[gdal-dev] Extra Decimal places added to ASCII gdal_translate mosaic

Jonathan Moules jonathanmoules at warwickshire.gov.uk
Fri Jan 24 07:01:43 PST 2014

Hi List,
I'm trying to mosaic some ASCII grid tiles into a single large ASCII file
(which can then easily be handled).

I'm using this process:

> REM Create list of files
> dir /b /s *.asc > asc_list.txt

> REM Turn into VRT
> gdalbuildvrt -srcnodata "-9999" -vrtnodata "0" -a_srs "EPSG:27700"
> -input_file_list "asc_list.txt" abc.vrt

> REM actual mosaicing
> gdal_translate -of AAIGrid abc.vrt abc.asc

The input files are like:

> ncols         500
> nrows         500
> xllcorner     432000.000
> yllcorner     243000.000
> cellsize      2
> nodata_value  -9999.0
> 98.354 98.449 98.658 98.874 99.038 99.096

But the outputs are like:

fncols        500
> nrows        1000
> xllcorner    432000.000000000000
> yllcorner    242000.000000000000
> cellsize     2.000000000000
> NODATA_value  0
>  98.353996276855469 98.448997497558594 98.657997131347656
> 98.874000549316406

Suddenly everything has a dozen extra decimal places. Not only does this
induce the False Precision problem (we don't have heights to the
femtometer!), it also massively increases the filesize.

How can I get this to not happen?


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