Image Node

After Import Image(s) via File, an icon will appear on the Barista thumbnail view.

Image node icon will be shown as a thumbnail of the original image. Double Click on the image icon opens an ImageView on the Barista workspace. Right Click on the image icon opens an Image icon popup menu with the following options:

Image node popup menu

The functionalities of the image popup menu are described in more detail here:

• 2D Point node
• RPC node
• PushBroomScanner node
• Affine node
• TFW node
• Import Orbit
• Import Generic PushBroom Sensor
• Init FrameCamera
• Create TFW
• Create 2D Conformal
• Orthoimage generation
• Apply Transfer Function permanently
• Image Properties
• Export Image
• Generate NDVI

Among the various sub-nodes of image nodes, the nodes describing a sensor model are of special importance. These nodes contain the transformation parameters between object space and image space and are thus used whenever such a transformation is required, e.g. for orthophoto generation, for adjustment, or for monoplotting. Currently, there may be four such nodes for each image node:

• RPC node: The transformation uses the RPC model.
• PushBroomScanner Node: The transformation uses the generic pushbroom scanner model.
• Frame camera node: The transformation uses the perspective transformation.
• Affine node: The transformation uses an affine model.

An image node can have none, one, or both of these nodes. If it has more than one such node, any Barista function requiring a transformation between object space and image space will require specification of an available sensor model to be used. The user can declare one of the sensor models to be the current sensor model (cf. RPC node, PushBroomScanner Node, Frame camera node, or Affine node), which will by default be used for any such action.

Compute Forward Affine

In order to use the affine sensor model in an adjustment each image has to have a an Affine parameter node, which is initially computed with Compute Forward Affine. Alternativly it can also be imported from an textfile.

Generate NDVI

Choosing Generate NDVI from the Image icon popup menu results in the generation of an image representing the Normalised Difference Vegetation Index (NDVI) of that image, along with an image representing the standard deviation of the NDVI. If the image is geocoded, i.e., if it has a TFW node, the resulting images will also be geocoded and receive a TFW node containing the same values. The NDVI can only be computed for images having three or four bands; if this is not the case, an error message will be issued. The following rules apply:

1. If the image has three bands, it is assumed that the image is a colour infrared image, thus, that its bands are (band1, band2, band3) = (IR,R,G). The NDVI will be computed from:
   NDVI = 100% * (IR - R) / (IR + R) = 100% * (band1 - band2) / (band1 + band2)
   If the image is an RGB image, thus (band1, band2, band3) = (R,G,B), the resulting image will not be a correct NDVI image.

2. If the image has four bands, it is assumed that its bands are (band1, band2, band3, band4) = (R,G,B,IR) (cf.Image Import). The NDVI will be computed from:
   NDVI = 100% * (IR - R) / (IR + R) = 100% * (band4 - band1) / (band4 + band1)

3. If the filename displayed on the screen is PATH\FILE.EXT, the name of the NDVI image will be displayed as PATH\FILE_NDVI.EXT, and the image containing the standard deviations of the NDVI will be called PATH\FILE_NDVI_SIG.EXT.

Image Properties

Choosing Display Image Properties from the Image icon popup menu opens an image properties table in the Barista workspace:

Image properties table

To ImageView

To Thumbnail View