Longtime users of XMap will know that ImageReg is not a new feature of the software. This useful and often overlooked tab has been included with XMap for many years and it continues to serve an invaluable role in the XMap suite. ImageReg is used to register or align digital images or scanned maps or photographs to an underlying base map. This process allows you to create a raster map layer from any image by applying geographic coordinates to the image file.
Two versions of the ImageReg tool are offered in XMap: A multi-point registration tool is available to users of either the Enterprise or Editor editions, while a simpler two-point registration function is included with XMap Professional. The registration process is the similar in either case.
The first step in the process of registering an image is to ensure that the source file is in the correct format. If the map or image in question is in paper form, you must first scan it and save it in an image file format. The ImageReg tool supports all common image formats, including .jpg, .gif, .tif, and .bmp.
Using the ImageReg tab, follow these steps to register your image:
- Click the Load Image button and browse to the location of the required image file.
- After selecting the file, a second window opens, displaying the image at a level of magnification that allows it to fit in the window. This can be adjusted as needed using the Magnify drop-down menu above the image window.
- In the accompanying map window, locate the same area that is represented in the imported image and adjust the zoom level so that key features can be identified. Note that for more precise registration, an aerial or satellite image works better than a vector-based map due to the improved horizontal accuracy of the map features.
- Before beginning the registration procedure, users of either the Editor or Enterprise version of XMap can choose between several alternative solutions that modify the behavior of the registration process. The drop-down list to the right of the ImageReg tab lists these options and the adjacent window displays a description of each and the situations for which they should be selected.
- The next phase of the process entails identifying and selecting physical or man-made features that can be seen in both the map window and in the imported image. Use the select tool to first click the point on the image and then the subsequent location on the map. If you know the coordinates of the selected points, you can type these values into the appropriate columns in the ImageReg tab instead of manually selecting the corresponding point on the adjacent map.
- Make sure that when selecting additional locations that the points are widely dispersed on the map. For XMap Professional users, who are limited to a two-point registration process, the ideal position of the two points are at opposite corners of the image.
- When selecting points, avoid features that might have moved from the time the map was created or the aerial image was captured. For instance, a river course is often subject to seasonal or even permanent fluctuation. Features such as road intersections are usually a better alternative assuming the same intersections are clearly discernable in the imported image.
- For multi-point registration, add as many points as necessary to ensure the accuracy of the registration process and, if necessary, to stretch or rubber-sheet the image to accurately align it with the map. After the second point is added, the corresponding cursor position will be shown on both the image and on the map; by checking the Link to Map box above the image window, the two views can be linked so that as one is zoomed or panned, the other will follow. This feature helps with the location and identification of additional map points.
- Several additional functions are available in the multi-point version of ImageReg. These buttons are located above the image window:
The Reduce button reduces the color depth of the image from 24- to 8-bit.- The Transparency tool renders a selected color of the imported image invisible. Often this function is used to remove the white background of an imported map. Note that this function is only available for 8-bit images.
- The adjacent color selection drop-down list is used to choose a color by which all non-transparent objects will be highlighted.
- The Crop tool is used to draw a polygon around the required portion of the imported image. The area outside of this polygon will not appear in the final map layer.
- After all of the required points are added, click the Create Data button in the tab, type a name for the new dataset, and click the Process button. A registered version of the layer will be displayed in the map window and the file will automatically be saved to the ImageReg folder in your DeLorme Docs folder.
- Before closing the image window, you have the option to save a Workfile containing all of the points that were selected in the registration process as well as the path to the source image file. This Workfile can be reopened if a modification to the original registration points is required.
- You can now manage the new data layer in the same way you manage other XMap datasets. Within the Map Data tab, layers added using ImageReg are listed under ImageData Series and you can turn them on or off as needed. Furthermore, you can adjust certain settings for the dataset, such as layering and zoom level extent. To establish these settings, right-click the name of the registered image and select Properties.
There are an infinite number of uses for the ImageReg tab; from digitizing cadastral or property maps to creating geo-referenced versions of historical charts. For many XMap users, ImageReg offers and easy-to-learn tool for helping make the transition from paper maps to digital mapping technology.
When it was first released, the Earthmate PN-40 was designed to work exclusively with DeLorme software. Users of XMap and Topo USA could send maps to the device, collect waypoints and tracks on the PN-40, and exchange this data with the PC software. As the popularity of the PN-40 grew, due in large part to its durability, versatility, and capacity for displaying a wide variety of map types, questions such as the one asked in the title of this article, started to appear with increasing regularity in DeLorme’s email inboxes. It was decided, after consultation with ESRI representatives, that DeLorme would develop a tool to allow ESRI software users to work directly with the PN-40. What emerged from this effort is the Earthmate PN-40 Extension for ESRI software.
In recent years, there has been a surge in interest in a location-based technology among organizations and agencies that would previously have considered these tools to be beyond their means. The emergence of low-cost and Web-based mapping applications and the ubiquitous availability of worldwide satellite-enabled navigation have instilled a spatial mindset within a broad cross-section of the population. Software offerings such as DeLorme’s XMap and Global Positioning System (GPS) receivers like the rugged Earthmate PN-40 are bringing this technology firmly down to earth.
It is frequently assumed that GIS and GPS are inherently connected; however, the interoperability of these two technologies is often a difficult process requiring the conversion of files to allow the exchange of data from one platform to the other. Few GPS receivers offer the option of viewing GIS layers or aerial imagery, a feature that serves to extend the reach of the GIS infrastructure to remote locations. It was with this in mind that DeLorme developed the Earthmate PN-40, a GPS receiver that offers a unique set of capabilities.
Starting at under $200,
Several representatives from DeLorme will be attending and exhibiting at the Windpower 2009 conference at Chicago’s McCormick Place Convention Center from Monday, May 4 to Thursday, May 7. Over the four days of the conference, we will be showcasing the latest version of XMap as well as the new Earthmate PN-40 GPS handheld receiver and other DeLorme products.