Hi, I have a google earth engine code in Javascript. I want to carry out a trend analysis of Mann Kendall from the year 1985 to 2019 pixel by pixel taking the annual medians of the ARVI vegetation index, from the Landsat 8, 7, and 5 images. When I run the code I get the following error " kendallVariance: Layer error: Image.subtract: If one image has no bands, the other must also have no bands. Got 0 and 1.". I can't identify or fix the error. Please review the code thoroughly, identify the error, and show me the solution. Here is my code:
https://code.earthengine.google.com/e7f790504b34667e500b7271f99b5a16
Deyvis Cano
Hi , I can offer some general guidance to help you identify and resolve the error you encountered in your Google Earth Engine code.
The error message you mentioned, "kendallVariance: Layer error: Image.subtract: If one image has no bands, the other must also have no bands. Got 0 and 1," indicates a problem with the bands of the images you're trying to subtract.
Based on your query, you mentioned that you are calculating the trend analysis using the Mann-Kendall method on the annual medians of the ARVI vegetation index from Landsat 8, 7, and 5 images. To troubleshoot the issue, here are a few steps you can take:
However, by following the steps outlined above and reviewing your code thoroughly, you should be able to identify and resolve the issue.
If you encounter any further difficulties or have specific code-related questions, please provide relevant code snippets or error messages, and I'll be glad to assist you further.
Please if this reply is helpful , recommend it .Thanks
The error you're encountering is related to the number of bands in the images used for the Kendall trend analysis. The error message "kendallVariance: Layer error: Image.subtract: If one image has no bands, the other must also have no bands. Got 0 and 1" indicates that one of the images used in the subtraction operation has no bands.
To fix the error, you need to ensure that the images used for the Kendall trend analysis have the same number of bands. In your code, you are merging Landsat 8, 7, and 5 images and selecting only the 'ARVI' band. However, the merging operation might result in some images with no bands, causing the error.
To resolve this, you can modify your code as follows:
var filteredColt = colt.filter(ee.Filter.listContains('band_names', 'ARVI'));
2. Update the subsequent code that relies on the colt collection to use the filteredColt collection instead.
var lsCol = ee.ImageCollection(filteredColt)
.filter(ee.Filter.dayOfYear(1, 365))
// Add the observation year as a property to each image.
.map(function(img) {
return img.set('year', ee.Image(img).date().get('year'));
});
By filtering out the images without the 'ARVI' band, you ensure that all the images used in the trend analysis have the same band structure, eliminating the error you encountered.
Please try these modifications in your code and see if it resolves the issue.
Step-1
// Load the Landsat 8, 7, and 5 collections and filter by date and region
var l8 = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA')
.filterDate('1985-01-01', '2020-01-01')
.filterBounds(geometry);
var l7 = ee.ImageCollection('LANDSAT/LE07/C01/T1_TOA')
.filterDate('1985-01-01', '2020-01-01')
.filterBounds(geometry);
var l5 = ee.ImageCollection('LANDSAT/LT05/C01/T1_TOA')
.filterDate('1985-01-01', '2012-01-01')
.filterBounds(geometry);
Step-2( cont..)
// Function to calculate ARVI
var calculateARVI = function(image) {
var nir = image.select('B4');
var red = image.select('B3');
var blue = image.select('B1');
var arvi = nir.subtract(red).divide(nir.add(red).subtract(blue)).rename('ARVI');
return image.addBands(arvi);
};
// Map the ARVI calculation function over the image collections
var l8_arvi = l8.map(calculateARVI);
var l7_arvi = l7.map(calculateARVI);
var l5_arvi = l5.map(calculateARVI);
Step-3 ( count..)
// Merge the image collections
var mergedCollection = l8_arvi.merge(l7_arvi).merge(l5_arvi);
// Calculate annual medians
var annualMedians = ee.ImageCollection.fromImages(
years.map(function(year) {
var start = ee.Date(year);
var end = start.advance(1, 'year');
var median = mergedCollection.filterDate(start, end).median();
return median.set('year', year);
})
);
Step-4 (cont..)
// Function to compute Mann-Kendall trend
var computeMannKendall = function(image) {
var trend = image.select('ARVI').reduceRegion({
reducer: ee.Reducer.kendallsCorrelation(),
geometry: geometry,
scale: 30
});
return image.set(trend);
};
// Apply Mann-Kendall trend analysis to each image
var trendCollection = annualMedians.map(computeMannKendall);
// Print the result
print(trendCollection);
Step-5 (cont..)
In this code, you'll need to define the geometry variable to specify the region of interest where you want to perform the analysis. Additionally, make sure you have defined the years variable as an array of years for which you want to calculate the annual medians.
Please note that this is a general example, and you may need to modify it according to your specific needs. If you encounter any specific errors or issues while running this code or modifying it, please let me know, and I'll be happy to assist you further.
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