Questions about worldwide radar
Posted: Fri Jul 07, 2006 1:51 pm
I would like to create configuration lines for some radar sites in Europe.
However, I am encountering a few problems that I am not sure how to deal with.
1) Many of the radar sites I know only present a "discretized" color scale with, for instance, blue being "light rain", green being "moderate rain", etc (often the figure in mm/h is indicated, too). How should I deal with these? Should I assign them values in dBZ based on the indicated mm/h figures, or perhaps should I avoid this kind of radar sites entirely (but there are quite a few)? Even if I assign "reasonable" dBZ figures to the colors, the fact remains that the values will be much coarser than with radars that give a nearly-continuous dBz color scale.
2) A few of the radar images are composite of two or three separate radars, and the images for the single radars are not available. How should I deal with these, especially with respect to the "Center", "Range", "Latitude" and "Longitude" configuration parameters? Can I just elect one of the radars as "the" radar and use its data, while choosing a "reasonable" value for "Range"?
3) What if I cannot obtain the precise data about the location of the radar(s)? Is it acceptable to use a "fake" location for the radar (like the center of the image) -- while obviously making it so that the image will fit on the correct geographical coordinates?
4) While some radar sites give the radar data as colored pixel superimposed on the background image (map), some others use more problematic approaches: first, it can happen that radar data is a layer *below* the map, so country borders, rivers, city names etc. obscure some of the radar data; second, sometimes the maps are shaded by elevation (i.e. they show the mountains), and the radar data is blended into them, which makes the radar colors non-consistent (well, I suppose that color is consistent, but luminosity isn't. Can these be dealt with in any way?
However, I am encountering a few problems that I am not sure how to deal with.
1) Many of the radar sites I know only present a "discretized" color scale with, for instance, blue being "light rain", green being "moderate rain", etc (often the figure in mm/h is indicated, too). How should I deal with these? Should I assign them values in dBZ based on the indicated mm/h figures, or perhaps should I avoid this kind of radar sites entirely (but there are quite a few)? Even if I assign "reasonable" dBZ figures to the colors, the fact remains that the values will be much coarser than with radars that give a nearly-continuous dBz color scale.
2) A few of the radar images are composite of two or three separate radars, and the images for the single radars are not available. How should I deal with these, especially with respect to the "Center", "Range", "Latitude" and "Longitude" configuration parameters? Can I just elect one of the radars as "the" radar and use its data, while choosing a "reasonable" value for "Range"?
3) What if I cannot obtain the precise data about the location of the radar(s)? Is it acceptable to use a "fake" location for the radar (like the center of the image) -- while obviously making it so that the image will fit on the correct geographical coordinates?
4) While some radar sites give the radar data as colored pixel superimposed on the background image (map), some others use more problematic approaches: first, it can happen that radar data is a layer *below* the map, so country borders, rivers, city names etc. obscure some of the radar data; second, sometimes the maps are shaded by elevation (i.e. they show the mountains), and the radar data is blended into them, which makes the radar colors non-consistent (well, I suppose that color is consistent, but luminosity isn't. Can these be dealt with in any way?