Lunar Orbiter - calculating the corner coordinates, I need to calculate these for myself for a new project Options

[Phil Stooke]

I was going to suggest that you ask on the ISIS/GIS discission forum at USGS, but I see you have done that. I don't use this pointing data myself (I warp images to fit modern control using multiple tie points).

The Orbiter images were used in a new version of the lunar basemap at USGS, as you say.

http://astrogeology.usgs.gov/Projects/Luna...rameMosaics.pdf


My reading of that suggests that they fitted reseau mark locations to the ULCN and used them as tie points to warp the images to the required projection. No pointing data needed. I suspect that the old coordinate data which you have are only predictions based on the orbit data and viewing geometry. It would be reliable enough for the first exploratory maps of the far side (know to have errors as large as 20 or 30 km) and the published index maps, but not for modern mapping.

So I'm going to suggest you do an experiment to assess the quality of the data you have. Take one specific image from your list, one with all four corners on the disk. Find the image here:

http://www.lpi.usra.edu/resources/lunarorbiter/


Then, as accurately as possible, locate the corners (by comparing nearby features) on these maps:

http://planetarynames.wr.usgs.gov/Page/moo...edRelief?map=lo


Then, compare those four coordinate pairs (which will be in ULCN, the best coordinates we have until LRO data are fully processed) with the numbers in your list. If they are very close, your numbers are OK. If not, you may have to resort to the other approach and 'georectify' the images (warp them using many tie points) in a GIS.

What I'm describing will not take long for one image but it will teach you - and everyone else - something very useful. I could do it easily, but I have my own projects. This is not defending old data, it's being realistic about limitations of old data.

Phil

[Qmantoo]

OK, thanks to all of you for your help on this. For my project, I do not think it is worth getting to know how to match up points on the images with other points on other images and to stretch them to fit. Besides, the project does not really involve placing images onto a larger map but more about placing features onto images - similar to what others have done.

I will do some experiments and probably use a 'best-fit' approach.