Filtering across image collections based on a minimum pixel value

Question

I am using the MODIS Terra Continuous Vegetation Fields Global Yearly 250m dataset to derive PTC values for forests. For this, I need to filter pixels that have PTC values that are at least 10%. While I know how to do it on individual images, I am not sure as to how I can apply the same condition for a pixel throughout the image collection (10 years).[for all 10 years, the pixel must be at least 10%] I've tried the filter.Metadata() but I don't think the dataset has a metadata property for me to use. Any ideas as to how I can go about implementing the condition?

var PTC = ee.ImageCollection('MODIS/006/MOD44B')
  .filterDate('2001-01-01','2011-01-01')
  .filterBounds(MYR) //you could use a sample region
  .select('Percent_Tree_Cover')
  .map(function(image) { return image.clip(MYR)});

print(PTC);

var PTC_forests = PTC
  .filterMetadata('system:bands', 'not_less_than', 10); // not too sure which property I should use

Will mapping a function work instead? I believe this might only filter out pixels that fulfil the criteria within the image, rather than applying the same criteria on a pixel throughout the 10 years.

var PTC_forests = PTC.map(function (image){
    var forest = image.gte(10)
     return image.mask(forest)
});

Answer 1

By using gte(10), you'll make an image collection where each image with a pixel less than 10% of forest, becomes 0. If then the number of images equals the number of ones in that imageCollection, the pixel always has more than 10% of pixel throughout all images.

// the binary image collection 
var PTC_maskImgCol = PTC.map(function (image){
  return image.gte(10);
});

// make a single mask image from the collection
var maskImg = PTC_maskImgCol.sum().eq(PTC.size());

// Use the mask image to mask every single image in the original collection
var PTC_masked = PTC.map(function(image){
  return image.updateMask(maskImg);
});

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