Q. Should I pre-process the pictures (e.g., sharpen it with Photoshop) or crop the pictures for your program?
A. Do not process or crop the photographs in any way using any photo processing software. Some software can inadvertently strip off important header information that is needed to process your pictures correctly.

Q. The metrology engine says that my camera's make/model is not recognized. What does that mean?
A. Certain brand/model specific information of your camera is needed in our metrology algorithm. We have already constructed a database containing such information for over a thousand digital cameras. If your camera happens to be one that is not in our database, we will obtain the information from the camera manufacturers for you. You do not need to do anything. Please be patient and we should email you, usually within 24 hours, to let you know when we can process your pictures.

Q. Why are there four displays (two for the left and two for the right pictures) in the graphical user interface (GUI)?
A. The upper displays allow you to always see the full pictures, and the lower displays allow you to zoom in on any part of the pictures.

Q. How are the upper and lower displays related?
A. The view port (the red rectangle) in the upper window shows the image area that is being displayed in the corresponding lower window.

Q. How do I move the view port?
A. You can move the view port by holding down on the left mouse button and dragging the mouse around (in both the upper and lower displays) or by clicking the left mouse button at the location you want to center the view port (in the upper displays only).

Q. How do I zoom?
A. You can zoom by using the middle mouse wheel in either the upper or lower displays. If your computer's mouse does not have a middle mouse wheel, you can use "z" to zoom in and "x" to zoom out. The point under the mouse cursor will not move during the zoom. So you should first move the mouse cursor to the rough location of a feature point, and then zoom in to it.

Q. Do I need to use zoom?
A. To ensure high metrology accuracy, it is strongly recommended that you locate features as precisely as possible using a high zoom setting in the lower displays.

Q. I cannot see the corners clearly even with a high zoom, what should I do?
A. If the problem is due to poor picture contrast, please retake the pictures using better lighting (e.g., use flash).

Q. How do the left and right windows differ?
A. The left is the master and the right is the slave. You can change the role of maser and slave using the setting button at the top right corner of the GUI.

Q. What can I do in the right (slave) window?
A. (1) Middle mouse wheel (or "z" and "x" keys) to zoom, (2) left mouse button click to enter new point or select an existing point or line, (3) left mouse button drag to move the view port or an existing point, and (4) left mouse button double click to delete a point or a line.

Q. What can I do in the left (master) window?
A. All the things that you can do in the right (slave) window, plus mode selection (image/measure/reference) and geometry selection (polygon/line/point).

Q. What can I measure using your metrology engine?
A. Currently, you can measure length (using the line tool) and area (using the polygon tool). Other options (e.g., angle) will be added later.

Q. Can I measure in the metric system?
A. Yes, you can select the metric system by choosing setting in the upper right corner of the GUI and changing the measurement units.

Q. Do I need to specify the image locations of the reference first?
A. It is recommended that the user specifies the location and dimension of the reference first. However, you can also locate the objects that you want to measure first. But no measurement results will be available until the locations and dimension of the reference are known.

Q. Can I change the reference used?
A. Yes, you can change the identity and dimension of the reference at any time. Once the reference is changed, all measurements will be updated accordingly.

Q. How do I enter a new feature point?
A. By clicking the left mouse button with the mouse cursor at the desired location. The points you click on the left and right pictures must represent the same 3D point. Also, you must enter points in the same order in both pictures.

Q. How do I select an existing feature point (e.g., to move it to a new location)?
A. Move the mouse cursor over the point, hold down the left mouse button to select it, and then drag the mouse cursor to move the point to a new location.

Q. I made a mistake in entering points or lines. How do I delete those erroneous points and lines?
A. Double click on them and they should go away.

Q. How do I annotate a point or a line?
A. Select the point or the line by moving the mouse cursor over it and clicking the left mouse button. Then enter the label information in either upper window.

Q. The display is quite cluttered; can I move the labels around?
A. Yes. Select the line whose label you want to move. Then use the "Label Position" scroll bar in the upper displays to scroll the label along the length of the line.

Q. How come I do not see the area measurements in the GUI?
A. To avoid cluttering the display, area measurements are not shown in the GUI. You can view the area measurements by clicking the "View Report" button at the top right corner of the GUI.

Q. For some pictures, I got a message saying "Please specify at least 6 correspondences for further processing". I don't see that message for other pictures, why?
A. When the message is displayed the metrology engine has failed to infer the movement of the camera in between the two camera shots automatically. You can still process the pictures even if you see the warning message. However, you will have to specify at least 6 pairs of corresponding features (including the reference) to obtain measurements.

Q. If I see the message "Please specify at least 6 correspondences for further processing", can I specify more than 6 pairs of correspondences or I can only specify six?
A. If you see the warning message, you will need to specify at least 6 pairs of correspondences in order to get measurement results back. You can certainly specify more. In fact, the more correspondence pairs you specify, the more accurate the metrology results can get (assuming that the matches are correct and the locations are accurate). There is no such restriction if you do not see the warning message.

Q. What is auto correspondence?
A. Usually, the user specifies the locations of a feature in both the left and right pictures. If auto correspondence is on, the engine will try to "guess" the location of the matching feature in the other image based on the user-specified feature location in one image.
By default, auto correspondence is off. You can turn it on using the setting button on the upper right corner of the GUI. However, be warned that while feature matching is trivial for human beings, it can be extremely difficult for computers. Auto correspondence may incur significant delay and may not produce the correct match or any match at all. To ensure high accuracy, please inspect each correspondence carefully and make adjustment if necessary.

Q. Why some times when I turn on auto correspondence the system will turn it off and still asks me to specify at least 6 correspondences manually?
A. If the metrology engine fails to infer the movement of the camera in between the two camera shots automatically, then it is not possible to provide auto correspondence assistance and the functionality will be turned off even if the user requests it.

Q. What do you mean by "inferring the movement of the camera in between the two camera shots automatically"?
A. This is a step in our metrology algorithm. We will try to solve this step automatically if possible. If not, we will rely on the user to provide at least 6 correspondences manually to solve this step. If the manual mode is used, auto correspondence will have to be turned off.

Q. Can I save my project?
A. The functionality will be added later. Right now, you can obtain a computer print out of all points, lines, and area measurements using the "View Report" button at the top right corner of the GUI.

Q. The GUI seems to be very complicated.
A. Please view the short, 5-minute tutorial video to see the metrology engine in action.

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