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Frequently Asked Questions How is it used? What kind of objects can iWitness measure and 3D model? What are the PC system requirements to run iWitness? What monitor screen settings are required? What type of camera can I use? How can I tell if my camera is already in the iWitness Camera Database? Is there a tip sheet I can refer to for basic steps of the iWitness software? How do I "unReference" a point without deleting it? 64Kb video; Unreferenceprocedure.wmv Are there any special settings that are required on my PC to run iWitness? What does the “Quality” and the “Angle” represent in the 3D Point List? Is there a quick reference guide for the criteria regarding the "iWitness Project Status Summary"? How come when I try to calibrate my camera, using the supplied target sheets, I can't get the Relative Orientation or Green Tick Marks after marking all of the 18 black dots? Is there a way to map really small objects like blood spatter at a homicide scene, to sub millimeter measurement accuracy? When I open up the project .iwp the image thumbnails are pink. How do I fix this? iWitness is a MS Windows™ based software program for measuring and modeling objects and scenes. iWitness uses the technology of close-range photogrammetry, where the three-dimensional coordinates (X,Y,Z) of feature points on an object photographed from two or more locations can be accurately determined by making two-dimensional measurements on digital images. Designed for use by non-photogrammetrists, iWitness is a powerful yet easy-to-use tool. iWitness builds 3D models and measurements after a few easy clicks on the digital images imported into the program. iWitness is the world leader in low-cost, close-range photogrammetry. It is unmatched in its abilities to solve easily and accurately for 3D image coordinates using consumer grade or fully metric digital cameras. How is iWitness used? A few simple steps:
To learn more, please take the iWitness Tour. What type of objects can iWitness measure and 3D model? iWitness is optimized for use by law enforcement agencies, specifically in traffic accident reconstruction and forensic measurement. iWitness' powerful data acquisition and rigorous photogrammetric processing create fast, comprehensive 3D measurements as well as a permanent visual record of the scene being recorded. The value of iWitness is not, however, restricted to the law enforcement sector. As a full-featured, close-range photogrammetric software system, iWitness can be applied to 3D reconstruction tasks in architecture, archaeology, engineering and medicine. iWitness handles the most complex measurement tasks: there are no restrictions on the number of images and measurement points. What are the PC system requirements to run iWitness? What monitor screen settings are required? iWitness requires a personal computer with:
iWitness requires the "Color Quality" in the "Display Properties Settings" set at the highest possible settings (typically 32 bit). To achieve this, select the Control Panel+Display to assure the setting is made correctly. Depending on the computers graphic card, there is a chance of experiencing OpenGL Hardware Acceleration problems, for the first time, when importing images or in the 3D graphics view of iWitness. This is easily corrected by adjusting the settings on the Hardware Acceleration Slider in the Control Panel+Display+Settings+ Advanced+Troubleshoot (tab). What type of camera can I use? iWitness works with any digital camera that reads the Exchangeable Image File Format (EXIF). Most digital cameras now use the EXIF format. The format is part of the DCF standard created by JEITA to encourage interoperability between imaging devices. For more information on EXIF reference the website http://www.exif.org. We recommend a digital camera with at least 4.0 megapixel ccd resolution for use with iWitness. Remember, a higher camera pixel resolution creates more accurate photogrammetric results in iWitness. How can I tell if my camera is already in the iWitness Camera Database? iWitness stores most digital camera make and models in its Global database, but not all of them, as digital cameras are updated almost weekly. The Global database is continuously updated with new cameras. One can download the latest Global Database by clicking on the Global Camera Database's "Auto Update Button" (assuming one has an Internet connection).
To access the Global database, click on the menu of: Edit | Camera database... | Global. If your camera is not in the Global database, please refer to PART C of the iWitness Users Manual. NOTE: we strongly recommend that one calibrate their camera before initial project use, regardless of whether the camera is present in the Global database. How long does it take to create 3D models and measurements in iWitness? Speed and efficiency separate iWitness from its competitors. The program's fast point marking and automatic camera orientation methods make it a breeze to operate, even by non-photogrammetrists. Using iWitness, a simple project can be modeled in as little as five minutes. Very complex scenes can take up to several hours. Generally, the time required depends on the number of images being processed and the number of 3D objects requiring measurement and modeling. In the examples premiered on this website, operators with a basic understanding of the iWitness program created each project in under two hours. What do I need to know in advance of using the iWitness software? It's easy to use iWitness. All you need is a basic understanding of the MS Windows™ operating system. No formal photogrammetry training is necessary. Additional experience with CAD drawing programs or other optical metrology instruments (such as a total station theodolite or 3D laser) will benefit operators, but are not requisites to begin using iWitness. Importing digital images into iWitness is easy as well. In addition, the easy-to-follow documentation and tutorial project will help prepare you for your first project. Is there a quick reference guide or a 'tip sheet' available? Yes, the tip sheet is compiled in a one page PDF form - click here to download it. Are there any special settings that are required on my PC to run iWitness? SCREEN DISPLAY COLORS HARDWARE ACCELERATION Why is it that when I take my calibration pictures and import them into iWitness, two cameras are presented for my one camera that I used to take the images? In this instance, it is very likely that your camera images were recorded with Auto Rotate On. To use your digital images in iWitness, ensure that the Auto Rotate is set to Off.
