Hi,
I have produced a spatial plot using AMETv1.4. I am having a hard time understanding the term “coverage limit = 25%” on the plot.
Would you please help me to understand the term?
Thanks in advance
Hi,
Coverage limit is actually a data completeness limit. Observation data completeness is calculated for the specified time period for each individual site based on the number of valid observations divided by the total number of observations available for the time period. For example, if a site has 75 valid observations and 25 missing or invalid observations, the “coverage” for that site would be calculated as 75/100 * 100 or 75%. If the coverage limit is specified as 75%, all sites with at least 75% observation data completeness for the specified time period would be included in the spatial plot, while any sites with less than 75% would be excluded from the plot.
Note that the data completeness (coverage) only applies currently to spatial plots in AMET. It is ignored for all other types of plots. Also note that the data completeness is only calculated based on the available observations for a site (valid, invalid, or missing). It does not account for completely missing observations. So, if a site has daily measurements, but several of the daily measurements are missing completely from the data record, those missing data points are not accounted for in the data completeness calculation. For example, for a site that measures daily values for the month of January that has 20 valid observations, 5 missing values indicated by -999, and 6 completely missing value, the completeness would be calculated as 20 divided by 25. The 6 completely missing records are not accounted for in the calculation.
Hopefully that answers your question. Let me know if you need more details.
Wyat
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Thank you so much for the response. I calculated the IMPROVE and CSN data for 2016 that came with the AMETv1.4, EPA2016v1 modeling platform. Where I can see about 75% of total data for the EC is -999, Which means 25% coverage.
Hi @wyat.appel ,
Okay, So, I crossed check observed data for the PM25_TOT is 1830, of which 428 missing value. So, “coverage” should be (1830-428)/1830 *100 =76%. But my plot still showing 25%
Am I right about the 76% coverage ?. If so, would you please help me?
Thanks in advance
The coverage limit you’re seeing is something you set as the limit, it’s not a report of the coverage for the sites you’re seeing on the plot.
So, the 25% you see means that any site with a completeness of 25% or greater will be plotted. You control the coverage limit in the all_scripts.input file. In there you can change it to any value between 0 and 100. Right now it is apparently set to 25%. If you set it to 75%, you should not see many, if any, sites disappear from your plot. If you do, it means that site has a data completeness less than 75%.
Wyat
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