Sedimetrics® Digital Gravelometer™ documentation (version 1.0)

Get started


If you are unfamiliar with the purpose of the Digital Gravelometer you should read the Overview in this documentation. The quickest way to get started using Digital Gravelometer is to work through this section of the documentation. However, before relying on the results obtained from the software you are strongly advised to familiarise yourself with the remainder of the documentation.

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Terminology – the project

The basic unit of work in Digital Gravelometer is the project, and each has a project file (with a .dgp – Digital Gravelometer Project – extension) associated with it. The project file is a database containing general information about the project (e.g. its title, the name of the client), along with information about each of the images associated with it, and (once the measurements have been made) the sizes of the grains within each image and the parameters used to make the measurements. To avoid using unnecessary hard disk space storing copies of each image, the image files themselves are not kept in the project file. However, the locations of the images are stored, so it is important that the image files are not moved or the program will not know where to find them. It is recommended that project file and the images are all stored in the same folder so that they can all be moved together if necessary. Only one project can be open and worked on at a time.

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The program structure

The operation of the program is quite simple and logical. Each step towards producing grain-size information is initiated from the main program window, the components of which are illustrated below.

Annotated image of the main program window

The basic steps are to create a project, add images to the project, measure the size of the grains in each image, then analyse the results to produce a report about the grain-size distribution. If you wish to correct for the effects of radial lens distortion in your images, you will also need to create a lens correction file if one does not already exist for your camera. Each step is associated with a menu in the main program window and illustrated in the flow diagram below.

Annotated image of the main program window

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Brief tutorial

This section assumes that you have already read the preceding parts of the Get started section of the documentation and are familiar with the idea of Digital Gravelometer projects and the overall structure of the program. It also assumes you are familiar with using Windows applications and have already installed the program.

The tutorial will guide you through creating a project, adding images to it, measuring the grains in each image and viewing information about the resulting grain-size distribution.

Start Digital Gravelometer

To start Digital Gravelometer using the Start menu, click Start on the Windows taskbar. From the menu, select Programs > Digital Gravelometer > Digital Gravelometer.

To start Digital Gravelometer from the desktop icon (if you chose to add one during installation), double click on the Digital Gravelometer icon on your desktop.

If you are within the program's 21-day evaluation period, or have already activated it by entering a valid activation code, press Continue to enter the program. If the evaluation period has expired see the Installation and activation section of this documentation for instructions on how to purchase an activation code.

There will be a short delay whilst the program loads. Please be patient.

Create a new project

Select File > New Project…. In the Edit project properties dialogue box enter the information as below:

Image of the Edit project properties dialogue box

Click OK to continue. Navigate to an appropriate folder, enter the project filename: tutorial, and click Save to save your project.

Add an image to the project

Select Image Management > Add image…, navigate to the Program Files\Sedimetrics\Digital Gravelometer\examples folder and select sample_image_1.jpg. If the image is located in a different location to the project, you will be asked whether to copy the image to the project folder. Click OK to continue. After a few seconds the image will appear in a window entitled Control-point identification. The software requires each image to contain four control points defining a rectangular area of a known size. The first step is to identify the four points in the image. The image is zoomed in to the top-left corner and you should see a small black-and-white target. Click on this with the mouse. If the target isn’t visible in the part of the image shown on the screen, you can use the scroll bars or drag the blue rectangle in the thumbnail to move around the image.

Image of the Control-point identification dialogue

Once the first control point is selected, the status area on the right-hand side of the window is updated and the program automatically moves to the top-right corner of the image. Select the control point and repeat for the bottom-right and bottom-left corner control points. Once the fourth point has been selected the program will show the whole image with the controlled area outlined in red. If you are satisfied with the locations that you have selected click Continue or click Clear to start again.

The Edit image properties dialogue will now open. Enter the information as below:

The edit image properties dialogue

The site name is the location at which the image was taken. This may be a particular river or a particular bar depending on the scale of the project. The Sample ID many be numeric or alphabetic (or a mixture). The Width and Height of the controlled area represent the actual distances (in mm) between the control points that you identified in the image. The Image Information (with the exception of the name of the photographer) is extracted from the information stored in the image file by the camera. When you have finished, click OK to continue.

View information about the image

The image will now be listed in the Image information panel of the Digital Gravelometer main window. Make sure that Show image information on mouse hover is checked in the Options panel of the main window then move your mouse pointer over the name of the image file. Some basic information about the image should be shown as a tooltip. If you find these intrusive, they can be turned off by unselecting the check box.

The main program window showing the Show image information on mouse hover option

To view some more information about the image, right click over the name of the image file and select View Image Data (or select Image Management > View Image Data). The Image data window shows a thumbnail of the image (with the option of opening it in the image viewer) along with a variety of information about the image. When the grains in the image have been measured, the window will also show the parameters used. The date and time at which the last grain-size distribution report was generated will also be shown once this information is available. Click Close to return to the main program window.

The Image data dialogue

Add additional images to the project

Use the same procedure to add sample_image_2.jpg and sample_image_3.jpg to the project. When the project already contains an image the Edit image properties dialogue uses the previously entered values as defaults (except for the Sample ID which is blank). Add Sample IDs of 2 and 3 respectively and leave the remainder of the options alone.

Measure the size of the grains in the images

Select Measure Grains > All Images… to open the Measure grains dialogue. The top of the dialogue box identifies the number of images selected for measurement, in this case three. The Output options panel summarises which of the intermediate stages in the grain-measurement procedure will be shown on the screen and saved to image files.

By default, none of the stages are saved and only the final stage is displayed along with an overlay of this stage on the original image. You will change the setting to display all of the intermediate stages. Click Change in the Output options panel to open the Output options dialogue. The measure grains dialogueIn the Output Options dialogue, check View all at the bottom of the dialogue and click OK to continue.

The output options dialogue The Measure grains dialogue has now been updated to reflect the change. Do not make any changes to the default processing options (information about all of the processing options is contained in the Program operation (measure grains) part of this documentation). Enter your name as the operator then click Measure grains. A progress indicator will appear, and when each image has finished processing a window will show each of the intermediate stages in the processing. When using the software to process your own images, it is strongly recommended that you examine these intermediate stages carefully to determine whether a satisfactory image segmentation has been achieved. When you have finished examining these, close them and return to the main program window. Intermediate stages in the grain-identification procedureThe project has now been updated and contains the measurements of each of the images in the project and information about the parameters used to obtain them. Look at the information about each image now by right clicking over the image name and selecting View Image Data (or select Image Management > View Image Data).

Save the project

Before continuing, save the project. Select File > Save Project.

View a grain-size report

Once the grain measurements have been made you can analyse the results to obtain information about the grain-size distribution of each image. The three images in the project were collected from close together on the same bar, so they may be grouped together to generate aggregate grain-size statistics. Select Report > All Measured Images > Aggregate Analysis... to open the Report options dialogue. The dialogue presents a host of options to enable customisation of the grain-size report. Further options are available by clicking the Change grain-size options... and Change plot options... buttons, details of which are contained in the Program operation (report) part of this documentation.

Delete the existing contents of the Lower truncation edit box and enter the value 4. Change the entry in the adjacent listbox to Psi and click Apply. The grain-size report will now include a lower truncation at 4 psi (16 mm). This is reflected in Cumulative plot preview panel. Leave the remainder of the options unchanged and click Generate report. After a few seconds, the default system browser will be launched and the grain-size report displayed.The report options dialogue

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