Latest Contributions by TimSzeliga

I have hundreds of snow maps to convert from BIL/HDR to geoTIFF format. Each raster is in Albers projection, covering one of a dozen standard regions. Each region has a consistent number of rows and columns and the same corner points. The unique raster values are (0=NULL, 50=LAND, 100=CLOUD, 250=SNOW). I have HDR and PRJ files with each BIL.  I would like to export these using a common color map (black/blue/cyan/red).  As these came from 20 archival CDs, I would like to use compression to try to get them all onto one or two DVDs. I can do it by hand, loading the BIL, setting display to Unique Values, modifying the colors, then exporting to PNG.  There are so many rasters, I have to come up with an automated method.  I am running in 9.3.1 with Spatial Analyst, but have access to 10.1 as well. This is where it gets tricky.  I've included a .CLR file with the BIL/HDR/PRJ, but it ignores it.  I've tried including only (0/50/100/250) in the .CLR and also filling in every value from (0-255).  Exporting as TIFF is preferred, but it assigns random colors and does not allow compression, even though the input is 8-bit unsigned integer.  PNG with a world file would work, but again, it does not preserve colors. Should there be an intermediate step, converting BIL to GRID, modifying colors and computing unique values, followed by the export to PNG/TIFF?  How can these display functions be incorporated into a script? Tim Szeliga timothy.szeliga@noaa.gov National Weather Service ... View more

I've got 30,000 BIL/HDR pairs I need to convert to GEOTIFF in 9.3. This is thirteen year's of snow maps, all classified as -9999/0/50/150/250 for NODATA/NotMapped/LAND/CLOUD/SNOW, displayed as blank/gray/blue/cyan/red.  The early ones are in USGS_Albers and the later in WGS84. If I was doing them by hand, I would display BIL, Define Projection, Display as Unique Values (Build Raster Attribute Table), Add Colormap (or predefined layer), and remap the Albers to WGS84 and output as TIF.   Disk space is a problem, so I'd avoid pyramids and unnecessary tmp files. Is the mere presence of a matching .PRJ and .CLR file in the directory with the .BIL/.HDR enough to have Arc recognize these?  Do I have to make an intermediate conversion to GRID format? The USGS_Image_Toolbox_v1_5 looks promising, but doesn't seem to like .BIL or .ASC as input. Can these be batched up easily? Tim Szeliga National Weather Service timothy.szeliga@noaa.gov ... View more

I'm processing a LiDAR survey along the Connecticut River.  The LiDAR spacing is around 7 feet.  The survey follows the river but is only 1-6 miles wide. The hydrologists want to use it for flood inundation mapping, but need the DEM raster expanded to the entire hydrologic basin, thirty or more miles wide. Conn. has a state-wide LiDAR survey available at ~28 foot resolution, including and surrounding my area.  I've got ASCII XYZ sets for both surveys, broken into tiles. I've read Clayton Crawford's excellent series on LiDAR Solutions in ArcGIS. Also the Basic Terrain Modeling outline from Harvard. I still have a few questions. Q: how best to embed the hi-res points in the low-res? Q: The final product should be a DEM raster, so they can generate flow-direction grids. What is the highest raster resolution I can push out of this data?  Can I get a 10-foot DEM that is detailed along the river and blurrier elsewhere? Q: Should the processing go {points, 2-D breaklines} -> {Terrain} -> DEM? Is TIN involved at any point? Q: Most of the river and lake linework don't have elev or have a field ELEVATION=0. Can/should elev be set?  Some provide river channels, others just centerlines. How should SFType be set in terrain builder? Q: Should the low-res background and the hi-res river area be processed separately, then merged as terrains or rasters?  Or just dump all the points into one big mixed-res multipoint file and process that from start to finish? Q: The high-res is too dense to process all at once and presumably there are similar limits on the low res.  How best to process tiles and match and merge? This is for hydrology, so a 6-foot difference between adjoining tiles amounts to a dam (or a waterfall). Any insights?  Contact in the forum or off-line. Tim Szeliga National Weather Service timothy.szeliga@noaa.gov ... View more

L71070332011071EDC00 This LANDSAT-7 TM pass went over Japan Saturday.  It is available through the Earth Explorer interface from the EROS Data Center.  LANDSAT-7 has the well-known "venetian-blind" artifact and this image has lots of cumulus cloud, but the ETM+ sensor also has the pan-chromatic 15-meter band 8, which allows extra high resolution colorized images.  These two zooms select bands {721}, which pick up the fires and smoke plumes, as well as the saturated land and standing water.  I'm sure others in the Remote Sensing community can improve on these images. Tim Szeliga / NOHRSC-NOAA-NWS ... View more

We're doing a mixed-resolution comparison between MODIS and TM data. I'm required to do the analysis using the original unprojected MODIS 1km satellite raster.  The MODIS comes with a pair of lat/lon rasters, in floating point, same size as the image bands, indicating the latitude and longitude of each image pixel. I'm working from raw MOD03, MOD021KM, MOD02QKM, etc from LAADS through rapidfire.sci.gsfc.nasa.gov and with TM from glovis.usgs.gov. Is there a mechanism in ArcGis 9.3.1 to use this information to navigate the image, without first reprojecting to geographic or UTM?   There is a warp function, and I will eventually need to pick matching landmarks.  The goal is to warp projected TM data into the "satellite-projection" MODIS space. The TM is in UTM, in meters, while the MODIS has lat/lon given (although is not in an actual "geographic" projection).  The lat/lon does not progress regularly across the image.  If I stick to a TM scene falling in the center of the MODIS swath, the distortion is not too bad. Do I need to transform the target lat/lons to some kind of relative meter-based extents?  Can warp work from meters->degrees? The snow classifications don't have any detail, so I'd have to use the MODIS and TM images to pick landmarks and build a file of correspondences, then apply this to the two snowmaps to do the final warp.  I have ENVI and the MODIS-SWATH_MRT available.  We're investigating a MODIS snow cover classification scheme, and using the TM-derived snow as ground truth to examine fractional snow cover.  The scene looks like a postage stamp affixed to a poster, but blown up to 30m TM resolution, the MODIS drapes over like a 1km checkerboard.  Counting the ratio of Snow/No_Snow TM pixels falling in each MODIS box gives a good assessment of fractional snow cover. The big problem will be warping the TM scene (in UTM-17N) to the MODIS (in satellite projection).  I plan to build a fishnet at 1km the size of the smaller TM coverage, convert to polygon and use Zonal Statistics to make the count.   Do any of the standard raster/math/feature operations refuse to work in an unprojected background?  Is there a list anywhere? Yes, I know this would be a trivial matter if I could project the MODIS to match the TM in UTM, but I am required to do it in this ass-backwards manner. Tim Szeliga timothy.szeliga@noaa.gov ... View more