Measuring Areas and Distances on Images Using SigmaScanPro
 

Power On and Log In

Confirm that the scanner HP ScanJet 3c is on (green LED) and attached to Geos-07.  If the scanner is not on, turn it on (rocker switch in the back-left) and restart Geos-07.

Logon at GEOS-07 using your BEDROCK username and password.  A standard desktop will come up.

Scan Photograph and Save as Image File

For small (<8.5" x 14") flat originals the simplest way to acquire the images for analysis is to use a scanner.

From Start … Programs … HP DeskScan II … select the HP DeskScan II icon.  This will bring up the DeskScan II dialog Box.

The scanner can scan color or B&W images.  Color images take more storage space than B&W.  In order to conserve disk space select B&W drawing for B&W line drawings and B&W photos.  Select Color photographs for color images.

Open the scanner lid.  The green and white arrow indicates the top left corner of the scanned image.  Place the photograph on the glass platen (keep the glass clean) and press the preview button in the Scanner Dialog box.  Check that the photo is properly oriented (e.g., top is north) and adjust if necessary.

Once you have the image properly oriented, press the Final button in the Scanner Dialog Box.  In the Save As dialog box, browse to your network server directory ("username" on BEDROCK (N:)).  Check that Save As Type: is set to TIFF 5.0.  Press Save and the scanner will complete the scan.

Note that image files are large. On the Deskscan Dialog Box in the lefthand lower corner the file size is shown in kilobytes.  After you have finished analyzing the images delete the image files from your directory.

To exit DeskScan click the close box on the DeskScan dialog box.

Acquire Digital Photographs and Save as Image File

For large maps or 3D originals (rocks, etc.) a digital camera may be the most effective way to capture the image for analysis.

The Geology & Geophysics Department has an Olympus D-500L digital camera which can be checked out for class or research use.  The camera has a versatile lens which can focus down to ~1.5 ft. and has complete instructions in the case.  Depending on the resolution of the image, the camera can hold between 3 and 20 images on a single card.  The images can be downloaded through its cable to a PC or MAC workstation.  Ask the TA or computer coordinator about these and other accessories (additional cards, rechargeable batteries, etc.).

Once the image has been acquired, save the image in standard JPEG format using the Olympus software.

Launch SigmaScanPro (v2.0) and open Image File

Launch the SigmaScanPro application (under Jandel Scientific) from the Programs Menu on the Start button.  If an image window is loaded (possibly from the previous user), close the image window.

From the menu bar select File … Open … Image.  A Open Image File dialog box will appear, browse to the location of your file.  Select the image file you saved from the scanner and click OK.  Your image will appear in a new window.  You can scroll around the image using the conventional scroll bars and zoom in and out using the + or - magnifying glass.

Verify that the features you are interested in measuring, as well as your 3 calibration points, are visible in the window.

Calibrate Photograph Scale

In the case of an aerial photograph, pick 3 calibration points which enclose the object to be scanned and determine X,Y coordinates for the points.  The X,Y coordinates can be UTM coordinates or coordinates based on any (arbitrary) orthogonal rectangular system (as an example, Latitude and Longitude coordinates WOULD NOT be a good choice, kilometers North and East along township boundaries WOULD be a good choice).  Your choice of length units will determine your square units; for example, kilometers North and East along township boundaries (which are approximately orthogonal) will yield square kilometers units for area.

From the menu bar select Measure … Calibrate Distance and Area.  Click on the 3 - point calibration radio button.  Enter the X,Y (generally East and North for a aerial photograph) coordinates of the calibration points into the 3-point - calibration dialog under the Calibrated (X,Y) heading.  After all 6 coordinates are entered, click the image button to the right of the 3 point - calibration dialog.  The cursor pointer will change to a square C icon.  At this time, click on the 3 calibration points on the image in the same order as their coordinates were entered.

After the third calibration point is clicked, the dialog box returns with information about the calibration.  The aspect ratio should be nearly 1.0 - indicating the X scale is nearly the same as the Y scale.  Moving the cursor over the image should yield coordinates (in the lower left hand corner) which match the coordinate system you chose.

Define Quantities to be measured

From the menu bar select Measure … Trace Measurement Options, to select the types of measurements to be performed.  Click Remove All, to remove any measurements which might have been previously selected.  In the left hand column (Available Measurements) select "Area", and then click "Add >" to move the area measurement into the right hand column (Active Measurements).  If you wish to measure lengths of curves, add the cumulative distances to the Active Measurements.  Click the close button.

Define Region(s) to be measured

From the menu bar select View … Measurement Toolbar, to display the measurement tools. From the menu bar select Window and select the window in which your scanned image resides.  Maximize the size of the image window and click the Trace Measurements option on the Measurement Toolbar (Upper Right button).  In the image window trace the area to be measured with the mouse on a sufficient number of points to define the area.  Right click on the mouse to close the area.  The area will be outlined and filled in red and areas will be consecutively numbered.

The area (and other measured quantities) can be found in a spreadsheet form in the measurement window.  You can view the image and the measurement results simultaneously if you select Window … Tile (resize the spreadsheet if it was minimized).

Miscellaneous

After your measurements are complete, clean up your work area.  Delete any files you will not be using from your working directories, especially image files which will be large.  If you intend to store your images for a while, then convert them from the uncompressed TIFF format to the compressed JPEG format.  CorelDraw and Corel Photo-Paint can perform these conversions for you.
 

Revised January 2001