Size Matters

Below is a copy of an email I sent to lizardtech.com Wednesday
night . They have not yet responded . I'm hoping one or more
of you guys can help instead .

WARNING : The zip files available from the FTP server below
are about 8.5 megabytes each .

_________________________________________________


I am a Surveying & CAD technician, but a newbie when it
comes to GIS. I am interested in purchasing a GeoExpress
View (with MrSID) license if the program can do what I
need it to do, which is report the actual size (either
in Lat/Lon or UTM coordinates) of files I download from

http://www.tnris.state.tx.us


One example would be

ftp://ftp2.tnris.org/Imagery/NAIP04/1m/3294/d329419_1.zip

which contains a MrSID file and three metadata files. Two
statements from d329419_1.txt are as follows:

"The tiling format of NAIP imagery is based on a
3.75'x 3.75' quarter quadrangle with a 360 meter
buffer on all four sides."

....but much further down in the same text file....

"These final DOQQ sheets contain a 300m minimum buffer."

The MrSID files supposedly have a resolution of one meter
per pixel, but the actual dimensions (in meters) of each
edge of the MrSID file do *NOT* correspond to the number of
pixels along each edge of said file.

I could find no statements within d329419_1.txt
that told me the actual outer limits of the d329419_1.sid
buffer zone, either in latitude & longitude or UTM NAD 83
coordinates.

Yet I know that one of the metadata files (or the SID file
itself) included in the zip file contains exact georeference
data, because Lizardtech Software's GeoExpress View program
can seamlessly merge the d329419_1.sid image with the (South
adjoining) d329419_3.sid image. When viewed on screen there
is an obvious East-West offset, and a larger North-South
overlap, involved in merging the two images correctly.

I need to know the true limits (not the nominal 3.75' x 3.75'
"boundary"), either in Lat/Lon or UTM coordinates, of each SID
image I download from the aforementioned ftp server so I can
properly size a resulting TIFF or JPG image inserted into an
AutoCad or IntelliCad DWG file. This would allow me to query
the CAD program about the approximate UTM distance between any
two visible features contained in each SID image.

Thanks for your help.

Joe Johnston
joejohn@sbcglobal.net

____________________________________________________

Would you try Global Mapper?
It would took you two seconds to load d329419_1.zip.
Metadata:
FILENAME=d329419_1.sid (C:\DOCUMENTS AND SETTINGS\ALL
USERS\DOCUMENTS\TESTS\D329419_1.ZIP)
DESCRIPTION=d329419_1.sid
UPPER LEFT X=335628.000
UPPER LEFT Y=3625237.000
LOWER RIGHT X=342218.000
LOWER RIGHT Y=3617592.000
WEST LONGITUDE=94.754580° W
NORTH LATITUDE=32.753695° N
EAST LONGITUDE=94.682967° W
SOUTH LATITUDE=32.683799° N
NUM COLUMNS=6590
NUM ROWS=7645
PIXEL WIDTH=1 meters
PIXEL HEIGHT=1 meters

Projection :
UTM15/NAD83

Then, maybe a little more seconds to export to a GeoTIFF or JPG format (+
PRJ + JPW) with the registered version which is affordable.
Cheers


JQ1ch.1702$Py2.866@newssvr27.news.prodigy.net...

Thanks for your reply !

Yes, I will try Global Mapper .

Joe

It appears I was just plain wrong when I wrote this statement
in my first post:

"The MrSID files supposedly have a resolution of one meter
per pixel, but the actual dimensions (in meters) of each
edge of the MrSID file do *NOT* correspond to the number of
pixels along each edge of said file."

It appears that the UTM/NAD83 size in meters of each of the
MrSID files available from that particular ftp server IS one
meter per pixel .

Phillipe, thanks again .

Joe

I've used it since v4.x. Great piece of software, and every release gets
better, plus more features, including DEM and Terraserver downloads directly
from within the software.