From the Rectification Control Points module in GTK+ GRASS the user can edit and manually enter control points.
Rectification Control Points
From this menu the user can:
- Turn control points on or off.
- Highlight the selected control point on the display.
- Check the Root Mean Square (RMS) error for the selected points.
- Manually enter known control points.
- Automatically project manually entered geographic coordinates to the users coordinate system (e.g. UTM).
This is a useful option for selecting geographic graticules on scanned maps.
The control points can be saved to a re-loadable XML points file. The XML file includes the image name, location and format, plus the complete list of control points. Using this format the image and control points can be easily re-loaded in a single step. The following is a sample control points XML file …
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A rectification Control Points module is added to the GTK+ GRASS Interface to make selecting and manipulating control points easier.
Image Rectification Window
The Control Points window opens in the GRASS Interface, as a special, split-pane, tabbed window. Users can select rectification control points for a GRASS raster file or an external image. Control points are saved to an XML file with optional output to a gdal_translate compatible file.
Features
The features for the Control Points Rectification module include:
- Control point selection for both GRASS rasters and external image files (TIFF, PNG, etc).
- Image file name and type, plus selected control points saved to a simple XML file.
- Control points selection from existing GRASS rasters and vectors or manually entered points.
- Control points manually entered from geographic coordinates or from the user’s projection coordinates (eg. UTM).
- Edit menu that displays RMS for selected points based on the chosen rectification order.
- Edit menu that lets users turn control points on or off.
- Predicted location for a selected point that displays in both panes to help users locate control points.
- Full zoom and pan functions for both panes in the rectification tab window.
The GTK+ GRASS Interface 3D View lets the user save a keyframe animation directly to a supported animation format. The 3D view uses the GRASS ogsf library to render an animation. If the GRASS ogsf library has been built with the optional FFMPEG library, movies can be directly rendered to any supported format.
Save Keyframe Animation Dialog
If FFMPEG support is not available, the animation can be saved as individual images.
By default, the animation is rendered off-screen. The user can optionally turn this off and render the animation in the current 3D View. The advantage of off-screen rendering is that other windows and screen-savers do not interfere with the saved animation.
The animation dialog shows the rendering progress by frame number.
The GTK+ GRASS Interface uses a simple XML interface to save the 3D state, keyframe animations, and run scripts.
XML State File
The 3D View module uses a simple XML format to save and load the 3D state. Supported fields include view position, lighting, and loaded GRASS objects (eg. raster). A sample script might look like the following:
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The GTK+ GRASS Interface supports the following overlays in the 3D View:
- Scalebar.
- Cutting Plane.
- Location Map Inset.
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Introduction
The GTK+ GRASS Interface can be built with an optional port to the GRASS ogsf library providing 3-D visualization support. This requires the user to install GtkGLExt, an OpenGL extension to GTK+ 2.0.
Screen shot of the GRASS Spearfish data set in 3-D view
The 3D View is loaded as a special tab in the Map Display. The 3D View is created with the GRASS settings (i.e. region). The user can easily switch between loaded map views and the 3D View.
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The size (width) of the profile (cross-section) can now be set with a map scale size. The existing Size (pixels ) is still available.
Display Options -- Plot Size
Setting the profile size with the Scale (1: ) option allows profiles to be saved at a set map size. This option is useful when presenting a profile with the map from which it was generated. If the map is presented at a scale of 1:2000, an associated profile can also be saved at a scale of 1:2000.
The size, in inches, of the output profile is displayed in red below the Scale (1: ) option.
The GTK+ Profile Plotter has numerous options to control the plot appearance. From the main window, the vertical exaggeration of the plot can be set. This will effect the height of the plot image. The width of the plot is set by the user.
From the Options dialog, the user can set the plot variables.
Options Dialog
These plot variables include:
- XY Axis grid and grid labels.
- XY Axis min/max values.
- XY Axis labels.
- Line color legend.
- Grid line color.
- Font control for annotations and labels.
- Plot size (width) in pixels.
From the Data Options dialog, the user can set display properties for each loaded dataset. These Data options include:
Data Options Dialog
- Legend label (default = filename).
- Line color.
- Line thickness.
