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zooniverse / planet-four

Identify and measure features on the surface of Mars
https://www.planetfour.org/
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Update north and sub-solar azimuth data #97

Closed michaelaye closed 9 years ago

michaelaye commented 10 years ago

The current meta-data for sub-solar azimuth and north azimuth has been taken from the fields for map-projected images, while P4 is using non-map-projected images.

The new angle data is in this file:

https://www.dropbox.com/s/ggzn4js6e7bfes6/Hirise_angles_updates.csv

mschwamb commented 10 years ago

Can you explain where the 0 angle for each of those angles is in a non-map projected image/cutout? Might be good to have it documented here

michaelaye commented 10 years ago

Here's what I wrote in the forum here:

On the HiRISE image webpages all important observational parameters are given in the Observation toolbox.

Concerning the sun direction, we call that azimuth in astronomy (at least in some of the many coordinate systems possible), and the full name here is sub-solar azimuth, in other words, in what direction of the image is the point on the surface that lies directly under the sun, i.e. sub-solar.

Now, first one needs to take the correct angle for the actual image product of interest: all azimuth angles are both provided for map-projected and non-map-projected images. And we use non-map-projeced images, so that's what we need to consider.

Now, how to apply that angle: 0 is defined as a straight line to the right (= 3 o'clock), starting from the image center and increasing the angles clock-wise.

In this example, looking at a non-map-projected image, the sub-solar azimuth is given as 53.7 degrees, so starting from '3 o'clock, an angle of approx 54 degrees is the well-known lower right that we have in most of our images in Planet4.

mschwamb commented 10 years ago

Also if updates are being made to the database to correct the fan spread angle, would it worth also updating the meta data so the values for north_azimuth and sub_solar_azimuth are corrected to what's in the linked csv files discussed above?

Cheers,

~Meg

mschwamb commented 9 years ago

@chrissnyder is something that could be done with the season 4 inca city metadata updates? It would be good to get the database having the correct info if possible.

Thanks, ~Meg

chrissnyder commented 9 years ago

Done.