What is HRV RGB and how to create it?
I already have the data format (MSG HRIT HRV)
HRV image
Re: HRV image
Hello -
For information on HRV RGBs, I would suggest you look at EUMETRAIN's RGB Colour Interpretation Guide. This site goes over a variety of MSG RGBs, including ones involving HRV. For example, one RGB that uses HRV is Low Level Water Clouds. There's a link for Recipe on the left side of this page, which explains the bands and scaling used to generate the RGB. Note that this HRV RGB, and others I checked, involve not just HRV but also the full disk data. In this case, you use HRV for red and green, but you use the 10.8um FD data for blue. This means you need both HRV and FD data for each timestep.
Once you get this data, the easiest way to create the RGB would be to create a function to later call through a script or formula. Here's how you can go about the formula route:
Here's my image from 12Z on 12/13/2017:
One thing to note is that the 10.8um data covers the full disk, while HRV doesn't. Because this full disk data is used for blue, anything outside the HRV domain will be pretty saturated with blue. In regions where the HRV and FD domains overlap, you'll get your desired RGB display.
If you have any questions about this, please let me know.
Thanks -
Bob Carp
McIDAS Help Desk
For information on HRV RGBs, I would suggest you look at EUMETRAIN's RGB Colour Interpretation Guide. This site goes over a variety of MSG RGBs, including ones involving HRV. For example, one RGB that uses HRV is Low Level Water Clouds. There's a link for Recipe on the left side of this page, which explains the bands and scaling used to generate the RGB. Note that this HRV RGB, and others I checked, involve not just HRV but also the full disk data. In this case, you use HRV for red and green, but you use the 10.8um FD data for blue. This means you need both HRV and FD data for each timestep.
Once you get this data, the easiest way to create the RGB would be to create a function to later call through a script or formula. Here's how you can go about the formula route:
- From the Jython Library, add a function like:
Code: Select all
def hrvCloudRgb(red, grn, blu):
red = rescale(red, 0, 100, 0, 255)
grn = rescale(grn, 0, 100, 0, 255)
blu = rescale(blu, 323, 203, 0, 255)
hrv_cld_rgb = mycombineRGB(red, grn, blu)
return hrv_cld_rgb
- Note that this makes use of rescale() from JPythonMethods.
- The 0-100 and 323-203 values in rescale come from the Recipe page linked above.
- Red, grn, and blu are all scaled to 0-255 so things are consistent between the colors. - Create a formula to call this function. For example:
- Formula Editor
- With your HRV and FD data sources loaded, from the Field Selector select Formulas on the left side of the tab. You should see the "HRV Cloud RGB" formula listed. Choose that formula and your display type (I like using "RGB Composite" for the most part with RGBs) and click Create Display.
- In the Field Selector, choose HRV>Reflectivity for red and green. Choose FD>10.8um>Temperature for blue. Click OK.
- At this point, you'll get a RGB display in your Main Display window. You can adjust the gamma value of the RGB in the Layer Controls that will make the display appear brighter or dimmer. In my display below, I'm using a gamma value of 0.4.
Here's my image from 12Z on 12/13/2017:
- RGB Image
One thing to note is that the 10.8um data covers the full disk, while HRV doesn't. Because this full disk data is used for blue, anything outside the HRV domain will be pretty saturated with blue. In regions where the HRV and FD domains overlap, you'll get your desired RGB display.
If you have any questions about this, please let me know.
Thanks -
Bob Carp
McIDAS Help Desk