Sharing Like Camera Model Calibrations On Multiple Computers (for iWitness V1.08 and higher version releases) The process of adding a calibrated camera description to the iWitness Local Camera Database from the 'Host computer' to the 'Remote computer' can be accomplished with any project.iwp file, in which the camera calibration had already been performed. The camera must have a Unique ID assigned. In our example below, we are using the actual ‘calibration.iwp’ file to demonstrate the steps. i) When first calibrating the camera on the Host computer, assign a Unique ID to the camera, in the Camera Parameters dialog box. Enter a specific camera name for the camera, (for example, you might enter the last 5 digits of the cameras serial number. ii) After you've calibrated the camera with the Unique ID on the Host computer, the iWitness Local Camera Database is automatically updated.
When images are imported into iWitness, a warning dialog box reads: "This camera is not in the database. Cameras details must be completed manually" The iWitness camera database is continuously updated with digital camera information. However, there may be cases when your specific camera is not in the camera database, and a few simple actions are required before the camera can be calibrated. If the images were taken in JPEG format, there's a high probability that the images support the Exchangeable Image File (EXIF) header information. iWitness will read the EXIF header, thus we recommend the user takes their pictures in the highest resolution in JPEG format. The iWitness User Manual, Part C, as well as Movie #2 on the iWitness CD Media provides an in-depth explanation of what actions are required when the images are EXIF, and also when they are not EXIF. We have prepared a PDF file than explains the most typical situation (i.e., when the images are EXIF, and are not in the iWitness Local or Global Database).
Click here for an example PDF file, with picture illustrations (325kb).
The camera icon in iWitness appears as a “cartoon camera”. Is there a way to update the cartoon camera so that my cameras specific make\model is displayed when I import images?” Yes. We have created a simple procedure for this, and it is noted in the below PDF file. Click here for the procedure to revise the Cartoon Camera to actual Camera Make\Model (46kb).
I can't seem to find the specific pixel height and width of my digital cameras Sensor Type. Is there a reference guide I can use to determine this? Yes. We have compiled a list of the most common sensors in the below noted PDF reference guide. The reference guide also provides an example of how to use the sensor size in iWitness, prior to conducting the camera calibration. Click here for the Sensor size and reference guide (43kb).
When I use the "Export TXT" function in the 3D Points List, and open up the file, I see seven columns of numbers. What are these numbers?
What does the “Quality” and the “Angle” represent in the 3D Point List? Quality is the RMS value of image coordinate residuals for a given point. It is an internal measure of the network consistency. The quality value is influenced by the camera type, the precision of the point marking/referencing. With a commercial grade digital camera that has been calibrated by iWitness, the quality value will typically be in the range of 0.1 to 1.5 when proper image-marking is achieved. The lower the Quality number the better. It should be noted that estimates of Quality will likely appear artificially low when there are only two images and less than 8-12 referenced points. More representative quality estimates are obtained when the points are imaged from at least three camera positions (or sightings). The Angle value is determined from the 'n' intersecting light rays to a point. The Angle is then defined by the maximum angle of intersection subtended by the pairs of two light rays that intersect at the point. It is desirable that the Angle value be higher than 20 degrees or so, and Angles of less than 10 degrees should be avoided where possible. iWitness will not allow a point to be referenced if its Angle value is less than 3 degrees. Is there a quick reference guide for the criteria regarding the "iWitness Project Status Summary"? Yes. We have compiled some helpful text boxes adjacent the Project Status Summary dialog box for quick reference - PDF form. Click here for the Project Status Summary Reference Guide (39kb).
Possible problems achieving the "RO" or Green Tick Marks while accomplishing a camera calibration. One issue might be the focal length of the camera is grossly in error. This is becomingly increasingly less of a concern as more cameras record the nominal focal length in the EXIF header of the jpeg images. iWitness initially looks in the local camera database for the appropriate focal length. If the camera is not found, it will then look for the focal length in the global camera database. Once it locates the camera, it reads the focal length from the EXIF header. Only in the situation where no focal length is stored in the image file, will iWitness use the default value in the global camera database. This may or may not be sufficiently representative depending upon what zoom setting is adopted. If you are in doubt of the proper focal length, go through the simple procedure in Section C3.1 of the Users Manual to determine an initial value for the focal length. Your local camera database will be updated with the result of this procedure. Then, re-start the camera calibration; the estimated focal length value will now be used and the calibration process will be successful.
Is there a way to use iWitness to measure really small objects, like blood spatter? Yes. We have compiled a helpful tip sheet. It will require that you calibrate your camera for close-up photography. Click here for the "close up measurement guide" for iWitness (295kb). Click here for the "close up calibration target sheet" (11kb).
When I open up the project .iwp, the image thumbnails are pink. How do I fix this? When renaming a project iwp, or moving the project folder with its images to e.g., a CD or DVD, the directory path to ‘point’ and acquire the project images is temporarily disconnected. The image thumbnails will appear as pink rectangles. To ‘point’ the iwp to the directory with the images, simply right mouse click with the cursor over any of the pink thumbnails which sets the Image Path. Path to your working folder where you’ve stored your images. Click on the image ‘xxxxxx.jpg’ that’s presented in the “Open” dialog box. Click the Open button Click “Yes” for “Set path for all images? Select the Save icon to save this new image path setting. Click here for the "pink image thumbnail conversion guide" for iWitness (120kb PDF - (requires Acrobat Reader version 6 or higher).
Is there an easy to follow procedure for using the "3D Transformation to Control" feature in iWitness? We've created a very simple to follow process guide for using the 3D Transformation to Control using two networks stitched with four control points.
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