Calculating the Azimuth angle and the Zenith angle

Prev Go to previous topic

Go to next topic

Last Post 17 Dec 2007 01:44 PM by anon

1 Replies

Sort:


You are not authorized to post a reply.

Author

Messages

anon

New Member

Posts:

17 Dec 2007 01:44 PM
Hello, I’m trying to use Flaash to correct my image and I’m not sure about how to calculate the Azimuth angle and the Zenith angle that Flaash needs as input in the advanced settings. I know that the solar zenith is (90 – elevation angle) but the zenith angle that Flaash needs should be different because the help said that it should be between 90 and 180. I would be very grateful should somebody help me. The information of my image is the following: Product Image ID: 000 Sensor: IKONOS-2 Acquired Nominal GSD Cross Scan: 0.84 meters Along Scan: 0.84 meters Scan Azimuth: 90.00 degrees Scan Direction: Forward Panchromatic TDI Mode: 13 Nominal Collection Azimuth: 314.3057 degrees = naz Nominal Collection Elevation: 78.21024 degrees = nel Sun Angle Azimuth: 146.9436 degrees = saz Sun Angle Elevation: 66.98717 degrees = sel Thanks.

MariM

Veteran Member

Posts:2396
Veteran Member

17 Dec 2007 01:44 PM
These terms are defined in the FLAASH help (ENVI 4.4): ------------------------------- The zenith angle is defined as the angle between the line of sight and the zenith (180 for nadir-viewing sensors). Zenith angles must be positive and between 90 and 180 degrees. The azimuth angle is defined as the azimuth (the angle between the line of sight and due North) of the sensor as viewed from the ground. This angle is arbitrary for nadir-viewing sensors. For example, if your azimuth from the sensor is 90 degrees (due east), then the azimuth from the ground that you specify should be 270 degrees (due west). --------------------------------- I assume that IKONOS defines zenith as 90 degrees and nadir as 0 degrees. FLAASH defines zenith as 90 degrees and nadir as 180 degrees. So, it seems in FLAASH 4.4 the zenith would be 90 + elevation angle.

You are not authorized to post a reply.