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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>
<br>
<br>
On 2/12/2015 5:58 AM, Andrew Simpson wrote:
<blockquote type="cite">
<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 class="gmail_signature">
<div dir="ltr">Andrew Simpson</div>
</div>
</div>
</div>
<br>
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