Histograms ?

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JPNIII
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Joined: Tue Mar 24, 2009 5:31 am

Histograms ?

Post by JPNIII »

Hi - I was interested in how to create a histogram of GOES Sounder band 15 (4.45um) brightness temperatures (Tbb). The areafile is already saved locally on my computer. I would want a range of Tbb's on the X-axis, presumably ranging from minimum -> maximum Tbb, whereas the Y-axis would simply be N (# of occurances).

I fiddle a bit with Hydra, but no go.

Thank you!

JPNIII
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barryr
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Re: Histograms ?

Post by barryr »

Hi Jim,
It's pretty much a work in progress, but there is an option to do a histogram with the regular satellite imagery chooser (rather than the HYDRA chooser, which currently works only with some types of multispectral images).

After you've loaded your satellite data, go to the Field Selector tab in the Data Explorer window, and click "Charts" in the "Displays" panel to expand its options. The options should be "Scatter Plot Chart" and "Histogram". Click on the latter and then the "Create Display" button at the bottom. It should then take you to the Layer Controls tab and display the basic histogram. It currently has fairly limited controls, but you can do things like left-click and drag to zoom so you can re-display it so it shows the region (and ranges) you're interested in. You can also right-click on the histogram and choose "Zoom" to change the display, or click "Properties" and change things like the title, line widths and colors, etc.

Hope that helps!
barryr
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JPNIII
Posts: 11
Joined: Tue Mar 24, 2009 5:31 am

Re: Histograms ?

Post by JPNIII »

Very good, Barry -- Thank you!

It appears that the histogram is of "raw" areafile pixel values (i.e., numbers ranging from 0 -> 25000+).

1.) I would like to be able to select the calibration to use when generating my histogram (e.g., TEMP, BRIT, ALB, etc.)
2.) I am looking at a GOES-12 Sounder image. When going through Charts->Histogram, I didn't see how to select a
specific band or calibration. I suspect my problem goes back to how I loaded the image.

Bottom line: Are you able to get a histogram of channel 15 GOES-12 Sounder brightness temperatures?
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beckys
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Joined: Wed Jan 07, 2009 7:50 pm

Re: Histograms ?

Post by beckys »

Hi, Jim -

You are correct -- the histogram will be plotted in the same units in which the image was displayed. (e.g. if you displayed Raw, the histogram will be in Raw; if you displayed Temp, the histogram will be in Temp).

So, yes, you are able to get a histogram of channel 15 GOES-12 Sounder brightness temperatures.

Hope this helps!
- Becky
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barryr
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Re: Histograms ?

Post by barryr »

Hi Jim,
As we discussed on the phone, if your area file with multiple calibrations (raw, brit, rad, temp, albedo, etc) is local, you do NOT get to choose the calibration if you use the General > Files/Directories chooser. Instead, you must use the Satellite > Imagery chooser, which lets you select the desired calibration type in its "Data Type" pulldown.

(Note that in order to get at the local file from the Satellite > Imagery chooser, it must be in a dataset [which you can create using Tools > Local ADDE Data].)

Barry
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