Probleme to calibrate New-Hampshire DRG

Anonymous · 17. November 2004

Hi,

I'm trying to calibrate 1:24000 USA New Hampshire maps from this web site :

http://www.granit.sr.unh.edu/cgi-bin/load_file?PATH=/data

The DRG files come with TFW files that should contain the calibration data.

I read on the web site that the maps are calibrated using the following projection :

Projection: Stateplane
Zone: 4676 (This is the USGS zone. The FIPSZONE is 2800.)
Datum: NAD83
Units: Feet

The NAD83 New Hampshire State Plane Coordinate System is defined as follows:

Projection: Transverse Mercator
Spheroid: GRS1980
Scale Factor: .9999666667
Central Meridian: -71 40 00
Origin: 42 30 00
False Easting: 300000 m (984,250 ft)
False Northing 0

I don't thinks that the State Plane projection is in Touratech by default so I tried to create a new National Meter Grid with the data that is shown above.

This is what I entered :

Name : New Hampshire Stape Plane
Datum : NAD83
Prefix : NH1
Lat_0 : 42.5
Lon_0 : -71,6666666666667
False Northing : 0
False Easting : 300000

All min/max are set to -9999999/9999999

Now when I calibrate the map, I chose the New Hampshire State Plane National Meter Grid that I created with the map TFW file. Whit this, I get a map that is offset of approximately 553 Km N and 425 km E.

Map TWG file :

8.25292021292262
0.00000000000000
0.00000000000000
-8.25292021292262
896840.75146010646000
638036.65899820731000

The four corner of the map should be :

West_Bounding_Coordinate: -72.000
East_Bounding_Coordinate: -71.875
North_Bounding_Coordinate: 44.250
South_Bounding_Coordinate: 44.125

I there something that I'm doing wrong? Can you help me with this?

Thanks.

Franco

jockel · 17. November 2004

Hi,

had some problems downloading DRG files from there, the zips are corrupted
in a way, that a portion of the html is included as a header of a zip ?!
Some hex-editing did the trick. Any I dea what´s wrong with that ?

Import: Obviously TTQV does not recognize, that the units given in *.tfw are
in feet, not in meter. An other software I used to check the files says,
that the units can not be detected automatically and you have to select
them manually. Anyway, I do not expect this to be a big problem.
Progi will look into this, I ll be back

Anonymous · 18. November 2004

Hi jockel,

that it, all the number are in feet. I converted them in meters and it works.

I downloaded all 213 drg maps from the Granit web site and I had no corrupted ZIP file.

Thanks a lot

Franco

jockel · 18. November 2004

Hi,

Zitat von "Anonymous"

that it, all the number are in feet. I converted them in meters and it works.

Progi will add a workaround to "national meter grid setup", so you can advice
TTQV3 in the future to expect a *.tfw beeing in feet instead of meters. Will
happen by inserting a line like "units=feet" (has yet to be defined) into
the info field of the "national meter grid setup"

@corrupted downloads
I saw this is strange, possibly related here to local firewalls or similar. I will check.

jockel · 1. Dezember 2004

Hi Franco,

TTQV3.0.101 will now import your NH geotif maps(and others) without any
user intervention in one rush from geotif infos. No recalculation of *.tfw file
required, i. E. they should no longer be recalculated.

3.0.101 is still a development release, you can download it here:
http://www.ttqv2.de/files9/qv3upd_101.exe

Anonymous · 5. Dezember 2004

Hi jockel,

Thanks for this sofware update. It's very usefull! It works well with map that have calibration files in meter but I still have problem with the NH map. The *.tfw that are in feet are read as if they were in meters. Is it normal?

Thanks

Franco

jockel · 6. Dezember 2004

Hi Franco,

take a look, whether there are previous cal-files aside the map files.
Delete them, then import the maps in TTQV again. I tried it with a "feet" file
an it imported correctly.
If you think it does not work, please post a direct link to such a problem file
and I will test.

...maybe remove the *.tfw also prior to importing. TTQV does not need it.
The maps are calibrated from the internal geotiff info. You must reimport
the files anew. You must use the original files! I you opened and saved them
with a picture editor(Paintshop, Photoshop...), the geotif information is
destroyed!

Anonymous · 15. Dezember 2004

Hi Jockel,

I put a NH drg file at this location :

http://www3.sympatico.ca/francoislach/drg38.tif

it seems that TTQV dosen't see the calibration information that is inside the file because when I import it the Calibration window appears. I have the version 3.0.101. I try other geotiff files from other USA states and the import worked well.

I only have problems with the NH files.

Thanks

Franco

Teilen