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Here is another example. I want to select elevations above 996. So i Write ELEVATION > '996' And it only sort of does what I want. In the picture below, you can see it selected 26 lines... but it did not select a line with elevation of 9650 which is clearly above 996.
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07-31-2015
10:19 PM
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Hello, I'm trying to run a simple query and I don't know why it's not working. I have a US cities shapefile with an "Population" field and I'm just running this: Select * FROM cities WHERE: POPULATION > '400000' But it doesn't select populations that are above 400,000. It seems to just select whatever it wants - including cities with a population of 96, 3000, or 500,000. I don't know how it's deciding to select what it does but it selects about half of them with no logic to it. Any ideas?
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07-31-2015
10:04 PM
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Here, have a jpeg of the raster information. I obviously have no idea what im doing haha. All i know is that they are .SID files and the cell resolution is 0.5. There are three bands... Red Green and Blue. Previously my superior mapped impervious surfaces of land parcels by hand.... it took her a long time. Thanks!!
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07-29-2015
12:46 AM
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I'd love to be able to use the function.... but I can't find "tasseled cap" in any of the toolbars or commands in ArcMap 10....
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07-28-2015
12:09 PM
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Thanks guys, great info here. I should be able to get everything I need done. Darren: I apologize if this is silly question but where in the expression does the raster name go? And as there are only three bands... do i need the rest of the coefficients? Also, do i put parentheses around the bands? Once I figure how to input this correctly.... Float "Aerials\142140.sid" (((-0.2728)*"Band_1") - ((0.2174)*"Band_2") - ((0.5508)*"Band_3") + ((0.7221)*TM4) + ((0.0733)*TM5) - ((0.1648)*TM7)) Something like that....? I really should learn some more SQL....
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07-28-2015
12:07 PM
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Good morning, I'm a beginner analyst attempting to map impervious water surfaces of land parcels in a city. The research I did suggested I use what is called the "Tasseled Cap" function in GIS to estimate the vegetation aka "Greenness" factor of the raster image to automatically make a distinction between pixels that are vegetation (some minimum level of green) and not vegetation (impervious). I have no idea how to do this as my experience with Python and SQL is extremely limited and I can't find a built in function to do this for me. Would anyone happen to have any helpful hints? Cheers
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07-27-2015
09:11 AM
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