applied to each input point and the distance between the transformed point and the desired position for that point (residual error) is calculated. Details for each point are shown.

After calculating the transformation, the World File parameters are set and the image is redrawn. The control points now reflect the new position of the image.

Return to Table of Contents

Installation Instructions

Register Image can be downloaded from www.spatial-online.com. The file will be called RegisterImage.exe.

In order to install Register Image, save RegisterImage.exe to temporary space on your disk. Double click it to run the install. An install wizard will appear to guide you through the installation process.

To find Register Image in ArcView, activate the project window and from the file menu, choose Extensions. In the Extensions dialog, click the box beside Register Image. When a view is open, a Register Image menu will appear to evoke Register Image. It will contain a link to this help.

Return to Table of Contents

Registering an Image

The Register Image will provide three choices:

The last item will evoke this help in your default browser.

To register an image, open a view and add the shape files that are in the vicinity of the image. Make the files active by clicking them in the View Table of Contents and click the Zoom to Active Themes button. Then add the image with View > Add Theme. In the bottom left corner of the dialog, set the Data Source Types to Image Data Source. Choose your image and click OK. Make the image visible by clicking the box beside its name in the ArcView Table of Contents.

Quite possibly, your image will not appear in the view. To make it centered in the current view:

  • Make it the active theme by clicking on it in the View Table of Contents.
  • Click Register Image > Move Image to View.
Prior to evoking Register Image, control points need to be defined. The process is started by clicking Register Image > Initialize Control Points. If you have previously built some control points for this image, you will be asked if you wish to use the previous points. You can either choose Yes to utilize them, or No to start anew. In case you do not have any control points, the system will start with four points at the four corners of the image, labeled TL, TR, BL and BR. The image points are in aqua and the map points in yellow such as seen in the screen below.

The Register Image menu label is changed to Register name.tiff identifying the name of the image your are registering. In addition to the control points, there will be two new buttons and two new tools. There purposes are as follows:

LabelPositionPurpose
RButtonCauses the image to be registered to the current control points
QButtonQuits the registration process and clears the control points
AToolAdds a new control point
ZToolZooms to closest control point

The labels on the screen must be dragged to appropriate positions for the control points. The precise position of the point is the bottom left corner of the box that is being dragged. The aqua label must be dragged to a position on the image while the corresponding yellow label is dragged to the corresponding position on the map. For more accurate positioning, you may wish to zoom in on each point. Click the Z tool, then click near the control point of interest and the view will zoom into the point.

Points can be deleted in the usual manner or added using the tool labeled A. This transformation needs only three points. However, specifying more than three points is likely to avoid problems caused by slight inaccuracies in the point input process.

In the example, there are no easily identifiable points in the corners, so each control point has been dragged to a position that can be identified in both the image and the map.

You can register the image using the current control points in two manners. Clicking the button labeled R will cause the image to move. Clicking Register Image > Register Image will provide feedback on the effect on each point, as well as move the image.

In either case, when the product is running in trial mode, the following registration screen will appear.

Clicking the purchase button will evoke your browser with www.spatial-online.com to enable you to purchase the product on-line, through the Fax or via Purchase Order. When you purchase the product, you will be required to supply your site code (just below the Purchase button). In return, you will get a product key. Insert that key into the Text Box next to Product Key and click OK to register the product. Once you have done this, this registration box will no longer appear.

To run the product in trial mode, click the Run in Demo Mode button. Below the button, the remaining trial period is shown.

Clicking the Cancel button will stop the process.

If you clicked the button labeled R, the image will move immediately to the best fit to the control points. The control points should now be closer. You can examine each one to see how closely they could be fit.

In case you utilized the Register Image > Register Image process, the dialog below will appear.

The list box contains the labels for each point followed by the image column and row, the map control position, the position that the image control was translated to, and the residual error. The residual error is the distance between the desired position (the map control position) and the translated position (where the image control position is moved to).

In case a point has a very high residual error, and is likely to be in error, that point can be excluded from the transformation process by selecting it and then clicking the Remove Point button. At least two points are required to define the transformation. However, using a larger number of points minimizes the effects of small errors in defining the points.

The buttons on the next line are the following:

  • Restore: This button will restore all control points, in case you have previously removed one or more, and recalculate the transformation and the residual errors.
  • Remove Point: This button will remove the selected point and recalculate the transformation and the residual errors. In case one point has a very large residual error, you may decide it is incorrect and remove it to avoid an inappropriate influence over the transformation calculations.
  • Cancel: This button will cancel the process, returning to ArcView without moving the image.
  • Accept: This button will accept the transformation, returning to ArcView and moving the image.
  • Help: This button will cause this help to be evoked in your default browser.
Along the bottom of the screen is the name of the file that contains the image control points.

Whether you examine the above details and accept, or just click the button labeled R, the image will be re-positioned and World File written. You can modify the control points until you are comfortable with the position of the image. Then click the button labeled Q to complete the registration process.

Return to Table of Contents

Frequently Asked Questions

  • How many control points do I need?
    • This transformation needs only two points. However, specifying more than two points is likely to avoid problems caused by slight inaccuracies in the point input process.
  • Where should the control points be?
    • The control points should be as evenly spaced throughout the data as possible. The four corners of the image make a good choice.
Return to Table of Contents

Other Spatial Transformation Products

Spatial Transformation offers other products for transforming data.

  • nOrderTransform applies an arbitrary n order polygonal transformation to any shape file. Click here for more information about nOrderTransform or here to download a free evaluation of this product.
  • Stretch Image applies a linear transformation to an image producing a new image file and registering it in ArcView. Click here for more information about Stretch Image or here to download a free evaluation of this product.
  • Warp Image applies an arbitrary n order polygonal transformation to an image producing a new image file and registering it in ArcView. Click here for more information about Warp Image or here to download a free evaluation of this product.

Return to Table of Contents

About Register Image

    Register Image Copyright ©2000 is a product of Spatial Solutions Inc, dba Spatial Transformation. All rights reserved.

    Warning: This computer program is protected by copyright law and international treaties. Unauthorized reproduction of it, or any portion of it, may result in severe civil and criminal penalties, and will be prosecuted to the maximum extent possible under the law.

    The software comes "as is". Neither Spatial Solutions Inc or www.spatial-online.com make any warranty, representation, promise or guarantee of any kind, either expressed or implied, statutory or otherwise, including, but not limited to the implied warranties of quality, performance, non-infringement, merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the software is with the user. We do not warrant that the functions contained in the software will meet your requirements or that the operation of the software will be uninterrupted or error free.

    Return to Table of Contents