Take the 2-minute tour ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

I have a satellite image that has a few bands in it. But I don't know what colors they are supposed to represent, nor do I know where to look for this information--the file's metadata say nothing about this. Is there a way to determine what color each band represents? How can I find out which band is red, blue, NIR, etc.?

share|improve this question
    
What software are you using to look at the imagery? –  artwork21 Jun 9 at 13:45
    
Where did you get the imagery? –  blah238 Jun 9 at 13:45
    
I'm using ERDAS imagine. I have 2 such images: 1)From homework of week4 here: gis.usu.edu/~chrisg/python/2009 ,its called "aster" and it have 3 bands: ASTER_Band1, ASTER_Band2, ASTER_Band3N. 2)Second is RapidEye image that i was given. It have 3 files in it: first is "RGB" - i can understand this, quite easy, second is "NIRREG" - it also have 3 bands, i suppose there is NIR and somthing else, but how do i know for sure? Third is called "CIR2", also have 3 bands, i have no idea what are they. –  user32162 Jun 9 at 13:51
add comment

4 Answers 4

up vote 1 down vote accepted

As others have mentioned, the best practical way to determine which bands are which is to look at the source metadata, which is widely available for common products like ASTER and Rapideye.

You can also derive much information about the bands doing a little legwork in Erdas. This is a useful skill to have if you are given, for example, a Rapideye image with only 3 or 4 bands. Investigating spectral reflectance properties of water yields particularly useful information. To illustrate, the attached image shows a Rapideye scene with 5 spectral bands. I used the Spectral Profile tool located under Raster > Utilities > Spectral Profile. Four samples were taken: water, forest, farmland, and developed (Figure 1).

We know that water is very good at absorbing longer wavelengths (e.g. RE, NIR) and very good at reflecting shorter wavelengths (Figure 2). If you take a look at the spectral reflectance curve of the Rapideye imagery (Figure 3) that correspond to the sample points in Figure 1, it quickly becomes clear which bands are which. Based on the comparison of theoretical Figure 2 and empirical Figure 3: Blue is band 1, green is band 2, red is band 3, Red edge is band 4 and NIR is band 5.


Figure 1

enter image description here


Figure 2

enter image description here


Figure 3

enter image description here

share|improve this answer
    
Thank you mr.Aaron. All those pictures make it clear and easy to understand. Thanks for putting time to answer this question. –  user32162 Jun 9 at 20:15
add comment

In order to know the wavelengths or colors that bands in a raster represent, you typically need to know what instrument they were created with. Some software can make automatic assignments based on the file format, but the labels might not always be clear. I recall doing some work in ENVI where it would give you the wavelengths but not the band numbers. I had to track down the specs on a chart that gave band number, width, and color.

Based on your comment, you have Aster and RapidEye data. An Aster band list can be found on the Wiki for that instrument and will tell you Band 1 = visible green/yellow, Band 2 = Visible Red, and Band 3N = Nadir NIR. I'll leave the RapidEye band determination to you, but give you that hint.

share|improve this answer
    
Thank you, mister Chris, this is a good idea. Thanks for putting time in answering my question. –  user32162 Jun 9 at 20:12
add comment

For your Aster Image, 1 is green, 2 is red and 3 is near infra-red

For RapidEye, 1 is blue, 2 is green, 3 is red, 4 is red edge and 5 is near infra-red.

So your second image is Near Infra-Red/RedEdge/Green

Usually, with 3 bands the image is either RGB or NIR/R/G. When I don't have a clue, I try 321 and 123 composites. With RGB one of the combination should give your true colors. With NRG, one of the combination should give you an image where water is black, vegetation is red, bare soil is cyan.

share|improve this answer
    
Thank you, radouxju. This was helpful, this combination indeed looks like you described. Thanks you for putting time in answering this question. –  user32162 Jun 9 at 20:13
add comment

Look here for Aster info.

  • VNIR_Band1 = 0.52-0.60 (green)
  • VNIR_Band2 = 0.63-0.69 (red)
  • VNIR_Band3N = 0.76-0.86 (NIR)

Rapid eye comes in GeoTiff format comprised of 5 bands (listed here). The images that you have are probably composites.

RGB is Red, Green, Blue that represent RGB, NIRREG (possibly NIR and near edge), and color infrared (CIR). In CIR, NIR is seen as red, green as blue, and red as green.

share|improve this answer
    
Thank you mister Barbarossa. They are indeed compositions. The total number of 9 bands just confused me for a moment. Now i understand this better. Thanks for putting time for answering this question. –  user32162 Jun 9 at 20:17
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.