4/24/2024 0 Comments Erdas imagine free trialPlease Wait" window will remain on the screen even after Orthomaxis fully loaded. Atthis point, you have encountered your first glitch in Orthomax. Click on this button.ģ) Wait a couple of seconds. General Procedure for Preparing Imagery for Photogrametric Analysis:ġ) Open up Orthomax: first, open ERDAS Imagine by either selecting itfrom the applications menu on Alai or by typing "imagine" at the UNIX prompt.Ģ) You will see an option for "Orthomax" at the right extreme of the Imaginetoolbar after Imagine starts up. _ Common Ground Control Points are known. _ You can figure out which camera was used by trial and error, assumingĬamera is contained within Orthomax database. _ Camera is contained within Orthomax database. _ Camera distortion parameters must be known. _ Focal length of the camera must be known. The air photo datasets adequate for photogrametry must poses the followingattributes: These marks must be present onthe scan of the air photos in order to allow Orthomax to correctly orient thephoto relative to the principle point (point of no distortion in the photo). These ticks are generally cross-hairs inthe corners and on the sides of the air photos. * Fiducial Tics: There are markings on the air photos which orient the photorelative to the inside of the camera. These parameters, aswell as the camera focal length, must be known to perform photogrametry usingOrthomax. There are three parameters which are commonly used to define the lensdistortion of the camera: the Ko, K1, and K2 parameters. In order to find the points common to each stereo photo which isnecessary to calculate the elevation of the point, the lens distortion must beknown. This distortion can be characterized by a polynomialfunction. This distortion generally increases away from thecenter of the photo. Depending on the lens in the camera and the focal length, the camerawill distort the image. * Cameras: Each type of air photo camera takes photos differently than theother. If common points on each photo can be identifiedand the three dimensional position and orientation at which each photo wastaken are known, the elevation of that point can be determined. Commonly, a 40%/60% overlap is commonfor air photo lines taken. These areas are termedthe overlap areas of the stereo pairs. * Stereo Pairs: Air photos which are taken at intervals such that there is acommon area of ground that can be seen on two or more photos containsinformation about the elevation in the common areas. While it is a commonpractice to change the scale of the air photo through photographic enlargementor reduction, it is important for the software that you use a photo that hasnot been enlarged or reduced for the photogrametric analyses. * Air Photos: Air photos are taken with special long-focal length cameras.Air photos have an inherent scale to them which is related to the focal lengthof the camera and the height at which the photo is taken. Several important concepts and terms will be important to understandthe analyses described below: In addition, severalflowcharts and checklists are provided to aide in performing the photogrametricanalyses. This document will serve to develop some of the important concepts inphotogrametry, the basics of how the Orthomax software works, and step-by-stepinstructions explaining how to use stereo imagery to extract Digital ElevationModels (DEM) and then orthorectify the imagery. The software package wasoriginally designed by a small company called Autometric however, ERDAS haspurchased the right to distribute the software as an add-in to Imagine.Consequently, Orthomax and Imagine do not always work seamlessly together buttransfer between the two programs is usually problem free. Orthomax is an ERDAS Image add-on program that allows one to performquantitative photogrametry on stereo imagery. Using Orthomax Active Tectonics, Quantitative Structural Geology and Geomorphology
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