"Envi Getting Started tutorial 06" Custom RPC file image ortho correction, positive shot correction section using classic

The article deals with 5. x version inside the Ortho correction method, here I use the ENVI Classic section for the same effect operation, convenient 5. X the following version of the reference, the method has incorrect parts please contact me to correct.

(i) Open and associate a Dem
Opens the SPOT4 (that is, the RPC info) image that completes the first step, while opening the DEM data.
In the Spot4.tif right-click Edit HEADER, here choose the Edit attributes->associate dem file, select existing files, that is, the DEM Layer-1 here, click OK.

(b) Forward-firing correction
In classic, the tool for the Ortho correction is inside the map->orthorectification, and the tools involved here are map->orthorectification->generic RPC and RSM, The reason for selecting the above tool or the next column based on the ground control point is whether there is a reference image (base image base image), and there is a napp_2m_ortho image in the Envi tutorial, but I am not sure if it is an accurate image because it lacks information such as elevation and projection 2 , but its accuracy is higher than the image we are correcting. In summary, I use a non-GCP-based approach, that is, orthorectification using RPC or RSM.

Then select the image that we need to correct now.

Here I would like to explain the parameter problems I set. Resampling of source Images I chose bilinear interpolation (Bilinear),
Background set to 0 indicates that the background color is black, dem file because I'm already connected in the first step, if there is no association, you can re-select the Dem files here. Method of DEM Resampling I chose three convolution (Cubic convolution), which can be arbitrarily selected by the two resampling, keeping the default bilinear interpolation, but I do not have GCP so I think the DEM is more accurate some changes the sampling method.
(1) Here you can choose to save to the folder or memory, save in memory, close the ENVI image will lose the correction results. It is recommended that you save the path by choosing Save.
(2) The output of the projection and map extent can be inconsistent with the DEM, the default is the projection information of the DEM, here I changed the projection, keep the original projection, the steps see the right 2 small boxes.
(3) The cell size of the output image, this parameter I refer to the settings in the Envi tutorial, x and Y set to 10.

Click OK to complete the operation, then wait for about 5 minutes.

(iii) Results display

Open the corrected image, which already contains the DEM information in the data value.

These are the results of my own practice with reference to the ENVI05 and ENVI06 tutorials, which may not be correct and welcome communication and correction. Off-topic, about ortho correction belongs to advanced preprocessing, we generally do not use when the general preprocessing, or incomplete information,"Image ortho Correction (ortho-rectification): With the help of terrain Elevation model (DEM), the image of each cell to the terrain correction, Make the image conform to the requirements of orthographic projection. The aim is to eliminate the influence of topography or the deformation caused by the orientation of the camera, and to produce the process of plane ortho image. Conditions for Ortho correction in the ENVI: image data, required PRC (rational polynomial coefficients) or RMS (replacement sensor model), elevation information (DEM or average elevation), Ground Control point (optional), Geoid (elevation difference of the geoid and average elevation of the image data acquisition). "Note: The above quoted sentences come from the Web" my own understanding is to give the image the correct elevation information, even if the data has a DEM value.

"Envi Getting Started tutorial 06" Custom RPC file image ortho correction, positive shot correction section using classic