Crater Counting Layer

From JMARS Wiki

The Crater Counting Layer allows users to mark craters and then output the locations and diameters to a shape file. This data can then be used for small-scale studies or combined with similar data from multiple users to enable large-scale crater studies.

[edit] Marking Craters

Open the Crater Counting Layer: In the Layer Manager, chose "Add New Layer" -> "Crater Counting"

Select the Crater Counting Tab: The Crater Counting tab in the Layer Manager allows users to see the details of the crater markers they have entered in the Main View.

Choose a Crater to Mark: Users should adjust the resolution (using the pull-down menu at the top-right of the Main View) and pan around in the Main View as needed to find a crater they want to mark.

Re-Center the Map Projection: In the Main View, choose "View" -> "Re-Center Projection"

The Crater Counting layer will only draw circles. However, if users move too far away from the center of the current map projection, circular craters will appear increasingly non-circular. To ensure the correct diameter is being chosen, users should re-center the projection whenever they pan away from the last point they centered over.

Set the Crater Diameter: By placing the cursor over the Main View, a semi-transparent black circle will appear. Users can adjust the diameter using the center scrollwheel on their mouse.

- The default diameter increment is 1km.

- On most systems, each tick of the mouse scrollwheel moves ten increments.

- Holding shift will change each mouse scrollwheel tick to a single increment.

- Users can change the diameter interval in the "Settings" tab within the "Crater Counting" tab.

Entering a Crater Marker: Once the correct diameter has been selected, the marker can be entered into JMARS by clicking in the Main View. An entry for the marker will be added to the table under the "Crater Counting" tab.

[edit] Counting Craters within Parameters

Depending on the study being performed, it might be useful to automatically count how many craters fall within a given range of parameters. Users can perform basic searches by entering minimum and maximum values for Latitude, Longitude and Diameter at the bottom of the "Craters" tab within the "Counting Craters" tab. The number of marked craters matching the criteria will be outputted at the bottom of the tab.

[edit] Saving (Exporting) Crater Markers

1. In the Crater Counting tab, click "Save/Export Craters"
2. Choose a location to save the file, assign the file a name and set a file type (ESRI or CSV).
3. Click "Save"

[edit] Loading (Importing) Crater Markers

1. In the Crater Counting tab, click "Load/Import Craters"
2. Choose a previously-created Crater Counting layer shape file (ESRI or CSV) to load.
3. Click "Load"

[edit] Adjusting the Layer Settings

Under the "Settings" tab within the "Crater Counting" tab, users can change many of the layer's default settings.

Change Circle Color: Users can choose from any of the colors available in the pull-down menu.

Change Circle Transparency: The transparency of the circle markers can be adjusted using the "Fill Alpha" slider bar.

Manually Change New Crater Diameter: By default, the starting diameter of a crater marker is the diameter of the last crater marker entered. If users want to manually change this value, they can do so using the "New Crater Diameter" input field.

Note: Make sure to use meters and not kilometers!

Change Diameter Increment Size: Users can choose from the standard diameter increments of 10km, 1km, 100m and 10m or they can specify their own.

Note: On most systems, each tick of the mouse scrollwheel moves ten increments.

Note: Holding shift will change each mouse scrollwheel tick to a single increment.

[edit] Using the Colors Tab

Different-colored circles can be used in the Main View to represent different types of craters (ie: preserved/modified/destroyed). Using the "Colors" tab within the "Crater Counting" tab, users can assigned a comment to each available color (ie: blue=preserved, green=modified, etc). Then, when users enter crater markers of these colors in the Main View, the Crater Counting layer will not only record the location and diameter of the crater, but also the comments that were assigned to them. Those comments are preserved when the output files are imported/exported.