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9 votes

MOD09A1 QC layer

This is a good question, naturally isn't obvious how to handle this kind of data. For example, the product State QA has 16 bits and there are single, double and triple bit flags combinations: For ...
aldo_tapia's user avatar
  • 13.7k
6 votes
Accepted

Parsing MODIS QA layers

Answer from LPDAAC: It goes from 0000 to 1111, with 0000 being the best and 1111 worst. For some reason the table on the product page wasn't complete. To understand what it means and how ...
DJack's user avatar
  • 458
5 votes

How to check accuracy of Roads

Rather relying on online service, you should download a high resolution imagery, geo-reference it accurately and then use as reference for quality assurance. See the resources for fundamentals of ...
Junaid Abdul Jabbar's user avatar
5 votes
Accepted

What are the other bits in Sentinel's QA60 band?

You are correct: the QA60 bitmask has a value of 1024 for opaque clouds and a value of 2048 for cirrus clouds. The sentinel 2 products are distributed with vector masks that we converted into raster ...
DuckyGoogle's user avatar
4 votes
Accepted

When working with MOD09GA product, is supposed QC bitmask for high aerosol quantity to return 4 values?

However, as I noted above, bitmasks for cloud state, cloud shadow and land/water only return two values, 0 and 1. I think there could be a problem with my approach, therefore my question is raised: ...
Nikos Alexandris's user avatar
4 votes

How to check accuracy of Roads

Satellite data is always shifted. The reason is that accuracy of raster data for large area is not so high (1m, sometimes even 10m) and it will always generate errors. I would suggest to use some ...
Losbaltica's user avatar
  • 1,469
3 votes

LiDAR returns over water bodies?

A far as I know, LiDAR signals do not get returned over water bodies. It depends which laser wavelength was used in the survey. If it was a wavelength near the infrared (> 700 nm) it should be ...
Andre Silva's user avatar
  • 10.3k
3 votes

Identifying missing sidewalks in OpenStreetMap data

I created a pretty good "missing sidewalk map" for the City of Bloomington, Indiana. In this case they had performed a LIDAR scan of every City street and had a complete map of all the ...
Mark Stosberg's user avatar
2 votes

Parsing MODIS QA layers

The answer is option 2. As also documented in this post there are undocumented QA-values in the MOD13Q1. I have yet to find a good reason for the lack of documentation, and I expect that you'd have to ...
Mikkel Lydholm Rasmussen's user avatar
2 votes

How to check accuracy of Roads

My answer doesn't provide a proper solution to your issue but just trying to explain the reason of the shift. Any imagery, be it aerial or satellite, intended for mapping has to go through several ...
Techie_Gus's user avatar
  • 2,130
2 votes
Accepted

NDVI index based on QA bands for MCD43A4 , in GEE

If you're interested in just using QA information from Bands 1 and 2, this should get you started. Note that most of the code below is the same as yours, just re-organized a bit. You're off to a great ...
JepsonNomad's user avatar
  • 2,166
2 votes

Problems filtering MOD09A1 in GEE using the QA layer

You have to do some bitwise operations when using these types of bands. If you look at the image collection in the catalog, you'll find this under Bitmask for QA: Bits 0-1: MODLAND QA bits 0: ...
Daniel Wiell's user avatar
  • 14.3k
1 vote
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Working with 8-bit image in Earth Engine

ee.Image.bitCount counts the number of bits set in each pixel. var count = image.bitCount()
Noel Gorelick's user avatar
1 vote
Accepted

Remove bad quality pixels from daily PROBA-V images

You need to map the mask_vnpa2_img() function to the image collection and select the NDVI band after mapping. The bitwiseExtract() function was missing in your code, I added it. var bitwiseExtract = ...
Padmanabha's user avatar
  • 1,394
1 vote
Accepted

Download NASA's Black Marble VNPA2 nighttime light data using Google Earth Engine

Maybe you messed up the bit fiddling? I've got a little utility function that I always use, so I don't have to think about it every time: var mask_vnpa2_img = function(image) { var qa = image.select(...
Daniel Wiell's user avatar
  • 14.3k
1 vote

Obtain product quality for the (Sentinel-5P OFFL NO2: Offline Nitrogen Dioxide) mean image

As I said before, you need the collection before applying mean. Then, you can convert it into a table, selecting the PRODUCT_QUALITY metadata. Now, you can check this metadata either by printing it or ...
HMSP's user avatar
  • 1,640
1 vote

Landsat 8 extracted pixel values for up North: 'pixel_qa' value of 322

I got a reply from someone at USGS: "You want low confidence in clouds, that means that there is very little chance that there is a cloud there when there shouldn't be. A value of 322 means that ...
user7831861's user avatar
1 vote

When working with MOD09GA product, is supposed QC bitmask for high aerosol quantity to return 4 values?

For anyone struggling with bitpacked mask values in MODIS (like I was), I made a package to deal with them more easily. Details are here https://pypi.org/project/unpackqa/ Code to pull the aerosol ...
Shawn's user avatar
  • 1,837
1 vote
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Google Earth Engine Mask application

When you select the QA band, the QA image has only one band (you selected one image). Applying a function expression on that image with other band numbers than zero is not possible, because there is ...
Kuik's user avatar
  • 10.1k
1 vote
Accepted

Select observations based on Quality Bands , Google Earth Engine

When you select NDVI band, you are only keeping that band, so you cannot use other band. Replace var modisNDVI = modis.select("NDVI"); with var modisNDVI = modis.select(["NDVI", "SummaryQA"]);
Rodrigo E. Principe's user avatar
1 vote

Does the MODIStsp package computes the QA's and eventually corrects the bad quality pixels?

The package computes the QA's but it does not produce new images which contain only the pixels with the best quality.
Dolby's user avatar
  • 91
1 vote

Hansen loss and lossyear bands do not always match in Earth Engine

This question is out of date, and not sure if who asked still needs the answer, but I'll do it for anyone else who may have the same doubt. I think the assumption is not correct, at least not in the ...
Rodrigo E. Principe's user avatar
1 vote

How to extract MODIS QA informaton

Let us start from the top. Assuming you have LDOPE installed on Windows, you can start working with it. To open the command line, you open start and search for and run cmd. With the command line open,...
Mikkel Lydholm Rasmussen's user avatar

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