SRTM PROCESSING-Erdas
Leica Geo-Systems Imagine 8.7 Version 1: BEFORE GETTING STARTED:
Download SRTM data from ftp://edcftp.cr.usgs.gov/pub/data/srtm/ The SRTMGRID.AML provided by USGS Flagstaff will allow users
to generate ESRI ArcGRID files in batch mode. The
following procedure should be applied if ArcInfo is
not available. IMPORT USING GENERIC BINARY -On the Imagine Icon Panel -Click on the Import/Export icon button -On the Import/Export panel -Select Type: Generic Binary -Select Media Type: File -Navigate to data directory and select *.hgt file -In the output file textbox > replace the filename.img with '_' -Press OK twice to proceed to Generic Binary Import panel -Input the following values: (If srtm.gen
file is available, select the Load Options... command button and proceed to
load parameters). -Data Format: BIL -Data Type: Signed 16 -Select the Swap Bytes: checkbox (files are stored Big Endian) -#Rows: 1201 -#Cols: 1201 -Click on the Import Options... Command Button -Input the Following Values: Output Data Compression: None Output Data Type: Signed 16-bit (Should be defaulted) Block Size: 512 (Image tiling breaks at 1/4 the image array) -Uncheck Create Pyramid Layers: checkbox -Uncheck Ignore Zero in Output Stats: checkbox (No data values are set to -32768) -Press OK to accept changes -Click on the Batch: command button -On the Batch Commands panel -Select the Modify commands automatically: radio button -Select the Next command button -Select the Next command button again -Click on the "Select files to add" icon -On the Select Batch Files panel -Choose the Multiple File Selection tab -Select the "Use the following Selection Pattern": checkbox (Selection pattern is activated and defaults on input directory) (Ex. e:/zwork/srtm/*.hgt) -Press OK to accept changes -Select the Next: command button -Select the Finish: command button to execute batch process ADD MODEL INFO AND PROJECTION TO IMAGERY -Select Tools|Image Command Tool -On the Image Commands: (No File) panel -Click on the folder icon -On the Image File: panel -Navigate to ../SRTM/OUTPUT folder -Choose an imported Image to modify -Press OK to load initial image -Enable the Change Map Model: checkbox -Click on the Options: command button -Input the following values: Pixel Size X: 0.000833333333333 Pixel Size Y: 0.000833333333333 Projection: Geographic (Lat/Lon) Units: DD -Press OK to accept changes -Enable the Change Map Projection: checkbox -Click on the Options: command button -On the Map Projection Options panel -Verify Input Values -Category: Geographic -Select Lat/Lon (WGS 84) in the Projection: listbox -Click OK to accept changes -Click on the Batch: command button to update Map Model for all images -On the Batch Commands panel -Select the Modify commands automatically: radio button -Select the Next command button -Select the Next command button again -Click on the "Select files to add" icon -On the Select Batch Files panel -Choose the Multiple File Selection tab -Select the "Use the following Selection Pattern": checkbox (Selection pattern is activated and defaults on input directory) (Ex. ../srtm/output/*.img) -Press Finish to initialize batch routine -On the Imagine Icon Panel -Click on Tools command -Select File|Open|Raster Layer -Navigate to ../SRTM/ folder -Choose an Image to modify -Press OK to load image -Select Edit|Change Map Model... -On the Change Map Info panel -Input the following Values: Upper Left X: (longitude) NW Corner X Upper Left Y: (Latitude) NW
Corner Y
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