Earthdata Forum

I have few question regarding the ANDVI product (MOD13Q1).I encountered a problem when downloading MODIS data. I went to this website (https://ladsweb.modaps.eosdis.nasa.gov/search/), I chose to download NDVI data from 2016 to 2017 and post-process it. The region I chose is the United States. In the preprocessing, I only selected NDVI as the variable, and performed Mosaic processing and reprojection to Geographic.Why did the processing fail? If someone specifically guide about preprocessing through, I'll be thankful.

Hello @q1w2e3r4
Please take a look at the AppEEARS tool: https://lpdaac.usgs.gov/tools/appeears/
I am not sure which interface you had initially tried, but I believe AppEEARS will perform the processing that you desire. Please let me know if you have any questions.
Thanks,
Brett

I had the same problem as you, and I was wondering if you've solved it now?

LP DAAC - lien wrote:
> Hello @q1w2e3r4
> Please take a look at the AppEEARS tool:
> https://lpdaac.usgs.gov/tools/appeears/
> I am not sure which interface you had initially tried, but I believe
> AppEEARS will perform the processing that you desire. Please let me know
> if you have any questions.
> Thanks,
> Brett

Hello @LP DAAC - lien
Thank you!! Using AppEEARS is much more efficient!

LP DAAC - lien wrote:
> Hello @q1w2e3r4
> Please take a look at the AppEEARS tool:
> https://lpdaac.usgs.gov/tools/appeears/
> I am not sure which interface you had initially tried, but I believe
> AppEEARS will perform the processing that you desire. Please let me know
> if you have any questions.
> Thanks,
> Brett

Hello @LP DAAC - lien
I have the same problem as @q1w2e3r4. According to the method you provided, I tried to use AppEEARS to extract and download EVI and NDVI data from MOD13Q1 dataset, which really improved the success rate.
However, I have the following questions. For the data downloaded by the same method as @q1w2e3r4, the EVI value ranges from -2000 to 10000, while the EVI value downloaded by AppEEARS ranges from -0.2 to 1. I would like to know whether AppEEARS has standardized the EVI data? How to standardize the EVI data? Is it the original EVI value multiplied by the scale factor (0.00001)?
I didn't find information about that on the AppEEARS help page or in the supporting files I downloaded with EVI. Hope to get an answer, thank you!

Please note the .csv file AppEEARS outputs does incorporate the scaling factor. However, the pixel values in the output raster images are not scaled. So yes, the csv values are scaled.
Thanks,
LPDAAC

LP DAAC - lien wrote:
> Please note the .csv file AppEEARS outputs does incorporate the scaling
> factor. However, the pixel values in the output raster images are not
> scaled. So yes, the csv values are scaled.
> Thanks,
> LPDAAC
Yes! Previously I used terra to read nc file and tif file, pixel value is scaled. But according to the way you said, I read the.tif file by raster, and the pixel values are not scaled, and they are basically the same as the data downloaded by the method of @q1w2e3r4. Thanks!!

Hello, I downloaded MOD09GA in HDF format. Does it need preprocessing? If yes, what kind of processing should I perform?

For the rest of the user community with the same question, the answer to googlecolab2023's processing MODIS data question can be found here: viewtopic.php?p=21357#p21357