IPB

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
HiRise Image Orientation?, What does it mean when North is not at 0 degrees?
Bobby Richardson
post Oct 31 2015, 09:29 AM
Post #1


Newbie
*

Group: Members
Posts: 3
Joined: 26-September 15
Member No.: 7792



HI everyone.

I've been following MSL's meanderings since Day One, but I still find myself going to HiRise.

I just realized that on the HiRise image info pages they list the map-projected & non-map projected North Azimuth at some angle other than 0 degrees; e.g., 'Map Projected North Azimuth - 274'. 'Non Map Projected North Azimuth - 103' And yet, when I overlay either HiRise image on Goggle Mars, a line drawn parallel to the sides of the imaged surface will extend up to the North Pole.

Does this mean that Map Projected North is located toward the left side of the image instead of toward the top, and Non-Map Projected North is toward the right side of the image? And if so, what's up with the GM overlay?

I hate to bother ya'll if this is a really 'duh' question, but my google-fu just isn't as strong as I thought it was.

TIA
Bobby R.
Go to the top of the page
 
+Quote Post
Phil Stooke
post Oct 31 2015, 11:43 AM
Post #2


Senior Member
****

Group: Members
Posts: 6477
Joined: 5-April 05
From: Canada
Member No.: 227



I think you will find that azimuth in the image is measured relative to the scan line direction (rows of pixels). To convert it to north azimuth on the planet you have to rotate by the angles you quote. Then the sides of the image will point towards the pole - roughly. The orientation is still a little bit off straight N-S, which is why the angles are not 90 and 270.

Phil

.


--------------------
... because the Solar System ain't gonna map itself.
Go to the top of the page
 
+Quote Post
JohnVV
post Nov 1 2015, 12:49 AM
Post #3


Member
***

Group: Members
Posts: 706
Joined: 18-November 08
Member No.: 4489



it has been a very long time since i used the Jpg2000 images
i grab the PSD img files and combine the columns

the lat and long of the jpg2000 images should be for the CENTER pixel
and the N azimuth ( as phil stated) is relative to the rows of pixels ( scan lines)


the mapped image is in "Equirectangular" format while the NON mapped should be loosely a "Orthographic" ( with camera tilt) projection

from 45 N to 45 S this will not make much of a difference in the two if the spacecraft is not too tilted off the center ( looking directly down)

the ground track for HIRISE is small enough that there will not be to much warping do to mapping ( unless near a pole and using simplecylindrical )




Go to the top of the page
 
+Quote Post
Bobby Richardson
post Nov 10 2015, 07:18 PM
Post #4


Newbie
*

Group: Members
Posts: 3
Joined: 26-September 15
Member No.: 7792



Phil & John, thanks so much for your responses! Phil your answer provided great info on mapping and John your info will come in handy when I start to drape HiRise images over 3D terrain meshes.
Go to the top of the page
 
+Quote Post
JohnVV
post Nov 10 2015, 07:26 PM
Post #5


Member
***

Group: Members
Posts: 706
Joined: 18-November 08
Member No.: 4489



for draping the hirise images over a mesh

there is a blender plugin just for that

also depending on what you are using for terrain ( MOLA will not work well !!! )
the set of programs that make up " stereopipeline "
can drape the image over the point cloud
Go to the top of the page
 
+Quote Post

Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 7th February 2016 - 05:24 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is a project of the Planetary Society and is funded by donations from visitors and members. Help keep this forum up and running by contributing here.