I have a drone raster file which I want to use for some calculation. Before the calculation, I need to loose some extreme values. I want to do something like a percentile calculation where you get all values, order them and loose the top 10%. For this, I need to get all values first which can be slow when using a large file.
I looked at the statistics (band.GetStatistics) but that doesn't work well. I thought I could use 2 times the standard deviation added to the mean to get roughly 97%. But with these statistics: STATISTICS_MAXIMUM=33.186080932617 STATISTICS_MEAN=24.840205979603 STATISTICS_MINIMUM=1.5951598882675 STATISTICS_STDDEV=4.7285348016053 Mean + 2*std is larger than the max. So I moved to the histogram. It is also very fast, but I'm not sure how to use it. I have this: 256 buckets from 1.53322 to 33.248: 410 77 66 66 65 58 56 45 42 87 57 72 61 65 68 70 73 82 93 ... Does this mean, bucket 1 = 410 that I have 410 pixels of value 1.53322 and the second bucket means I have 77 pixels between 1.53322 and 1.657? 1.657 = 1.53322 + ((33.248 - 1.53322)/256) Is this a good approach? Or can/should I use a different one. Thanks, Paul
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