Page 1 of 1

something apparently wrong with longitudes in altika

PostPosted: Mon Jul 04, 2016 12:55 pm
by dornina
Hi there

I'm trying to extract significant wave height from altika in the Southern Atlantic. The descending tracks seem to be ok, but apparently there's something wrong with the longitudes in ascending tracks. I've been playing with tracks 0205 and 0749 over the period 2013-2015.

just wondering if someone could give me some tips, cheers!

Nina

Re: something apparently wrong with longitudes in altika

PostPosted: Thu Jul 07, 2016 10:32 am
by podaac
Hi Nina,

Did you extract the AltiKa data from RADS? PO-DAAC does not have AltiKa. The RADS mailing list would be the correct forum.

Thank you for your request.

Re: something apparently wrong with longitudes in altika

PostPosted: Fri Jul 08, 2016 10:10 am
by dornina
Hi there!

Thanks for your answer. Actually I'm getting data from a ftp, which is "ftp://podaac-ftp.jpl.nasa.gov/allData", where you can find the saral option, go further a few more options and get the file with altika data products inside. So, I am getting altika data from this website.

The problem that I am having is because I am trying to work with two tracks which are plotting at wrong location. We can see the nominal position of Saral/Altika tracks through the "Visu Nominal Tracks" on Google Earth. The tracks that I want to work are 0749 and 0205 and should be on Southern Atlantic Ocean, close to Rio de Janeiro's coast, but it is located at Pacific Ocean instead. Another problem is because both tracks are plotting at same position (two different tracks located at same position, it is weird). Besides that, I worked with another track from the same ftp database. I used the same data for the track 0648 and the data was all right! All data that I tryied to work with was from 2013 to 2015.
So, the data looks to be wrong. I would like to know if you guys can give me some tips or if there is a problem with Altika data.

Cheers,

Nina Dorian

Re: something apparently wrong with longitudes in altika

PostPosted: Fri Jul 08, 2016 10:40 am
by vzlotnic
Nina

Thank you for bringing this problem to our attention. Yes, there seems to be a problem with longitudes. I doubt it will be fixed soon. Also, the key person at PO-DAAC specializing in this dataset is on travel.

In the meantime, I suggest you try to get the AltiKa data from

http://rads.tudelft.nl/rads/rads.shtml

Victor Zlotnicki

Re: something apparently wrong with longitudes in altika

PostPosted: Mon Jul 11, 2016 2:17 pm
by jhausman
Hi Nina
The data we have at PO.DAAC are near real time with a GPS based orbit for AltiKa. I highly suggest that you download the GDR data from either RADS or AVISO if you are doing science research for long time series. These data are meant for operational use or until the GDR are available. The near real time are also organized differently, they typically contain an entire revolution or more of data, rather than a single pass. The GDR data are organized by passes. This is most likely why you see data on both sides of the planet, the 205 file contains data for 205 and 206, and 749 also contains 750.