Reprojecting MODIS Sinusoidal Data?

[LearningToFly]

Greetings HDF-EOS Community!

I am having difficulty re-projecting the data tiles I have downloaded from the NASA MODIS Data Pool from the MODIS Sinusoidal projection to say WGS84 geographic coordinates. I have searched and searched online to find ways of calculating the conversion between the datum-less sinusoidal projection and something with a datum such as WGS84 Lat/Long. I have used the MODIS Reprojection Tool and it does not seem to be accurately re-projecting the datasets, namely because I need to calculate the bounding rectangle in the output coordinate system in order to properly subset the resulting re-projected image. Is there a good resource to learn to do this? If so can you point me in that direction? Any help would be more than appreciated.

Thanks for checking out this post!

Best Wishes From Alaska!

[hyoklee]

Hi,

I'm not familiar with WGS84 but are you looking for a MODIS projection tip like this?

http://www.dfanning.com/map_tips/modis_overlay.html

[LearningToFly]

Hi Hyoklee!

Thanks for the link, was a good read, but I think that I am requiring information on how I would get a tile out of the sinusoidal projection into something that is better suited to North America (particularly Alaska) maybe an Albers Equal Area or something of the like. I just cannot seem to calculate what he bounding polygon would be if I wanted to take a tile from the sinusoidal projection coordinates to those of another projection. I feel like I am missing something that others are aware of when trying to convert to another projection.

Thanks for your reply!

[kyang]

The quick thought:
MRT may be the best tool I can think of. Have you tried HEG or HDFLook and see if those tools can help?

A little bit more thoughts and maybe more work for you to do:

First a question:
What if you get the geo-location(latitude and longitude) values for each data point, can you use that information to re-project your data to whatever projection you want to use?

For example, you want to plot temp[100][200], you are given the latitude and longitude values at each point, lat[100][200] and lon[100][200]; (for sinusoidal projection, lat[100][200] can become latnew[100]), is this piece of information enough for you to plot the data at the given projection you want to plot? If yes, you can check http://hdfeos.org/examples/c_grid_lonlat.php on how to retrieve lat and lon. If you hope to get a tool to help you to do the calculation, send an email to eoshelp@hdfgroup.org. We can help you to obtain the lat/lon with ascii format.


After you obtain lat and lon, personally I think many GIS packages(GMT ) can help you draw plots at the projection you wish to use.

We are still learning and maybe we miss something, I hope to hear from your thoughts.
Kent

[hyoklee]

Hmm, are you looking for this kind of calculator?

http://landweb.nascom.nasa.gov/cgi-b...er/tilemap.cgi

Originally Posted by LearningToFly

Hi Hyoklee!

Thanks for the link, was a good read, but I think that I am requiring information on how I would get a tile out of the sinusoidal projection into something that is better suited to North America (particularly Alaska) maybe an Albers Equal Area or something of the like. I just cannot seem to calculate what he bounding polygon would be if I wanted to take a tile from the sinusoidal projection coordinates to those of another projection. I feel like I am missing something that others are aware of when trying to convert to another projection.

Thanks for your reply!

[LearningToFly]

Greetings Kent,

Sorry for my delay, I have been out of town for a few days and am just getting back. I can't thank you enough for your reply. I am going through the information you have sent and am going to see if that is what I am looking for. This list is fantastic and I am grateful for all the responses I have received. I am still new to this whole MODIS projection and I thank you for dealing with my possibly strange (obvious) questions about reprojection. I will post back if I am able to get it to work. Again, many thanks!!!!

Best Wishes from Fairbanks!

Michael

[kyang]

No problems. Hopefully you've gotten what you want. Now we find a way to calculate latitude and longitude. We then use IDL to generate plots for sinusoidal projection. The results look right.