Author Topic: Working with maps?  (Read 436 times)

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Offline WeatherHost

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Working with maps?
« on: March 02, 2018, 07:25:18 PM »
Anybody know how to fill a GIS map to depict flood levels?  G Earth shows me the elevations and I know what is flooded where, so I can estimate the levels.  I'd be curious to see a map 'filled' below that level to give me an idea of how widespread the coverage is.

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Offline floodcaster

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Re: Working with maps?
« Reply #1 on: March 02, 2018, 09:27:41 PM »
The only thing I can think of would be inundation maps. NOAA/NWS has inundation mapping at a few sites across the country. You can download kmz files for those locations from each individual site (download link):
https://water.weather.gov/ahps/inundation.php

Also may want to check out the USGS inundation sites:
https://wimcloud.usgs.gov/apps/FIM/FloodInundationMapper.html
Bill


Offline WeatherHost

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Re: Working with maps?
« Reply #2 on: March 03, 2018, 07:14:33 AM »
I found a way to approximate it using a Filled Polygon.  It isn't exact, but it's good enough for my use.  The camera is in the area of the red circle.

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Offline Farmtalk

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Re: Working with maps?
« Reply #3 on: March 04, 2018, 05:02:23 PM »
I did a lot of projects that were raster-based in college (GIS emphasis physical geography major). I use ArcMap for most of my projects, especially ones involving rasters. I investigated situations like these using the Spatial Analyst option of tools, the most common of which is the Nibble tool.

Basically, using the tool assigns each raster replaces results of a raster (such as terrain background, which in this case would be elevation in ft.) and assigns a normalized set of values to each raster in the image based on the nearest neighbors of each raster cell.

That may sound wordy, but if you have good elevation data available in a TIFF or other quality imagery format, and have a license for ArcMap, it's a fairly simple process that requires just a little bit of reading for utilizing the specific tool in question.

For what it's worth, I love ArcMap, and though I'm in news for now, I hope to have a GIS-related career in the future. So much application one can analyze with it.
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