<div dir="ltr"><div><div>Thanks for the reply. I've included the input file information below.<br><br></div>I understand that I should see skewing. What's the best method for correction of the skew?<br><br></div>I misspoke a bit about the tiles. I had a few sets of 100 tiles each. on each 100 tile set, the output size was 30gb. The total size of the input files were only about 7.5GB. I think what actually is happening is that when I received the tiles from my source, i did not get the entire set. Instead I got an "L" shape of actual data. When I go to build the vrt/single .tif file, I'm getting a black layer added to the missing tiles. In essence, gdal is filling in the missing data with black tiles, thus increasing the size. I was also adding pyramids, which is adding some to the size. For my application, I do not need the pyramids, so I will just not at them going forward.<br><div><div><br>Here is the input info:<br>PROJCS["NAD_1983_UTM_Zone_12N",<br> GEOGCS["NAD83",<br> DATUM["North_American_Datum_1983",<br> SPHEROID["GRS 1980",6378137,298.2572221010002,<br> AUTHORITY["EPSG","7019"]],<br> AUTHORITY["EPSG","6269"]],<br> PRIMEM["Greenwich",0],<br> UNIT["degree",0.0174532925199433],<br> AUTHORITY["EPSG","4269"]],<br> PROJECTION["Transverse_Mercator"],<br> PARAMETER["latitude_of_origin",0],<br> PARAMETER["central_meridian",-111],<br> PARAMETER["scale_factor",0.9996],<br> PARAMETER["false_easting",500000],<br> PARAMETER["false_northing",0],<br> UNIT["meters",1],<br> AUTHORITY["EPSG","26912"]]<br>Origin = (300000.000000000000000,3537000.000000000000000)<br>Pixel Size = (0.300000000000000,-0.300000000000000)<br>Metadata:<br> AREA_OR_POINT=Area<br> TIFFTAG_RESOLUTIONUNIT=1 (unitless)<br> TIFFTAG_SOFTWARE=Inpho GmbH<br> TIFFTAG_XRESOLUTION=1<br> TIFFTAG_YRESOLUTION=1<br>Image Structure Metadata:<br> INTERLEAVE=PIXEL<br>Corner Coordinates:<br>Upper Left ( 300000.000, 3537000.000) (113d 6'57.86"W, 31d57' 4.92"N)<br>Lower Left ( 300000.000, 3535500.000) (113d 6'56.75"W, 31d56'16.23"N)<br>Upper Right ( 301500.000, 3537000.000) (113d 6' 0.76"W, 31d57' 5.87"N)<br>Lower Right ( 301500.000, 3535500.000) (113d 5'59.65"W, 31d56'17.18"N)<br>Center ( 300750.000, 3536250.000) (113d 6'28.76"W, 31d56'41.05"N)<br>Band 1 Block=128x128 Type=Byte, ColorInterp=Red<br>Band 2 Block=128x128 Type=Byte, ColorInterp=Green<br>Band 3 Block=128x128 Type=Byte, ColorInterp=Blue<br>PROJ.4 string is:<br>'+proj=utm +zone=12 +datum=NAD83 +units=m +no_defs '<br><br><br></div></div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature"><div dir="ltr">Andrew Simpson</div></div></div>
<br><div class="gmail_quote">On Thu, Feb 12, 2015 at 4:20 PM, David Strip <span dir="ltr"><<a href="mailto:gdal@stripfamily.net" target="_blank">gdal@stripfamily.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
While you've shown us your output is in unprojected (lon/lat) WGS84
coordinates, you haven't told us about your input - only that it's
datum is NAD83. If the inputs are projected, you should expect to
see skewing, since a rectangular area in projected coordinates in
general does not map to a rectangle<i></i> in lon/lat.<br>
<br>
As to size - you took 300 tiles each about 50-75M and made a single
file. Your input is in the 20GB range, so 30 GB is not out of hand.
Are your input tiles compressed? Your output is NOT compressed, so
that would go a long way towards explaining things. <br><div><div class="h5">
<br>
<br>
On 2/12/2015 5:58 AM, Andrew Simpson wrote:
</div></div><blockquote type="cite"><div><div class="h5">
<div dir="ltr"><span style="font-size:12.8000001907349px">I'm new
to learning GDAL (mapping in general). I have a bunch of tif
files (300+) that are in NAD83, but my mapping application
only uses WGS84. The tiles are all around 50-75Mb each</span>
<div style="font-size:12.8000001907349px"><br>
</div>
<div style="font-size:12.8000001907349px">I'm able to use gdal
warp to convert the projection properly to WGS84, but the
images (tiles) come out skewed.</div>
<div style="font-size:12.8000001907349px"><br>
</div>
<div style="font-size:12.8000001907349px">I tried using
bdalbuildvrt first to create the vrt, then gdalwarp with the
following options: -co TILED=YES -co BIGTIFF=YES -of GTIFF
-t_srs "+proj=longlat +datum=WGS84 + no_defs" input.vrt
output.vrt</div>
<div style="font-size:12.8000001907349px"><br>
</div>
<div style="font-size:12.8000001907349px">Ok, so this mostly
works, but I have 2 questions/issues:</div>
<div style="font-size:12.8000001907349px">1. what is the best
way to convert the projection and eliminate the skewing?</div>
<div style="font-size:12.8000001907349px">2. The single .tif
produced is now >30GB! significantly larger. why does
this occur and how can I keep this file size down?</div>
<div style="font-size:12.8000001907349px"><br>
</div>
<div style="font-size:12.8000001907349px"><br>
</div>
<div style="font-size:12.8000001907349px">Thanks for any info!</div>
<div>
<div>
<div dir="ltr">Andrew Simpson</div>
</div>
</div>
</div>
<br>
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