Wednesday, November 21, 2012

Lidar-Report Sharing Links & Data -

We have been using the hydrology tool in ArcMap's spatial analysis toolbox to explore it's function.  Our data comes from the Appalachian Mountain, SRTM study zone covering 5 states: Tennessee, Kentucky, North Carolina, Virginia and West Virginia.   It's derived from the overall study found at htt;://eros.usgs.gov/#/Find_Data/Products_and_Data_Available/SRTM  .      Our Group 5 used 4 DEMS from LandSat to convert our data into usable form.  Each DEM was 1201 x 1201 pixels, 16 bit signed, already orthorectified to GCS WGS 1984 UTM 17N, based on one band.
They are:  n36_w083_3arc_v1.tif
                 n36_w084_3arc_v1.tif
                 n37_w083_3arc_v1.tif
                 n37_w084_3arc_v1.tif

The final products were 1- a stream feature shapefile showing the streams of the mosaiced DEM and 2- the basin zones as a raster.  Both of these files along with a .mxd of the layers can be accessed from a combined zipped layer package compatible with Arcmap 10.1 at this address which map be copied & pasted:  http://students.uwf.edu/kfm4/Group5StreamBasin.zip
One may need to create a geodatabase to import the layers for extraction. 


Taking the clipped mosaic through the hydrology study process resulted in these individual layers being created as shown in the map below:




Data Process:
1- The originating DEMS have the characteristics as described above.
2- A mosaic was created with the 4 DEMS, which was clipped to the study area.
3- Using the spatial analyst tool in arcmap 10.1 the fill tool was the first step.
4- The resulting fill layer was run through the flow direction tool without any errors.
5- A stream raster (flow accumulation) was created from the flow direction result.
6- The total raster count was taken from the attribute table- sum value. One (1%) percent was calculated as 46,140.20.
7- The con tool was run using the stream raster as input; with an expression of value>46140, with a constant value of 1.
8- Although the stream to feature layer continually gave an error, a check in arcatalog reveiled it ran correctly but needed the coordinate system manually established. WGS 1984 UTM 17N was set.
This steam feature is the final output in the layer file provided.
9- A final hydrology analysis was created as the basin DEM which is the second layer of the map.

The layer zipped file will appear similar to this map without the study area zone and street basemap from arcgis online.

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